由于排版原因文章下面的部分承接ActivityManagerService之深入理解Activity启动流程(二)
二、第二阶段 应用进程创建
2.1.1 AMS startProcessLocked
final ProcessRecord startProcessLocked(String processName,
ApplicationInfo info, boolean knownToBeDead, int intentFlags,
String hostingType, ComponentName hostingName, boolean allowWhileBooting,
boolean isolated, boolean keepIfLarge) {
return startProcessLocked(processName, info, knownToBeDead, intentFlags, hostingType,
hostingName, allowWhileBooting, isolated, 0 /* isolatedUid */, keepIfLarge,
null /* ABI override */, null /* entryPoint */, null /* entryPointArgs */,
null /* crashHandler */);
}
final ProcessRecord startProcessLocked(String processName, ApplicationInfo info,
boolean knownToBeDead, int intentFlags, String hostingType, ComponentName hostingName,
boolean allowWhileBooting, boolean isolated, int isolatedUid, boolean keepIfLarge,
String abiOverride, String entryPoint, String[] entryPointArgs, Runnable crashHandler) {
long startTime = SystemClock.elapsedRealtime();
ProcessRecord app;
if (!isolated) {
//根据processName和uid寻找是否已经存在ProcessRecord
app = getProcessRecordLocked(processName, info.uid, keepIfLarge);
checkTime(startTime, "startProcess: after getProcessRecord");
if ((intentFlags & Intent.FLAG_FROM_BACKGROUND) != 0) {
// If we are in the background, then check to see if this process
// is bad. If so, we will just silently fail.
//如果是后台进程并且启动的是奔溃的进程
if (mAppErrors.isBadProcessLocked(info)) {
if (DEBUG_PROCESSES) Slog.v(TAG, "Bad process: " + info.uid
+ "/" + info.processName);
return null;
}
} else {
// When the user is explicitly starting a process, then clear its
// crash count so that we won't make it bad until they see at
// least one crash dialog again, and make the process good again
// if it had been bad.
if (DEBUG_PROCESSES) Slog.v(TAG, "Clearing bad process: " + info.uid
+ "/" + info.processName);
mAppErrors.resetProcessCrashTimeLocked(info);
if (mAppErrors.isBadProcessLocked(info)) {
EventLog.writeEvent(EventLogTags.AM_PROC_GOOD,
UserHandle.getUserId(info.uid), info.uid,
info.processName);
mAppErrors.clearBadProcessLocked(info);
if (app != null) {
app.bad = false;
}
}
}
} else {
// If this is an isolated process, it can't re-use an existing process.
app = null;
}
// We don't have to do anything more if:
// (1) There is an existing application record; and
// (2) The caller doesn't think it is dead, OR there is no thread
// object attached to it so we know it couldn't have crashed; and
// (3) There is a pid assigned to it, so it is either starting or
// already running.
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES, "startProcess: name=" + processName
+ " app=" + app + " knownToBeDead=" + knownToBeDead
+ " thread=" + (app != null ? app.thread : null)
+ " pid=" + (app != null ? app.pid : -1));
if (app != null && app.pid > 0) {
if ((!knownToBeDead && !app.killed) || app.thread == null) {
// We already have the app running, or are waiting for it to
// come up (we have a pid but not yet its thread), so keep it.
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES, "App already running: " + app);
// If this is a new package in the process, add the package to the list
app.addPackage(info.packageName, info.versionCode, mProcessStats);
checkTime(startTime, "startProcess: done, added package to proc");
return app;
}
// An application record is attached to a previous process,
// clean it up now.
if (DEBUG_PROCESSES || DEBUG_CLEANUP) Slog.v(TAG_PROCESSES, "App died: " + app);
checkTime(startTime, "startProcess: bad proc running, killing");
killProcessGroup(app.uid, app.pid);//杀死进程
handleAppDiedLocked(app, true, true);
checkTime(startTime, "startProcess: done killing old proc");
}
String hostingNameStr = hostingName != null
? hostingName.flattenToShortString() : null;
if (app == null) {
checkTime(startTime, "startProcess: creating new process record");
//创建一个ProcessRecord，并保存到mProcessNames中。注意，此时还没有创建实际进程
app = newProcessRecordLocked(info, processName, isolated, isolatedUid);
if (app == null) {
Slog.w(TAG, "Failed making new process record for "
+ processName + "/" + info.uid + " isolated=" + isolated);
return null;
}
app.crashHandler = crashHandler;
app.isolatedEntryPoint = entryPoint;
app.isolatedEntryPointArgs = entryPointArgs;
checkTime(startTime, "startProcess: done creating new process record");
} else {
// If this is a new package in the process, add the package to the list
app.addPackage(info.packageName, info.versionCode, mProcessStats);
checkTime(startTime, "startProcess: added package to existing proc");
}
// If the system is not ready yet, then hold off on starting this
// process until it is.
if (!mProcessesReady
&& !isAllowedWhileBooting(info)
&& !allowWhileBooting) {
if (!mProcessesOnHold.contains(app)) {
mProcessesOnHold.add(app);
}
if (DEBUG_PROCESSES) Slog.v(TAG_PROCESSES,
"System not ready, putting on hold: " + app);
checkTime(startTime, "startProcess: returning with proc on hold");
return app;
}
checkTime(startTime, "startProcess: stepping in to startProcess");
//②调用另外一个startProcessLocked函数
startProcessLocked(app, hostingType, hostingNameStr, abiOverride);
checkTime(startTime, "startProcess: done starting proc!");
return (app.pid != 0) ? app : null;
}
2.1.2 AMS startProcessLocked
private final void startProcessLocked(ProcessRecord app, String hostingType,
String hostingNameStr, String abiOverride) {
long startTime = SystemClock.elapsedRealtime();
if (app.pid > 0 && app.pid != MY_PID) {
checkTime(startTime, "startProcess: removing from pids map");
synchronized (mPidsSelfLocked) {
mPidsSelfLocked.remove(app.pid);//移除app.pid的进程
mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
}
checkTime(startTime, "startProcess: done removing from pids map");
app.setPid(0);//初始化pid值0
}
if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG_PROCESSES,
"startProcessLocked removing on hold: " + app);
mProcessesOnHold.remove(app); //mProcessesOnHold用于保存那些在系统还没有准备好就提前请求启动的ProcessRecord
checkTime(startTime, "startProcess: starting to update cpu stats");
updateCpuStats();//更新cpu状态
checkTime(startTime, "startProcess: done updating cpu stats");
try {
try {
final int userId = UserHandle.getUserId(app.uid);
AppGlobals.getPackageManager().checkPackageStartable(app.info.packageName, userId);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
/// M: onStartProcess @{
mAmsExt.onStartProcess(hostingType, app.info.packageName);
/// M: onStartProcess @}
int uid = app.uid;
int[] gids = null;
int mountExternal = Zygote.MOUNT_EXTERNAL_NONE;
if (!app.isolated) {
int[] permGids = null;
try {
checkTime(startTime, "startProcess: getting gids from package manager");
final IPackageManager pm = AppGlobals.getPackageManager();
//从PKMS中查询该进程所属的gid
permGids = pm.getPackageGids(app.info.packageName,
MATCH_DEBUG_TRIAGED_MISSING, app.userId);
StorageManagerInternal storageManagerInternal = LocalServices.getService(
StorageManagerInternal.class);
mountExternal = storageManagerInternal.getExternalStorageMountMode(uid,
app.info.packageName);
} catch (RemoteException e) {
throw e.rethrowAsRuntimeException();
}
/*
* Add shared application and profile GIDs so applications can share some
* resources like shared libraries and access user-wide resources
*/
if (ArrayUtils.isEmpty(permGids)) {
gids = new int[3];
} else {
gids = new int[permGids.length + 3];
System.arraycopy(permGids, 0, gids, 3, permGids.length);
}
gids[0] = UserHandle.getSharedAppGid(UserHandle.getAppId(uid));
gids[1] = UserHandle.getCacheAppGid(UserHandle.getAppId(uid));
gids[2] = UserHandle.getUserGid(UserHandle.getUserId(uid));
// Replace any invalid GIDs
if (gids[0] == UserHandle.ERR_GID) gids[0] = gids[2];
if (gids[1] == UserHandle.ERR_GID) gids[1] = gids[2];
}
checkTime(startTime, "startProcess: building args");
if (mFactoryTest != FactoryTest.FACTORY_TEST_OFF) {
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL
&& mTopComponent != null
&& app.processName.equals(mTopComponent.getPackageName())) {
uid = 0;
}
if (mFactoryTest == FactoryTest.FACTORY_TEST_HIGH_LEVEL
&& (app.info.flags&ApplicationInfo.FLAG_FACTORY_TEST) != 0) {
uid = 0;
}
}
int debugFlags = 0;
//下面添加debugFlags属性都是为了后续在Zygote创建进程而准备的
if ((app.info.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
debugFlags |= Zygote.DEBUG_ENABLE_JDWP;
debugFlags |= Zygote.DEBUG_JAVA_DEBUGGABLE;
// Also turn on CheckJNI for debuggable apps. It's quite
// awkward to turn on otherwise.
debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
// Run the app in safe mode if its manifest requests so or the
// system is booted in safe mode.
