Android PackageManagerService分析一：PMS的启动

从这一章开始，我们来分析Android的PackageManagerService，后面简称PMS。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、ActivityMangerService等等service和application使用到。PMS有几个比较重要的命令可以用于我们debug中：

adb shell dumpsys package (dump出系统中所有的application信息)

adb shell dumpsys package “com.android.contacts" p (dump出系统中特定包名的application信息)

首先来看SystemServer中PMS的构造以及注册：

            pm = PackageManagerService.main(context, installer,factoryTest != SystemServer.FACTORY_TEST_OFF,onlyCore);try {firstBoot = pm.isFirstBoot();} catch (RemoteException e) {}try {pm.performBootDexOpt();} catch (Throwable e) {reportWtf("performing boot dexopt", e);}try {pm.systemReady();} catch (Throwable e) {reportWtf("making Package Manager Service ready", e);}

首先来看PMS的main方法：

    public static final IPackageManager main(Context context, Installer installer,boolean factoryTest, boolean onlyCore) {PackageManagerService m = new PackageManagerService(context, installer,factoryTest, onlyCore);ServiceManager.addService("package", m);return m;}

首先构造一个PMS对象，然后调用ServiceManager的addService注册这个服务。构造函数的第二个参数是一个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与vold相关，我们以后再分析，这里也为false。PMS的构造函数比较长，我们首先来看一下大概的流程图，然后我们分段来分析代码：

    public PackageManagerService(Context context, Installer installer,boolean factoryTest, boolean onlyCore) {mContext = context;mFactoryTest = factoryTest;mOnlyCore = onlyCore;mNoDexOpt = "eng".equals(SystemProperties.get("ro.build.type"));mMetrics = new DisplayMetrics();mSettings = new Settings(context);mSettings.addSharedUserLPw("android.uid.system", Process.SYSTEM_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.phone", RADIO_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.log", LOG_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.nfc", NFC_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.bluetooth", BLUETOOTH_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);mSettings.addSharedUserLPw("android.uid.shell", SHELL_UID,ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PRIVILEGED);

上面首先做一个变量的赋值，然后取出"ro.build.type"属性值，build版本分为user和eng两种，一种是面向user，一种是用于engineer debug版，这里假设mNoDexOpt为false。然后构造一个Settings对象，Settings是Android的全局管理者，用于协助PMS保存所有的安装包信息，PMS和Settings之间的类图关系如下：

来看一下Settings的构造函数：

    Settings(Context context) {this(context, Environment.getDataDirectory());}Settings(Context context, File dataDir) {mContext = context;mSystemDir = new File(dataDir, "system");mSystemDir.mkdirs();FileUtils.setPermissions(mSystemDir.toString(),FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IROTH|FileUtils.S_IXOTH,-1, -1);mSettingsFilename = new File(mSystemDir, "packages.xml");mBackupSettingsFilename = new File(mSystemDir, "packages-backup.xml");mPackageListFilename = new File(mSystemDir, "packages.list");FileUtils.setPermissions(mPackageListFilename, 0660, SYSTEM_UID, PACKAGE_INFO_GID);mStoppedPackagesFilename = new File(mSystemDir, "packages-stopped.xml");mBackupStoppedPackagesFilename = new File(mSystemDir, "packages-stopped-backup.xml");}

Environment.getDataDirectory()返回/data目录，然后创建/data/system/目录，并设置它的权限，并在/data/system目录中创建mSettingsFilename、mBackupSettingsFilename、mPackageListFilename、mStoppedPackagesFilename和mBackupStoppedPackagesFilename几个文件。packages.xml就是保存了系统所有的Package信息，packages-backup.xml是packages.xml的备份，防止在写packages.xml突然断电等问题。回到PMS的构造函数，调用addSharedUserLPw将几种SharedUserId的名字和它对应的UID对应写到Settings当中。关于SharedUserId的使用，我们在后面介绍APK的安装过程中再来分析。这里先简单看一下Process中提供的UID列表：

