---

一、概述

在Android的中，桌面应用Launcher由Launcher演变到Launcher2，再到现在的Launcher3，Google也做了很多改动。

Launcher不支持桌面小工具动画效果，Launcher2添加了动画效果和3D初步效果支持，从Android 4.4 (KK)开始Launcher默认使用Launcher3， Launcher3加入了透明状态栏，增加overview模式，可以调整workspace上页面的前后顺序，可以动态管理屏幕数量，widget列表与app list分开显示等功能。

本文主要研究Launcher3的启动过程。

1.1 核心源码

/frameworks/base/core/java/com/android/internal/os/ZygoteInit.java
/frameworks/base/core/java/com/android/internal/os/ZygoteServer.java
/frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java
/frameworks/base/core/java/com/android/internal/os/Zygote.java
/frameworks/base/core/java/com/android/internal/os/RuntimeInit.java
/frameworks/base/services/java/com/android/server/SystemServer.java
/frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
/frameworks/base/services/core/java/com/android/server/am/ProcessList.java
/frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
/frameworks/base/services/core/java/com/android/server/wm/ActivityStartController.java
/frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java
/frameworks/base/services/core/java/com/android/server/wm/ActivityStack.java
/frameworks/base/services/core/java/com/android/server/wm/ActivityStackSupervisor.java
/frameworks/base/services/core/java/com/android/server/wm/RootActivityContainer.java
/frameworks/base/services/core/java/com/android/server/wm/ClientLifecycleManager.java
/frameworks/base/core/java/android/os/Process.java
/frameworks/base/core/java/android/os/ZygoteProcess.java
/frameworks/base/core/java/android/app/ActivityThread.java
/frameworks/base/core/java/android/app/Activity.java
/frameworks/base/core/java/android/app/ActivityManagerInternal.java
/frameworks/base/core/java/android/app/servertransaction/ClientTransaction.java
/frameworks/base/core/java/android/app/servertransaction/ClientTransaction.aidl
/frameworks/base/core/java/android/app/ClientTransactionHandler.java
/frameworks/base/core/java/android/app/servertransaction/TransactionExecutor.java
/frameworks/base/core/java/android/app/servertransaction/LaunchActivityItem.java
/frameworks/base/core/java/android/app/Instrumentation.java
/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java

从上面的代码路径可以看出，Android10.0中 Activity的相关功能被放到了wm的目录中，在Android9.0中是在am目录中，Google 最终的目的是把activity 和window融合，在Android10中只是做了简单的代码路径的变更，正在的功能还要到后面的版本才能慢慢融合。

1.2 主要代码作用

名称	作用
Instrumentation	负责调用Activity和Application生命周期。
ActivityTaskManagerService	负责Activity管理和调度等工作。ATM是Android10中新增内容
ActivityManagerService	负责管理四大组件和进程，包括生命周期和状态切换。
ActivityTaskManagerInternal	是由ActivityTaskManagerService对外提供的一个抽象类，真正的实现是在 ActivityTaskManagerService#LocalService
ActivityThread	管理应用程序进程中主线程的执行
ActivityStackSupervisor	负责所有Activity栈的管理
TransactionExecutor	主要作用是执行ClientTransaction
ClientLifecycleManager	生命周期的管理调用

---

二、源码分析

上一节在AMS启动过程中，知道了AMS启动完成前，在systemReady()中会去调用startHomeOnAllDisplays()来启动Launcher，本次就从startHomeOnAllDisplays()函数入口，来看看Launcher是如何被启动起来的。

[ActivityManagerService.java]

public void systemReady(final Runnable goingCallback, TimingsTraceLog 
traceLog) {...//启动Home ActivitymAtmInternal.startHomeOnAllDisplays(currentUserId, "systemReady");...
}

Launcher的启动由三部分启动：

SystemServer完成启动Launcher Activity的调用
Zygote()进行Launcher进程的Fork操作
进入ActivityThread的main()，完成最终Launcher的onCreate操作

接下来分别从源码部分来分析这三个启动过程。

2.1 第一阶段SystemServer 启动HomeActivity的调用阶段

调用栈：

[ActivityTaskManagerService.java] startHomeOnAllDisplays()

说明：ActivityTaskManagerInternal是 ActivityTaskManagerService的一个抽象类，正在的实现是在ActivityTaskManagerService的LocalService，所以mAtmInternal.startHomeOnAllDisplays()最终调用的是ActivityTaskManagerService的startHomeOnAllDisplays()方法

源码：

public boolean startHomeOnAllDisplays(int userId, String reason) {synchronized (mGlobalLock) {//一路调用到 RootActivityContainer 的startHomeOnDisplay()方法，参考[2.2]return mRootActivityContainer.startHomeOnAllDisplays(userId, reason);}
}

2.2 [RootActivityContainer.java] startHomeOnDisplay()