if ((app.info.flags & ApplicationInfo.FLAG_VM_SAFE_MODE) != 0 ||
mSafeMode == true) {
debugFlags |= Zygote.DEBUG_ENABLE_SAFEMODE;
}
if ("1".equals(SystemProperties.get("debug.checkjni"))) {
debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
}
String genDebugInfoProperty = SystemProperties.get("debug.generate-debug-info");
if ("true".equals(genDebugInfoProperty)) {
debugFlags |= Zygote.DEBUG_GENERATE_DEBUG_INFO;
}
if ("1".equals(SystemProperties.get("debug.jni.logging"))) {
debugFlags |= Zygote.DEBUG_ENABLE_JNI_LOGGING;
}
if ("1".equals(SystemProperties.get("debug.assert"))) {
debugFlags |= Zygote.DEBUG_ENABLE_ASSERT;
}
if (mNativeDebuggingApp != null && mNativeDebuggingApp.equals(app.processName)) {
// Enable all debug flags required by the native debugger.
debugFlags |= Zygote.DEBUG_ALWAYS_JIT; // Don't interpret anything
debugFlags |= Zygote.DEBUG_GENERATE_DEBUG_INFO; // Generate debug info
debugFlags |= Zygote.DEBUG_NATIVE_DEBUGGABLE; // Disbale optimizations
mNativeDebuggingApp = null;
}
String invokeWith = null;
if ((app.info.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
// Debuggable apps may include a wrapper script with their library directory.
String wrapperFileName = app.info.nativeLibraryDir + "/wrap.sh";
StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
try {
if (new File(wrapperFileName).exists()) {
invokeWith = "/system/bin/logwrapper " + wrapperFileName;
}
} finally {
StrictMode.setThreadPolicy(oldPolicy);
}
}
//动态库abi
String requiredAbi = (abiOverride != null) ? abiOverride : app.info.primaryCpuAbi;
if (requiredAbi == null) {
requiredAbi = Build.SUPPORTED_ABIS[0];
}
String instructionSet = null;
if (app.info.primaryCpuAbi != null) {
instructionSet = VMRuntime.getInstructionSet(app.info.primaryCpuAbi);
}
app.gids = gids;
app.requiredAbi = requiredAbi;
app.instructionSet = instructionSet;
// the per-user SELinux context must be set
if (TextUtils.isEmpty(app.info.seInfoUser)) {
Slog.wtf(TAG, "SELinux tag not defined",
new IllegalStateException("SELinux tag not defined for "
+ app.info.packageName + " (uid " + app.uid + ")"));
}
final String seInfo = app.info.seInfo
+ (TextUtils.isEmpty(app.info.seInfoUser) ? "" : app.info.seInfoUser);
// Start the process. It will either succeed and return a result containing
// the PID of the new process, or else throw a RuntimeException.
final String entryPoint = "android.app.ActivityThread";
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Start proc: " +
app.processName);
checkTime(startTime, "startProcess: asking zygote to start proc");
//发送消息给Zygote，它将派生一个子进程，该子进程执行ActivityThread的main函数
//注意，我们传递给Zygote的参数并没有包含任何与Activity相关的信息。现在仅仅启动
//一个应用进程
ProcessStartResult startResult;
if (hostingType.equals("webview_service")) {
startResult = startWebView(entryPoint,
app.processName, uid, uid, gids, debugFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, null, null);
} else {
startResult = Process.start(entryPoint,
app.processName, uid, uid, gids, debugFlags, mountExternal,
app.info.targetSdkVersion, seInfo, requiredAbi, instructionSet,
app.info.dataDir, invokeWith, null);
}
checkTime(startTime, "startProcess: returned from zygote!");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
//电量统计项
mBatteryStatsService.noteProcessStart(app.processName, app.info.uid);
checkTime(startTime, "startProcess: done updating battery stats");
EventLog.writeEvent(EventLogTags.AM_PROC_START,
UserHandle.getUserId(uid), startResult.pid, uid,
app.processName, hostingType,
hostingNameStr != null ? hostingNameStr : "");
try {
//app进程log启动
AppGlobals.getPackageManager().logAppProcessStartIfNeeded(app.processName, app.uid,
seInfo, app.info.sourceDir, startResult.pid);
} catch (RemoteException ex) {
// Ignore
}
/// M: Boot time profiling @{
sMtkSystemServerIns.addBootEvent("AP_Init:["
+ hostingType
+ "]:[" + app.processName
+ ((hostingNameStr != null) ? "]:[" + hostingNameStr : "")
+ "]:pid:" + startResult.pid
+ (app.persistent ? ":(PersistAP)" : ""));
/// M: @}
if (app.persistent) {//看门狗监听进程
Watchdog.getInstance().processStarted(app.processName, startResult.pid);
}
checkTime(startTime, "startProcess: building log message");
StringBuilder buf = mStringBuilder;
buf.setLength(0);
buf.append("Start proc ");
buf.append(startResult.pid);
buf.append(':');
buf.append(app.processName);
buf.append('/');
UserHandle.formatUid(buf, uid);
if (app.isolatedEntryPoint != null) {
buf.append(" [");
buf.append(app.isolatedEntryPoint);
buf.append("]");
}
buf.append(" for ");
buf.append(hostingType);
if (hostingNameStr != null) {
buf.append(" ");
buf.append(hostingNameStr);
}
Slog.i(TAG, buf.toString());
app.setPid(startResult.pid);//重新设置pid
app.usingWrapper = startResult.usingWrapper;
app.removed = false;
app.killed = false;
app.killedByAm = false;
checkTime(startTime, "startProcess: starting to update pids map");
ProcessRecord oldApp;
//mPidsSelfLocked里面还保持startResult.pid进程信息，后续会把它清空，保证是一个新的进程
synchronized (mPidsSelfLocked) {
oldApp = mPidsSelfLocked.get(startResult.pid);
}
// If there is already an app occupying that pid that hasn't been cleaned up
if (oldApp != null && !app.isolated) {
// Clean up anything relating to this pid first
Slog.w(TAG, "Reusing pid " + startResult.pid
+ " while app is still mapped to it");
cleanUpApplicationRecordLocked(oldApp, false, false, -1,
true /*replacingPid*/);
}
synchronized (mPidsSelfLocked) {
//重新把此进程存储到mPidsSelfLocked
//正常的超时时间为10秒。不过如果该应用进程通过valgrind加载，则延长到1200秒
//valgrind是Linux平台上一款检查内存泄露的程序，被加载的应用将在它的环境中工作
this.mPidsSelfLocked.put(startResult.pid, app);
Message msg = mHandler.obtainMessage(PROC_START_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg, startResult.usingWrapper
? PROC_START_TIMEOUT_WITH_WRAPPER : PROC_START_TIMEOUT);
}
checkTime(startTime, "startProcess: done updating pids map");
} catch (RuntimeException e) {
Slog.e(TAG, "Failure starting process " + app.processName, e);
// Something went very wrong while trying to start this process; one
// common case is when the package is frozen due to an active
// upgrade. To recover, clean up any active bookkeeping related to
// starting this process. (We already invoked this method once when
// the package was initially frozen through KILL_APPLICATION_MSG, so
// it doesn't hurt to use it again.)
