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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,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;
- }
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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