说明：在[2.1]中，获取的displayId为DEFAULT_DISPLAY， 首先通过getHomeIntent 来构建一个category为CATEGORY_HOME的Intent，表明是Home Activity；然后通过resolveHomeActivity()从系统所用已安装的引用中，找到一个符合HomeItent的Activity，最终调用startHomeActivity()来启动Activity

源码：

boolean startHomeOnDisplay(int userId, String reason, int displayId, boolean allowInstrumenting,boolean fromHomeKey) {...if (displayId == DEFAULT_DISPLAY) {//构建一个category为CATEGORY_HOME的Intent，表明是Home Activity，参考[2.2.1]homeIntent = mService.getHomeIntent();//通过PKMS从系统所用已安装的引用中，找到一个符合HomeItent的Activity参考[2.2.2]aInfo = resolveHomeActivity(userId, homeIntent); } ...//启动Home Activity，参考[2.3]mService.getActivityStartController().startHomeActivity(homeIntent, aInfo, myReason,displayId);return true;
}

2.2.1 [ActivityTaskManagerService.java] getHomeIntent()

说明：构建一个category为CATEGORY_HOME的Intent，表明是Home Activity。

Intent.CATEGORY_HOME = "android.intent.category.HOME"

这个category会在Launcher3的 AndroidManifest.xml中配置，表明是Home Acivity

源码：

Intent getHomeIntent() {Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);intent.setComponent(mTopComponent);intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);//不是生产模式，add一个CATEGORY_HOMEif (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) {intent.addCategory(Intent.CATEGORY_HOME);}return intent;
}

2.2.2 [RootActivityContainer.java] resolveHomeActivity()

说明：通过Binder跨进程通知PackageManagerService从系统所用已安装的引用中，找到一个符合HomeItent的Activity。

源码：

ActivityInfo resolveHomeActivity(int userId, Intent homeIntent) {final int flags = ActivityManagerService.STOCK_PM_FLAGS;final ComponentName comp = homeIntent.getComponent(); //系统正常启动时，component为nullActivityInfo aInfo = null;...if (comp != null) {// Factory test.aInfo = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);} else {//系统正常启动时，走该流程final String resolvedType =homeIntent.resolveTypeIfNeeded(mService.mContext.getContentResolver());//resolveIntent做了两件事：1.通过queryIntentActivities来查找符合HomeIntent需求Activities//            2.通过chooseBestActivity找到最符合Intent需求的Activity信息final ResolveInfo info = AppGlobals.getPackageManager().resolveIntent(homeIntent, resolvedType, flags, userId);if (info != null) {aInfo = info.activityInfo;}}...aInfo = new ActivityInfo(aInfo);aInfo.applicationInfo = mService.getAppInfoForUser(aInfo.applicationInfo, userId);return aInfo;
}

2.3 [ActivityStartController.java ] startHomeActivity()

说明：正在的启动Home Activity入口。obtainStarter() 方法返回的是 ActivityStarter 对象，它负责 Activity 的启动，一系列 setXXX() 方法传入启动所需的各种参数，最后的 execute() 是真正的启动逻辑。另外如果home activity处于顶层的resume activity中，则Home Activity 将被初始化，但不会被恢复。并将保持这种状态，直到有东西再次触发它。需要进行另一次恢复。

源码：

void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason, int displayId) {....//返回一个 ActivityStarter 对象，它负责 Activity 的启动//一系列 setXXX() 方法传入启动所需的各种参数，最后的 execute() 是真正的启动逻辑//最后执行 ActivityStarter的execute方法mLastHomeActivityStartResult = obtainStarter(intent, "startHomeActivity: " + reason).setOutActivity(tmpOutRecord).setCallingUid(0).setActivityInfo(aInfo).setActivityOptions(options.toBundle()).execute();  //参考[2.3.1]mLastHomeActivityStartRecord = tmpOutRecord[0];final ActivityDisplay display =mService.mRootActivityContainer.getActivityDisplay(displayId);final ActivityStack homeStack = display != null ? display.getHomeStack() : null;if (homeStack != null && homeStack.mInResumeTopActivity) {//如果home activity 处于顶层的resume activity中，则Home Activity 将被初始化，但不会被恢复（以避免递归恢复），//并将保持这种状态，直到有东西再次触发它。需要进行另一次恢复。mSupervisor.scheduleResumeTopActivities();}
}

2.3.1 [ActivityStarter.java] execute()

说明：在[2.3]中obtainStarter没有调用setMayWait的方法，因此mRequest.mayWait为false，走startActivity流程。

源码：

int execute() {...if (mRequest.mayWait) {return startActivityMayWait(...)} else {return startActivity(...) //参考[2.3.2]}...
}

2.3.2 [ActivityStarter.java] startActivity()

