PackageManagerService初始化

2023-11-05 06:12
文章标签 初始化 packagemanagerservice

本文主要是介绍PackageManagerService初始化，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

参考资料：PMS 第 1 篇 - PackageManagerService 初始化

这个是基于Android 7的，我看的代码是Android 9

前言

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 其他 service 和 application 使用到。

一、PMS的启动

先来看 SystemServer 中 PackageManagerService 的启动代码：
位置：frameworks/base/services/java/com/android/server/SystemServer.java

private void startBootstrapServices() {//...这里的installer也是一个系统服务traceBeginAndSlog("StartInstaller");Installer installer = mSystemServiceManager.startService(Installer.class);traceEnd();//...traceBeginAndSlog("StartPackageManagerService");mPackageManagerService = PackageManagerService.main(mSystemContext, installer,mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);mFirstBoot = mPackageManagerService.isFirstBoot();mPackageManager = mSystemContext.getPackageManager();traceEnd();//...
}

main 函数很简单，只有短短几行代码，执行时间却较长，主要原因是 PKMS 在其构造函数中做了很多“重体力活”，这也是 Android 启动速度慢的主要原因之一。
位置：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();		//检测和设置某些编译器相关的属性PackageManagerService m = new PackageManagerService(context, installer,factoryTest, onlyCore);	//构造一个 PMS 对象m.enableSystemUserPackages();		//启用系统用户的包，可确保在Android系统启动时，系统应用程序已正确安装并可用ServiceManager.addService("package", m);		//调用 ServiceManager 的 addService 注册 PackageManagerService 服务final PackageManagerNative pmn = m.new PackageManagerNative();ServiceManager.addService("package_native", pmn);		//启动了PackageManagerNative的服务return m;}

构造函数有如下 4 个参数：

  • 第一个参数：系统进程的上下文实例；
  • 第二个参数：Installer 对象，用于和 Installd 通信使用，我们后面分析 Installd 再来介绍；
  • 第三个参数：factoryTest 为出厂测试，默认为 false；
  • 第四个参数：onlyCore 表示是否只加载核心的应用，默认也为 false。

整个函数的作用是创建和配置PackageManagerService对象，并将其注册到系统服务中，以便其他组件可以访问它。

二、PMS的初始化

位置：frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java
PackageManagerService 的构造器代码结构如下

    public PackageManagerService(Context context, Installer installer,boolean factoryTest, boolean onlyCore) {LockGuard.installLock(mPackages, LockGuard.INDEX_PACKAGES);Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "create package manager");EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,SystemClock.uptimeMillis());//...synchronized (mInstallLock) {synchronized (mPackages) {// Expose private service for system components to use.LocalServices.addService(PackageManagerInternal.class, new PackageManagerInternalImpl());sUserManager = new UserManagerService(context, this,new UserDataPreparer(mInstaller, mInstallLock, mContext, mOnlyCore), mPackages);mPermissionManager = PermissionManagerService.create(context,new DefaultPermissionGrantedCallback() {@Overridepublic void onDefaultRuntimePermissionsGranted(int userId) {synchronized(mPackages) {mSettings.onDefaultRuntimePermissionsGrantedLPr(userId);}}}, mPackages /*externalLock*/);mDefaultPermissionPolicy = mPermissionManager.getDefaultPermissionGrantPolicy();mSettings = new Settings(mPermissionManager.getPermissionSettings(), mPackages);}//...// Create sub-components that provide services / data. Order here is important.synchronized (mInstallLock) {synchronized (mPackages) {//....EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,startTime);//...if (!mOnlyCore) {EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,SystemClock.uptimeMillis());}//...EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,SystemClock.uptimeMillis());Slog.i(TAG, "Time to scan packages: "+ ((SystemClock.uptimeMillis()-startTime)/1000f)+ " seconds");//...Runtime.getRuntime().gc();Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);// The initial scanning above does many calls into installd while// holding the mPackages lock, but we're mostly interested in yelling// once we have a booted system.mInstaller.setWarnIfHeld(mPackages);Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);Log.d("preinstall"," start preinstall"+System.currentTimeMillis());mHandler.postDelayed(new Runnable() {public void run() {try{SystemProperties.set("ctl.start", "preinstall");}catch (Exception e){Log.d("preinstall"," preinstall failed");e.printStackTrace();}}},1200);}

根据 EventLog 可以将 PMS 的初始化分为以下几个过程：

  • 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

下面，来看看 PackageManangerService 的构造器方法代码，为了便于分析，我们把 PackageManagerService 构造器的代码分为如下几个部分：

