PMS服务启动原理详解

Posted 2023-03-15 杨斌并

PMS服务启动原理详解

从开机到app启动PMS服务处理机制与流程

• Apk安装是怎么进行的，PMS如何分析APK压缩文件

• 开机时PMS做了什么，data/app目录下的扫描与分析
• PakageParse类源码解读
• androidManifest为什么要按照Google设计的写，PMS告诉你真相
• AMS与PMS交互过程解析

PackageInstaller 原理简述

应用安装是智能机的主要特点，即用户可以把各种应用（如游戏等）安装到手机上，并可以对其进行卸载等管理操作。APK是Android Package的缩写，即Android安装包。APK是类似Symbian Sis或Sisx的文件格式。通过将APK文件直接传到Android模拟器或Android手机中执行即可安装。

Android应用安装有如下四种方式

• 系统应用安装――开机时完成，没有安装界面

• 网络下载应用安装――通过market应用完成，没有安装界面

• ADB工具安装――没有安装界面。

• 第三方应用安装――通过SD卡里的APK文件安装，有安装界面，由packageinstaller.apk应用处理安装及卸载过程的界面。

应用安装的流程及路径

• 应用安装涉及到如下几个目录:
  system/app系统自带的应用程序，无法删除data/app: 用户程序安装的目录，有删除权限。

安装时把apk文件复制到此目录data/app存放应用程序的数据data/dalvik-cache将apk中的dex文件安装到dalvik-cache目录下(dex文件是dalvik虚拟机的可执行文件,其大小约为原始apk文件大小的四分之一)

安装过程：复制APK安装包到data/app目录下，解压并扫描安装包，把dex文件(Dalvik字节码)保存到dalvik-cache目录，并data/data目录下创建对应的应用数据目录。
卸载过程：删除安装过程中在上述三个目录下创建的文件及目录。

一、系统应用安装：

PackageManagerService处理各种应用的安装，卸载，管理等工作，开机时由systemServer启动此服务

(源文件路径：android\\frameworks\\base\\services\\java\\com\\android\\server\\PackageManagerService.java)

PackageManagerService服务启动的流程：

• 首先扫描安装“system\\framework”目录下的jar包

• scanDirLI(mFrameworkDir,PackageParser.PARSE_IS_SYSTEM, scanMode | SCAN_NO_DEX);

• 第二步扫描安装“system\\app”目录下的各个系统应用

• scanDirLI(mSystemAppDir,PackageParser.PARSE_IS_SYSTEM,scanMode);

• 第三步扫描“data\\app”目录，即用户安装的第三方应用
  scanDirLI(mAppInstallDir, 0, scanMode);

• 第四步扫描" data\\app-private"目录，即安装DRM保护的APK文件（目前没有遇到过此类的应用）。
  scanDirLI(mDrmAppPrivateInstallDir,0, scanMode | SCAN_FORWARD_LOCKED);

安装应用的过程

1. scanDirLI(Filedir, int flags, int scanMode) 遍历安装指定目录下的文件

2.scanPackageLI(FilescanFile,File destCodeFile, FiledestResourceFile, int parseFlags,int scanMode) //安装package文件

3.scanPackageLI(File scanFile, File destCodeFile, FiledestResourceFile,PackageParser.Package pkg, intparseFlags, int scanMode)//通过解析安装包parsePackage获取到安装包的信息结构

4.mInstaller.install(pkgName,pkg.applicationInfo.uid,pkg.applicationInfo.uid);//实现文件复制的安装过程（源文件路径：frameworks\\base\\cmds\\installd\\installd.install）

PMS 作用

PMS 快速定位到 某个类 activity 的入口

• 时期： 开机时
• Android 5s 手机启动
• PMS 耗费70%
• 缓存 信息缓存到我的数据库

PackageParser.java

  /**
     * Representation of a full package parsed from APK files on disk. A package
     * consists of a single base APK, and zero or more split APKs.
     *
     * Deprecated internally. Use AndroidPackage instead.
     */
 public final static class Package implements Parcelable 

        @UnsupportedAppUsage
        public String packageName;

        // The package name declared in the manifest as the package can be
        // renamed, for example static shared libs use synthetic package names.
        public String manifestPackageName;

        /** Names of any split APKs, ordered by parsed splitName */
        public String[] splitNames;

        // TODO: work towards making these paths invariant

        public String volumeUuid;

        /**
         * Path where this package was found on disk. For monolithic packages
         * this is path to single base APK file; for cluster packages this is
         * path to the cluster directory.
         */
        public String codePath;