    public static final int SYSTEM_UID = 1000;public static final int PHONE_UID = 1001;public static final int SHELL_UID = 2000;public static final int LOG_UID = 1007;public static final int WIFI_UID = 1010;public static final int MEDIA_UID = 1013;public static final int DRM_UID = 1019;public static final int VPN_UID = 1016;public static final int NFC_UID = 1027;public static final int BLUETOOTH_UID = 1002;public static final int MEDIA_RW_GID = 1023;public static final int PACKAGE_INFO_GID = 1032;public static final int FIRST_APPLICATION_UID = 10000;public static final int LAST_APPLICATION_UID = 19999;

上面定义了一系列的UID，其中applicantion的uid从10000开始到19999结束。来看addSharedUserLPw函数的实现：

    SharedUserSetting addSharedUserLPw(String name, int uid, int pkgFlags) {SharedUserSetting s = mSharedUsers.get(name);if (s != null) {if (s.userId == uid) {return s;}PackageManagerService.reportSettingsProblem(Log.ERROR,"Adding duplicate shared user, keeping first: " + name);return null;}s = new SharedUserSetting(name, pkgFlags);s.userId = uid;if (addUserIdLPw(uid, s, name)) {mSharedUsers.put(name, s);return s;}return null;}private boolean addUserIdLPw(int uid, Object obj, Object name) {if (uid > Process.LAST_APPLICATION_UID) {return false;}if (uid >= Process.FIRST_APPLICATION_UID) {int N = mUserIds.size();final int index = uid - Process.FIRST_APPLICATION_UID;while (index >= N) {mUserIds.add(null);N++;}if (mUserIds.get(index) != null) {PackageManagerService.reportSettingsProblem(Log.ERROR,"Adding duplicate user id: " + uid+ " name=" + name);return false;}mUserIds.set(index, obj);} else {if (mOtherUserIds.get(uid) != null) {PackageManagerService.reportSettingsProblem(Log.ERROR,"Adding duplicate shared id: " + uid+ " name=" + name);return false;}mOtherUserIds.put(uid, obj);}return true;}

mSharedUsers是一个HashMap，保存着所有的name和SharedUserSetting的映射关系。这里先调用addUserIdLPw将uid和SharedUserSetting添加到mOtherUserIds中，然后将name和SharedUserSetting添加到mSharedUsers中方便以后查找。接着来看PMS的构造函数：

        mInstaller = installer;WindowManager wm = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);Display d = wm.getDefaultDisplay();d.getMetrics(mMetrics);synchronized (mInstallLock) {// writersynchronized (mPackages) {mHandlerThread.start();mHandler = new PackageHandler(mHandlerThread.getLooper());Watchdog.getInstance().addThread(mHandler, mHandlerThread.getName(),WATCHDOG_TIMEOUT);File dataDir = Environment.getDataDirectory();mAppDataDir = new File(dataDir, "data");mAppInstallDir = new File(dataDir, "app");mAppLibInstallDir = new File(dataDir, "app-lib");mAsecInternalPath = new File(dataDir, "app-asec").getPath();mUserAppDataDir = new File(dataDir, "user");mDrmAppPrivateInstallDir = new File(dataDir, "app-private");sUserManager = new UserManagerService(context, this,mInstallLock, mPackages);readPermissions();

上面首先获得显示屏的相关信息并保存在mMetrics中。然后启动“PackageManager”的HandleThread并绑定到PackageHandler上，这就是最后处理所有的跨进程消息的handler。接着调用readPermissions()来处理系统的permissions相关的文件。在/etc/permissions的文件大多来源于代码中的framworks/native/data/etc，这些文件的作用是表明系统支持的feature有哪些，例如是否支持蓝牙、wifi、P2P等。文件目录如下：

android.hardware.bluetooth.xml
android.hardware.bluetooth_le.xml
android.hardware.camera.autofocus.xml
android.hardware.camera.flash-autofocus.xml
android.hardware.camera.front.xml
android.hardware.camera.xml

android.software.sip.xml
com.android.nfc_extras.xml
com.nxp.mifare.xml
handheld_core_hardware.xml

