Android应用程序安装过程源代码分析（3）

      Step 7. PackageManagerService.main

     这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

 
     
     class PackageManagerService extends IPackageManager.Stub {
    ......

 
     
         public static final IPackageManager main(Context context, boolean factoryTest) {
 
     
             PackageManagerService m = new PackageManagerService(context, factoryTest);
 
     
             ServiceManager.addService("package", m);
 
     
             return m;
    }

    ......
}

        这个函数创建了一个PackageManagerService服务实例，然后把这个服务添加到ServiceManager中去，ServiceManager是Android系统Binder进程间通信机制的守护进程，负责管理系统中的Binder对象，具体可以参考 浅谈Service Manager成为Android进程间通信（IPC）机制Binder守护进程之路 一文。

       在创建这个PackageManagerService服务实例时，会在PackageManagerService类的构造函数中开始执行安装应用程序的过程：

 
     
     class PackageManagerService extends IPackageManager.Stub {
    ......

 
     
         public PackageManagerService(Context context, boolean factoryTest) {
        ......

 
     
             synchronized (mInstallLock) {
 
     
                 synchronized (mPackages) {
                ......

                File dataDir = Environment.getDataDirectory();
 
     
                     mAppDataDir = new File(dataDir, "data");
 
     
                     mSecureAppDataDir = new File(dataDir, "secure/data");
 
     
                     mDrmAppPrivateInstallDir = new File(dataDir, "app-private");

                ......

 
     
                     mFrameworkDir = new File(Environment.getRootDirectory(), "framework");
 
     
                     mDalvikCacheDir = new File(dataDir, "dalvik-cache");

                ......

 
     
                     // Find base frameworks (resource packages without code).
 
     
                     mFrameworkInstallObserver = new AppDirObserver(
 
     
                     mFrameworkDir.getPath(), OBSERVER_EVENTS, true);
                mFrameworkInstallObserver.startWatching();
                scanDirLI(mFrameworkDir, PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR,
 
     
                         scanMode | SCAN_NO_DEX, 0);

 
     
                     // 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);

 
     
                     mDrmAppInstallObserver = new AppDirObserver(
 
     
                         mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);
                mDrmAppInstallObserver.startWatching();
                scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
 
     
                         scanMode, 0);

                ......
            }
        }
    }

    ......
}

        这里会调用scanDirLI函数来扫描移动设备上的下面这五个目录中的Apk文件

         /system/framework

        /system/app

        /vendor/app

        /data/app

        /data/app-private

       Step 8. PackageManagerService.scanDirLI
       这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

 
     
     class PackageManagerService extends IPackageManager.Stub {
    ......

 
     
         private void scanDirLI(File dir, int flags, int scanMode, long currentTime) {
        String[] files = dir.list();
        ......

 
     
             int i;
 
     
             for (i=0; i<files.length; i++) {
 
     
                 File file = new File(dir, files[i]);
 
     
                 if (!isPackageFilename(files[i])) {
 
     
                     // Ignore entries which are not apk's
 
     
                     continue;
            }
            PackageParser.Package pkg = scanPackageLI(file,
                flags|PackageParser.PARSE_MUST_BE_APK, scanMode, currentTime);
 
     
                 // Don't mess around with apps in system partition.
 
     
                 if (pkg == null && (flags & PackageParser.PARSE_IS_SYSTEM) == 0 &&
                mLastScanError == PackageManager.INSTALL_FAILED_INVALID_APK) {
 
     
                         // Delete the apk
 
     
                         Slog.w(TAG, "Cleaning up failed install of " + file);
                    file.delete();
            }
        }
    }


    ......
}

         对于目录中的每一个文件，如果是以后Apk作为后缀名，那么就调用scanPackageLI函数来对它进行解析和安装。

     Step 9. PackageManagerService.scanPackageLI
   这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

 
      
      class PackageManagerService extends IPackageManager.Stub {
    ......

 
      
          private PackageParser.Package scanPackageLI(File scanFile,
 
      
                  int parseFlags, int scanMode, long currentTime) {
        ......

        String scanPath = scanFile.getPath();
        parseFlags |= mDefParseFlags;
 
      
              PackageParser pp = new PackageParser(scanPath);

        ......

 
      
              final PackageParser.Package pkg = pp.parsePackage(scanFile,
            scanPath, mMetrics, parseFlags);

        ......

 
      
              return scanPackageLI(pkg, parseFlags, scanMode | SCAN_UPDATE_SIGNATURE, currentTime);
    }

    ......
}

        这个函数首先会为这个Apk文件创建一个PackageParser实例，接着调用这个实例的parsePackage函数来对这个Apk文件进行解析。这个函数最后还会调用另外一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存在PackageManagerService中。