2.1 BOOT_PROGRESS_PMS_START

public PackageManagerService(Context context, Installer installer,boolean factoryTest, boolean onlyCore) {LockGuard.installLock(mPackages, LockGuard.INDEX_PACKAGES);Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "create package manager");EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,SystemClock.uptimeMillis());if (mSdkVersion <= 0) {//【1】mSdkVersion 是 PKMS 的成员变量，定义的时候进行赋值//其值取自系统属性“ro.build.version.sdk”，即编译的 SDK 版本Slog.w(TAG, "**** ro.build.version.sdk not set!");}mContext = context;mFactoryTest = factoryTest;		// 默认为 false，即运行在非工厂模式下mOnlyCore = onlyCore;		// 默认为 false,标记是否是只加载核心服务mMetrics = new DisplayMetrics();	//【2】用于存储与显示屏相关的一些属性，例如屏幕的宽 / 高尺寸，分辨率等信息。mInstaller = installer;	//【3】初始化 mInstaller 对象，installer 对象和 Native 进程 installd 交互！// Create sub-components that provide services / data. Order here is important.//使用synchronized关键字来同步访问mInstallLock和mPackages。这是为了保证在多线程环境下的数据安全性，确保只有一个线程可以同时执行这段代码块synchronized (mInstallLock) {synchronized (mPackages) {// Expose private service for system components to use.LocalServices.addService(PackageManagerInternal.class, new PackageManagerInternalImpl());sUserManager = new UserManagerService(context, this,new UserDataPreparer(mInstaller, mInstallLock, mContext, mOnlyCore), mPackages);mPermissionManager = PermissionManagerService.create(context,new DefaultPermissionGrantedCallback() {@Overridepublic void onDefaultRuntimePermissionsGranted(int userId) {synchronized(mPackages) {mSettings.onDefaultRuntimePermissionsGrantedLPr(userId);}}}, mPackages /*externalLock*/);//【10】创建 DefaultPermissionGrantPolicy 对象，用于给某些预制的apk，给予权限,也可以撤销mDefaultPermissionPolicy = mPermissionManager.getDefaultPermissionGrantPolicy();mSettings = new Settings(mPermissionManager.getPermissionSettings(), mPackages);}}//【3】在 Settings 中，创建 packages.xml、packages-backup.xml、packages.list 等文件对象// 并添加 system, phone, log, nfc, bluetooth, shell 这六种 shareUserId 到 mSettings，后面扫描和安装有用！mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.log", LOG_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.shell", SHELL_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.se", SE_UID,ApplicationInfo.FLAG_SYSTEM, ApplicationInfo.PRIVATE_FLAG_PRIVILEGED);String separateProcesses = SystemProperties.get("debug.separate_processes");if (separateProcesses != null && separateProcesses.length() > 0) {if ("*".equals(separateProcesses)) {mDefParseFlags = PackageParser.PARSE_IGNORE_PROCESSES;mSeparateProcesses = null;Slog.w(TAG, "Running with debug.separate_processes: * (ALL)");} else {mDefParseFlags = 0;mSeparateProcesses = separateProcesses.split(",");Slog.w(TAG, "Running with debug.separate_processes: "+ separateProcesses);}} else {mDefParseFlags = 0;mSeparateProcesses = null;}//【4】创建 PackageDexOptimizer 对象，用于 dex 优化！mPackageDexOptimizer = new PackageDexOptimizer(installer, mInstallLock, context,"*dexopt*");DexManager.Listener dexManagerListener = DexLogger.getListener(this,installer, mInstallLock);mDexManager = new DexManager(mContext, this, mPackageDexOptimizer, installer, mInstallLock,dexManagerListener);mArtManagerService = new ArtManagerService(mContext, this, installer, mInstallLock);//【5】创建 MoveCallbacks 对象，用于操作回滚！mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());//【6】创建 OnPermissionChangeListeners 对象，用于监听权限改变！mOnPermissionChangeListeners = new OnPermissionChangeListeners(FgThread.get().getLooper());getDefaultDisplayMetrics(context, mMetrics);	// 获得默认的显示//【7】创建 SystemConfig 对象，用于获取系统配置信息// 主要有 /system/etc/ 目录和 /system/etc/sysconfig 目录下的 sysconfig 和 permissions 文件夹xml文件Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "get system config");SystemConfig systemConfig = SystemConfig.getInstance();mAvailableFeatures = systemConfig.getAvailableFeatures();Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);mProtectedPackages = new ProtectedPackages(mContext);synchronized (mInstallLock) {// writersynchronized (mPackages) {//【8】建立并启动一个名为 “PackageManager” 的 HandlerThread，类型是 ServiceThread，处理安装卸载的消息！mHandlerThread = new ServiceThread(TAG,Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);mHandlerThread.start();//【9】创建一个 PackageHandler 对象，绑定前面创建的 HandlerThread！mHandler = new PackageHandler(mHandlerThread.getLooper());mProcessLoggingHandler = new ProcessLoggingHandler();Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);mInstantAppRegistry = new InstantAppRegistry(this);//【13】处理共享库！ArrayMap<String, String> libConfig = systemConfig.getSharedLibraries();final int builtInLibCount = libConfig.size();for (int i = 0; i < builtInLibCount; i++) {String name = libConfig.keyAt(i);String path = libConfig.valueAt(i);addSharedLibraryLPw(path, null, name, SharedLibraryInfo.VERSION_UNDEFINED,SharedLibraryInfo.TYPE_BUILTIN, PLATFORM_PACKAGE_NAME, 0);}SELinuxMMAC.readInstallPolicy();Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "loadFallbacks");FallbackCategoryProvider.loadFallbacks();Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "read user settings");// 判断是否是第一次开机！并获得上一次的安装信息！mFirstBoot = !mSettings.readLPw(sUserManager.getUsers(false));Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);// Clean up orphaned packages for which the code path doesn't exist// and they are an update to a system app - caused by bug/32321269// 移除哪些 codePath 无效的 Package，恢复处于 system 目录下的同名 packagefinal int packageSettingCount = mSettings.mPackages.size();for (int i = packageSettingCount - 1; i >= 0; i--) {PackageSetting ps = mSettings.mPackages.valueAt(i);if (!isExternal(ps) && (ps.codePath == null || !ps.codePath.exists())&& mSettings.getDisabledSystemPkgLPr(ps.name) != null) {mSettings.mPackages.removeAt(i);mSettings.enableSystemPackageLPw(ps.name);}}if (mFirstBoot) {	// 如果是第一次开机，从另外一个系统拷贝 odex 文件到当前系统的 data 分区requestCopyPreoptedFiles();}//获取和设置定制的解决方案组件名称，以便在后续的操作中使用它//传入config_customResolverActivity字符串资源的ID，以获取系统配置文件中定制的解决方案组件名称。String customResolverActivity = Resources.getSystem().getString(R.string.config_customResolverActivity);//如果获取到的字符串为空，则将customResolverActivity变量赋值为null。if (TextUtils.isEmpty(customResolverActivity)) {customResolverActivity = null;} else {mCustomResolverComponentName = ComponentName.unflattenFromString(customResolverActivity);}long startTime = SystemClock.uptimeMillis();//...这里开始是第二阶段	EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,startTime);

