Android系统启动流程四Launcher启动过程与系统启动流程.docx

1、Android系统启动流程四Launcher启动过程与系统启动流程Android系统启动流程（四）Launcher启动过程与系统启动流程前言此前的文章我们学习了init进程、Zygote进程和SyetemServer进程的启动过程，这一篇文章我们就来学习Android系统启动流程的最后一步：Launcher的启动流程，并结合本系列的前三篇文章的内容来讲解Android系统启动流程。建议读这篇文章前要通读本系列的前三篇文章，否则你可能不会理解我在讲什么。1.Launcher概述Android系统启动的最后一步是启动一个Home应用程序，这个应用程序用来显示系统中已经安装的应用程序，这个Home应

2、用程序就叫做Launcher。应用程序Launcher在启动过程中会请求PackageManagerService返回系统中已经安装的应用程序的信息，并将这些信息封装成一个快捷图标列表显示在系统屏幕上，这样用户可以通过点击这些快捷图标来启动相应的应用程序。2.Launcher启动流程SyetemServer进程在启动的过程中会启动PackageManagerService，PackageManagerService启动后会将系统中的应用程序安装完成。在此前已经启动的ActivityManagerService会将Launcher启动起来。 启动Launcher的入口为ActivityManag

3、erService的systemReady函数，如下所示。 frameworks/base/services/Java/com/android/server/SystemServer.java private void startOtherServices() . mActivityManagerService.systemReady(new Runnable() Override public void run() Slog.i(TAG, Making services ready); mSystemServiceManager.startBootPhase( SystemService.P

4、HASE_ACTIVITY_MANAGER_READY);.在startOtherServices函数中，会调用ActivityManagerService的systemReady函数： frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.javapublic void systemReady(final Runnable goingCallback) .synchronized (this) . mStackSupervisor.resumeFocusedStackTopActivit

5、yLocked(); mUserController.sendUserSwitchBroadcastsLocked(-1, currentUserId); systemReady函数中调用了ActivityStackSupervisor的resumeFocusedStackTopActivityLocked函数： frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.javaboolean resumeFocusedStackTopActivityLocked( ActivityStac

6、k targetStack, ActivityRecord target, ActivityOptions targetOptions) if (targetStack != null & isFocusedStack(targetStack) return targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);/1 final ActivityRecord r = mFocusedStack.topRunningActivityLocked(); if (r = null | r.state != RESUME

7、D) mFocusedStack.resumeTopActivityUncheckedLocked(null, null); return false; 在注释1处会调用ActivityStack的resumeTopActivityUncheckedLocked函数，ActivityStack对象是用来描述Activity堆栈的，resumeTopActivityUncheckedLocked函数如下所示。 frameworks/base/services/core/java/com/android/server/am/ActivityStack.java boolean resumeTopA

8、ctivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) if (mStackSupervisor.inResumeTopActivity) / Dont even start recursing. return false; boolean result = false; try / Protect against recursion. mStackSupervisor.inResumeTopActivity = true; if (mService.mLockScreenShown = ActivityMana

9、gerService.LOCK_SCREEN_LEAVING) mService.mLockScreenShown = ActivityManagerService.LOCK_SCREEN_HIDDEN; mService.updateSleepIfNeededLocked(); result = resumeTopActivityInnerLocked(prev, options);/1 finally mStackSupervisor.inResumeTopActivity = false; return result; 注释1调用了resumeTopActivityInnerLocked

10、函数： private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) . return isOnHomeDisplay() & mStackSupervisor.resumeHomeStackTask(returnTaskType, prev, prevFinished); . resumeTopActivityInnerLocked函数的代码很长，我们截取我们要分析的关键的一句：调用ActivityStackSupervisor的resumeHomeStackTask函数，

11、代码如下所示。 frameworks/base/services/core/java/com/android/server/am/ActivityStackSupervisor.javaboolean resumeHomeStackTask(int homeStackTaskType, ActivityRecord prev, String reason) . if (r != null & !r.finishing) mService.setFocusedActivityLocked(r, myReason); return resumeFocusedStackTopActivityLock

12、ed(mHomeStack, prev, null); return mService.startHomeActivityLocked(mCurrentUser, myReason);/1在注释1处调用了ActivityManagerService的startHomeActivityLocked函数，如下所示。 frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java boolean startHomeActivityLocked(int userId, String reason)

13、 if (mFactoryTest = FactoryTest.FACTORY_TEST_LOW_LEVEL & mTopAction = null) /1 return false; Intent intent = getHomeIntent();/2 ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId); if (aInfo != null) intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.