说明：延时布局，然后通过startActivityUnchecked()来处理启动标记 flag ，要启动的任务栈等，最后恢复布局。

源码：

private int startActivity(final ActivityRecord r, ActivityRecord sourceRecord,IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,ActivityRecord[] outActivity, boolean restrictedBgActivity) {...try {//延时布局mService.mWindowManager.deferSurfaceLayout();//调用 startActivityUnchecked ,一路调用到resumeFocusedStacksTopActivities()，参考[2.3.4]result = startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor,startFlags, doResume, options, inTask, outActivity, restrictedBgActivity);} finally {//恢复布局mService.mWindowManager.continueSurfaceLayout();}...
}

2.3.3 [RootActivityContainer.java] resumeFocusedStacksTopActivities()

说明：获取栈顶的Activity，恢复它

源码：

boolean resumeFocusedStacksTopActivities(ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {...//如果秒表栈就是栈顶Activity，启动resumeTopActivityUncheckedLocked()if (targetStack != null && (targetStack.isTopStackOnDisplay()|| getTopDisplayFocusedStack() == targetStack)) {result = targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);...if (!resumedOnDisplay) {// 获取  栈顶的 ActivityRecordfinal ActivityStack focusedStack = display.getFocusedStack();if (focusedStack != null) {//最终调用startSpecificActivityLocked(),参考[2.3.4]focusedStack.resumeTopActivityUncheckedLocked(target, targetOptions);}}}
}

2.3.4 [ActivityStackSupervisor.java] startSpecificActivityLocked()

说明：发布消息以启动进程，以避免在ATM锁保持的情况下调用AMS时可能出现死锁,最终调用到ATM的startProcess()。

源码：

void startSpecificActivityLocked(ActivityRecord r, boolean andResume, boolean checkConfig) {...//发布消息以启动进程，以避免在ATM锁保持的情况下调用AMS时可能出现死锁//最终调用到AMS的startProcess()，参考[2.3.5]final Message msg = PooledLambda.obtainMessage(ActivityManagerInternal::startProcess, mService.mAmInternal, r.processName,r.info.applicationInfo, knownToBeDead, "activity", r.intent.getComponent());mService.mH.sendMessage(msg);...
}

2.3.5 [ActivityManagerService.java] startProcess()

说明：一路调用Process start()，最终到ZygoteProcess的attemptUsapSendArgsAndGetResult()，用来fork一个新的Launcher的进程。

源码：

public void startProcess(String processName, ApplicationInfo info,boolean knownToBeDead, String hostingType, ComponentName hostingName) {..//同步操作，避免死锁synchronized (ActivityManagerService.this) {//调用startProcessLocked,然后到 Process的start，最终到ZygoteProcess的attemptUsapSendArgsAndGetResult()//用来fork一个新的Launcher的进程，参考[2.3.6]startProcessLocked(processName, info, knownToBeDead, 0 /* intentFlags */,new HostingRecord(hostingType, hostingName),false /* allowWhileBooting */, false /* isolated */,true /* keepIfLarge */);}...
}

2.3.6 [ZygoteProcess.java] attemptZygoteSendArgsAndGetResult()

说明：通过Socket连接Zygote进程，把之前组装的msg发给Zygote，其中processClass =“android.app.ActivityThread”，通过Zygote进程来Fork出一个新的进程，并执行 "android.app.ActivityThread"的main方法。

源码：

private Process.ProcessStartResult attemptZygoteSendArgsAndGetResult(ZygoteState zygoteState, String msgStr) throws ZygoteStartFailedEx {try {//传入的zygoteState为openZygoteSocketIfNeeded()，里面会通过abi来检查是第一个zygote还是第二个final BufferedWriter zygoteWriter = zygoteState.mZygoteOutputWriter;final DataInputStream zygoteInputStream = zygoteState.mZygoteInputStream;zygoteWriter.write(msgStr);  //把应用进程的一些参数写给前面连接的zygote进程，包括前面的processClass ="android.app.ActivityThread"zygoteWriter.flush(); //进入Zygote进程，处于阻塞状态， 参考[2.4]//从socket中得到zygote创建的应用pid，赋值给 ProcessStartResult的对象Process.ProcessStartResult result = new Process.ProcessStartResult();result.pid = zygoteInputStream.readInt();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);}
}

2.4 第二阶段Zygote fork一个Launcher进程的阶段

说明：Zygote的启动过程前面有详细讲到过。SystemServer的AMS服务向启动Home Activity发起一个fork请求，Zygote进程通过Linux的fork函数，孵化出一个新的进程。

由于Zygote进程在启动时会创建Java虚拟机，因此通过fork而创建的Launcher程序进程可以在内部获取一个Java虚拟机的实例拷贝。fork采用copy-on-write机制，有些类如果不做改变，甚至都不用复制，子进程可以和父进程共享这部分数据，从而省去不少内存的占用。

2.4.1 [ZygoteInit.java] main()