流程总结：

  • 创建 Settings 对象，创建 packages.xml、packages-backup.xml、packages.list
    等文件对象并添加 system, phone, log, nfc, bluetooth, shell 这六种 shareUserId 到
    mSettings，后面扫描和安装有用；
  • 初始化 mInstaller 对象，用于和 installed 交互；
  • 创建 PackageDexOptimizer 对象，用于 dex 优化；
  • 创建 OnPermissionChangeListeners 对象，用于监听权限改变；
  • 创建 SystemConfig 对象，用于获取系统配置信息；
  • 创建用户管理服务！
  • 获得权限信息！
  • 获得系统共享库！

2.2 PMS_SYSTEM_SCAN_START

接上面

			//...long startTime = SystemClock.uptimeMillis();EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,startTime);// 获得环境变量：BOOTCLASSPATH 和 SYSTEMSERVERCLASSPATH！final String bootClassPath = System.getenv("BOOTCLASSPATH");final String systemServerClassPath = System.getenv("SYSTEMSERVERCLASSPATH");if (bootClassPath == null) {Slog.w(TAG, "No BOOTCLASSPATH found!");}if (systemServerClassPath == null) {Slog.w(TAG, "No SYSTEMSERVERCLASSPATH found!");}// 获得目录 /system/framework，对其目录下的文件进行优化File frameworkDir = new File(Environment.getRootDirectory(), "framework");// 获得系统版本信息final VersionInfo ver = mSettings.getInternalVersion();// 判断是否是 OTA 升级mIsUpgrade = !Build.FINGERPRINT.equals(ver.fingerprint);if (mIsUpgrade) {logCriticalInfo(Log.INFO,"Upgrading from " + ver.fingerprint + " to " + Build.FINGERPRINT);}// when upgrading from pre-M, promote system app permissions from install to runtime// 判断是否是从 Android 6.0 升级过来的，如果是就需要把系统 app 的权限从安装时提高到运行时mPromoteSystemApps =mIsUpgrade && ver.sdkVersion <= Build.VERSION_CODES.LOLLIPOP_MR1;// When upgrading from pre-N, we need to handle package extraction like first boot,// as there is no profiling data available.// 判断是否是从 Android 7.0 升级过来的mIsPreNUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N;// 判断是否是从 Android 7.1 升级过来的mIsPreNMR1Upgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N_MR1;// save off the names of pre-existing system packages prior to scanning; we don't// want to automatically grant runtime permissions for new system apps// 保存从 Android 6.0 升级前已经存在的系统应用包，并对他们进行优先扫描！if (mPromoteSystemApps) {Iterator<PackageSetting> pkgSettingIter = mSettings.mPackages.values().iterator();while (pkgSettingIter.hasNext()) {PackageSetting ps = pkgSettingIter.next();if (isSystemApp(ps)) {mExistingSystemPackages.add(ps.name);}}}//为包解析器准备一个缓存目录，并将其赋值给mCacheDir变量，以便在后续的包解析操作中使用mCacheDir = preparePackageParserCache(mIsUpgrade);// Set flag to monitor and not change apk file paths when// scanning install directories.// 设置扫描参数！int scanFlags = SCAN_BOOTING | SCAN_INITIAL;if (mIsUpgrade || mFirstBoot) {scanFlags = scanFlags | SCAN_FIRST_BOOT_OR_UPGRADE;}// Collect vendor/product overlay packages. (Do this before scanning any apps.)// For security and version matching reason, only consider// overlay packages if they reside in the right directory.// 扫描收集目录 /vendor/overlay 下的供应商应用包！scanDirTracedLI(new File(VENDOR_OVERLAY_DIR),mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR,0);// 扫描收集目录 /product/overlayscanDirTracedLI(new File(PRODUCT_OVERLAY_DIR),mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRODUCT,0);mParallelPackageParserCallback.findStaticOverlayPackages();// Find base frameworks (resource packages without code).// 扫描收集目录 /system/framework 下的应用包！scanDirTracedLI(frameworkDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_NO_DEX| SCAN_AS_SYSTEM| SCAN_AS_PRIVILEGED,0);// Collect privileged system packages.// 扫描收集目录 /system/priv-app 下的应用包！ final File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");scanDirTracedLI(privilegedAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRIVILEGED,0);// 扫描收集目录 /system/app 下的应用包！ // Collect ordinary system packages.final File systemAppDir = new File(Environment.getRootDirectory(), "app");scanDirTracedLI(systemAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM,0);// Collect privileged vendor packages.// 扫描收集目录 /vendor/priv-app 下的应用包！File privilegedVendorAppDir = new File(Environment.getVendorDirectory(), "priv-app");try {privilegedVendorAppDir = privilegedVendorAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}// 扫描收集目录 /vendor/app 下的应用包！scanDirTracedLI(privilegedVendorAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR| SCAN_AS_PRIVILEGED,0);// Collect ordinary vendor packages.// 扫描收集目录 /vendor/app 下的应用包！ File vendorAppDir = new File(Environment.getVendorDirectory(), "app");try {vendorAppDir = vendorAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}scanDirTracedLI(vendorAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR,0);// Collect privileged odm packages. /odm is another vendor partition// other than /vendor.// 扫描收集目录 /odm/priv-app 下的应用包！