Android(安卓)FrameWork——PackageManager框架

1.接着前面讲的ActivityManager框架，继续说一下系统另一个重要的框架，PackagerManager
同样先看一下静态类结构图：

大部分情况我们是在Activity中使用getPackageManager方法获取一个ApplicationPackageManager的对象，ApplicationPackageManager实际上是包装了一个IPackageManager.Stub.Proxy的对象
由IPackageManager.Stub.Proxy代理执行PackageManager相关操作，IPackageManager.Stub.Proxy实际代理的是PackageManagerService,
2.看了前面说的，可能你有点晕，我们再来重新理一下：
首先是IPackageManager是通过IPackageManager.aidl文件生成，同时生成了存根类IPackageManager.Stub，代理类：IPackageManager.Stub.Proxy
这个是packageManager进程通信的基本框架，我前面blog有说，不多加说明了
然后PackageManagerService，它继承了IPackageManager.Stub,它作为PackageManager动作的实际执行者，在system_process中存在
再是我们用户应用程序中的ApplicationPackageManager,先看它如何被获取的：
ContextImpl.java中有一个方法：
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实际上是包装了一个IPackageManager对象(IPackageManager.Stub.Proxy),当我们调用queryIntentActivities时，实际通过代理对象去执行：
public List<ResolveInfo> queryIntentActivities(Intent intent,
int flags) {
try {
return mPM.queryIntentActivities(//mPM是IPackageManager.Stub.Proxy对象
intent,
intent.resolveTypeIfNeeded(mContext.getContentResolver()),
flags);
} catch (RemoteException e) {
throw new RuntimeException("Package manager has died", e);
}
}
进过进程通信，在PackageManagerService执行对应操作：
3.PackageManagerService的构建与获取
--PackageManagerService的构建：在system_process进程加载时，PackageManagerService被构建，在SystemServer.ServerThread.run中有如下一段代码，它就是加载 PackageManagerService的：
Slog.i(TAG, "Package Manager");
pm = PackageManagerService.main(context,
factoryTest != SystemServer.FACTORY_TEST_OFF);//启动PackageManagerService
///////////////////////PackageManagerService///////////////////////////////////////////////////////////////////////////
public static final IPackageManager main(Context context, boolean factoryTest) {
PackageManagerService m = new PackageManagerService(context, factoryTest);
ServiceManager.addService("package", m);
return m;
}
--PackageManagerService获取:
先看前面在ContextImpl.java->getPackagerManager中：
IPackageManager pm = ActivityThread.getPackageManager();
/////////////////////ActivityThread////////////////
public 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;
}
从ServiceManager中获取的服务pakager,该服务在.PackageManagerService的构建时被注册到ServiceManager中的，ServiceManager机制暂时没有深入了解，后面再发blog专门说一下ServiceManager

就到此为止，11点了，希望大家看过后多留几个脚印，也算是我一晚上辛苦的慰劳，也欢迎大家随时拍砖。

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