一. 概述
PackageManagerService(简称PKMS)，是Android系统中核心服务之一，管理着所有与package相关的工作，常见的比如安装、卸载应用, 信息查询等工作, 主要完成以下核心功能
1. 解析AndroidManifest.xml清单文件，解析清单文件中的所有节点信息
2. 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。
3. 管理本地apk，主要包括安装、删除等等
4. 管理设备上安装的所有应用程序，并在系统启动时加载应用程序
5. 根据请求的Intent匹配到对应的Activity、Provider、Service，提供包含包名和Component的信息对象
6. 调用需要权限的系统函数时，检查程序是否具备相应权限从而保证系统安全
7. 提供应用程序的安装、卸载的接口
二. PKMS启动过程
在Android系统启动过程中，程序会执行到SystemServer中，然后调用startBootstrapServices()方法启动核心服务，在startBootstrapServices()方法中完成PMS的启动：
private void startBootstrapServices() {
....
//注释1
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
//注释2
mPackageManager = mSystemContext.getPackageManager();
.....
}注释1处:调用PackageManagerService.main()方法，在main()方法中创建PMS的对象，并向
ServiceManager注册Binder
接下来看一下PKMS的main方法:
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
// Self-check for initial settings.
PackageManagerServiceCompilerMapping.checkProperties();
// 1、创建PMS对象
PackageManagerService m = new PackageManagerServiceEx(context, installer,
factoryTest, onlyCore);
m.enableSystemUserPackages();
// 2、注册PMS对象到ServiceManager中
ServiceManager.addService("package", m);
//3、 创建 PMN对象
final PackageManagerNative pmn = m.new PackageManagerNative();
//4、注册PMN对象
ServiceManager.addService("package_native", pmn);
return m;
}注释2处: 初始化PackageManager对象.
通过调用ContextImpl.getPackageManager()获取PackageManager对象
@Override
public PackageManager getPackageManager() {
if (mPackageManager != null) {
return mPackageManager;
}
IPackageManager pm = ActivityThread.getPackageManager();
if (pm != null) {
// Doesn't matter if we make more than one instance.
return (mPackageManager = new ApplicationPackageManager(this, pm));
}
return null;
}getPackageManager方法中使用ActivityThread.getPackageManager()获取前面创建并注册的Binder对象，然后创建ApplicationPackageManager实例
frameworks/base/core/java/android/app/ActivityThread.java
@UnsupportedAppUsage
public static IPackageManager getPackageManager() {
if (sPackageManager != null) {
return sPackageManager;
}
// 获取注册Binder
IBinder b = ServiceManager.getService("package");
// sPackageManager就是服务端PKMS的代理proxy对象
sPackageManager = IPackageManager.Stub.asInterface(b);
return sPackageManager;
}上面的这段代码, sPackageManager 就是服务端PKMS的 代理proxy对象, 客户端拿到sPackageManager这个代理对象,就可以跨进程调用PKMS中的方法了.
先来小结一下, 从上面的3个过程可以得出以下结论：
1. PMS使用Binder通信机制，最终IPackageManager接口的实现类为PackageManagerService类
2. 系统中获取的PackageManager对象具体实现的子类是ApplicationPackageManager对象
类图:
PKMS初始化时的核心部分为PackageManagerService()构造函数的内容,我们下面就来分析该流程
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
// Self-check for initial settings.
//检查Package编译相关系统属性
PackageManagerServiceCompilerMapping.checkProperties();
// 调用PackageManagerService构造方法,
PackageManagerService m = new PackageManagerServiceEx(context, installer,
factoryTest, onlyCore);
//启用部分应用服务于多用户场景
m.enableSystemUserPackages();
//往ServiceManager中注册”package”和”package_native”。
ServiceManager.addService("package", m);
final PackageManagerNative pmn = m.new PackageManagerNative();
ServiceManager.addService("package_native", pmn);
return m;
}三. PKMS 构造函数分析
PKMS的构造方法代码比较长, 我们通过EventLog(事件日志)的打印,可以分为5个过程
1. BOOT_PROGRESS_PMS_START（开始阶段）
2. BOOT_PROGRESS_PMS_SYSTEM_SCAN_START（扫描系统阶段）
3. BOOT_PROGRESS_PMS_DATA_SCAN_START（扫描Data分区阶段）
4. BOOT_PROGRESS_PMS_SCAN_END（扫描结束阶段）
5. BOOT_PROGRESS_PMS_READY（准备阶段）
3.1 BOOT_PROGRESS_PMS_START 开始阶段
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");
//第一阶段BOOT_PROGRESS_PMS_START 开始
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_START,
SystemClock.uptimeMillis());
if (mSdkVersion <= 0) {
Slog.w(TAG, "**** ro.build.version.sdk not set!");
}
mContext = context;
// 一般为false，即非工厂生产模式
mFactoryTest = factoryTest;
mOnlyCore = onlyCore; //标记是否只加载核心服务
//1. 构造 DisplayMetrics ，保存分辨率等相关信息
mMetrics = new DisplayMetrics();
//2. 创建Installer对象，与installd交互；
mInstaller = installer;
// Create sub-components that provide services / data. Order here is important.