        /** Path of base APK */
        public String baseCodePath;
        /** Paths of any split APKs, ordered by parsed splitName */
        public String[] splitCodePaths;

        /** Revision code of base APK */
        public int baseRevisionCode;
        /** Revision codes of any split APKs, ordered by parsed splitName */
        public int[] splitRevisionCodes;

        /** Flags of any split APKs; ordered by parsed splitName */
        public int[] splitFlags;

        /**
         * Private flags of any split APKs; ordered by parsed splitName.
         *
         * @hide
         */
        public int[] splitPrivateFlags;

        public boolean baseHardwareAccelerated;

        // For now we only support one application per package.
        @UnsupportedAppUsage
        public ApplicationInfo applicationInfo = new ApplicationInfo();

        @UnsupportedAppUsage
        public final ArrayList<Permission> permissions = new ArrayList<Permission>(0);
        @UnsupportedAppUsage
        public final ArrayList<PermissionGroup> permissionGroups = new ArrayList<PermissionGroup>(0);
        @UnsupportedAppUsage
        public final ArrayList<Activity> activities = new ArrayList<Activity>(0);
        @UnsupportedAppUsage
        public final ArrayList<Activity> receivers = new ArrayList<Activity>(0);
        @UnsupportedAppUsage
        public final ArrayList<Provider> providers = new ArrayList<Provider>(0);
        @UnsupportedAppUsage
        public final ArrayList<Service> services = new ArrayList<Service>(0);
        @UnsupportedAppUsage
        public final ArrayList<Instrumentation> instrumentation = new ArrayList<Instrumentation>(0);

SystemServer

        // Start services.
        try 
            t.traceBegin("StartServices");
            //启动引导服务 引导服务中启动 AMS, WMS, PMS
            startBootstrapServices(t);
            //启动核心服务
            startCoreServices(t);
            //启动其他服务
            startOtherServices(t);
         catch (Throwable ex) 
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
         finally 
            t.traceEnd(); // StartServices
        

PackageParser.java

//解析AndroidManifest.xml
private Package parseBaseApk(File apkFile, AssetManager assets, int flags)
            throws PackageParserException 
        final String apkPath = apkFile.getAbsolutePath();

        String volumeUuid = null;
        if (apkPath.startsWith(MNT_EXPAND)) 
            final int end = apkPath.indexOf('/', MNT_EXPAND.length());
            volumeUuid = apkPath.substring(MNT_EXPAND.length(), end);
        

        mParseError = PackageManager.INSTALL_SUCCEEDED;
        mArchiveSourcePath = apkFile.getAbsolutePath();

        if (DEBUG_JAR) Slog.d(TAG, "Scanning base APK: " + apkPath);

        XmlResourceParser parser = null;
        try 
            final int cookie = assets.findCookieForPath(apkPath);
            if (cookie == 0) 
                throw new PackageParserException(INSTALL_PARSE_FAILED_BAD_MANIFEST,
                        "Failed adding asset path: " + apkPath);
            
            
            /解析AndroidManifest.xml///
            
            parser = assets.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);
            final Resources res = new Resources(assets, mMetrics, null);

            final String[] outError = new String[1];
            final Package pkg = parseBaseApk(apkPath, res, parser, flags, outError);
            if (pkg == null) 
                throw new PackageParserException(mParseError,
                        apkPath + " (at " + parser.getPositionDescription() + "): " + outError[0]);
            

            pkg.setVolumeUuid(volumeUuid);
            pkg.setApplicationVolumeUuid(volumeUuid);
            pkg.setBaseCodePath(apkPath);
            pkg.setSigningDetails(SigningDetails.UNKNOWN);

            return pkg;

         catch (PackageParserException e) 
            throw e;
         catch (Exception e) 
            throw new PackageParserException(INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION,
                    "Failed to read manifest from " + apkPath, e);
         finally 
            IoUtils.closeQuietly(parser);
        
    

• PMS 用来管理所有的package信息，包括安装、卸载、更新以及解析AndroidManifest.xml以组织相应的数据结构这些数据结构将会被PMS、
• data/app/pakage/base.apk
• system/app/pakage/base.apk
• systemService 启动 让后 在run 方法中启动 引导服务， 引导服务中启动 packageManageService, 然后 packageManageService 扫描 data/app/pakage/base.apk， system/app/pakage/base.apk 包下的文件，加载base.apk 储存到Package 对象里面，方便与查找 四大组件
• pms 解析手机里面所有apk的manifest.xml 文件
• ams pms交互，快速找到Activity(javabean) 再来反射 启动Activity 对象