Android 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。