说明：Zygote先fork出SystemServer进程，接着进入循环等待，用来接收Socket发来的消息，用来fork出其他应用进程，比如Launcher。

源码：

public static void main(String argv[]) {...Runnable caller;....if (startSystemServer) {//Zygote Fork出的第一个进程 SystmeServerRunnable r = forkSystemServer(abiList, zygoteSocketName, zygoteServer);if (r != null) {r.run();return;}}...//循环等待fork出其他的应用进程，比如Launcher//最终通过调用processOneCommand()来进行进程的处理，参考[2.4.2]caller = zygoteServer.runSelectLoop(abiList);...if (caller != null) {caller.run(); //执行返回的Runnable对象，进入子进程}
}

2.4.2 [ZygoteConnection.java] processOneCommand()

说明：通过forkAndSpecialize()来fork出Launcher的子进程，并执行handleChildProc，进入子进程的处理。

源码：

Runnable processOneCommand(ZygoteServer zygoteServer) {int pid = -1;...//Fork子进程，得到一个新的pid/fork子进程,采用copy on write方式，这里执行一次，会返回两次///pid=0 表示Zygote  fork子进程成功//pid > 0 表示子进程 的真正的PIDpid = Zygote.forkAndSpecialize(parsedArgs.mUid, parsedArgs.mGid, parsedArgs.mGids,parsedArgs.mRuntimeFlags, rlimits, parsedArgs.mMountExternal, parsedArgs.mSeInfo,parsedArgs.mNiceName, fdsToClose, fdsToIgnore, parsedArgs.mStartChildZygote,parsedArgs.mInstructionSet, parsedArgs.mAppDataDir, parsedArgs.mTargetSdkVersion);...if (pid == 0) {// in child, fork成功，第一次返回的pid = 0...//参考[2.4.3]return handleChildProc(parsedArgs, descriptors, childPipeFd,parsedArgs.mStartChildZygote);} else {//in parent...childPipeFd = null;handleParentProc(pid, descriptors, serverPipeFd);return null;}
}

2.4.3 [ZygoteConnection.java] handleChildProc()

说明：进行子进程的操作，最终获得需要执行的ActivityThread的main()。

源码：

private Runnable handleChildProc(ZygoteArguments parsedArgs, FileDescriptor[] descriptors,FileDescriptor pipeFd, boolean isZygote) {...if (parsedArgs.mInvokeWith != null) {...throw new IllegalStateException("WrapperInit.execApplication unexpectedly returned");} else {if (!isZygote) {// App进程将会调用到这里，执行目标类的main()方法return ZygoteInit.zygoteInit(parsedArgs.mTargetSdkVersion,parsedArgs.mRemainingArgs, null /* classLoader */);} else {return ZygoteInit.childZygoteInit(parsedArgs.mTargetSdkVersion,parsedArgs.mRemainingArgs, null /* classLoader */);}}
}

zygoteInit 进行一些环境的初始化、启动Binder进程等操作：

public static final Runnable zygoteInit(int targetSdkVersion, String[] argv,ClassLoader classLoader) {RuntimeInit.commonInit(); //初始化运行环境 ZygoteInit.nativeZygoteInit(); //启动Binder线程池 //调用程序入口函数  return RuntimeInit.applicationInit(targetSdkVersion, argv, classLoader);
}

把之前传来的"android.app.ActivityThread" 传递给findStaticMain：

protected static Runnable applicationInit(int targetSdkVersion, String[] argv,ClassLoader classLoader) {...// startClass: 如果AMS通过socket传递过来的是 ActivityThreadreturn findStaticMain(args.startClass, args.startArgs, classLoader);
}

通过反射，拿到ActivityThread的main()方法：

protected static Runnable findStaticMain(String className, String[] argv,ClassLoader classLoader) {Class<?> cl;try {cl = Class.forName(className, true, classLoader);} catch (ClassNotFoundException ex) {throw new RuntimeException("Missing class when invoking static main " + className,ex);}Method m;try {m = cl.getMethod("main", new Class[] { String[].class });} catch (NoSuchMethodException ex) {throw new RuntimeException("Missing static main on " + className, ex);} catch (SecurityException ex) {throw new RuntimeException("Problem getting static main on " + className, ex);}int modifiers = m.getModifiers();if (! (Modifier.isStatic(modifiers) && Modifier.isPublic(modifiers))) {throw new RuntimeException("Main method is not public and static on " + className);}return new MethodAndArgsCaller(m, argv);
}

把反射得来的ActivityThread main()入口返回给ZygoteInit的main，通过caller.run()进行调用：

static class MethodAndArgsCaller implements Runnable {/** method to call */private final Method mMethod;/** argument array */private final String[] mArgs;public MethodAndArgsCaller(Method method, String[] args) {mMethod = method;mArgs = args;}//调用ActivityThread的main()public void run() {try {mMethod.invoke(null, new Object[] { mArgs });} catch (IllegalAccessException ex) {throw new RuntimeException(ex);} catch (InvocationTargetException ex) {Throwable cause = ex.getCause();if (cause instanceof RuntimeException) {throw (RuntimeException) cause;} else if (cause instanceof Error) {throw (Error) cause;}throw new RuntimeException(ex);}}
}