//如果出错的话就暂停进程
forceStopPackageLocked(app.info.packageName, UserHandle.getAppId(app.uid), false,
false, true, false, false, UserHandle.getUserId(app.userId), "start failure");
}
}
2.1.3 Process.start
public static final ProcessStartResult start(final String processClass,
final String niceName,
int uid, int gid, int[] gids,
int debugFlags, int mountExternal,
int targetSdkVersion,
String seInfo,
String abi,
String instructionSet,
String appDataDir,
String invokeWith,
String[] zygoteArgs) {
return zygoteProcess.start(processClass, niceName, uid, gid, gids,
debugFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, zygoteArgs);
}
2.1.4 zygoteProcess.start
public final Process.ProcessStartResult start(final String processClass,
final String niceName,
int uid, int gid, int[] gids,
int debugFlags, int mountExternal,
int targetSdkVersion,
String seInfo,
String abi,
String instructionSet,
String appDataDir,
String invokeWith,
String[] zygoteArgs) {
try {
return startViaZygote(processClass, niceName, uid, gid, gids,
debugFlags, mountExternal, targetSdkVersion, seInfo,
abi, instructionSet, appDataDir, invokeWith, zygoteArgs);
} catch (ZygoteStartFailedEx ex) {
Log.e(LOG_TAG,
"Starting VM process through Zygote failed");
throw new RuntimeException(
"Starting VM process through Zygote failed", ex);
}
}
2.1.5 zygoteProcess.startViaZygote
private Process.ProcessStartResult startViaZygote(final String processClass,
final String niceName,
final int uid, final int gid,
final int[] gids,
int debugFlags, int mountExternal,
int targetSdkVersion,
String seInfo,
String abi,
String instructionSet,
String appDataDir,
String invokeWith,
String[] extraArgs)
throws ZygoteStartFailedEx {
ArrayList<String> argsForZygote = new ArrayList<String>();
// --runtime-args, --setuid=, --setgid=,
// and --setgroups= must go first
argsForZygote.add("--runtime-args");
argsForZygote.add("--setuid=" + uid);
argsForZygote.add("--setgid=" + gid);
if ((debugFlags & Zygote.DEBUG_ENABLE_JNI_LOGGING) != 0) {
argsForZygote.add("--enable-jni-logging");
}
if ((debugFlags & Zygote.DEBUG_ENABLE_SAFEMODE) != 0) {
argsForZygote.add("--enable-safemode");
}
if ((debugFlags & Zygote.DEBUG_ENABLE_JDWP) != 0) {
argsForZygote.add("--enable-jdwp");
}
if ((debugFlags & Zygote.DEBUG_ENABLE_CHECKJNI) != 0) {
argsForZygote.add("--enable-checkjni");
}
if ((debugFlags & Zygote.DEBUG_GENERATE_DEBUG_INFO) != 0) {
argsForZygote.add("--generate-debug-info");
}
if ((debugFlags & Zygote.DEBUG_ALWAYS_JIT) != 0) {
argsForZygote.add("--always-jit");
}
if ((debugFlags & Zygote.DEBUG_NATIVE_DEBUGGABLE) != 0) {
argsForZygote.add("--native-debuggable");
}
if ((debugFlags & Zygote.DEBUG_JAVA_DEBUGGABLE) != 0) {
argsForZygote.add("--java-debuggable");
}
if ((debugFlags & Zygote.DEBUG_ENABLE_ASSERT) != 0) {
argsForZygote.add("--enable-assert");
}
if (mountExternal == Zygote.MOUNT_EXTERNAL_DEFAULT) {
argsForZygote.add("--mount-external-default");
} else if (mountExternal == Zygote.MOUNT_EXTERNAL_READ) {
argsForZygote.add("--mount-external-read");
} else if (mountExternal == Zygote.MOUNT_EXTERNAL_WRITE) {
argsForZygote.add("--mount-external-write");
}
argsForZygote.add("--target-sdk-version=" + targetSdkVersion);
// --setgroups is a comma-separated list
if (gids != null && gids.length > 0) {
StringBuilder sb = new StringBuilder();
sb.append("--setgroups=");
int sz = gids.length;
for (int i = 0; i < sz; i++) {
if (i != 0) {
sb.append(',');
}
sb.append(gids[i]);
}
argsForZygote.add(sb.toString());
}
if (niceName != null) {
argsForZygote.add("--nice-name=" + niceName);
}
if (seInfo != null) {
argsForZygote.add("--seinfo=" + seInfo);
}
if (instructionSet != null) {
argsForZygote.add("--instruction-set=" + instructionSet);
}
if (appDataDir != null) {
argsForZygote.add("--app-data-dir=" + appDataDir);
}
if (invokeWith != null) {
argsForZygote.add("--invoke-with");
argsForZygote.add(invokeWith);
}
argsForZygote.add(processClass);
if (extraArgs != null) {
for (String arg : extraArgs) {
argsForZygote.add(arg);
}
}
synchronized(mLock) {
return zygoteSendArgsAndGetResult(openZygoteSocketIfNeeded(abi), argsForZygote);
}
}
private ZygoteState openZygoteSocketIfNeeded(String abi) throws ZygoteStartFailedEx {
Preconditions.checkState(Thread.holdsLock(mLock), "ZygoteProcess lock not held");
if (primaryZygoteState == null || primaryZygoteState.isClosed()) {
try {
primaryZygoteState = ZygoteState.connect(mSocket);
} catch (IOException ioe) {
throw new ZygoteStartFailedEx("Error connecting to primary zygote", ioe);
}
}
if (primaryZygoteState.matches(abi)) {
return primaryZygoteState;
}
// The primary zygote didn't match. Try the secondary.
if (secondaryZygoteState == null || secondaryZygoteState.isClosed()) {
try {
secondaryZygoteState = ZygoteState.connect(mSecondarySocket);
} catch (IOException ioe) {
throw new ZygoteStartFailedEx("Error connecting to secondary zygote", ioe);
}
}
if (secondaryZygoteState.matches(abi)) {
return secondaryZygoteState;
}
throw new ZygoteStartFailedEx("Unsupported zygote ABI: " + abi);
}
private static Process.ProcessStartResult zygoteSendArgsAndGetResult(
ZygoteState zygoteState, ArrayList<String> args)
throws ZygoteStartFailedEx {
try {
// Throw early if any of the arguments are malformed. This means we can
// avoid writing a partial response to the zygote.
int sz = args.size();
for (int i = 0; i < sz; i++) {
if (args.get(i).indexOf('\n') >= 0) {
throw new ZygoteStartFailedEx("embedded newlines not allowed");
}
}
/**
* See com.android.internal.os.SystemZygoteInit.readArgumentList()
* Presently the wire format to the zygote process is:
* a) a count of arguments (argc, in essence)
* b) a number of newline-separated argument strings equal to count
*
* After the zygote process reads these it will write the pid of
* the child or -1 on failure, followed by boolean to
* indicate whether a wrapper process was used.
*/
final BufferedWriter writer = zygoteState.writer;
final DataInputStream inputStream = zygoteState.inputStream;
writer.write(Integer.toString(args.size()));
writer.newLine();
for (int i = 0; i < sz; i++) {
String arg = args.get(i);
writer.write(arg);
writer.newLine();
}
writer.flush();
// Should there be a timeout on this?
Process.ProcessStartResult result = new Process.ProcessStartResult();
// Always read the entire result from the input stream to avoid leaving
// bytes in the stream for future process starts to accidentally stumble
// upon.
result.pid = inputStream.readInt();
result.usingWrapper = inputStream.readBoolean();
if (result.pid < 0) {
throw new ZygoteStartFailedEx("fork() failed");
}
return result;
} catch (IOException ex) {
zygoteState.close();
throw new ZygoteStartFailedEx(ex);
}
}
上面三个函数，给argsForZygote添加时候的参数，连接Zogte Socket，向Zogte SocketServer 写入值。那么Zogte SocketServer在哪里接受这些信息？答案是ZygoteInit
2.1.6 ZygoteInit.main
public static void main(String argv[]) {
ZygoteServer zygoteServer = new ZygoteServer();
// Mark zygote start. This ensures that thread creation will throw
// an error.
ZygoteHooks.startZygoteNoThreadCreation();
// Zygote goes into its own process group.
try {
Os.setpgid(0, 0);
} catch (ErrnoException ex) {
throw new RuntimeException("Failed to setpgid(0,0)", ex);
}
final Runnable caller;
try {
// Report Zygote start time to tron unless it is a runtime restart
if (!"1".equals(SystemProperties.get("sys.boot_completed"))) {
MetricsLogger.histogram(null, "boot_zygote_init",
(int) SystemClock.elapsedRealtime());
}
String bootTimeTag = Process.is64Bit() ? "Zygote64Timing" : "Zygote32Timing";
TimingsTraceLog bootTimingsTraceLog = new TimingsTraceLog(bootTimeTag,
Trace.TRACE_TAG_DALVIK);
bootTimingsTraceLog.traceBegin("ZygoteInit");
RuntimeInit.enableDdms();
boolean startSystemServer = false;
String socketName = "zygote";
String abiList = null;
boolean enableLazyPreload = false;
for (int i = 1; i < argv.length; i++) {
if ("start-system-server".equals(argv[i])) {
startSystemServer = true;
} else if ("--enable-lazy-preload".equals(argv[i])) {
enableLazyPreload = true;
} else if (argv[i].startsWith(ABI_LIST_ARG)) {
abiList = argv[i].substring(ABI_LIST_ARG.length());
} else if (argv[i].startsWith(SOCKET_NAME_ARG)) {
socketName = argv[i].substring(SOCKET_NAME_ARG.length());
} else {
throw new RuntimeException("Unknown command line argument: " + argv[i]);
}
}
if (abiList == null) {
throw new RuntimeException("No ABI list supplied.");
}
zygoteServer.registerServerSocket(socketName);
// In some configurations, we avoid preloading resources and classes eagerly.
// In such cases, we will preload things prior to our first fork.
if (!enableLazyPreload) {
bootTimingsTraceLog.traceBegin("ZygotePreload");
EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_START,
SystemClock.uptimeMillis());
/// M: Added for BOOTPROF
addBootEvent("Zygote:Preload Start");
/// @}
preload(bootTimingsTraceLog);
EventLog.writeEvent(LOG_BOOT_PROGRESS_PRELOAD_END,
SystemClock.uptimeMillis());
bootTimingsTraceLog.traceEnd(); // ZygotePreload
} else {
Zygote.resetNicePriority();
}
// Do an initial gc to clean up after startup
bootTimingsTraceLog.traceBegin("PostZygoteInitGC");
gcAndFinalize();
bootTimingsTraceLog.traceEnd(); // PostZygoteInitGC
bootTimingsTraceLog.traceEnd(); // ZygoteInit
// Disable tracing so that forked processes do not inherit stale tracing tags from
// Zygote.
Trace.setTracingEnabled(false, 0);
// Zygote process unmounts root storage spaces.