File privilegedOdmAppDir = new File(Environment.getOdmDirectory(),"priv-app");try {privilegedOdmAppDir = privilegedOdmAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}scanDirTracedLI(privilegedOdmAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR| SCAN_AS_PRIVILEGED,0);// Collect ordinary odm packages. /odm is another vendor partition// other than /vendor.// 扫描收集目录 /odm/app 下的应用包！File odmAppDir = new File(Environment.getOdmDirectory(), "app");try {odmAppDir = odmAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}scanDirTracedLI(odmAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR,0);// Collect all OEM packages.// 扫描收集目录 /oem/app 下的应用包！ final File oemAppDir = new File(Environment.getOemDirectory(), "app");scanDirTracedLI(oemAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_OEM,0);// Collected privileged product packages.// 扫描收集目录 /product/priv-app 下的应用包！ File privilegedProductAppDir = new File(Environment.getProductDirectory(), "priv-app");try {privilegedProductAppDir = privilegedProductAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}scanDirTracedLI(privilegedProductAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRODUCT| SCAN_AS_PRIVILEGED,0);// Collect ordinary product packages.// 扫描收集目录 /product/app 下的应用包！File productAppDir = new File(Environment.getProductDirectory(), "app");try {productAppDir = productAppDir.getCanonicalFile();} catch (IOException e) {// failed to look up canonical path, continue with original one}scanDirTracedLI(productAppDir,mDefParseFlags| PackageParser.PARSE_IS_SYSTEM_DIR,scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRODUCT,0);Log.d("preinstall", "scanDirTracedLI: "+System.currentTimeMillis());// Prune any system packages that no longer exist.// 删除已经不存在的系统应用包！// possiblyDeletedUpdatedSystemApps 和 stubSystemApps 用于存储可能已删除或更新的系统应用的包名和存根应用的包名final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<>();// Stub packages must either be replaced with full versions in the /data// partition or be disabled.final List<String> stubSystemApps = new ArrayList<>();if (!mOnlyCore) {// do this first before mucking with mPackages for the "expecting better" casefinal Iterator<PackageParser.Package> pkgIterator = mPackages.values().iterator();while (pkgIterator.hasNext()) {final PackageParser.Package pkg = pkgIterator.next();if (pkg.isStub) {	//对于标记为存根应用的包，将其包名添加到 stubSystemApps 列表中stubSystemApps.add(pkg.packageName);}}final Iterator<PackageSetting> psit = mSettings.mPackages.values().iterator();while (psit.hasNext()) {PackageSetting ps = psit.next();// 如果不是系统应用，跳过！if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) == 0) {continue;}final PackageParser.Package scannedPkg = mPackages.get(ps.name);if (scannedPkg != null) {		// 如果系统应用包已经被扫描到了（scannedPkg ！= null），就不会被删掉！/** If the system app is both scanned and in the* disabled packages list, then it must have been* added via OTA. Remove it from the currently* scanned package so the previously user-installed* application can be scanned.*/// 如果系统应用包不仅被扫描过（在mPackages中），并且在不可用列表中！// 说明一定是通过覆盖安装的，移除之前扫描的结果，保证之前用户安装的应用能够被扫描！if (mSettings.isDisabledSystemPackageLPr(ps.name)) {logCriticalInfo(Log.WARN,"Expecting better updated system app for " + ps.name+ "; removing system app.  Last known"+ " codePath=" + ps.codePathString+ ", versionCode=" + ps.versionCode+ "; scanned versionCode=" + scannedPkg.getLongVersionCode());// 将之前的扫描结果移除！removePackageLI(scannedPkg, true);// 将这包添加到 mExpectingBetter 列表中！mExpectingBetter.put(ps.name, ps.codePath);}// 跳出循环，确保不会被删掉！continue;}// 如果系统应用包没有被扫描，并且他也不在不可用的列表中，移除它，这个包不存在！if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {psit.remove();logCriticalInfo(Log.WARN, "System package " + ps.name+ " no longer exists; it's data will be wiped");// Actual deletion of code and data will be handled by later// reconciliation step} else {// 如果系统应用包没有被扫描，却在不可用的列表中，就将他加入到 // possiblyDeletedUpdatedSystemApps 集合中，需要被删除！final PackageSetting disabledPs =mSettings.getDisabledSystemPkgLPr(ps.name);if (disabledPs.codePath == null || !disabledPs.codePath.exists()|| disabledPs.pkg == null) {possiblyDeletedUpdatedSystemApps.add(ps.name);}}}}//delete tmp files // 移除临时文件deleteTempPackageFiles();final int cachedSystemApps = PackageParser.sCachedPackageReadCount.get();// Remove any shared userIDs that have no associated packages// 移除没有和应用程序包相关联的共享用户 id！mSettings.pruneSharedUsersLPw();final long systemScanTime = SystemClock.uptimeMillis() - startTime;final int systemPackagesCount = mPackages.size();Slog.i(TAG, "Finished scanning system apps. Time: " + systemScanTime+ " ms, packageCount: " + systemPackagesCount+ " , timePerPackage: "+ (systemPackagesCount == 0 ? 0 : systemScanTime / systemPackagesCount)+ " , cached: " + cachedSystemApps);if (mIsUpgrade && systemPackagesCount > 0) {MetricsLogger.histogram(null, "ota_package_manager_system_app_avg_scan_time",((int) systemScanTime) / systemPackagesCount);}//...