//创建提供服务/数据的子组件。这里的顺序很重要,使用到了两个重要的同步锁
synchronized (mInstallLock) {
synchronized (mPackages) {
// Expose private service for system components to use.
// 公开系统组件使用的私有服务
// 本地服务
LocalServices.addService(
PackageManagerInternal.class, new PackageManagerInternalImpl());
// 多用户管理服务
sUserManager = new UserManagerService(context, this,
new UserDataPreparer(mInstaller, mInstallLock, mContext, mOnlyCore), mPackages);
//解析所有Android组件类型对象[activities, services, providers and receivers]
mComponentResolver = new ComponentResolver(sUserManager,
LocalServices.getService(PackageManagerInternal.class),
mPackages);
//3. 创建mPermissionManager对象，进行权限管理；
mPermissionManager = PermissionManagerService.create(context,
mPackages /*externalLock*/);
mDefaultPermissionPolicy = mPermissionManager.getDefaultPermissionGrantPolicy();
//创建Settings对象
//构造Settings类，保存安装包信息，清除路径不存在的孤立应用，
// 主要涉及 /data/system/目录的packages.xml，packages-backup.xml， packages.list， packages-stopped.xml，packages-stopped-backup.xml等文件。
mSettings = new Settings(Environment.getDataDirectory(),
mPermissionManager.getPermissionSettings(), mPackages);
}
}
// 添加system, phone, log, nfc, bluetooth, shell，se，networkstack 这8种 shareUserId 到 mSettings；
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);
mSettings.addSharedUserLPw("android.uid.networkstack", NETWORKSTACK_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;
}
//5. 构造PackageDexOptimizer及DexManager类，处理dex优化
//DexOpt优化
mPackageDexOptimizer = new PackageDexOptimizer(installer, mInstallLock, context,
"*dexopt*");
mDexManager = new DexManager(mContext, this, mPackageDexOptimizer, installer, mInstallLock);
// ART虚拟机管理服务
mArtManagerService = new ArtManagerService(mContext, this, installer, mInstallLock);
mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());
mViewCompiler = new ViewCompiler(mInstallLock, mInstaller);
//权限变化监听器
mOnPermissionChangeListeners = new OnPermissionChangeListeners(
FgThread.get().getLooper());
// 获取默认分辨率
getDefaultDisplayMetrics(context, mMetrics);
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "get system config");
//6.创建SystemConfig实例，获取系统配置信息，配置共享lib库；
// 拿到SystemConfig()的对象，其中会调用SystemConfig的readPermissions()完成权限的读取
SystemConfig systemConfig = SystemConfig.getInstance();
//获取该设备支持的功能，这些功能是从系统配置文件中读取的
mAvailableFeatures = systemConfig.getAvailableFeatures();
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
mProtectedPackages = new ProtectedPackages(mContext);
mApexManager = new ApexManager(context);
//启动"PackageManager"线程，负责apk的安装、卸载, 用HanderThread来实现
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
mHandlerThread.start();
// 应用handler PackageHandler是PKMS中的内部类
mHandler = new PackageHandler(mHandlerThread.getLooper());
// 进程记录handler
mProcessLoggingHandler = new ProcessLoggingHandler();
//Watchdog监听ServiceThread是否超时：10分钟
Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);
// Instant应用注册
mInstantAppRegistry = new InstantAppRegistry(this);
// 共享lib库配置
ArrayMap<String, SystemConfig.SharedLibraryEntry> libConfig
= systemConfig.getSharedLibraries();
final int builtInLibCount = libConfig.size();
for (int i = 0; i < builtInLibCount; i++) {
String name = libConfig.keyAt(i);
SystemConfig.SharedLibraryEntry entry = libConfig.valueAt(i);
addBuiltInSharedLibraryLocked(entry.filename, name);
}
// Now that we have added all the libraries, iterate again to add dependency
// information IFF their dependencies are added.
