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:

Android FrameWork——PackageManager框架_第1张图片

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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