2.2.1 主要流程：

  • 获得环境变量：BOOTCLASSPATH 和 SYSTEMSERVERCLASSPATH！

  • 对共享库进行 odex 优化操作！

  • 判断是否是通过 OTA 升级的

    • 如果是从 6.0 升级过来的，保存从 Android 6.0 升级前已经存在的系统应用包，并对他们进行优先扫描！

  • 扫描收集以下目录中的供应商应用包！

    • /vendor/overlay
    • /system/framework
    • /system/priv-app
    • /system/app
    • /vendor/app
    • /oem/app
    • …

  • 删除已经不存在的系统应用包！

  • 清理所有安装不完全的应用包！

  • 移除临时文件

  • 移除没有和应用程序包相关联的共享用户 id

2.2.2 细节分析

环境变量

我们可以通过 adb shell env 来查看系统所有的环境变量及相应值。也可通过命令：adb shell echo $var 来看指定的环境变量的值！

  • SYSTEMSERVERCLASSPATH
evk_8mm:/ # echo $SYSTEMSERVERCLASSPATH
/system/framework/services.jar:
/system/framework/ethernet-service.jar:
/system/framework/wifi-service.jar:
/system/framework/com.android.location.provider.jar
  • BOOTCLASSPATH
    该环境变量内容较多，第三方定制的系统可能有所不同，原生内容包含 /system/framework目录下的framework.jar，ext.jar，core-libart.jar，telephony-common.jar，ims-common.jar，core-junit.jar等文件！
evk_8mm:/ # echo $BOOTCLASSPATH
/system/framework/core-oj.jar:
/system/framework/core-libart.jar:
/system/framework/conscrypt.jar:
/system/framework/okhttp.jar:
/system/framework/bouncycastle.jar:
/system/framework/apache-xml.jar:
/system/framework/ext.jar:
/system/framework/framework.jar:
/system/framework/telephony-common.jar:
/system/framework/voip-common.jar:
/system/framework/ims-common.jar:
/system/framework/android.hidl.base-V1.0-java.jar:
/system/framework/android.hidl.manager-V1.0-java.jar:
/system/framework/framework-oahl-backward-compatibility.jar:
/system/framework/android.test.base.jar
dexopt 优化

执行 dex 优化操作的文件有以下几类：

  • mSharedLibraries：该共享库下的所有文件，是由 SystemConfig 构造函数中赋值的；
  • /system/framework：该目录的所有 apk 和 jar 文件；
scanDirLI 扫描系统目录

扫描指定目录下的 apk 文件，最终调用 PackageParser.parseBaseApk 来完成 AndroidManifest.xml 文件的解析，生成 Application，activity，service，broadcast，provider 等信息。

  • /vendor/overlay
  • /system/framework
  • /system/priv-app
  • /system/app
  • /vendor/app
  • /oem/app

2.3 BOOT_PROGRESS_PMS_DATA_SCAN_START

			//... 接上面if (!mOnlyCore) {EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,SystemClock.uptimeMillis());//这里似乎还是在扫描scanDirTracedLI(sAppInstallDir, 0, scanFlags | SCAN_REQUIRE_KNOWN, 0);scanDirTracedLI(sDrmAppPrivateInstallDir, mDefParseFlags| PackageParser.PARSE_FORWARD_LOCK,scanFlags | SCAN_REQUIRE_KNOWN, 0);// Remove disable package settings for updated system apps that were// removed via an OTA. If the update is no longer present, remove the// app completely. Otherwise, revoke their system privileges.// 执行最终的清理工作，以确保系统中不存在已删除或更新的系统应用的残留文件和数据，并撤消相关应用的系统权限。for (String deletedAppName : possiblyDeletedUpdatedSystemApps) {PackageParser.Package deletedPkg = mPackages.get(deletedAppName);mSettings.removeDisabledSystemPackageLPw(deletedAppName);final String msg;if (deletedPkg == null) {// should have found an update, but, we didn't; remove everythingmsg = "Updated system package " + deletedAppName+ " no longer exists; removing its data";// Actual deletion of code and data will be handled by later// reconciliation step} else {// found an update; revoke system privilegesmsg = "Updated system package + " + deletedAppName+ " no longer exists; revoking system privileges";// Don't do anything if a stub is removed from the system image. If// we were to remove the uncompressed version from the /data partition,// this is where it'd be done.final PackageSetting deletedPs = mSettings.mPackages.get(deletedAppName);deletedPkg.applicationInfo.flags &= ~ApplicationInfo.FLAG_SYSTEM;deletedPs.pkgFlags &= ~ApplicationInfo.FLAG_SYSTEM;}logCriticalInfo(Log.WARN, msg);}// 确保所有在用户 data 分区的应用都显示出来了，如果无法显示// 那就回滚，显示 system 分区的！for (int i = 0; i < mExpectingBetter.size(); i++) {final String packageName = mExpectingBetter.keyAt(i);if (!mPackages.containsKey(packageName)) {final File scanFile = mExpectingBetter.valueAt(i);logCriticalInfo(Log.WARN, "Expected better " + packageName+ " but never showed up; reverting to system");// 设置扫描参数，不同的目录，扫描参数不同！final @ParseFlags int reparseFlags;final @ScanFlags int rescanFlags;if (FileUtils.contains(privilegedAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRIVILEGED;} else if (FileUtils.contains(systemAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM;} else if (FileUtils.contains(privilegedVendorAppDir, scanFile)|| FileUtils.contains(privilegedOdmAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR| SCAN_AS_PRIVILEGED;} else if (FileUtils.contains(vendorAppDir, scanFile)|| FileUtils.contains(odmAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_VENDOR;} else if (FileUtils.contains(oemAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_OEM;} else if (FileUtils.contains(privilegedProductAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRODUCT| SCAN_AS_PRIVILEGED;} else if (FileUtils.contains(productAppDir, scanFile)) {reparseFlags =mDefParseFlags |PackageParser.PARSE_IS_SYSTEM_DIR;rescanFlags =scanFlags| SCAN_AS_SYSTEM| SCAN_AS_PRODUCT;} else {Slog.e(TAG, "Ignoring unexpected fallback path " + scanFile);continue;}// 设置系统 package 可用！mSettings.enableSystemPackageLPw(packageName);// 重新解析 system 分区的 package！try {scanPackageTracedLI(scanFile, reparseFlags, rescanFlags, 0, null);} catch (PackageManagerException e) {Slog.e(TAG, "Failed to parse original system package: "+ e.getMessage());}}}// Uncompress and install any stubbed system applications.// This must be done last to ensure all stubs are replaced or disabled.decompressSystemApplications(stubSystemApps, scanFlags);final int cachedNonSystemApps = PackageParser.sCachedPackageReadCount.get()- cachedSystemApps;final long dataScanTime = SystemClock.uptimeMillis() - systemScanTime - startTime;final int dataPackagesCount = mPackages.size() - systemPackagesCount;Slog.i(TAG, "Finished scanning non-system apps. Time: " + dataScanTime+ " ms, packageCount: " + dataPackagesCount+ " , timePerPackage: "+ (dataPackagesCount == 0 ? 0 : dataScanTime / dataPackagesCount)+ " , cached: " + cachedNonSystemApps);if (mIsUpgrade && dataPackagesCount > 0) {MetricsLogger.histogram(null, "ota_package_manager_data_app_avg_scan_time",((int) dataScanTime) / dataPackagesCount);}}mExpectingBetter.clear();		// 清空 mExpectingBetter 列表！// Resolve the storage manager.mStorageManagerPackage = getStorageManagerPackageName();// Resolve protected action filters. Only the setup wizard is allowed to// have a high priority filter for these actions.mSetupWizardPackage = getSetupWizardPackageName();if (mProtectedFilters.size() > 0) {if (DEBUG_FILTERS && mSetupWizardPackage == null) {Slog.i(TAG, "No setup wizard;"+ " All protected intents capped to priority 0");}for (ActivityIntentInfo filter : mProtectedFilters) {if (filter.activity.info.packageName.equals(mSetupWizardPackage)) {if (DEBUG_FILTERS) {Slog.i(TAG, "Found setup wizard;"+ " allow priority " + filter.getPriority() + ";"+ " package: " + filter.activity.info.packageName+ " activity: " + filter.activity.className+ " priority: " + filter.getPriority());}// skip setup wizard; allow it to keep the high priority filtercontinue;}if (DEBUG_FILTERS) {Slog.i(TAG, "Protected action; cap priority to 0;"+ " package: " + filter.activity.info.packageName+ " activity: " + filter.activity.className+ " origPrio: " + filter.getPriority());}filter.setPriority(0);}}mSystemTextClassifierPackage = getSystemTextClassifierPackageName();mDeferProtectedFilters = false;mProtectedFilters.clear();// 这里，我们已经找到了所有的共享库文件！// 我们需要更新所有的应用，保证他们有正确的共享库路径。updateAllSharedLibrariesLPw(null);for (SharedUserSetting setting : mSettings.getAllSharedUsersLPw()) {// NOTE: We ignore potential failures here during a system scan (like// the rest of the commands above) because there's precious little we// can do about it. A settings error is reported, though.final List<String> changedAbiCodePath =adjustCpuAbisForSharedUserLPw(setting.packages, null /*scannedPackage*/);if (changedAbiCodePath != null && changedAbiCodePath.size() > 0) {for (int i = changedAbiCodePath.size() - 1; i >= 0; --i) {final String codePathString = changedAbiCodePath.get(i);try {mInstaller.rmdex(codePathString,getDexCodeInstructionSet(getPreferredInstructionSet()));} catch (InstallerException ignored) {}}}// Adjust seInfo to ensure apps which share a sharedUserId are placed in the same// SELinux domain.setting.fixSeInfoLocked();}// 到这里，系统中所有的 package 都被扫描到了，这里是更新他们上一次的使用信息！mPackageUsage.read(mPackages);mCompilerStats.read();//....