Zygote.nativeUnmountStorageOnInit();
// Set seccomp policy
Seccomp.setPolicy();
/// M: Added for BOOTPROF
addBootEvent("Zygote:Preload End");
/// @}
ZygoteHooks.stopZygoteNoThreadCreation();
if (startSystemServer) {
Runnable r = forkSystemServer(abiList, socketName, zygoteServer);
// {@code r == null} in the parent (zygote) process, and {@code r != null} in the
// child (system_server) process.
if (r != null) {
r.run();
return;
}
}
Log.i(TAG, "Accepting command socket connections");
// The select loop returns early in the child process after a fork and
// loops forever in the zygote.
caller = zygoteServer.runSelectLoop(abiList);
} catch (Throwable ex) {
Log.e(TAG, "System zygote died with exception", ex);
throw ex;
} finally {
zygoteServer.closeServerSocket();
}
// We're in the child process and have exited the select loop. Proceed to execute the
// command.
if (caller != null) {
caller.run();
}
}
这个函数是Zygote进程启动的主入口，在上面的函数可以看到zygoteServer.registerServerSocket(socketName);这个就是我们之前连接的socketServer的创建入口。zygoteServer.runSelectLoop(abiList);这个函数就是不停的从socket那边获取信息创建进程
2.1.6 ZygoteServer.runSelectLoop
Runnable runSelectLoop(String abiList) {
ArrayList<FileDescriptor> fds = new ArrayList<FileDescriptor>();
ArrayList<ZygoteConnection> peers = new ArrayList<ZygoteConnection>();
fds.add(mServerSocket.getFileDescriptor());
peers.add(null);
while (true) {
StructPollfd[] pollFds = new StructPollfd[fds.size()];
for (int i = 0; i < pollFds.length; ++i) {
pollFds[i] = new StructPollfd();
pollFds[i].fd = fds.get(i);
pollFds[i].events = (short) POLLIN;
}
try {
Os.poll(pollFds, -1);
} catch (ErrnoException ex) {
throw new RuntimeException("poll failed", ex);
}
for (int i = pollFds.length - 1; i >= 0; --i) {
if ((pollFds[i].revents & POLLIN) == 0) {
continue;
}
if (i == 0) {
ZygoteConnection newPeer = acceptCommandPeer(abiList);
peers.add(newPeer);
fds.add(newPeer.getFileDesciptor());
} else {
try {
ZygoteConnection connection = peers.get(i);
final Runnable command = connection.processOneCommand(this);
if (mIsForkChild) {
// We're in the child. We should always have a command to run at this
// stage if processOneCommand hasn't called "exec".
if (command == null) {
throw new IllegalStateException("command == null");
}
return command;
} else {
// We're in the server - we should never have any commands to run.
if (command != null) {
throw new IllegalStateException("command != null");
}
// We don't know whether the remote side of the socket was closed or
// not until we attempt to read from it from processOneCommand. This shows up as
// a regular POLLIN event in our regular processing loop.
if (connection.isClosedByPeer()) {
connection.closeSocket();
peers.remove(i);
fds.remove(i);
}
}
} catch (Exception e) {
if (!mIsForkChild) {
// We're in the server so any exception here is one that has taken place
// pre-fork while processing commands or reading / writing from the
// control socket. Make a loud noise about any such exceptions so that
// we know exactly what failed and why.
Slog.e(TAG, "Exception executing zygote command: ", e);
// Make sure the socket is closed so that the other end knows immediately
// that something has gone wrong and doesn't time out waiting for a
// response.
ZygoteConnection conn = peers.remove(i);
conn.closeSocket();
fds.remove(i);
} else {
// We're in the child so any exception caught here has happened post
// fork and before we execute ActivityThread.main (or any other main()
// method). Log the details of the exception and bring down the process.
Log.e(TAG, "Caught post-fork exception in child process.", e);
throw e;
}
}
}
}
}
}
看connection.processOneCommand这个方法
2.1.7 ZygoteConnection.processOneCommand
Runnable processOneCommand(ZygoteServer zygoteServer) {
String args[];
Arguments parsedArgs = null;
FileDescriptor[] descriptors;
try {
args = readArgumentList();
descriptors = mSocket.getAncillaryFileDescriptors();
} catch (IOException ex) {
throw new IllegalStateException("IOException on command socket", ex);
}
// readArgumentList returns null only when it has reached EOF with no available
// data to read. This will only happen when the remote socket has disconnected.
if (args == null) {
isEof = true;
return null;
}
int pid = -1;
FileDescriptor childPipeFd = null;
FileDescriptor serverPipeFd = null;
parsedArgs = new Arguments(args);
if (parsedArgs.abiListQuery) {
handleAbiListQuery();
return null;
}
if (parsedArgs.preloadDefault) {
handlePreload();
return null;
}
if (parsedArgs.preloadPackage != null) {
handlePreloadPackage(parsedArgs.preloadPackage, parsedArgs.preloadPackageLibs,
parsedArgs.preloadPackageCacheKey);
return null;
}
if (parsedArgs.permittedCapabilities != 0 || parsedArgs.effectiveCapabilities != 0) {
throw new ZygoteSecurityException("Client may not specify capabilities: " +
"permitted=0x" + Long.toHexString(parsedArgs.permittedCapabilities) +
", effective=0x" + Long.toHexString(parsedArgs.effectiveCapabilities));
}
applyUidSecurityPolicy(parsedArgs, peer);
applyInvokeWithSecurityPolicy(parsedArgs, peer);
applyDebuggerSystemProperty(parsedArgs);
applyInvokeWithSystemProperty(parsedArgs);
int[][] rlimits = null;
if (parsedArgs.rlimits != null) {
rlimits = parsedArgs.rlimits.toArray(intArray2d);
}
int[] fdsToIgnore = null;
if (parsedArgs.invokeWith != null) {
try {
FileDescriptor[] pipeFds = Os.pipe2(O_CLOEXEC);
childPipeFd = pipeFds[1];
serverPipeFd = pipeFds[0];
Os.fcntlInt(childPipeFd, F_SETFD, 0);
fdsToIgnore = new int[]{childPipeFd.getInt$(), serverPipeFd.getInt$()};
} catch (ErrnoException errnoEx) {
throw new IllegalStateException("Unable to set up pipe for invoke-with", errnoEx);
}
}
/**
* In order to avoid leaking descriptors to the Zygote child,
* the native code must close the two Zygote socket descriptors
* in the child process before it switches from Zygote-root to
* the UID and privileges of the application being launched.
*
* In order to avoid "bad file descriptor" errors when the
* two LocalSocket objects are closed, the Posix file
* descriptors are released via a dup2() call which closes
* the socket and substitutes an open descriptor to /dev/null.
*/
int [] fdsToClose = { -1, -1 };
FileDescriptor fd = mSocket.getFileDescriptor();
if (fd != null) {
fdsToClose[0] = fd.getInt$();
}
fd = zygoteServer.getServerSocketFileDescriptor();
if (fd != null) {
fdsToClose[1] = fd.getInt$();
}
fd = null;
pid = Zygote.forkAndSpecialize(parsedArgs.uid, parsedArgs.gid, parsedArgs.gids,
parsedArgs.debugFlags, rlimits, parsedArgs.mountExternal, parsedArgs.seInfo,
parsedArgs.niceName, fdsToClose, fdsToIgnore, parsedArgs.instructionSet,
parsedArgs.appDataDir);
try {
if (pid == 0) {
// in child
zygoteServer.setForkChild();
zygoteServer.closeServerSocket();
IoUtils.closeQuietly(serverPipeFd);
serverPipeFd = null;
return handleChildProc(parsedArgs, descriptors, childPipeFd);
} else {
// In the parent. A pid < 0 indicates a failure and will be handled in
// handleParentProc.
IoUtils.closeQuietly(childPipeFd);
childPipeFd = null;
handleParentProc(pid, descriptors, serverPipeFd);
return null;
}
} finally {
IoUtils.closeQuietly(childPipeFd);
IoUtils.closeQuietly(serverPipeFd);
}
}
2.1.8 Zygote.forkAndSpecialize
public static int forkAndSpecialize(int uid, int gid, int[] gids, int debugFlags,
int[][] rlimits, int mountExternal, String seInfo, String niceName, int[] fdsToClose,
int[] fdsToIgnore, String instructionSet, String appDataDir) {
VM_HOOKS.preFork();
// Resets nice priority for zygote process.
resetNicePriority();
int pid = nativeForkAndSpecialize(
uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName, fdsToClose,
fdsToIgnore, instructionSet, appDataDir);
// Enable tracing as soon as possible for the child process.
if (pid == 0) {
Trace.setTracingEnabled(true, debugFlags);
// Note that this event ends at the end of handleChildProc,
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "PostFork");
}
VM_HOOKS.postForkCommon();
return pid;
}
最终会调用nativeForkAndSpecialize的native方法，而这个native方法的实现是在com_android_internal_os_Zygote.cpp会调用linux的方法pid_t pid = fork()。到此处我们的app进程创建完成，那app进程创建完成后怎么执行java程序呢？启动activity呢？在ZygoteConnection.processOneCommand方法中执行了Zygote.forkAndSpecialize 会判断pid是否为0，并且也会启动handleChildProc方法
2.1.9 ZygoteConnection.handleChildProc
private Runnable handleChildProc(Arguments parsedArgs, FileDescriptor[] descriptors,
FileDescriptor pipeFd) {
/**
* By the time we get here, the native code has closed the two actual Zygote
* socket connections, and substituted /dev/null in their place. The LocalSocket
* objects still need to be closed properly.