long undefinedVersion = SharedLibraryInfo.VERSION_UNDEFINED;
for (int i = 0; i < builtInLibCount; i++) {
String name = libConfig.keyAt(i);
SystemConfig.SharedLibraryEntry entry = libConfig.valueAt(i);
final int dependencyCount = entry.dependencies.length;
for (int j = 0; j < dependencyCount; j++) {
final SharedLibraryInfo dependency =
getSharedLibraryInfoLPr(entry.dependencies[j], undefinedVersion);
if (dependency != null) {
getSharedLibraryInfoLPr(name, undefinedVersion).addDependency(dependency);
}
}
}
// 读取安装相关SELinux策略
SELinuxMMAC.readInstallPolicy();
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "loadFallbacks");
// 返回栈加载
FallbackCategoryProvider.loadFallbacks();
Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "read user settings");
//读取并解析/data/system下的XML文件
//[这段代码 等下下面会分析]
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
// 清理代码路径不存在的孤立软件包
final 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);
}
}
// 如果不是首次启动，也不是CORE应用，则拷贝预编译的DEX文件
if (!mOnlyCore && mFirstBoot) {
requestCopyPreoptedFiles();
}
.....
.....
//好了到这里第一阶段就分析完了
注释1处, PKMS的构造函数中由两个重要的锁(mInstallLock、mPackages)
mInstallLock ：用来保护所有安装apk的访问权限，此操作通常涉及繁重的磁盘数据读写等操作，并且是单线程操作，故有时候会处理很慢.
mPackages: 用来解析内存中所有apk的package信息及相关状态。
重点看看 mFirstBoot = !mSettings.readLPw(sUserManager.getUsers(false)) 这句代码
mSettings.readLPw
readLPw()会扫描下面5个文件
1. "/data/system/packages.xml" 所有安装app信息
2. "/data/system/packages-backup.xml" 所有安装app信息之备份的信息记录
3. "/data/system/packages.list" 所有安装app信息
4. "/data/system/packages-stopped.xml" 所有强制停止app信息
5. "/data/system/packages-stopped-backup.xml" 所有强制停止app信息之备份的信息记录5个文件共分为三组，简单的作用描述如下：
packages.xml：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。
packages.list：描述系统中存在的所有APK的信息。当这些程序有变动时，PKMS就会更新该文件。packages-stopped.xml：从系统自带的设置程序中进入应用程序页面，然后在选择强制停止 （ForceStop）某个应用时，系统会将该应用的相关信息记录到此文件中。也就是该文件保存系统中被用户强制停止的Package的信息。
这些目录的指向,都是在Settings中的构造函数完成;
Settings(File dataDir, PermissionSettings permission,
Object lock) {
mLock = lock;
mPermissions = permission;
mRuntimePermissionsPersistence = new RuntimePermissionPersistence(mLock);
//mSystemDir指向目录"/data/system"
mSystemDir = new File(dataDir, "system");
//创建 "/data/system"
mSystemDir.mkdirs();
//设置权限
FileUtils.setPermissions(mSystemDir.toString(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG
|FileUtils.S_IROTH|FileUtils.S_IXOTH,
-1, -1);
//(1)指向目录"/data/system/packages.xml"
mSettingsFilename = new File(mSystemDir, "packages.xml");
//(2)指向目录"/data/system/packages-backup.xml
mBackupSettingsFilename = new File(mSystemDir, "packages-backup.xml");
//(3)指向目录"/data/system/packages.list"
mPackageListFilename = new File(mSystemDir, "packages.list");
FileUtils.setPermissions(mPackageListFilename, 0640, SYSTEM_UID, PACKAGE_INFO_GID);
final File kernelDir = new File("/config/sdcardfs");
mKernelMappingFilename = kernelDir.exists() ? kernelDir : null;
// Deprecated: Needed for migration
//(4)指向目录"/data/system/packages-stopped.xml"
mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");
//(5) 指 向 目 录 "/data/system/packages-stopped-backup.xml"
mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");
}好了,到这里 第一阶段的代码分析完成, 我们接下来分析第二阶段
3.2 BOOT_PROGRESS_PMS_SYSTEM_SCAN_START 扫描系统阶段
还在直接在源码中注释
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
......
//第二阶段,扫描系统阶段
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
startTime);
// 从init.rc中获取环境变量BOOTCLASSPATH和 SYSTEMSERVERCLASSPATH；
//获取环境变量，init.rc
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!");
}
// 获取system/framework目录
File frameworkDir = new File(Environment.getRootDirectory(), "framework");
// 获取内部版本
final VersionInfo ver = mSettings.getInternalVersion();
// 判断fingerprint是否有更新
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
//对于旧版本升级的情况，将安装时获取权限变更为运行时申请权限；
// 对于Android M之前版本升级上来的情况，需将系统应用程序权限从安装升级到运行时
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.