当mOnlyCore = false时，则 scanDirLI 还会收集如下目录中的 apk 的信息！

  • /data/app
  • /data/app-private

2.4 BOOT_PROGRESS_PMS_SCAN_END

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,SystemClock.uptimeMillis());Slog.i(TAG, "Time to scan packages: "+ ((SystemClock.uptimeMillis()-startTime)/1000f)+ " seconds");// If the platform SDK has changed since the last time we booted,// we need to re-grant app permission to catch any new ones that// appear.  This is really a hack, and means that apps can in some// cases get permissions that the user didn't initially explicitly// allow...  it would be nice to have some better way to handle// this situation.// 如果从我们上次启动，SDK 平台被改变了，我们需要重新授予应用程序权限。final boolean sdkUpdated = (ver.sdkVersion != mSdkVersion);if (sdkUpdated) {Slog.i(TAG, "Platform changed from " + ver.sdkVersion + " to "+ mSdkVersion + "; regranting permissions for internal storage");}// 赋予 package 相应请求的权限 mPermissionManager.updateAllPermissions(StorageManager.UUID_PRIVATE_INTERNAL, sdkUpdated, mPackages.values(),mPermissionCallback);ver.sdkVersion = mSdkVersion;// If this is the first boot or an update from pre-M, and it is a normal// boot, then we need to initialize the default preferred apps across// all defined users.// 如果这是第一次开机或前-M的更新，这是一个正常的启动，然后我们需要初始化默认的首选应用程序给所有已经定义的用户。if (!onlyCore && (mPromoteSystemApps || mFirstBoot)) {for (UserInfo user : sUserManager.getUsers(true)) {mSettings.applyDefaultPreferredAppsLPw(this, user.id);applyFactoryDefaultBrowserLPw(user.id);primeDomainVerificationsLPw(user.id);}}// Prepare storage for system user really early during boot,// since core system apps like SettingsProvider and SystemUI// can't wait for user to startfinal int storageFlags;if (StorageManager.isFileEncryptedNativeOrEmulated()) {storageFlags = StorageManager.FLAG_STORAGE_DE;} else {storageFlags = StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE;}List<String> deferPackages = reconcileAppsDataLI(StorageManager.UUID_PRIVATE_INTERNAL,UserHandle.USER_SYSTEM, storageFlags, true /* migrateAppData */,true /* onlyCoreApps */);mPrepareAppDataFuture = SystemServerInitThreadPool.get().submit(() -> {TimingsTraceLog traceLog = new TimingsTraceLog("SystemServerTimingAsync",Trace.TRACE_TAG_PACKAGE_MANAGER);traceLog.traceBegin("AppDataFixup");try {mInstaller.fixupAppData(StorageManager.UUID_PRIVATE_INTERNAL,StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE);} catch (InstallerException e) {Slog.w(TAG, "Trouble fixing GIDs", e);}traceLog.traceEnd();traceLog.traceBegin("AppDataPrepare");if (deferPackages == null || deferPackages.isEmpty()) {return;}int count = 0;for (String pkgName : deferPackages) {PackageParser.Package pkg = null;synchronized (mPackages) {PackageSetting ps = mSettings.getPackageLPr(pkgName);if (ps != null && ps.getInstalled(UserHandle.USER_SYSTEM)) {pkg = ps.pkg;}}if (pkg != null) {synchronized (mInstallLock) {prepareAppDataAndMigrateLIF(pkg, UserHandle.USER_SYSTEM, storageFlags,true /* maybeMigrateAppData */);}count++;}}traceLog.traceEnd();Slog.i(TAG, "Deferred reconcileAppsData finished " + count + " packages");}, "prepareAppData");// If this is first boot after an OTA, and a normal boot, then// we need to clear code cache directories.// Note that we do *not* clear the application profiles. These remain valid// across OTAs and are used to drive profile verification (post OTA) and// profile compilation (without waiting to collect a fresh set of profiles).// 如果这是在OTA升级后第一启动，这是正常的启动，然后我们需要清除代码缓存目录。if (mIsUpgrade && !onlyCore) {Slog.i(TAG, "Build fingerprint changed; clearing code caches");for (int i = 0; i < mSettings.mPackages.size(); i++) {final PackageSetting ps = mSettings.mPackages.valueAt(i);if (Objects.equals(StorageManager.UUID_PRIVATE_INTERNAL, ps.volumeUuid)) {// No apps are running this early, so no need to freezeclearAppDataLIF(ps.pkg, UserHandle.USER_ALL,StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE| Installer.FLAG_CLEAR_CODE_CACHE_ONLY);}}ver.fingerprint = Build.FINGERPRINT;}checkDefaultBrowser();// clear only after permissions and other defaults have been updated// 当权限和其他默认设置被更新后，执行清除操作。mExistingSystemPackages.clear();mPromoteSystemApps = false;// All the changes are done during package scanning.ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;// can downgrade to reader// 信息写回 packages.xml 文件Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "write settings");mSettings.writeLPr();Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);//...