2.5 第三个阶段，Launcher在自己的进程中进行onCreate等后面的动作

从[2.4]可以看到，Zygote fork出了Launcher的进程，并把接下来的Launcher启动任务交给了ActivityThread来进行，接下来就从ActivityThread main()来分析Launcher的创建过程。

2.5.1 [ActivityThread.java] main()

说明：主线程处理， 创建ActivityThread对象，调用attach进行处理，最终进入Looper循环

源码：

public static void main(String[] args) {// 安装选择性的系统调用拦截AndroidOs.install();...//主线程处理Looper.prepareMainLooper();...//之前SystemServer调用attach传入的是true，这里到应用进程传入false就行ActivityThread thread = new ActivityThread();thread.attach(false, startSeq);...//一直循环，如果退出，说明程序关闭Looper.loop();throw new RuntimeException("Main thread loop unexpectedly exited");
}

调用ActivityThread的attach进行处理

private void attach(boolean system, long startSeq) {sCurrentActivityThread = this;mSystemThread = system;if (!system) {//应用进程启动，走该流程...RuntimeInit.setApplicationObject(mAppThread.asBinder());//获取AMS的本地代理类final IActivityManager mgr = ActivityManager.getService();try {//通过Binder调用AMS的attachApplication方法，参考[2.5.2]mgr.attachApplication(mAppThread, startSeq);} catch (RemoteException ex) {throw ex.rethrowFromSystemServer();}...} else {//通过system_server启动ActivityThread对象...}// 为 ViewRootImpl 设置配置更新回调，当系统资源配置（如：系统字体）发生变化时，通知系统配置发生变化ViewRootImpl.ConfigChangedCallback configChangedCallback= (Configuration globalConfig) -> {synchronized (mResourcesManager) {...}};ViewRootImpl.addConfigCallback(configChangedCallback);
}

2.5.2 [ActivityManagerService.java] attachApplication()

说明：清除一些无用的记录，最终调用ActivityStackSupervisor.java的 realStartActivityLocked()，进行Activity的启动

源码：

public final void attachApplication(IApplicationThread thread, long startSeq) {synchronized (this) {//通过Binder获取传入的pid信息int callingPid = Binder.getCallingPid();final int callingUid = Binder.getCallingUid();final long origId = Binder.clearCallingIdentity();attachApplicationLocked(thread, callingPid, callingUid, startSeq);Binder.restoreCallingIdentity(origId);}
}

private final boolean attachApplicationLocked(IApplicationThread thread,int pid, int callingUid, long startSeq) {...//如果当前的Application记录仍然依附到之前的进程中，则清理掉if (app.thread != null) {handleAppDiedLocked(app, true, true);}·//mProcessesReady这个变量在AMS的 systemReady 中被赋值为true，//所以这里的normalMode也为trueboolean normalMode = mProcessesReady || isAllowedWhileBooting(app.info);...//上面说到，这里为true，进入StackSupervisor的attachApplication方法//去真正启动Activityif (normalMode) {...//调用ATM的attachApplication()，最终层层调用到ActivityStackSupervisor.java的 realStartActivityLocked()//参考[2.5.3]didSomething = mAtmInternal.attachApplication(app.getWindowProcessController());...}...return true;
}

2.5.3 [ActivityStackSupervisor.java] realStartActivityLocked()

说明：真正准备去启动Activity，通过clientTransaction.addCallback把LaunchActivityItem的obtain作为回调参数加进去，再调用ClientLifecycleManager.scheduleTransaction()得到LaunchActivityItem的execute()方法进行最终的执行。

源码：

boolean realStartActivityLocked(ActivityRecord r, WindowProcessController proc,boolean andResume, boolean checkConfig) throws RemoteException {// 直到所有的 onPause() 执行结束才会去启动新的 activityif (!mRootActivityContainer.allPausedActivitiesComplete()) {...return false;}try {// Create activity launch transaction.// 添加 LaunchActivityItemfinal ClientTransaction clientTransaction = ClientTransaction.obtain(proc.getThread(), r.appToken);//LaunchActivityItem.obtain(new Intent(r.intent)作为回调参数clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),System.identityHashCode(r), r.info,// TODO: Have this take the merged configuration instead of separate global// and override configs.mergedConfiguration.getGlobalConfiguration(),mergedConfiguration.getOverrideConfiguration(), r.compat,r.launchedFromPackage, task.voiceInteractor, proc.getReportedProcState(),r.icicle, r.persistentState, results, newIntents,dc.isNextTransitionForward(), proc.createProfilerInfoIfNeeded(),r.assistToken));...// 设置生命周期状态final ActivityLifecycleItem lifecycleItem;if (andResume) {lifecycleItem = ResumeActivityItem.obtain(dc.isNextTransitionForward());} else {lifecycleItem = PauseActivityItem.obtain();}clientTransaction.setLifecycleStateRequest(lifecycleItem);// Schedule transaction.// 重点关注：调用 ClientLifecycleManager.scheduleTransaction()，得到上面addCallback的LaunchActivityItem的execute()方法//参考[2.5.4]mService.getLifecycleManager().scheduleTransaction(clientTransaction);} catch (RemoteException e) {if (r.launchFailed) {// 第二次启动失败，finish activitystack.requestFinishActivityLocked(r.appToken, Activity.RESULT_CANCELED, null,"2nd-crash", false);return false;}// 第一次失败，重启进程并重试r.launchFailed = true;proc.removeActivity(r);throw e;}} finally {endDeferResume();}...return true;
}