*/
closeSocket();
if (descriptors != null) {
try {
Os.dup2(descriptors[0], STDIN_FILENO);
Os.dup2(descriptors[1], STDOUT_FILENO);
Os.dup2(descriptors[2], STDERR_FILENO);
for (FileDescriptor fd: descriptors) {
IoUtils.closeQuietly(fd);
}
} catch (ErrnoException ex) {
Log.e(TAG, "Error reopening stdio", ex);
}
}
if (parsedArgs.niceName != null) {
Process.setArgV0(parsedArgs.niceName);
}
// End of the postFork event.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
if (parsedArgs.invokeWith != null) {
WrapperInit.execApplication(parsedArgs.invokeWith,
parsedArgs.niceName, parsedArgs.targetSdkVersion,
VMRuntime.getCurrentInstructionSet(),
pipeFd, parsedArgs.remainingArgs);
// Should not get here.
throw new IllegalStateException("WrapperInit.execApplication unexpectedly returned");
} else {
return ZygoteInit.zygoteInit(parsedArgs.targetSdkVersion, parsedArgs.remainingArgs,
null /* classLoader */);
}
}
2.2.1WrapperInit.execApplication
public static void execApplication(String invokeWith, String niceName,
int targetSdkVersion, String instructionSet, FileDescriptor pipeFd,
String[] args) {
StringBuilder command = new StringBuilder(invokeWith);
final String appProcess;
if (VMRuntime.is64BitInstructionSet(instructionSet)) {
appProcess = "/system/bin/app_process64";
} else {
appProcess = "/system/bin/app_process32";
}
command.append(' ');
command.append(appProcess);
command.append(" /system/bin --application");
if (niceName != null) {
command.append(" '--nice-name=").append(niceName).append("'");
}
command.append(" com.android.internal.os.WrapperInit ");
command.append(pipeFd != null ? pipeFd.getInt$() : 0);
command.append(' ');
command.append(targetSdkVersion);
Zygote.appendQuotedShellArgs(command, args);
preserveCapabilities();
Zygote.execShell(command.toString());
}
从上面的代码就能比较容易的看出来通过shell脚本来启动Activity，这个方法主要是填写一些启动参数。查看execshell果然跟我们猜想的一样/system/bin/sh
public static void execShell(String command) {
String[] args = { "/system/bin/sh", "-c", command };
try {
Os.execv(args[0], args);
} catch (ErrnoException e) {
throw new RuntimeException(e);
}
}
到目前来说我们的app进程算是创建完成。
三、应用进程创建后activity的启动
那有个问题是应用进程运行的第一个java代码是哪个呢？答案是：ActivityThread.main .可能有些读者会问为什么呢？
还记得我们在AMS中startProcessLocked的方法里面有个字段 final String entryPoint = "android.app.ActivityThread";如果有兴趣的读者可以自己打印相关的信息以及追踪。
3.1.1 ActivityThread.main
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
// CloseGuard defaults to true and can be quite spammy. We
// disable it here, but selectively enable it later (via
// StrictMode) on debug builds, but using DropBox, not logs.
CloseGuard.setEnabled(false);
Environment.initForCurrentUser();
// Set the reporter for event logging in libcore
EventLogger.setReporter(new EventLoggingReporter());
// Make sure TrustedCertificateStore looks in the right place for CA certificates
final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId());
TrustedCertificateStore.setDefaultUserDirectory(configDir);
//设置进程名为"<pre-initialized>"
Process.setArgV0("<pre-initialized>");
Looper.prepareMainLooper();//准备主线程消息循环
ActivityThread thread = new ActivityThread();//创建一个ActivityThread对象
thread.attach(false);
if (sMainThreadHandler == null) {//app 进程第一次启动sMainThreadHandler=null，这也是主线程的handler
sMainThreadHandler = thread.getHandler();
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
/// M: ANR Debug Mechanism
mAnrAppManager.setMessageLogger(Looper.myLooper());
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
3.1.1 ActivityThread.attach
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {//应用进程的处理流程
//view在绘画的时候回调
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();//启动即时编译
}
});
android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());//设置IBinder，主要是为后续跨进程使用
//获取和AMS交互的Binder客户端
final IActivityManager mgr = ActivityManager.getService();
try {
//①调用AMS的attachApplication，mAppThread为ApplicationThread类型，它是应用进程和AMS交互的接口
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
// Watch for getting close to heap limit.
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
if (dalvikUsed > ((3*dalvikMax)/4)) {
if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
+ " total=" + (runtime.totalMemory()/1024)
+ " used=" + (dalvikUsed/1024));
mSomeActivitiesChanged = false;
try {
mgr.releaseSomeActivities(mAppThread);//清除这个进程中不活跃的ActivityRecord
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
});
} else {
// Don't set application object here -- if the system crashes,
// we can't display an alert, we just want to die die die.
//系统进程的处理流程
//设置DDM的进程名称system_process
android.ddm.DdmHandleAppName.setAppName("system_process",
UserHandle.myUserId());
try {
// 一个工具类,系统和组件之间的交互也将通过Instrumentation来传递，这样，Instrumentation就能监测系统和这些组件的交互情况了
mInstrumentation = new Instrumentation();
//创建属于这个进程的context
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
//启动application oncreate 方法
//Application是Android中的一个概念，可理解为一种容器，它内部包含四大组件。另外，一个进程可以运行多个Application。
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
// add dropbox logging to libcore
DropBox.setReporter(new DropBoxReporter());
//注册Configuration变化的回调通知
ViewRootImpl.ConfigChangedCallback configChangedCallback
= (Configuration globalConfig) -> {
synchronized (mResourcesManager) {
// We need to apply this change to the resources immediately, because upon returning
// the view hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(globalConfig,
null /* compat */)) {
updateLocaleListFromAppContext(mInitialApplication.getApplicationContext(),
mResourcesManager.getConfiguration().getLocales());
// This actually changed the resources! Tell everyone about it.
if (mPendingConfiguration == null
|| mPendingConfiguration.isOtherSeqNewer(globalConfig)) {
mPendingConfiguration = globalConfig;
sendMessage(H.CONFIGURATION_CHANGED, globalConfig);
}
}
}
};
ViewRootImpl.addConfigCallback(configChangedCallback);
}
3.1.2 AMS attachApplication
private final boolean attachApplicationLocked(IApplicationThread thread,
int pid) {
// Find the application record that is being attached... either via
// the pid if we are running in multiple processes, or just pull the
// next app record if we are emulating process with anonymous threads.
ProcessRecord app;
long startTime = SystemClock.uptimeMillis();
//MY_PID是AMS的服务进程id，这个判断就是不是系统进程
if (pid != MY_PID && pid >= 0) {
//mPidsSelfLocked管理所有的application进程
//那这个app进程是什么时候添加到mPidsSelfLocked？
//答案是：startProcessLocked函数中创建了新的进程，并且执行了this.mPidsSelfLocked.put(startResult.pid, app);
synchronized (mPidsSelfLocked) {
app = mPidsSelfLocked.get(pid);
}
} else {
app = null;
}
/*
如果该应用进程由AMS启动，则它一定在AMS中有对应的ProcessRecord，读者可回顾前面创建
应用进程的代码：AMS先创建了一个ProcessRecord对象，然后才发命令给Zygote。
如果此处app为null，表示AMS没有该进程的记录，故需要“杀死”它
*/
if (app == null) {
Slog.w(TAG, "No pending application record for pid " + pid
+ " (IApplicationThread " + thread + "); dropping process");
EventLog.writeEvent(EventLogTags.AM_DROP_PROCESS, pid);
if (pid > 0 && pid != MY_PID) {
killProcessQuiet(pid);
//TODO: killProcessGroup(app.info.uid, pid);
} else {
try {
//调用ApplicationThread的scheduleExit函数。应用进程完成处理工作
//将退出运行
thread.scheduleExit();
} catch (Exception e) {
// Ignore exceptions.
}
}
return false;
}
// If this application record is still attached to a previous
// process, clean it up now.
