http://blog.csdn.net/stonecao/article/details/6591454

1.接著前面講的ActivityManager框架，繼續說一下系統另一個重要的框架，PackagerManager
同樣先看一下靜態類結構圖：

大部分情況我們是在Activity中使用getPackageManager方法獲取一個ApplicationPackageManager的對象，ApplicationPackageManager實際上是包裝了一個IPackageManager.Stub.Proxy的對象 由IPackageManager.Stub.Proxy代理執行PackageManager相關操作，IPackageManager.Stub.Proxy實際代理的是PackageManagerService, 2.看了前面說的，可能你有點暈，我們再來重新理一下：首先是IPackageManager是通過IPackageManager.aidl文件生成，同時生成了存根類IPackageManager.Stub，代理類：IPackageManager.Stub.Proxy 這個是packageManager進程通信的基本框架，我前面blog有說，不多加說明了然后PackageManagerService，它繼承了IPackageManager.Stub,它作為PackageManager動作的實際執行者，在system_process中存在再是我們用戶應用程序中的ApplicationPackageManager,先看它如何被獲取的： ContextImpl.java中有一個方法：public PackageManager getPackageManager() {if (mPackageManager != null) {return mPackageManager;}IPackageManager pm = ActivityThread.getPackageManager();if (pm != null) {// Doesn't matter if we make more than one instance.return (mPackageManager = new ApplicationPackageManager(this, pm));}return null;} ApplicationPackageManager實際上是包裝了一個IPackageManager對象(IPackageManager.Stub.Proxy),當我們調用queryIntentActivities時，實際通過代理對象去執行：public List<ResolveInfo> queryIntentActivities(Intent intent,int flags) {try {return mPM.queryIntentActivities(//mPM是IPackageManager.Stub.Proxy對象intent,intent.resolveTypeIfNeeded(mContext.getContentResolver()),flags);} catch (RemoteException e) {throw new RuntimeException("Package manager has died", e);}} 進過進程通信，在PackageManagerService執行對應操作： 3.PackageManagerService的構建與獲取 --PackageManagerService的構建：在system_process進程加載時，PackageManagerService被構建，在SystemServer.ServerThread.run中有如下一段代碼，它就是加載 PackageManagerService的：Slog.i(TAG, "Package Manager");pm = PackageManagerService.main(context,factoryTest != SystemServer.FACTORY_TEST_OFF);//啟動PackageManagerService ///PackageManagerService///public static final IPackageManager main(Context context, boolean factoryTest) {PackageManagerService m = new PackageManagerService(context, factoryTest);ServiceManager.addService("package", m);return m;}--PackageManagerService獲取: 先看前面在ContextImpl.java->getPackagerManager中： IPackageManager pm = ActivityThread.getPackageManager(); /ActivityThreadpublic static IPackageManager getPackageManager() {if (sPackageManager != null) {//Slog.v("PackageManager", "returning cur default = " + sPackageManager);return sPackageManager;}IBinder b = ServiceManager.getService("package");//Slog.v("PackageManager", "default service binder = " + b);sPackageManager = IPackageManager.Stub.asInterface(b);//Slog.v("PackageManager", "default service = " + sPackageManager);return sPackageManager;}從ServiceManager中獲取的服務pakager,該服務在.PackageManagerService的構建時被注冊到ServiceManager中的，ServiceManager機制暫時沒有深入了解，后面再發blog專門說一下ServiceManager就到此為止，11點了，希望大家看過后多留幾個腳印，也算是我一晚上辛苦的慰勞，也歡迎大家隨時拍磚。

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