2.5 BOOT_PROGRESS_PMS_READY

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY,SystemClock.uptimeMillis());if (!mOnlyCore) {mRequiredVerifierPackage = getRequiredButNotReallyRequiredVerifierLPr();mRequiredInstallerPackage = getRequiredInstallerLPr();mRequiredUninstallerPackage = getRequiredUninstallerLPr();mIntentFilterVerifierComponent = getIntentFilterVerifierComponentNameLPr();if (mIntentFilterVerifierComponent != null) {mIntentFilterVerifier = new IntentVerifierProxy(mContext,mIntentFilterVerifierComponent);} else {mIntentFilterVerifier = null;}mServicesSystemSharedLibraryPackageName = getRequiredSharedLibraryLPr(PackageManager.SYSTEM_SHARED_LIBRARY_SERVICES,SharedLibraryInfo.VERSION_UNDEFINED);mSharedSystemSharedLibraryPackageName = getRequiredSharedLibraryLPr(PackageManager.SYSTEM_SHARED_LIBRARY_SHARED,SharedLibraryInfo.VERSION_UNDEFINED);} else {mRequiredVerifierPackage = null;mRequiredInstallerPackage = null;mRequiredUninstallerPackage = null;mIntentFilterVerifierComponent = null;mIntentFilterVerifier = null;mServicesSystemSharedLibraryPackageName = null;mSharedSystemSharedLibraryPackageName = null;}// 建立 PackageInstallerService 服务对象mInstallerService = new PackageInstallerService(context, this);final Pair<ComponentName, String> instantAppResolverComponent =getInstantAppResolverLPr();if (instantAppResolverComponent != null) {if (DEBUG_INSTANT) {Slog.d(TAG, "Set ephemeral resolver: " + instantAppResolverComponent);}mInstantAppResolverConnection = new InstantAppResolverConnection(mContext, instantAppResolverComponent.first,instantAppResolverComponent.second);mInstantAppResolverSettingsComponent =getInstantAppResolverSettingsLPr(instantAppResolverComponent.first);} else {mInstantAppResolverConnection = null;mInstantAppResolverSettingsComponent = null;}updateInstantAppInstallerLocked(null);// Read and update the usage of dex files.// Do this at the end of PM init so that all the packages have their// data directory reconciled.// At this point we know the code paths of the packages, so we can validate// the disk file and build the internal cache.// The usage file is expected to be small so loading and verifying it// should take a fairly small time compare to the other activities (e.g. package// scanning).final Map<Integer, List<PackageInfo>> userPackages = new HashMap<>();final int[] currentUserIds = UserManagerService.getInstance().getUserIds();for (int userId : currentUserIds) {userPackages.put(userId, getInstalledPackages(/*flags*/ 0, userId).getList());}mDexManager.load(userPackages);if (mIsUpgrade) {MetricsLogger.histogram(null, "ota_package_manager_init_time",(int) (SystemClock.uptimeMillis() - startTime));}} // synchronized (mPackages)} // synchronized (mInstallLock)// Now after opening every single application zip, make sure they// are all flushed.  Not really needed, but keeps things nice and// tidy.Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "GC");Runtime.getRuntime().gc();Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);// The initial scanning above does many calls into installd while// holding the mPackages lock, but we're mostly interested in yelling// once we have a booted system.mInstaller.setWarnIfHeld(mPackages);Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);Log.d("preinstall"," start preinstall"+System.currentTimeMillis());mHandler.postDelayed(new Runnable() {public void run() {try{SystemProperties.set("ctl.start", "preinstall");}catch (Exception e){Log.d("preinstall"," preinstall failed");e.printStackTrace();}}},1200);

