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Android Framework 分析-PackageManager 分析

热度:659   发布时间:2016-04-28 05:34:21.0
Android Framework 分析---PackageManager 分析

在windowphone,ios和android中到目前为止,还是android的市场份额最大。个人认为除了google开源外,广大开发者早就了android的霸主地位。各位兄弟姐妹开发出各种各样的apk,才组成android的广阔天下。本篇主要分析一下android系统是针对处理这些apk的,主要涉及到pm这块的代码。分析这种底层服务,最好从android的开启启动流程中开始分析。因为这样才能更清楚的了解服务的启动流程。

1.在SystemServer.java 中启动PM

  android 开机启动后加载的第一个java的程序就是SystemServer,在包含android系统的最主要的一些底层服务。在4.4kk之前都是建一个Thread线程来启动。4.4KK的启动机制就变了,具体后续的文章会讲解。

Installer installer = null;   Slog.i(TAG, "Waiting for installd to be ready.");            installer = new Installer();            installer.ping(); pm = PackageManagerService.main(context, installer,                    factoryTest != SystemServer.FACTORY_TEST_OFF,                    onlyCore);            boolean firstBoot = false;            try {                firstBoot = pm.isFirstBoot();            } catch (RemoteException e) {            }
 public static final IPackageManager main(Context context, Installer installer,            boolean factoryTest, boolean onlyCore) {        PackageManagerService m = new PackageManagerService(context, installer,                factoryTest, onlyCore);        ServiceManager.addService("package", m);        return m;    }
在systemServer中初始化了Installer,并将它传入PackageManagerService.main()中。在main函数中将pm添加到ServiceManager中,供开发者调用。

2.PackageManagerService启动安装分析

启动PackageManagerService后,主要完成以下几个步骤

2.1.初始化PackageSetting,设置sharedUserID

 

mSettings = new Settings(context);        mSettings.addSharedUserLPw("android.uid.system",                Process.SYSTEM_UID, ApplicationInfo.FLAG_SYSTEM);        mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID, ApplicationInfo.FLAG_SYSTEM);
2.2.获取屏幕参数:

 WindowManager wm = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);        Display d = wm.getDefaultDisplay();        d.getMetrics(mMetrics);
2.3.使用HandlerThread开启packagemanager工作线程和初始化app目录

mHandlerThread.start();            mHandler = new PackageHandler(mHandlerThread.getLooper());            File dataDir = Environment.getDataDirectory();            mAppDataDir = new File(dataDir, "data");            mAppInstallDir = new File(dataDir, "app");            mAppLibInstallDir = new File(dataDir, "app-lib");            mAsecInternalPath = new File(dataDir, "app-asec").getPath();            mUserAppDataDir = new File(dataDir, "user");            mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
2.4.加载Framework的主要jar和BOOTCLASSPATH

 mFrameworkDir = new File(Environment.getRootDirectory(), "framework");            mDalvikCacheDir = new File(dataDir, "dalvik-cache");            boolean didDexOpt = false;            /**             * Out of paranoia, ensure that everything in the boot class             * path has been dexed.             */            String bootClassPath = System.getProperty("java.boot.class.path");
2.5.安装system/app,vendor/app和data/app目录下apk

// Collect all system packages.            mSystemAppDir = new File(Environment.getRootDirectory(), "app");            mSystemInstallObserver = new AppDirObserver(                mSystemAppDir.getPath(), OBSERVER_EVENTS, true);            mSystemInstallObserver.startWatching();            scanDirLI(mSystemAppDir, PackageParser.PARSE_IS_SYSTEM                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);            // Collect all vendor packages.            mVendorAppDir = new File("/vendor/app");            mVendorInstallObserver = new AppDirObserver(                mVendorAppDir.getPath(), OBSERVER_EVENTS, true);            mVendorInstallObserver.startWatching();            scanDirLI(mVendorAppDir, PackageParser.PARSE_IS_SYSTEM                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);...... mAppInstallObserver = new AppDirObserver(                    mAppInstallDir.getPath(), OBSERVER_EVENTS, false);                mAppInstallObserver.startWatching();                scanDirLI(mAppInstallDir, 0, scanMode, 0);    

其中具体如果安装代码在scanDirLI()函数,最终调用scanPackageLI()进行安装。在安装过程中会搜集ApplicationInfo和ActivityInfo信息,比较签名,匹配本地so的目录。

具体细节参看PackageManagerService.java 中的

private PackageParser.Package scanPackageLI(PackageParser.Package pkg,
            int parseFlags, int scanMode, long currentTime, UserHandle user) {

函数。

3.在Activity使用PackageManger的分析

   我们在应用经常通过

   PackageManager pm = this.getPackageManager() 来获取pm。这部分主要从它的来源来深入分析。

  由于我们在Activity中使用this来获取pm,很容易想到到context类里去寻找实现。

 

 /** Return PackageManager instance to find global package information. */    public abstract PackageManager getPackageManager();
但是context是虚函数,因此要找到它的实现,由于context的实现采用 设计模式里面的 "桥接模式' 因此很容易想到从contextImpl.java 中寻找实现。

果然找到。

   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;    }

从代码上看获取IPackageManager,还是需要从ActivityThread中获取。我在Activity里面获取吗出现在ActivityThread 也不意外。

那我们就看看他是怎么实现的

 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;    }
原来是通过ServiceManager.getService("package").从上你们的代码知道,这句其实就是获取PackageManagerService 并赋给IBinder ,成为一个binder对象。

通过asInterface()函数,通过binder对象获取接口类IPackageManager的实例。并返回回去。

if (pm != null) {            // Doesn't matter if we make more than one instance.            return (mPackageManager = new ApplicationPackageManager(this, pm));        }


在接着同ApplicationPackageManager 创建PackageManager 对象。到此我们在Activity中就可以使用pm这个对象操作系统中的各种包。


4.Android 系统中PackageManager的关键类和UML的类图。

 在pm中主要涉及的类和路径如下:

 frameworks\base\services\java\com\android\server\pm\PackageManagerService.java 和 其他文件

frameworks\base\core\java\android\content\pm\IPackageManager.aidl

frameworks\base\core\java\android\app\ActivityThread.java ,context.java ,contextimpl.java

frameworks\base\core\java\android\content\pm\PackageManager.java





 






 



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