//app进程存在，并且之前也有主线程，清空已经存在的线程
if (app.thread != null) {
handleAppDiedLocked(app, true, true);
}
// Tell the process all about itself.
if (DEBUG_ALL) Slog.v(
TAG, "Binding process pid " + pid + " to record " + app);
/*
创建一个应用进程讣告接收对象。当应用进程退出时，该对象的binderDied将被调
用。这样，AMS就能做相应处理。binderDied函数将在另外一个线程中执行，其内部也会
调用handleAppDiedLocked。
*/
final String processName = app.processName;
try {
//app死亡监听服务
AppDeathRecipient adr = new AppDeathRecipient(
app, pid, thread);
thread.asBinder().linkToDeath(adr, 0);
app.deathRecipient = adr;
} catch (RemoteException e) {
app.resetPackageList(mProcessStats);
startProcessLocked(app, "link fail", processName);
return false;
}
EventLog.writeEvent(EventLogTags.AM_PROC_BOUND, app.userId, app.pid, app.processName);
//设置该进程的调度优先级和oom_adj等成员
app.makeActive(thread, mProcessStats);
app.curAdj = app.setAdj = app.verifiedAdj = ProcessList.INVALID_ADJ;
app.curSchedGroup = app.setSchedGroup = ProcessList.SCHED_GROUP_DEFAULT;
app.forcingToImportant = null;
updateProcessForegroundLocked(app, false, false);//更新作为前台进程
//在这个阶段是不允许进程被杀死。
app.hasShownUi = false;
app.debugging = false;
app.cached = false;
app.killedByAm = false;
app.killed = false;
// We carefully use the same state that PackageManager uses for
// filtering, since we use this flag to decide if we need to install
// providers when user is unlocked later
app.unlocked = StorageManager.isUserKeyUnlocked(app.userId);
//启动成功，从消息队列中撤销PROC_START_TIMEOUT_MSG消息
//那么这个广播是在什么时候发送的？
//startProcessLocked->Process.start 进程创建的时候就开始发送的。
mHandler.removeMessages(PROC_START_TIMEOUT_MSG, app);
//SystemServer早就启动完毕，所以normalMode为true
boolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);
//在该函数内部将查询（根据进程名，uid确定）PKMS以获取需运行在该进程中的ContentProvider
List<ProviderInfo> providers = normalMode ? generateApplicationProvidersLocked(app) : null;
if (providers != null && checkAppInLaunchingProvidersLocked(app)) {
Message msg = mHandler.obtainMessage(CONTENT_PROVIDER_PUBLISH_TIMEOUT_MSG);
msg.obj = app;
mHandler.sendMessageDelayed(msg, CONTENT_PROVIDER_PUBLISH_TIMEOUT);
}
checkTime(startTime, "attachApplicationLocked: before bindApplication");
if (!normalMode) {
Slog.i(TAG, "Launching preboot mode app: " + app);
}
if (DEBUG_ALL) Slog.v(
TAG, "New app record " + app
+ " thread=" + thread.asBinder() + " pid=" + pid);
try {
int testMode = ApplicationThreadConstants.DEBUG_OFF;
if (mDebugApp != null && mDebugApp.equals(processName)) {
testMode = mWaitForDebugger
? ApplicationThreadConstants.DEBUG_WAIT
: ApplicationThreadConstants.DEBUG_ON;
app.debugging = true;
if (mDebugTransient) {
mDebugApp = mOrigDebugApp;
mWaitForDebugger = mOrigWaitForDebugger;
}
}
ProfilerInfo profilerInfo = null;
String agent = null;
//用于记录性能文件
if (mProfileApp != null && mProfileApp.equals(processName)) {
mProfileProc = app;
profilerInfo = (mProfilerInfo != null && mProfilerInfo.profileFile != null) ?
new ProfilerInfo(mProfilerInfo) : null;
agent = mProfilerInfo != null ? mProfilerInfo.agent : null;
} else if (app.instr != null && app.instr.mProfileFile != null) {
profilerInfo = new ProfilerInfo(app.instr.mProfileFile, null, 0, false, false,
null);
}
boolean enableTrackAllocation = false;
if (mTrackAllocationApp != null && mTrackAllocationApp.equals(processName)) {
enableTrackAllocation = true;
mTrackAllocationApp = null;
}
// If the app is being launched for restore or full backup, set it up specially
boolean isRestrictedBackupMode = false;
if (mBackupTarget != null && mBackupAppName.equals(processName)) {
isRestrictedBackupMode = mBackupTarget.appInfo.uid >= FIRST_APPLICATION_UID
&& ((mBackupTarget.backupMode == BackupRecord.RESTORE)
|| (mBackupTarget.backupMode == BackupRecord.RESTORE_FULL)
|| (mBackupTarget.backupMode == BackupRecord.BACKUP_FULL));
}
if (app.instr != null) {
notifyPackageUse(app.instr.mClass.getPackageName(),
PackageManager.NOTIFY_PACKAGE_USE_INSTRUMENTATION);
}
if (DEBUG_CONFIGURATION) Slog.v(TAG_CONFIGURATION, "Binding proc "
+ processName + " with config " + getGlobalConfiguration());
ApplicationInfo appInfo = app.instr != null ? app.instr.mTargetInfo : app.info;
app.compat = compatibilityInfoForPackageLocked(appInfo);
if (profilerInfo != null && profilerInfo.profileFd != null) {
profilerInfo.profileFd = profilerInfo.profileFd.dup();
}
// We deprecated Build.SERIAL and it is not accessible to
// apps that target the v2 security sandbox. Since access to
// the serial is now behind a permission we push down the value.
String buildSerial = appInfo.targetSandboxVersion < 2
? sTheRealBuildSerial : Build.UNKNOWN;
// Check if this is a secondary process that should be incorporated into some
// currently active instrumentation. (Note we do this AFTER all of the profiling
// stuff above because profiling can currently happen only in the primary
// instrumentation process.)
if (mActiveInstrumentation.size() > 0 && app.instr == null) {
for (int i = mActiveInstrumentation.size() - 1; i >= 0 && app.instr == null; i--) {
ActiveInstrumentation aInstr = mActiveInstrumentation.get(i);
if (!aInstr.mFinished && aInstr.mTargetInfo.uid == app.uid) {
if (aInstr.mTargetProcesses.length == 0) {
// This is the wildcard mode, where every process brought up for
// the target instrumentation should be included.
if (aInstr.mTargetInfo.packageName.equals(app.info.packageName)) {
app.instr = aInstr;
aInstr.mRunningProcesses.add(app);
}
} else {
for (String proc : aInstr.mTargetProcesses) {
if (proc.equals(app.processName)) {
app.instr = aInstr;
aInstr.mRunningProcesses.add(app);
break;
}
}
}
}
}
}
// If we were asked to attach an agent on startup, do so now, before we're binding
// application code.
if (agent != null) {
thread.attachAgent(agent);
}
checkTime(startTime, "attachApplicationLocked: immediately before bindApplication");
mStackSupervisor.mActivityMetricsLogger.notifyBindApplication(app);
if(DEBUG_ACTIVITY_START)Log.i("ActivityManagerService-xiao", "bindApplication" );
if (app.isolatedEntryPoint != null) {
// This is an isolated process which should just call an entry point instead of
// being bound to an application.
thread.runIsolatedEntryPoint(app.isolatedEntryPoint, app.isolatedEntryPointArgs);
} else if (app.instr != null) {
//①通过ApplicationThread和应用进程交互，调用其bindApplication函数
thread.bindApplication(processName, appInfo, providers,
app.instr.mClass,
profilerInfo, app.instr.mArguments,
app.instr.mWatcher,
app.instr.mUiAutomationConnection, testMode,
mBinderTransactionTrackingEnabled, enableTrackAllocation,
isRestrictedBackupMode || !normalMode, app.persistent,
new Configuration(getGlobalConfiguration()), app.compat,
getCommonServicesLocked(app.isolated),
mCoreSettingsObserver.getCoreSettingsLocked(),
buildSerial);
} else {
thread.bindApplication(processName, appInfo, providers, null, profilerInfo,
null, null, null, testMode,
mBinderTransactionTrackingEnabled, enableTrackAllocation,
isRestrictedBackupMode || !normalMode, app.persistent,
new Configuration(getGlobalConfiguration()), app.compat,
getCommonServicesLocked(app.isolated),
mCoreSettingsObserver.getCoreSettingsLocked(),
buildSerial);
}
checkTime(startTime, "attachApplicationLocked: immediately after bindApplication");
updateLruProcessLocked(app, false, null);//更新进程
checkTime(startTime, "attachApplicationLocked: after updateLruProcessLocked");
//记录两个时间
app.lastRequestedGc = app.lastLowMemory = SystemClock.uptimeMillis();
} catch (Exception e) {
// todo: Yikes! What should we do? For now we will try to
// start another process, but that could easily get us in
// an infinite loop of restarting processes...