PKMS 初始化完成阶段，还会创建一个 PackageInstaller 服务。

四、总结

总结
PackageManagerService 的初始化工作都是在它的构造函数中完成的，主要完成一下任务：

  1. 添加一些用户 id，如 system、phone 等；
  2. 解析 /system/etc/permission 下的 xml 文件，主要 是 platform.xml，建立 permission 和 gid 之间的关系，可以指定一个权限与几个组对应，当一个 apk 被授予这个权限时它也同时属于这几个组，readPermission(parser， perm)；
    给一些底层用户分配一些权限，如 shell 授予各种 permission，把一个权限赋予一个 uid，当 apk 使用这个 uid 运行时，就具备了这个权限系统增加的一些应用需要 link 的扩展的 jar 库，系统每增加一个硬件，都要添加相应的 featrue，将解析结果放入 mAvailableFeatures;
  3. 建立并启动 PackageHandler 消息循环，用于处理 apk 安装请求如 adb install，package installer 安装 apk 时就会发送消息；
  4. 检查 /data/system/packages.xml 是否存在，里面记录了系统的 permission，以及每个apk的 name，codePath，flags，ts，version，userid 等，这些信息主要是通过 apk 安装的时候解析 AndroidManifest.xml 获取到的，解析完 apk 后将更新信息写入这个文件并保存到 flash，下次开机直接从里面读取相关信息添加到内存相关列表中，当有 apk 安装，升级，删除时会更新这个文件；
  5. 检查 BootClassPath，mSharedLibraries 及 /system/framework 下的jar是否需要 dexopt ，需要则通过 dexopt 进行优化，这里面主要是调用 mInstaller.dexopt 进行相应的优化；
  6. 建立 java 层的 installer 与 c 层的 installd 的 socket 联接，使得在上层的 install，remove，dexopt 等功能最终由 installd 在底层实现；
  7. 启动 AppDirObserver 线程往中监测 /system/framework，/system/app，/data/app/data/app-private 目录的事件，主要监听 add 和 remove 事件，对于目录监听底层通过 inotify 机制实现，inotify 是一种文件系统的变化通知机制如文件增加、删除等事件可以立刻让用户态得知，它为用户态监视文件系统的变化提供了强大的支持，当有 add event 时调用 scanPackageLI(File，in，int) 处理，当有 remove event 时调用 removePackageLI 处理；
  8. 调用 scanDirLI 启动 apk 解析，解析目录包括：/system/framework、/system/app、/vendor/app、/data/app、/data/app-private；
  9. 移除临时文件；
  10. 赋予 package 相应请求的权限；
  11. 将解析出的 Package 的相关信息保存到相关全局变量，还有文件。

这篇关于PackageManagerService初始化的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！


http://www.chinasem.cn/article/347963。

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c++的初始化列表与const成员

c++的初始化列表与const成员

初始化列表与const成员 const成员 使用const修饰的类、结构、联合的成员变量，在类对象创建完成前一定要初始化。 不能在构造函数中初始化const成员，因为执行构造函数时，类对象已经创建完成，只有类对象创建完成才能调用成员函数，构造函数虽然特殊但也是成员函数。 在定义const成员时进行初始化，该语法只有在C11语法标准下才支持。 初始化列表 在构造函数小括号后面，主要用于给
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@postconstruct初始化的操作

@postconstruct初始化的操作

从Java EE 5规范开始，Servlet中增加了两个影响Servlet生命周期的注解（Annotion）；@PostConstruct和@PreDestroy。这两个注解被用来修饰一个非静态的void()方法 。写法有如下两种方式： @PostConstruct Public void someMethod() {}
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spring和tomcat初始化的类和注解

spring和tomcat初始化的类和注解

1.InitializingBean接口为bean提供了初始化方法的方式，它只包括afterPropertiesSet方法，凡是继承该接口的类，在初始化bean的时候会执行该方法。 spring为bean提供了两种初始化bean的方式，实现InitializingBean接口，实现afterPropertiesSet方法，或者在配置文件中同过init-method指定，两种方式可以同时使用 实
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LabVIEW环境中等待FPGA模块初始化完成

LabVIEW环境中等待FPGA模块初始化完成

这个程序使用的是LabVIEW环境中的FPGA模块和I/O模块初始化功能，主要实现等待FAM（Field-Programmable Gate Array Module，FPGA模块）的初始化完成，并处理初始化过程中的错误。让我们逐步分析各部分的功能： 1. Wait for FAM Initialization框架 此程序框架用于等待I/O模块成功初始化。如果在5秒钟内模块没有完成配
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dp(背包问题) 恰好、至少、至多初始化

dp(背包问题) 恰好、至少、至多初始化

状态表示的初始化(一般情况) f[i][j] i:前i件物品 体积至少为j 枚举体积时可以是负数(体积为负数时等价于体积为0) max f[i][j] = {-0x3f} f[i][0] = 0min f[i][j] = { 0x3f} f[i][0] = 0cnt f[0][0] = 1 体积至多为j 枚举体积时不能是负数 max f[i][j] = 0min f[i][j]
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Windows11上使用WSL2，提示：系统尚未使用systemd作为初始化系统(PID 1)启动

Windows11上使用WSL2，提示：系统尚未使用systemd作为初始化系统(PID 1)启动

前言 略 报错信息 System has not been booted with systemd as init system (PID 1). Can't operate. Failed to connect to bus: Host is down 解决方法 使用如下命令 # windows终端，执行如下命令wsl --update# 登录ubuntu系统，执行如下命令s
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WapApp初始化样式表

WapApp初始化样式表

@charset "utf-8";/* 样式初始化--------------------------------------------------*/body {margin: 0;padding: 0;background-color: #f6f6f6;font: normal 67.5% Helvetica, Arial, sans-serif;min-width: 240px;}*
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Spark Core源码精读计划7 | Spark执行环境的初始化

Spark Core源码精读计划7 | Spark执行环境的初始化

推荐阅读 《Spark源码精度计划 | SparkConf》 《Spark Core源码精读计划 | SparkContext组件初始化》 《Spark Core源码精读计划3 | SparkContext辅助属性及后初始化》 《Spark Core源码精读计划4 | SparkContext提供的其他功能》 《Spark Core源码精读计划5 | 事件总线及ListenerBus》 《Spa
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Spark Core源码精读计划3 | SparkContext辅助属性及后初始化

Spark Core源码精读计划3 | SparkContext辅助属性及后初始化

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