2.5.4 [TransactionExecutor.java] execute()

说明：执行之前realStartActivityLocked()中的clientTransaction.addCallback

源码： [TransactionExecutor.java]

public void execute(ClientTransaction transaction) {...// 执行 callBack，参考上面的调用栈，执行回调方法，//最终调用到ActivityThread的handleLaunchActivity()参考[2.5.5]executeCallbacks(transaction);// 执行生命周期状态executeLifecycleState(transaction);mPendingActions.clear();
}

2.5.5 [ActivityThread.java] handleLaunchActivity()

说明：主要干了两件事，第一件：初始化WindowManagerGlobal；第二件：调用performLaunchActivity方法

源码：[ActivityThread.java]

public Activity handleLaunchActivity(ActivityClientRecord r,PendingTransactionActions pendingActions, Intent customIntent) {...//初始化WindowManagerGlobalWindowManagerGlobal.initialize();...//调用performLaunchActivity，来处理Activity，参考[2.5.6]final Activity a = performLaunchActivity(r, customIntent);..return a;
}

2.5.6 [ActivityThread.java] performLaunchActivity()

说明：获取ComponentName、Context，反射创建Activity，设置Activity的一些内容，比如主题等； 最终调用callActivityOnCreate()来执行Activity的onCreate()方法

源码：

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {// 获取 ComponentNameComponentName component = r.intent.getComponent();...// 获取 ContextContextImpl appContext = createBaseContextForActivity(r);Activity activity = null;try {// 反射创建 Activityjava.lang.ClassLoader cl = appContext.getClassLoader();activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);StrictMode.incrementExpectedActivityCount(activity.getClass());r.intent.setExtrasClassLoader(cl);r.intent.prepareToEnterProcess();if (r.state != null) {r.state.setClassLoader(cl);}} catch (Exception e) {...}try {// 获取 ApplicationApplication app = r.packageInfo.makeApplication(false, mInstrumentation);if (activity != null) {...//Activity的一些处理activity.attach(appContext, this, getInstrumentation(), r.token,r.ident, app, r.intent, r.activityInfo, title, r.parent,r.embeddedID, r.lastNonConfigurationInstances, config,r.referrer, r.voiceInteractor, window, r.configCallback,r.assistToken);if (customIntent != null) {activity.mIntent = customIntent;}...int theme = r.activityInfo.getThemeResource();if (theme != 0) {// 设置主题activity.setTheme(theme);}activity.mCalled = false;// 执行 onCreate()if (r.isPersistable()) {mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);} else {mInstrumentation.callActivityOnCreate(activity, r.state);}...r.activity = activity;}//当前状态为ON_CREATEr.setState(ON_CREATE);...} catch (SuperNotCalledException e) {throw e;} catch (Exception e) {...}return activity;
}

callActivityOnCreate先执行activity onCreate的预处理，再去调用Activity的onCreate，最终完成Create创建后的内容处理

public void callActivityOnCreate(Activity activity, Bundle icicle,PersistableBundle persistentState) {prePerformCreate(activity); //activity onCreate的预处理activity.performCreate(icicle, persistentState);//执行onCreate()postPerformCreate(activity); //activity onCreate创建后的一些信息处理
}

performCreate()主要调用Activity的onCreate()

final void performCreate(Bundle icicle, PersistableBundle persistentState) {...if (persistentState != null) {onCreate(icicle, persistentState);} else {onCreate(icicle);}...
}

至此，看到了最熟悉的Activity的onCreate()，Launcher的启动完成，Launcher被真正创建起来。

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三、总结

看到onCreate()后，进入到最熟悉的Activity的入口，Launcher的启动告一段落。整个Android的启动流程完整的分析完成。

Launcher的启动经过了三个阶段：

第一个阶段：SystemServer完成启动Launcher Activity的调用
第二个阶段：Zygote()进行Launcher进程的Fork操作
第三个阶段：进入ActivityThread的main()，完成最终Launcher的onCreate操作