14、name); aInfo = new ActivityInfo(aInfo); aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId); ProcessRecord app = getProcessRecordLocked(aInfo.processName, aInfo.applicationInfo.uid, true); if (app = null | app.instrumentationClass = null) /3 intent.setFlags(intent.getFlags() | I

15、ntent.FLAG_ACTIVITY_NEW_TASK); mActivityStarter.startHomeActivityLocked(intent, aInfo, reason);/4 else Slog.wtf(TAG, No home screen found for + intent, new Throwable(); return true; 注释1处的mFactoryTest代表系统的运行模式，系统的运行模式分为三种，分别是非工厂模式、低级工厂模式和高级工厂模式，mTopAction则用来描述第一个被启动Activity组件的Action，它的值为Intent.ACTION

16、_MAIN。因此注释1的代码意思就是mFactoryTest为FactoryTest.FACTORY_TEST_LOW_LEVEL（低级工厂模式）并且mTopAction=null时，直接返回false。注释2处的getHomeIntent函数如下所示。Intent getHomeIntent() Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null); intent.setComponent(mTopComponent); intent.addFlags(Intent.FLAG

17、_DEBUG_TRIAGED_MISSING); if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) intent.addCategory(Intent.CATEGORY_HOME); return intent;getHomeIntent函数中创建了Intent，并将mTopAction和mTopData传入。mTopAction的值为Intent.ACTION_MAIN，并且如果系统运行模式不是低级工厂模式则将intent的Category设置为Intent.CATEGORY_HOME。我们再回到ActivityManagerSe

18、rvice的startHomeActivityLocked函数，假设系统的运行模式不是低级工厂模式，在注释3处判断符合Action为Intent.ACTION_MAIN，Category为Intent.CATEGORY_HOME的应用程序是否已经启动，如果没启动则调用注释4的方法启动该应用程序。 这个被启动的应用程序就是Launcher，因为Launcher的Manifest文件中的intent-filter标签匹配了Action为Intent.ACTION_MAIN，Category为Intent.CATEGORY_HOME。Launcher的Manifest文件如下所示。 packages

19、/apps/Launcher3/AndroidManifest.xml . application . . 这样，应用程序Launcher就会被启动起来，并执行它的onCreate函数。3.Launcher中应用图标显示流程Launcher的onCreate函数如下所示。 packages/apps/Launcher3/src/com/android/launcher3/Launcher.java Override protected void onCreate(Bundle savedInstanceState) . LauncherAppState app = LauncherAppSta

20、te.getInstance();/1 mDeviceProfile = getResources().getConfiguration().orientation = Configuration.ORIENTATION_LANDSCAPE ? app.getInvariantDeviceProfile().landscapeProfile : app.getInvariantDeviceProfile().portraitProfile; mSharedPrefs = Utilities.getPrefs(this); mIsSafeModeEnabled = getPackageManag

21、er().isSafeMode(); mModel = app.setLauncher(this);/2 . if (!mRestoring) if (DISABLE_SYNCHRONOUS_BINDING_CURRENT_PAGE) mModel.startLoader(PagedView.INVALID_RESTORE_PAGE);/2 else mModel.startLoader(mWorkspace.getRestorePage(); . 注释1处获取LauncherAppState的实例并在注释2处调用它的setLauncher函数并将Launcher对象传入，LauncherAp

22、pState的setLauncher函数如下所示。 packages/apps/Launcher3/src/com/android/launcher3/LauncherAppState.java LauncherModel setLauncher(Launcher launcher) getLauncherProvider().setLauncherProviderChangeListener(launcher); mModel.initialize(uncher);/1 mAccessibilityDelegate = (launcher != null) & Utilities.ATLEA

23、ST_LOLLIPOP) ? new LauncherAccessibilityDelegate(launcher) : null; return mModel; 注释1处会调用LauncherModel的initialize函数：public void initialize(Callbacks callbacks) synchronized (mLock) unbindItemInfosAndClearQueuedBindRunnables(); mCallbacks = new WeakReference(callbacks); 在initialize函数中会将Callbacks，也就是传

24、入的Launcher 封装成一个弱引用对象。因此我们得知mCallbacks变量指的就是封装成弱引用对象的Launcher，这个mCallbacks后文会用到它。 再回到Launcher的onCreate函数，在注释2处调用了LauncherModel的startLoader函数： packages/apps/Launcher3/src/com/android/launcher3/LauncherModel.java. Thunk static final HandlerThread sWorkerThread = new HandlerThread(launcher-loader);/1 s

25、tatic sWorkerThread.start(); Thunk static final Handler sWorker = new Handler(sWorkerThread.getLooper();/2. public void startLoader(int synchronousBindPage, int loadFlags) s InstallShortcutReceiver.enableInstallQueue(); synchronized (mLock) synchronized (mDeferredBindRunnables) mDeferredBindRunnable

26、s.clear(); if (mCallbacks != null & mCallbacks.get() != null) stopLoaderLocked(); mLoaderTask = new LoaderTask(mApp.getContext(), loadFlags);/3 if (synchronousBindPage != PagedView.INVALID_RESTORE_PAGE &mAllAppsLoaded&mWorkspaceLoaded & !mIsLoaderTaskRunning) mLoaderTask.runBindSynchronousPage(synch

27、ronousBindPage); else sWorkerThread.setPriority(Thread.NORM_PRIORITY); sWorker.post(mLoaderTask);/4 注释1处创建了具有消息循环的线程HandlerThread对象。注释2处创建了Handler，并且传入HandlerThread的Looper。Hander的作用就是向HandlerThread发送消息。在注释3处创建LoaderTask，在注释4处将LoaderTask作为消息发送给HandlerThread 。 LoaderTask类实现了Runnable接口，当LoaderTask所描述的消息被处理时则会调用它的run函数，代码如下所示 private class LoaderTask implements Runnable . public void run() synchronized (mLock) if (mStopped) return; mIsLoaderTaskRunning = true; keep_running: if (DEBUG_LOADERS) Log.d(TAG, step 1: loading workspace); loadAndBindWorkspace();/1 if (mStopped) break keep_running; wa