核心功能

1.解析AndroidNanifest.xml清单文件，解析清单文件中的所有节点信息
2.扫描.apk文件，安装系统应用，安装本地应用等
3.管理本地应用，主要有， 安装，卸载，应用信息查询 等

启动流程

PackageManagerService和AMS一样都在SystemServer的startBootstrapServices中创建

Installer installer = mSystemServiceManager.startService(Installer.class);
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
               mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
//PackageManagerService
main(Context context, Installer installer,boolean factoryTest, boolean onlyCore) {
    PackageManagerService m = new PackageManagerService(injector, onlyCore, factoryTest);
    ServiceManager.addService("package", m);//将PMS注册到SM中

    final PackageManagerNative pmn = m.new PackageManagerNative();
    ServiceManager.addService("package_native", pmn);
}

public PackageManagerService(Injector injector, boolean onlyCore, boolean factoryTest) {
阶段1：BOOT_PROGRESS_PMS_START
阶段2：BOOT_PROGRESS_PMS_SYSTEM_SCAN_START
阶段3：BOOT_PROGRESS_PMS_DATA_SCAN_START
阶段4：BOOT_PROGRESS_PMS_SCAN_END
阶段5：BOOT_PROGRESS_PMS_READY
}

阶段1：BOOT_PROGRESS_PMS_START

public PackageManagerService(Injector injector, boolean onlyCore, boolean factoryTest) {
    mMetrics = new DisplayMetrics(); // 分辨率配置
    mInstaller = installer; //保存installer对象
    mPermissionManager = injector.getPermissionManagerServiceInternal();//创建权限管理服务
    mSettings = injector.getSettings();//创建setting 
    //添加system, phone, log, nfc, bluetooth, shell，se，networkstack 这8种shareUserId到mSettings；

    //DexOpt优化
    mPackageDexOptimizer = new PackageDexOptimizer(mInstaller, mInstallLock, mContext,"*dexopt*");
    mDexManager = new DexManager(mContext, this, mPackageDexOptimizer,installer, mInstallLock);
    // ART虚拟机管理服务
    mArtManagerService = new ArtManagerService(mContext, this, mInstaller, mInstallLock);
    //创建PackageManager的handler线程，循环处理外部安装相关消息
    mHandlerThread = new ServiceThread(TAG,Process.THREAD_PRIORITY_BACKGROUND, true/*allowIo*/);
    mHandlerThread.start();
    mHandler = new PackageHandler(mHandlerThread.getLooper());
}
//Settings  阶段1：BOOT_PROGRESS_PMS_START
Settings(File dataDir, PermissionSettings permission,Object lock) {
    //packages.xml 所有安装app信息  PKMS 扫描完目标文件夹后会创建该文件。
    //当系统进行程序安装、卸载和更新等操作时，均会更新该文件。该文件保存了系统中与 package 相关的一些信息。
    mSettingsFilename = new File(mSystemDir, "packages.xml");
    //所有安装app信息的备份
    mBackupSettingsFilename = new File(mSystemDir, "packages-backup.xml");
    //描述系统中存在的所有非系统自带的 APK 的信息。当这些程序有变动时，PKMS 就会更新该文件。
    mPackageListFilename = new File(mSystemDir, "packages.list");
    final File kernelDir = new File("/config/sdcardfs");
    mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");
    mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");
}
boolean readLPw(@NonNull List<UserInfo> users) {
    //解析"/data/system/packages.xml"
    XmlPullParser parser = Xml.newPullParser();
    parser.setInput(str, StandardCharsets.UTF_8.name());
}

阶段2：BOOT_PROGRESS_PMS_SYSTEM_SCAN_START

scanDirTracedLI()
扫描system/vendor/product/odm/oem等目录的priv-app、app、overlay包；系统apk的安装

private void scanDirLI(File scanDir, int parseFlags, int scanFlags, long currentTime,
    PackageParser2 packageParser, ExecutorService executorService) {
    ParallelPackageParser parallelPackageParser =new ParallelPackageParser(packageParser, executorService);
    for (File file : files) {
      parallelPackageParser.submit(file, parseFlags);//将apk放入队列中
    }
    for (; fileCount > 0; fileCount--) {
            ParallelPackageParser.ParseResult parseResult = parallelPackageParser.take();
            //下面去解析
            //PackageParser.parseBaseApk()主要是对AndroidManifest.xml进行解析，解析后所有的信息放在Package对象中
    }
}

阶段3：BOOT_PROGRESS_PMS_DATA_SCAN_START

scanDirTracedLI()
扫描data目录的应用信息，及时更新，祛除不必要的数据；应用apk的安装

阶段4：BOOT_PROGRESS_PMS_SCAN_END

sdk版本变更，更新权限；OTA升级后首次启动，清除不必要的缓存数据；权限等默认项更新完后，清理相关数据；更新package.xml

阶段5：BOOT_PROGRESS_PMS_READY

安装流程

image.png

安装时
1、把apk文件复制到data/app/包名目录下，
2、开辟应用程序的数据文件夹（so库，缓存）
3、将apk的dex安装到data/dalvik-cache目录下