2_2_PackageManagerService

PackageManagerService

PMS也是SystemServer中一个非常重要的服务，主要有以下功能：
1.管理apk 安装包、apk安装、删除等
2.解析AndroidManifest.xml文件，主要包括节点信息解析target-name的分析和提炼，与AMS和WMS联系紧密
3.扫描本地文件，主要针对apk，主要是系统应用、本地安装应用等等

1.PMS的启动

xref: /frameworks/base/services/java/com/android/server/SystemServer.java

SystemServer进程创建执行中，会调用 startBootstrapServices(); 此方法内进行PMS的初始化调用

private void startBootstrapServices() {
...
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
                mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
        mFirstBoot = mPackageManagerService.isFirstBoot();
        mPackageManager = mSystemContext.getPackageManager();
...
}

xref: /frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java

public static PackageManagerService main(Context context, Installer installer,
            boolean factoryTest, boolean onlyCore) {
        // Self-check for initial settings.
        PackageManagerServiceCompilerMapping.checkProperties();

        PackageManagerService m = new PackageManagerService(context, installer,
                factoryTest, onlyCore);
        m.enableSystemUserPackages();
        ServiceManager.addService("package", m);
        final PackageManagerNative pmn = m.new PackageManagerNative();
        ServiceManager.addService("package_native", pmn);
        return m;
    }    

构造函数中，有传一个installer

public class Installer extends SystemService {
...
}

Installer是一个负责package安装、删除、迁移、更新的系统服务，PMS中需要管理package，那么就需要installer实例的协助

接下来，我们来看PackageManagerService的构造方法

1.1 初始化package解析和管理的对象

1.PackageDexOptimizer
2.DexManager
3.ArtManagerService
4.ProtectedPackages
创建PackageHandler处理package管理中消息
扫描系统app和系统目录下的jar
扫描应用app和应用目录下的lib

            // Find base frameworks (resource packages without code).
            scanDirTracedLI(frameworkDir, mDefParseFlags
                    | PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR
                    | PackageParser.PARSE_IS_PRIVILEGED,
                    scanFlags | SCAN_NO_DEX, 0);

            // Collected privileged system packages.
            final File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
            scanDirTracedLI(privilegedAppDir, mDefParseFlags
                    | PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR
                    | PackageParser.PARSE_IS_PRIVILEGED, scanFlags, 0);

            // Collect ordinary system packages.
            final File systemAppDir = new File(Environment.getRootDirectory(), "app");
            scanDirTracedLI(systemAppDir, mDefParseFlags
                    | PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

都是调用scanDirTracedLI，然后检索的目录不同
而 Environment.getRootDirectory(),获取的就是系统目录路径

private static final File DIR_ANDROID_ROOT = getDirectory(ENV_ANDROID_ROOT, "/system");
private static final File DIR_ANDROID_DATA = getDirectory(ENV_ANDROID_DATA, "/data");
public static File getRootDirectory() {
        return DIR_ANDROID_ROOT;
    }

我们来看看 scanDirTracedLI(...)的具体调用流程
scanDirTracedLI——>scanDirLl——> new ParallelPackageParser()构造——> submit()——> ParsePackage()
——> PackageParser()构造——>parseClusterPackage()——>ParseBaseApk——>ParseBaseApkCommon()

做的事情比较简单，总结起来就是解析/system/app 目录下面的所有apk，然后解析其中的文件，例如解析AndroidManifest.xml，
解析assets，解析res等等，分别使用存储结构存储起来，这些数据在后面都会用到