// 对于Android N之前版本升级上来的情况，需像首次启动一样处理package
mIsPreNUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N;
mIsPreNMR1Upgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N_MR1;
mIsPreQUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.Q;
int preUpgradeSdkVersion = ver.sdkVersion;
// 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
// 在扫描之前保存预先存在的系统package的名称，不希望自动为新系统应用授予运行时权限
if (mPromoteSystemApps) {
Iterator<PackageSetting> pkgSettingIter = mSettings.mPackages.values().iterator();
while (pkgSettingIter.hasNext()) {
PackageSetting ps = pkgSettingIter.next();
if (isSystemApp(ps)) {
mExistingSystemPackages.add(ps.name);
}
}
}
// 准备解析package的缓存
mCacheDir = preparePackageParserCache();
// Set flag to monitor and not change apk file paths when
// scanning install directories.
// 设置flag，而不在扫描安装时更改文件路径
int scanFlags = SCAN_BOOTING | SCAN_INITIAL;
if (mIsUpgrade || mFirstBoot) {
scanFlags = scanFlags | SCAN_FIRST_BOOT_OR_UPGRADE;
}
// Collect vendor/product/product_services 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.
//扫描以下路径：
// /vendor/overlay、/product/overlay、/product_services/overlay、/odm/overlay、/oem/ overlay、
// /system/framework /system/priv-app、/system/app、/vendor/priv- app、
// /vendor/app、/odm/priv-app、/odm/app、/oem/app、/oem/priv-app、 /product/priv-app、
// /product/app、/product_services/priv- app、 /product_services/app、/product_services/priv-app
scanDirTracedLI(new File(VENDOR_OVERLAY_DIR),
mDefParseFlags
| PackageParser.PARSE_IS_SYSTEM_DIR,
scanFlags
| SCAN_AS_SYSTEM
| SCAN_AS_VENDOR,
0);
..... //省略相同的scanDirTracedLI方法
//delete tmp files
//(4)清除安装时临时文件以及其他不必要的信息。
deleteTempPackageFiles();
final int cachedSystemApps = PackageParser.sCachedPackageReadCount.get();
// Remove any shared userIDs that have no associated packages
//删除没有关联应用的共享UID标识
mSettings.pruneSharedUsersLPw();
...
...
//好了,到这里第二扫描系统阶段分析完成
}第二阶段的工作内容:
1 从init.rc中获取环境变量BOOTCLASSPATH和SYSTEMSERVERCLASSPATH；
2 对于旧版本升级的情况，将安装时获取权限变更为运行时申请权限；
3 扫描system/vendor/product/odm/oem等目录的priv-app、app、overlay包；
4 清除安装时临时文件以及其他不必要的信息。
3.3 BOOT_PROGRESS_PMS_DATA_SCAN_START（扫描Data分区阶段）
对于不仅仅解析核心应用的情况下，还处理data目录的应用信息，及时更新, 去除不必要的数据。
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
.....
//对于不仅仅解析核心应用的情况下，还处理data目录的应用信息，及时更新，去除不必要的数据。
if (!mOnlyCore) {
//第三阶段 开始扫描data分区
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
// 如果更新不再存在，则完全删除该应用。否则，撤消其系统权限
for (int i = possiblyDeletedUpdatedSystemApps.size() - 1; i >= 0; --i) {
final String packageName = possiblyDeletedUpdatedSystemApps.get(i);
final PackageParser.Package pkg = mPackages.get(packageName);
final String msg;
....
try {
//扫描apk
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.
// 解压缩并安装任何存根系统应用程序。必须最后执行此操作以确保替换或禁用所有存根
installSystemStubPackages(stubSystemApps, scanFlags);
// Resolve the storage manager.
// 获取storage manager包名
mStorageManagerPackage = getStorageManagerPackageName();
// 解决受保护的action过滤器。只允许setup wizard（开机向导）为这些action 设置高优先级过滤器
mSetupWizardPackage = getSetupWizardPackageName();
// 更新客户端以确保持有正确的共享库路径
updateAllSharedLibrariesLocked(null, Collections.unmodifiableMap(mPackages));
// Now that we know all the packages we are keeping,
// read and update their last usage times.