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四、相关日志

开机启动流程中关于Launcher关键字的log。

	行  6027: 05-08 18:46:58.502  1504  1504 I SystemServer: StartGestureLauncher行  6028: 05-08 18:46:58.502  1504  1504 I SystemServiceManager: Starting com.android.server.GestureLauncherService行  6029: 05-08 18:46:58.502  1504  1504 D SystemServerTiming: StartGestureLauncher took to complete: 0ms行  6089: 05-08 18:46:58.528  1504  1504 I SystemServer: StartLauncherAppsService行  6090: 05-08 18:46:58.528  1504  1504 I SystemServiceManager: Starting com.android.server.pm.LauncherAppsService行  6091: 05-08 18:46:58.529  1504  1504 D SystemServerTiming: StartLauncherAppsService took to complete: 1ms行  6891: 05-08 18:46:59.180  1504  1504 D SystemServiceManager: onStartUser-0 com.android.server.GestureLauncherService took to complete: 0ms行  6912: 05-08 18:46:59.182  1504  1504 D SystemServiceManager: onStartUser-0 com.android.server.pm.LauncherAppsService took to complete: 0ms行  7848: 05-08 18:46:59.809   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: bindService is called for service : com.android.launcher3/com.android.quickstep.TouchInteractionService and for client com.android.systemui行  7850: 05-08 18:46:59.809   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: total connections for service : com.android.launcher3/com.android.quickstep.TouchInteractionServiceare :1行  7879: 05-08 18:46:59.844  1504  1649 I am_proc_start: [0,2435,10112,com.android.launcher3,service,{com.android.launcher3/com.android.quickstep.TouchInteractionService}]行  7880: 05-08 18:46:59.844  1504  1649 I ActivityManager: Start proc 2435:com.android.launcher3/u0a112 for service {com.android.launcher3/com.android.quickstep.TouchInteractionService}行  7931: 05-08 18:46:59.905  1504  2231 I am_proc_bound: [0,2435,com.android.launcher3]行  7947: 05-08 18:46:59.912   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: startService() is called for servicecom.android.launcher3/com.android.quickstep.TouchInteractionService行  8237: 05-08 18:47:00.075  2435  2435 W ContextImpl: Failed to ensure /data/user/0/com.android.launcher3/cache: mkdir failed: ENOENT (No such file or directory)行  8368: 05-08 18:47:00.140  1504  1504 V NotificationListeners: enabling notification listener for 0: ComponentInfo{com.android.launcher3/com.android.launcher3.notification.NotificationListener}行  8370: 05-08 18:47:00.141  1504  1504 V NotificationListeners: binding: Intent { act=android.service.notification.NotificationListenerService cmp=com.android.launcher3/.notification.NotificationListener (has extras) }行  8371: 05-08 18:47:00.141  1504  1504 W ActivityManager: Unable to start service Intent { act=android.service.notification.NotificationListenerService cmp=com.android.launcher3/.notification.NotificationListener } U=0: not found行  8372: 05-08 18:47:00.141  1504  1504 W NotificationListeners: Unable to bind notification listener service: Intent { act=android.service.notification.NotificationListenerService cmp=com.android.launcher3/.notification.NotificationListener (has extras) } in user 0行 13479: 05-08 18:47:03.025  1504  1648 D SystemServiceManager: onUnlockUser-0 com.android.server.GestureLauncherService took to complete: 0ms行 13491: 05-08 18:47:03.026  1504  1648 D SystemServiceManager: onUnlockUser-0 com.android.server.pm.LauncherAppsService took to complete: 0ms行 13593: 05-08 18:47:03.068  1504  1648 V ActivityManager: Installing ContentProviderInfo{name=com.android.launcher3 className=com.android.quickstep.LauncherSearchIndexablesProvider}行 13594: 05-08 18:47:03.068  1504  1648 V ActivityManager: Installing ContentProviderInfo{name=com.android.launcher3.settings className=com.android.launcher3.LauncherProvider}行 13734: 05-08 18:47:03.171  1504  3109 I ActivityTaskManager: START u0 {act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10000100 cmp=com.android.launcher3/.Launcher} from uid 0行 13771: 05-08 18:47:03.228  1504  3109 I am_create_activity: [0,91065182,970,com.android.launcher3/.Launcher,android.intent.action.MAIN,NULL,NULL,268435712]行 13800: 05-08 18:47:03.246  1504  1504 V NotificationListeners: enabling notification listener for 0: ComponentInfo{com.android.launcher3/com.android.launcher3.notification.NotificationListener}行 13801: 05-08 18:47:03.246  1504  1504 V NotificationListeners: binding: Intent { act=android.service.notification.NotificationListenerService cmp=com.android.launcher3/.notification.NotificationListener (has extras) }行 13811: 05-08 18:47:03.249   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: unbindService is called for service : com.android.launcher3/com.android.quickstep.TouchInteractionService and for client com.android.systemui行 13812: 05-08 18:47:03.249   