Slog.wtf(TAG, "Exception thrown during bind of " + app, e);
app.resetPackageList(mProcessStats);
app.unlinkDeathRecipient();
startProcessLocked(app, "bind fail", processName);
return false;
}
// Remove this record from the list of starting applications.
mPersistentStartingProcesses.remove(app);
if (DEBUG_PROCESSES && mProcessesOnHold.contains(app)) Slog.v(TAG_PROCESSES,
"Attach application locked removing on hold: " + app);
mProcessesOnHold.remove(app);
boolean badApp = false;
boolean didSomething = false;
// See if the top visible activity is waiting to run in this process...
if (normalMode) {
try {
if (mStackSupervisor.attachApplicationLocked(app)) {
didSomething = true;
}
} catch (Exception e) {
Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
badApp = true;
}
}
// Find any services that should be running in this process...
if (!badApp) {
try {
didSomething |= mServices.attachApplicationLocked(app, processName);
checkTime(startTime, "attachApplicationLocked: after mServices.attachApplicationLocked");
} catch (Exception e) {
Slog.wtf(TAG, "Exception thrown starting services in " + app, e);
badApp = true;
}
}
// Check if a next-broadcast receiver is in this process...
if (!badApp && isPendingBroadcastProcessLocked(pid)) {
try {
didSomething |= sendPendingBroadcastsLocked(app);
checkTime(startTime, "attachApplicationLocked: after sendPendingBroadcastsLocked");
} catch (Exception e) {
// If the app died trying to launch the receiver we declare it 'bad'
Slog.wtf(TAG, "Exception thrown dispatching broadcasts in " + app, e);
badApp = true;
}
}
// Check whether the next backup agent is in this process...
if (!badApp && mBackupTarget != null && mBackupTarget.app == app) {
if (DEBUG_BACKUP) Slog.v(TAG_BACKUP,
"New app is backup target, launching agent for " + app);
notifyPackageUse(mBackupTarget.appInfo.packageName,
PackageManager.NOTIFY_PACKAGE_USE_BACKUP);
try {
thread.scheduleCreateBackupAgent(mBackupTarget.appInfo,
compatibilityInfoForPackageLocked(mBackupTarget.appInfo),
mBackupTarget.backupMode);
} catch (Exception e) {
Slog.wtf(TAG, "Exception thrown creating backup agent in " + app, e);
badApp = true;
}
}
if (badApp) {
app.kill("error during init", true);
handleAppDiedLocked(app, false, true);
return false;
}
if (!didSomething) {
updateOomAdjLocked();
checkTime(startTime, "attachApplicationLocked: after updateOomAdjLocked");
}
return true;
}
3.1.3 ActivityThread bindApplication
public final void bindApplication(String processName, ApplicationInfo appInfo,
List<ProviderInfo> providers, ComponentName instrumentationName,
ProfilerInfo profilerInfo, Bundle instrumentationArgs,
IInstrumentationWatcher instrumentationWatcher,
IUiAutomationConnection instrumentationUiConnection, int debugMode,
boolean enableBinderTracking, boolean trackAllocation,
boolean isRestrictedBackupMode, boolean persistent, Configuration config,
CompatibilityInfo compatInfo, Map services, Bundle coreSettings,
String buildSerial) {
if (services != null) {//保存AMS传递过来的系统Service信息
// Setup the service cache in the ServiceManager
ServiceManager.initServiceCache(services);
}
setCoreSettings(coreSettings);//向主线程消息队列添加SET_CORE_SETTINGS消息
AppBindData data = new AppBindData();//将AMS传过来的参数保存到AppBindData中
data.processName = processName;
data.appInfo = appInfo;
data.providers = providers;
data.instrumentationName = instrumentationName;
data.instrumentationArgs = instrumentationArgs;
data.instrumentationWatcher = instrumentationWatcher;
data.instrumentationUiAutomationConnection = instrumentationUiConnection;
data.debugMode = debugMode;
data.enableBinderTracking = enableBinderTracking;
data.trackAllocation = trackAllocation;
data.restrictedBackupMode = isRestrictedBackupMode;
data.persistent = persistent;
data.config = config;
data.compatInfo = compatInfo;
data.initProfilerInfo = profilerInfo;
data.buildSerial = buildSerial;
sendMessage(H.BIND_APPLICATION, data);//绑定data
}
3.1.4 ActivityThread handleBindApplication
private void handleBindApplication(AppBindData data) {
// Register the UI Thread as a sensitive thread to the runtime.
VMRuntime.registerSensitiveThread();
if (data.trackAllocation) {
DdmVmInternal.enableRecentAllocations(true);
}
// Note when this process has started.
//设置进程开始时间
Process.setStartTimes(SystemClock.elapsedRealtime(), SystemClock.uptimeMillis());
mBoundApplication = data;
mConfiguration = new Configuration(data.config);
mCompatConfiguration = new Configuration(data.config);
mProfiler = new Profiler();//初始化性能统计对象
if (data.initProfilerInfo != null) {
mProfiler.profileFile = data.initProfilerInfo.profileFile;
mProfiler.profileFd = data.initProfilerInfo.profileFd;
mProfiler.samplingInterval = data.initProfilerInfo.samplingInterval;
mProfiler.autoStopProfiler = data.initProfilerInfo.autoStopProfiler;
mProfiler.streamingOutput = data.initProfilerInfo.streamingOutput;
}
// send up app name; do this *before* waiting for debugger
Process.setArgV0(data.processName);//设置进程名称
android.ddm.DdmHandleAppName.setAppName(data.processName,
UserHandle.myUserId());
if (mProfiler.profileFd != null) {
mProfiler.startProfiling();//开启性能统计
}
// If the app is Honeycomb MR1 or earlier, switch its AsyncTask
// implementation to use the pool executor. Normally, we use the
// serialized executor as the default. This has to happen in the
// main thread so the main looper is set right.
if (data.appInfo.targetSdkVersion <= android.os.Build.VERSION_CODES.HONEYCOMB_MR1) {
AsyncTask.setDefaultExecutor(AsyncTask.THREAD_POOL_EXECUTOR);//SDK小于12，更改AsyncTask的初始值
}
Message.updateCheckRecycle(data.appInfo.targetSdkVersion);
/*
* Before spawning a new process, reset the time zone to be the system time zone.
* This needs to be done because the system time zone could have changed after the
* the spawning of this process. Without doing this this process would have the incorrect
* system time zone.
*/
TimeZone.setDefault(null);
/*
* Set the LocaleList. This may change once we create the App Context.
*/
LocaleList.setDefault(data.config.getLocales());//设置app的本地，locale
synchronized (mResourcesManager) {
/*
* Update the system configuration since its preloaded and might not
* reflect configuration changes. The configuration object passed
* in AppBindData can be safely assumed to be up to date
*/
//设置资源及兼容模式
mResourcesManager.applyConfigurationToResourcesLocked(data.config, data.compatInfo);
mCurDefaultDisplayDpi = data.config.densityDpi;//dpi
// This calls mResourcesManager so keep it within the synchronized block.
applyCompatConfiguration(mCurDefaultDisplayDpi);
}
data.info = getPackageInfoNoCheck(data.appInfo, data.compatInfo);
/**
* Switch this process to density compatibility mode if needed.
*/
if ((data.appInfo.flags&ApplicationInfo.FLAG_SUPPORTS_SCREEN_DENSITIES)
== 0) {
mDensityCompatMode = true;
Bitmap.setDefaultDensity(DisplayMetrics.DENSITY_DEFAULT);
}
updateDefaultDensity();
final String use24HourSetting = mCoreSettings.getString(Settings.System.TIME_12_24);//是时间默认格式
Boolean is24Hr = null;
if (use24HourSetting != null) {
is24Hr = "24".equals(use24HourSetting) ? Boolean.TRUE : Boolean.FALSE;
}
// null : use locale default for 12/24 hour formatting,
// false : use 12 hour format,
// true : use 24 hour format.
DateFormat.set24HourTimePref(is24Hr);
View.mDebugViewAttributes =
mCoreSettings.getInt(Settings.Global.DEBUG_VIEW_ATTRIBUTES, 0) != 0;
/**
* For system applications on userdebug/eng builds, log stack
* traces of disk and network access to dropbox for analysis.
*/
//对于系统APK，如果当前系统为userdebug/eng版，则需要记录log信息到dropbox的日志记录
if ((data.appInfo.flags &
(ApplicationInfo.FLAG_SYSTEM |
ApplicationInfo.FLAG_UPDATED_SYSTEM_APP)) != 0) {
StrictMode.conditionallyEnableDebugLogging();
}
/**
* For apps targetting Honeycomb or later, we don't allow network usage
* on the main event loop / UI thread. This is what ultimately throws
* {@link NetworkOnMainThreadException}.
*/
// 如目标SDK版本大于11，则不允许在主线程使用网络操作（如Socketconnect等）
if (data.appInfo.targetSdkVersion >= Build.VERSION_CODES.HONEYCOMB) {
StrictMode.enableDeathOnNetwork();
}
/**
* For apps targetting N or later, we don't allow file:// Uri exposure.
* This is what ultimately throws {@link FileUriExposedException}.
*/
if (data.appInfo.targetSdkVersion >= Build.VERSION_CODES.N) {
StrictMode.enableDeathOnFileUriExposure();
}
// We deprecated Build.SERIAL and only apps that target pre NMR1
// SDK can see it. Since access to the serial is now behind a
// permission we push down the value and here we fix it up
// before any app code has been loaded.
try {
Field field = Build.class.getDeclaredField("SERIAL");
field.setAccessible(true);
field.set(Build.class, data.buildSerial);
} catch (NoSuchFieldException | IllegalAccessException e) {
/* ignore */
}
if (data.debugMode != ApplicationThreadConstants.DEBUG_OFF) {
// XXX should have option to change the port.
Debug.changeDebugPort(8100);
if (data.debugMode == ApplicationThreadConstants.DEBUG_WAIT) {
Slog.w(TAG, "Application " + data.info.getPackageName()
+ " is waiting for the debugger on port 8100...");
IActivityManager mgr = ActivityManager.getService();
try {
mgr.showWaitingForDebugger(mAppThread, true);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
Debug.waitForDebugger();
try {
mgr.showWaitingForDebugger(mAppThread, false);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
} else {
Slog.w(TAG, "Application " + data.info.getPackageName()
+ " can be debugged on port 8100...");
}
}
// Allow application-generated systrace messages if we're debuggable.
boolean isAppDebuggable = (data.appInfo.flags & ApplicationInfo.FLAG_DEBUGGABLE) != 0;
Trace.setAppTracingAllowed(isAppDebuggable);
if (isAppDebuggable && data.enableBinderTracking) {
Binder.enableTracing();
}
/**
* Initialize the default http proxy in this process for the reasons we set the time zone.
