PackageManager框架

ActivityManager框架--PackagerManager
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。
        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);
            }
  }

 

经过进程通信，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。