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: size of service connections for service: com.android.launcher3/com.android.quickstep.TouchInteractionServiceafter removal is 0行 13814: 05-08 18:47:03.250   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: destroyService is called for service : com.android.launcher3/com.android.quickstep.TouchInteractionService行 13867: 05-08 18:47:03.271   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: bindService is called for service : com.android.launcher3/.notification.NotificationListener and for client system行 13868: 05-08 18:47:03.271   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: total connections for service : com.android.launcher3/.notification.NotificationListenerare :1行 13877: 05-08 18:47:03.277   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: startService() is called for servicecom.android.launcher3/.notification.NotificationListener行 13887: 05-08 18:47:03.283   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: bindService is called for service : com.android.launcher3/com.android.quickstep.TouchInteractionService and for client com.android.systemui行 13888: 05-08 18:47:03.284   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: total connections for service : com.android.launcher3/com.android.quickstep.TouchInteractionServiceare :1行 13890: 05-08 18:47:03.284  1504  1632 I ActivityTaskManager: The Process com.android.launcher3 Already Exists in BG. So sending its PID: 2435行 13892: 05-08 18:47:03.287  1504  1632 I am_restart_activity: [0,91065182,970,com.android.launcher3/.Launcher]行 13901: 05-08 18:47:03.288  1504  1632 I am_set_resumed_activity: [0,com.android.launcher3/.Launcher,minimalResumeActivityLocked]行 13903: 05-08 18:47:03.289  1504  1632 I am_add_to_stopping: [0,91065182,com.android.launcher3/.Launcher,makeInvisible]行 13906: 05-08 18:47:03.290  1504  1632 I am_pause_activity: [0,91065182,com.android.launcher3/.Launcher,userLeaving=false]行 13930: 05-08 18:47:03.309   722   761 I /vendor/bin/hw/vendor.qti.hardware.servicetracker@1.1-service: startService() is called for servicecom.android.launcher3/com.android.quickstep.TouchInteractionService行 13931: 05-08 18:47:03.309  1504  1632 I sysui_multi_action: [757,1144,758,8,806,com.android.launcher3,871,com.android.launcher3.Launcher]行 14061: 05-08 18:47:03.504  1504  1504 V NotificationListeners: 0 notification listener service connected: ComponentInfo{com.android.launcher3/com.android.launcher3.notification.NotificationListener}行 14132: 05-08 18:47:03.596  2435  2435 V Launcher: LauncherAppState initiated行 14803: 05-08 18:47:03.791  1504  1632 W ActivityTaskManager: Activity top resumed state loss timeout for ActivityRecord{56d8b5e u0 com.android.launcher3/.Launcher t970}行 14804: 05-08 18:47:03.791  1504  1632 W ActivityTaskManager: Activity pause timeout for ActivityRecord{56d8b5e u0 com.android.launcher3/.Launcher t970}行 14831: 05-08 18:47:03.799  1504  1632 I am_stop_activity: [0,91065182,com.android.launcher3/.Launcher]行 15393: 05-08 18:47:04.232  2435  2435 I am_on_create_called: [0,com.android.launcher3.Launcher,performCreate]行 15400: 05-08 18:47:04.242  2435  2435 I am_on_start_called: [0,com.android.launcher3.Launcher,handleStartActivity]行 15401: 05-08 18:47:04.243  2435  2435 I am_on_resume_called: [0,com.android.launcher3.Launcher,RESUME_ACTIVITY]行 15408: 05-08 18:47:04.255  2435  2435 I am_on_top_resumed_gained_called: [0,com.android.launcher3.Launcher,topStateChangedWhenResumed]行 15409: 05-08 18:47:04.255  2435  2435 I am_on_top_resumed_lost_called: [0,com.android.launcher3.Launcher,topStateChangedWhenResumed]行 15410: 05-08 18:47:04.255  2435  2435 I am_on_paused_called: [0,com.android.launcher3.Launcher,performPause]行 15411: 05-08 18:47:04.256  1504  3100 I am_failed_to_pause: [0,91065182,com.android.launcher3/.Launcher,(none)]行 15420: 05-08 18:47:04.268  2435  2435 I am_on_stop_called: [0,com.android.launcher3.Launcher,STOP_ACTIVITY_ITEM]行 16064: 05-08 18:47:05.573  1504  3106 I am_set_resumed_activity: [0,com.android.launcher3/.Launcher,resumeTopActivityInnerLocked]行 16065: 05-08 18:47:05.574  1504  3106 I am_resume_activity: [0,91065182,970,com.android.launcher3/.Launcher]行 16070: 05-08 18:47:05.590  2435  2435 I am_on_restart_called: [0,com.android.launcher3.Launcher,performRestartActivity]行 16071: 05-08 18:47:05.591  2435  2435 I am_on_start_called: [0,com.android.launcher3.Launcher,handleStartActivity]行 16072: 05-08 18:47:05.592  2435  2435 I am_on_resume_called: [0,com.android.launcher3.Launcher,RESUME_ACTIVITY]行 16073: 05-08 18:47:05.592  2435  2435 I am_on_top_resumed_gained_called: [0,com.android.launcher3.Launcher,topWhenResuming]

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