Android 源码分析Launcher 桌面程序启动分析 _启动分析

仓廪实则知礼节，衣食足则知荣辱。这篇文章主要讲述Android 源码分析Launcher 桌面程序启动分析相关的知识，希望能为你提供帮助。
一.前言: init进程 –> Zygote进程 –> SystemServer进程 –> Launcher桌面程序 -> 我们的App应用

init进程：linux的根进程，android系统是基于linux系统的，因此可以算作是整个android操作系统的第一个进程；

Zygote进程：android系统的根进程，主要作用：可以作用Zygote进程fork出SystemServer进程和各种应用进程；

SystemService进程：主要是在这个进程中启动系统的各项服务，比如ActivityManagerService，PackageManagerService，WindowManagerService服务等等；

Launcher桌面程序:就是我们平时看到的桌面程序，它其实也是一个android应用程序，只不过这个应用程序是系统默认第一个启动的应用程序.

二. Launcher 桌面程序启动 Launcher程序就是我们平时看到的桌面程序，它其实也是一个android应用程序，只不过这个应用程序是系统默认第一个启动的应用程序。
前一篇文章我们知道在SystemServer进程的启动过程中会调用其main静态方法，开始执行整个SystemServer的启动流程。在调用startOtherService方法中就会通过调用mActivityManagerService.systemReady()方法。

//SystemServer.java private void startOtherServices() { ...... // We now tell the activity manager it is okay to run third party // code.It will call back into us once it has gotten to the state // where third party code can really run (but before it has actually // started launching the initial applications), for us to complete our // initialization. mActivityManagerService.systemReady() ...... }

//ActivityManagerService.java public void systemReady(final Runnable goingCallback, BootTimingsTraceLog traceLog) { ...... startHomeActivityLocked(currentUserId, "systemReady"); ......}boolean startHomeActivityLocked(int userId, String reason) { if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL & & mTopAction == null) { // We are running in factory test mode, but unable to find // the factory test app, so just sit around displaying the // error message and don‘t try to start anything. return false; } Intent intent = getHomeIntent(); ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId); if (aInfo != null) { intent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name)); // Don‘t do this if the home app is currently being // instrumented. aInfo = new ActivityInfo(aInfo); aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId); ProcessRecord app = getProcessRecordLocked(aInfo.processName, aInfo.applicationInfo.uid, true); if (app == null || app.instr == null) { intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK); final int resolvedUserId = UserHandle.getUserId(aInfo.applicationInfo.uid); // For ANR debugging to verify if the user activity is the one that actually // launched. final String myReason = reason + ":" + userId + ":" + resolvedUserId; mActivityStarter.startHomeActivityLocked(intent, aInfo, myReason); } } else { Slog.wtf(TAG, "No home screen found for " + intent, new Throwable()); }return true; }Intent getHomeIntent() { Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null); intent.setComponent(mTopComponent); intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING); if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) { intent.addCategory(Intent.CATEGORY_HOME); } return intent; }

//ActivityStarter.java void startHomeActivityLocked(Intent intent, ActivityInfo aInfo, String reason) { mSupervisor.moveHomeStackTaskToTop(reason); mLastHomeActivityStartResult = startActivityLocked(null /*caller*/, intent, null /*ephemeralIntent*/, null /*resolvedType*/, aInfo, null /*rInfo*/, null /*voiceSession*/, null /*voiceInteractor*/, null /*resultTo*/, null /*resultWho*/, 0 /*requestCode*/, 0 /*callingPid*/, 0 /*callingUid*/, null /*callingPackage*/, 0 /*realCallingPid*/, 0 /*realCallingUid*/, 0 /*startFlags*/, null /*options*/, false /*ignoreTargetSecurity*/, false /*componentSpecified*/, mLastHomeActivityStartRecord /*outActivity*/, null /*container*/, null /*inTask*/, "startHomeActivity: " + reason); if (mSupervisor.inResumeTopActivity) { // If we are in resume section already, home activity will be initialized, but not // resumed (to avoid recursive resume) and will stay that way until something pokes it // again. We need to schedule another resume. mSupervisor.scheduleResumeTopActivities(); } }

【Android 源码分析Launcher 桌面程序启动分析】 后面就进入了Activity的启动流程了。