*/
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "Setup proxies");
final IBinder b = ServiceManager.getService(Context.CONNECTIVITY_SERVICE);
if (b != null) {
// In pre-boot mode (doing initial launch to collect password), not
// all system is up. This includes the connectivity service, so don't
// crash if we can't get it.
final IConnectivityManager service = IConnectivityManager.Stub.asInterface(b);
try {
final ProxyInfo proxyInfo = service.getProxyForNetwork(null);
Proxy.setHttpProxySystemProperty(proxyInfo);//设置Http代理信息
} catch (RemoteException e) {
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
throw e.rethrowFromSystemServer();
}
}
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
// Instrumentation info affects the class loader, so load it before
// setting up the app context.
final InstrumentationInfo ii;
if (data.instrumentationName != null) {//在正常情况下，此条件不满足
try {
ii = new ApplicationPackageManager(null, getPackageManager())
.getInstrumentationInfo(data.instrumentationName, 0);
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException(
"Unable to find instrumentation info for: " + data.instrumentationName);
}
//创建Instrumentation对象，在正常情况都再这个条件下执行
mInstrumentationPackageName = ii.packageName;
mInstrumentationAppDir = ii.sourceDir;
mInstrumentationSplitAppDirs = ii.splitSourceDirs;
mInstrumentationLibDir = getInstrumentationLibrary(data.appInfo, ii);
mInstrumentedAppDir = data.info.getAppDir();
mInstrumentedSplitAppDirs = data.info.getSplitAppDirs();
mInstrumentedLibDir = data.info.getLibDir();
} else {
ii = null;
}
//创建app 内部使用的Context
final ContextImpl appContext = ContextImpl.createAppContext(this, data.info);
//更新Locale信息
updateLocaleListFromAppContext(appContext,
mResourcesManager.getConfiguration().getLocales());
if (!Process.isIsolated()) {
setupGraphicsSupport(appContext);
}
// If we use profiles, setup the dex reporter to notify package manager
// of any relevant dex loads. The idle maintenance job will use the information
// reported to optimize the loaded dex files.
// Note that we only need one global reporter per app.
// Make sure we do this before calling onCreate so that we can capture the
// complete application startup.
if (SystemProperties.getBoolean("dalvik.vm.usejitprofiles", false)) {
BaseDexClassLoader.setReporter(DexLoadReporter.getInstance());
}
// Install the Network Security Config Provider. This must happen before the application
// code is loaded to prevent issues with instances of TLS objects being created before
// the provider is installed.
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "NetworkSecurityConfigProvider.install");
NetworkSecurityConfigProvider.install(appContext);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
// Continue loading instrumentation.
if (ii != null) {
final ApplicationInfo instrApp = new ApplicationInfo();
ii.copyTo(instrApp);
instrApp.initForUser(UserHandle.myUserId());
final LoadedApk pi = getPackageInfo(instrApp, data.compatInfo,
appContext.getClassLoader(), false, true, false);
//创建安装ContextImpl，这个需要用到framwork-res的资源
final ContextImpl instrContext = ContextImpl.createAppContext(this, pi);
try {
final ClassLoader cl = instrContext.getClassLoader();
mInstrumentation = (Instrumentation)
cl.loadClass(data.instrumentationName.getClassName()).newInstance();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate instrumentation "
+ data.instrumentationName + ": " + e.toString(), e);
}
//创建组件
final ComponentName component = new ComponentName(ii.packageName, ii.name);
mInstrumentation.init(this, instrContext, appContext, component,
data.instrumentationWatcher, data.instrumentationUiAutomationConnection);
if (mProfiler.profileFile != null && !ii.handleProfiling
&& mProfiler.profileFd == null) {
mProfiler.handlingProfiling = true;
final File file = new File(mProfiler.profileFile);
file.getParentFile().mkdirs();
Debug.startMethodTracing(file.toString(), 8 * 1024 * 1024);
}
} else {
mInstrumentation = new Instrumentation();
}
//如果Package中声明了FLAG_LARGE_HEAP，则可跳过虚拟机的内存限制，放心使用内存
if ((data.appInfo.flags&ApplicationInfo.FLAG_LARGE_HEAP) != 0) {
dalvik.system.VMRuntime.getRuntime().clearGrowthLimit();
} else {
// Small heap, clamp to the current growth limit and let the heap release
// pages after the growth limit to the non growth limit capacity. b/18387825
dalvik.system.VMRuntime.getRuntime().clampGrowthLimit();
}
// Allow disk access during application and provider setup. This could
// block processing ordered broadcasts, but later processing would
// probably end up doing the same disk access.
Application app;
final StrictMode.ThreadPolicy savedPolicy = StrictMode.allowThreadDiskWrites();
final StrictMode.ThreadPolicy writesAllowedPolicy = StrictMode.getThreadPolicy();
try {
// If the app is being launched for full backup or restore, bring it up in
// a restricted environment with the base application class.
//创建一个Application，data.info为LoadedApk类型，在其内部会通过Java反射机制
//创建一个在该APK AndroidManifest.xml中声明的Application对象
app = data.info.makeApplication(data.restrictedBackupMode, null);
mInitialApplication = app;
// don't bring up providers in restricted mode; they may depend on the
// app's custom Application class
if (!data.restrictedBackupMode) {
if (!ArrayUtils.isEmpty(data.providers)) {
installContentProviders(app, data.providers);
// For process that contains content providers, we want to
// ensure that the JIT is enabled "at some point".
mH.sendEmptyMessageDelayed(H.ENABLE_JIT, 10*1000);
}
}
// Do this after providers, since instrumentation tests generally start their
// test thread at this point, and we don't want that racing.
try {
//mInstrumentation 做一些初始化工作
mInstrumentation.onCreate(data.instrumentationArgs);
}
catch (Exception e) {
throw new RuntimeException(
"Exception thrown in onCreate() of "
+ data.instrumentationName + ": " + e.toString(), e);
}
try {
//调用Application的onCreate函数，做一些初始工作
mInstrumentation.callApplicationOnCreate(app);
} catch (Exception e) {
if (!mInstrumentation.onException(app, e)) {
throw new RuntimeException(
"Unable to create application " + app.getClass().getName()
+ ": " + e.toString(), e);
}
}
} finally {
// If the app targets < O-MR1, or doesn't change the thread policy
// during startup, clobber the policy to maintain behavior of b/36951662
if (data.appInfo.targetSdkVersion <= Build.VERSION_CODES.O
|| StrictMode.getThreadPolicy().equals(writesAllowedPolicy)) {
StrictMode.setThreadPolicy(savedPolicy);
}
}
// Preload fonts resources
FontsContract.setApplicationContextForResources(appContext);
try {
final ApplicationInfo info =
getPackageManager().getApplicationInfo(
data.appInfo.packageName,
PackageManager.GET_META_DATA /*flags*/,
UserHandle.myUserId());
if (info.metaData != null) {
final int preloadedFontsResource = info.metaData.getInt(
ApplicationInfo.METADATA_PRELOADED_FONTS, 0);
if (preloadedFontsResource != 0) {
data.info.getResources().preloadFonts(preloadedFontsResource);
}
}
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
其中创建了application，所以在在一个进程中只有一个application并且它的启动时间是最早的， mInstrumentation.onCreate，mInstrumentation.callApplicationOnCreate(app);会调用Application中的oncreate方法
3.1.5 之前的AMS attachApplicationLocked方法中，我们刚才只走了bindApplication的流程，其后面还有代码块mStackSupervisor.attachApplicationLocked(app)
boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
final String processName = app.processName;
boolean didSomething = false;
for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
final ActivityStack stack = stacks.get(stackNdx);
if (!isFocusedStack(stack)) {
continue;
}
stack.getAllRunningVisibleActivitiesLocked(mTmpActivityList);
//获取前台栈顶第一个非finishing的Activity
final ActivityRecord top = stack.topRunningActivityLocked();
final int size = mTmpActivityList.size();
for (int i = 0; i < size; i++) {
final ActivityRecord activity = mTmpActivityList.get(i);
//为什么是activity.app == null
//在进程启动前我们就创建了ActivityRecord，并且把它放在顶层的activity，但是我们并没有
//为它分配相应的进程，现在进程创建完了，我们再来找它，并且把进程分配给它
if (activity.app == null && app.uid == activity.info.applicationInfo.uid
&& processName.equals(activity.processName)) {
try {
//开始启动activity，
if (realStartActivityLocked(activity, app,
top == activity /* andResume */, true /* checkConfig */)) {
didSomething = true;
}
} catch (RemoteException e) {
Slog.w(TAG, "Exception in new application when starting activity "
+ top.intent.getComponent().flattenToShortString(), e);
throw e;
}
}
}
}
}
if (!didSomething) {
//启动Activity不成功，确保有可见的Activity
ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
}
return didSomething;
}
3.1.6 ActivityStackSuppervisor
