android开发基于Android10分析请求Zygote执行Fork一个新的应用程序的过程

android开发基于Android10分析请求Zygote执行Fork一个新的应用程序的过程

```
ActivityTaskManagerService.activityPaused

ActivityStack.activityPausedLocked

RootActivityContainer.resumeFocusedStacksTopActivities

ActivityStackSupervisor.startSpecificActivityLocked

void startSpecificActivityLocked(ActivityRecord r, boolean andResume, boolean checkConfig) {
// Is this activity's application already running?
//先mProcessNames缓存中查找是否存在这个进程
final WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);

if (wpc != null && wpc.hasThread()) {
try {
realStartActivityLocked(r, wpc, andResume, checkConfig); //如果已经存在，直接启动
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity " + r.intent.getComponent().flattenToShortString(), e);
}
return;
}
ActivityManagerInternal::startProcess //否则执行startProcess进行fork一个子进程
}

ActivityManagerService.startProcessLocked();

ProcessList.startProcessLocked(); // Process management

Process.start(entryPoint ...);

ZYGOTE_PROCESS.start(...);

ZygoteProcess.startViaZygote();

ZygoteProcess.zygoteSendArgsAndGetResult();

ZygoteProcess.attemptZygoteSendArgsAndGetResult();

private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(
ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {
try {
final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;
final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;
zygoteWriter.write(msgStr); //往zygote socket server写参数
zygoteWriter.flush();

Process.ProcessStartResult result = new Process.ProcessStartResult();
result.pid = zygoteInputStream.readInt(); //从zygote socket server读取fork出来的子进程pid
result.usingWrapper = zygoteInputStream.readBoolean();
if (result.pid < 0) {
throw new ZygoteStartFailedEx("fork() failed");
}
return result;
} catch (IOException ex) {
zygoteState.close();
Log.e(LOG_TAG, "IO Exception while communicating with Zygote - "
+ ex.toString());
throw new ZygoteStartFailedEx(ex);
}
}

ActivityManagerService.handleProcessStartedLocked();//mService.mPidsSelfLocked.put(app);//ProcessRecord缓存起来

//新进程创建，走android.app.ActivityThread类main方法，然后走attachApplication，接着回到ActivityManagerService
ActivityManagerService.attachApplication

ActivityTaskManagerInternal.LocalService.attachApplication();

RootActivityContainer.attachApplication(wpc)

ActivityStackSupervisor.realStartActivityLocked

clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent)..)
if (andResume) {
lifecycleItem = ResumeActivityItem.obtain(dc.isNextTransitionForward());
} else {
lifecycleItem = PauseActivityItem.obtain();
}
clientTransaction.setLifecycleStateRequest(lifecycleItem);
mService.getLifecycleManager().scheduleTransaction(clientTransaction);

//LaunchActivityItem
client.handleLaunchActivity(r, pendingActions, null /* customIntent */);
```