// 读取并更新要保留的package的上次使用时间
mPackageUsage.read(mPackages);
mCompilerStats.read();
....//到这里第三 扫描data分区阶段完毕
}再来总结一下:
/data可以称为Data分区，它用来存储所有用户的个人数据和配置文件。下面列出Data分区部分子目录：
| 目录 | 含义 |
| app | 存储用户自己安装的App |
| data | 存储所有已安装的App数据的目录，每个App都有自己单独的子目录 |
| app-private | App的私有存储空间 |
| app-lib | 存储所有App的Jni库 |
| system | 存放系统配置文件 |
| anr | 用于存储ANR发生时系统生成的traces.txt文件 |
第三扫描Data分区阶段主要做了以下几件事：
扫描/data/app和/data/app-private目录下的文件。
遍历possiblyDeletedUpdatedSystemApps列表，如果这个系统App的包信息不在PMS的变量mPackages中，说明是残留的App信息，后续会删除它的数据。如果这个系统App的包信息在mPackages中，说明是存在于Data分区，不属于系统App，那么移除其系统权限。
3.4 BOOT_PROGRESS_PMS_SCAN_END 扫描结束阶段
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
.....
//第四阶段 扫描结束阶段
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SCAN_END,
SystemClock.uptimeMillis());
....
// 如果这是第一次启动或来自Android M之前的版本的升级，并且它是正常启动，
// 那需要在所有已定义的用户中初始化默认的首选应用程序
if (!onlyCore && (mPromoteSystemApps || mFirstBoot)) {
for (UserInfo user : sUserManager.getUsers(true)) {
mSettings.applyDefaultPreferredAppsLPw(user.id);
primeDomainVerificationsLPw(user.id);
}
}
// 在启动期间确实为系统用户准备存储，因为像SettingsProvider和SystemUI这样的核心系统应用程序无法等待用户启动
final int storageFlags;
if (StorageManager.isFileEncryptedNativeOrEmulated()) {
storageFlags = StorageManager.FLAG_STORAGE_DE;
} else {
storageFlags = StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE;
}
....
// 如果是在OTA之后首次启动，并且正常启动，那需要清除代码缓存目录，但不清除应用程序配置文件
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 freeze
clearAppDataLIF(ps.pkg, UserHandle.USER_ALL,
FLAG_STORAGE_DE | FLAG_STORAGE_CE | FLAG_STORAGE_EXTERNAL
| Installer.FLAG_CLEAR_CODE_CACHE_ONLY);
}
}
ver.fingerprint = Build.FINGERPRINT;
}
....
//安装Android-Q前的非系统应用程序在Launcher中隐藏他们的图标
if (!onlyCore && mIsPreQUpgrade) {
Slog.i(TAG, "Whitelisting all existing apps to hide their icons");
int size = mSettings.mPackages.size();
for (int i = 0; i < size; i++) {
final PackageSetting ps = mSettings.mPackages.valueAt(i);
if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) != 0) {
continue;
}
ps.disableComponentLPw(PackageManager.APP_DETAILS_ACTIVITY_CLASS_NAME,
UserHandle.USER_SYSTEM);
}
}
// 仅在权限或其它默认配置更新后清除
mExistingSystemPackages.clear();
mPromoteSystemApps = false;
// All the changes are done during package scanning.
//所有变更均在扫描过程中完成
ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;
// can downgrade to reader
//把Settings的内容保存到packages.xml中
Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "write settings");
mSettings.writeLPr();
....
// 好了,第四阶段的源码分析完毕
}第4阶段主要工作：
1. sdk版本变更，更新权限；
2. OTA升级后首次启动，清除不必要的缓存数据；
3. 权限等默认项更新完后，清理相关数据；
4. 把Settings的内容保存到packages.xml中，这样此后PMS再次创建时会读到此前保存的Settings的内容。
3.5 BOOT_PROGRESS_PMS_READY 准备阶段
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
.....
//第五 准备阶段
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_READY,
SystemClock.uptimeMillis());
....
//创建PackageInstallerService对象
mInstallerService = new PackageInstallerService(context, this, mApexManager);
...
// 打开应用之后，及时回收处理
Runtime.getRuntime().gc();
.....//第5阶段完毕
}第五阶段主要工作有：
1. 创建PackageInstallerService对象, PackageInstallerService是用于管理安装会话的服务，它会为每次安装过程分配一个SessionId2. GC回收内存
四. 总结
本文大体内容分为 PKMS启动过程 和 PKMS构造方法分析, PKMS得构造方法中分为5个阶段:开始阶段, 扫描系统,扫描data分区,扫描介绍和准备阶段, 只是梳理了一下主线流程, 每个方法的细节没有一一再分析, 工作中再定位问题的时候可以再去细跟每个方法的逻辑. 后续有新理解加入本文中来.
五. 待更新
有新的理解会更新到这里