这里的文件内容很简单，例如android.hardware.bluetooth.xml的内容如下：

<permissions><feature name="android.hardware.bluetooth" />
</permissions>

在/etc/permissions中有一个platform.xml，它是来源于frameworks/base/data/etc/中，其中的内容大致如下：

<permissions><permission name="android.permission.BLUETOOTH_ADMIN" ><group gid="net_bt_admin" /></permission><permission name="android.permission.BLUETOOTH" ><group gid="net_bt" /></permission><permission name="android.permission.BLUETOOTH_STACK" ><group gid="net_bt_stack" /></permission><permission name="android.permission.NET_TUNNELING" ><group gid="vpn" /></permission><permission name="android.permission.INTERNET" ><group gid="inet" /></permission><assign-permission name="android.permission.MODIFY_AUDIO_SETTINGS" uid="media" /><assign-permission name="android.permission.ACCESS_SURFACE_FLINGER" uid="media" /><assign-permission name="android.permission.WAKE_LOCK" uid="media" /><assign-permission name="android.permission.UPDATE_DEVICE_STATS" uid="media" /><assign-permission name="android.permission.UPDATE_APP_OPS_STATS" uid="media" /><assign-permission name="android.permission.ACCESS_SURFACE_FLINGER" uid="graphics" /><library name="android.test.runner"file="/system/framework/android.test.runner.jar" /><library name="javax.obex"file="/system/framework/javax.obex.jar"/>

现在来看readPermissions()的实现：

    void readPermissions() {File libraryDir = new File(Environment.getRootDirectory(), "etc/permissions");if (!libraryDir.exists() || !libraryDir.isDirectory()) {Slog.w(TAG, "No directory " + libraryDir + ", skipping");return;}if (!libraryDir.canRead()) {Slog.w(TAG, "Directory " + libraryDir + " cannot be read");return;}for (File f : libraryDir.listFiles()) {if (f.getPath().endsWith("etc/permissions/platform.xml")) {continue;}if (!f.getPath().endsWith(".xml")) {Slog.i(TAG, "Non-xml file " + f + " in " + libraryDir + " directory, ignoring");continue;}if (!f.canRead()) {Slog.w(TAG, "Permissions library file " + f + " cannot be read");continue;}readPermissionsFromXml(f);}// Read permissions from .../etc/permissions/platform.xml last so it will take precedencefinal File permFile = new File(Environment.getRootDirectory(),"etc/permissions/platform.xml");readPermissionsFromXml(permFile);}

首先不断的读出/etc/permissions下面的文件，并依此处理除了platform.xml以外的其它xml文件，并最后处理platform.xml文件，来看readPermissionsFromXml()的实现，这个函数比较长，我们主要看处理feature、permission、assign-permission和library的代码：

private void readPermissionsFromXml(File permFile) {FileReader permReader = null;try {permReader = new FileReader(permFile);} catch (FileNotFoundException e) {}try {XmlPullParser parser = Xml.newPullParser();parser.setInput(permReader);XmlUtils.beginDocument(parser, "permissions");while (true) {XmlUtils.nextElement(parser);if (parser.getEventType() == XmlPullParser.END_DOCUMENT) {break;}String name = parser.getName();if ("group".equals(name)) {} else if ("permission".equals(name)) {String perm = parser.getAttributeValue(null, "name");if (perm == null) {Slog.w(TAG, "<permission> without name at "+ parser.getPositionDescription());XmlUtils.skipCurrentTag(parser);continue;}perm = perm.intern();readPermission(parser, perm);} else if ("assign-permission".equals(name)) {String perm = parser.getAttributeValue(null, "name");String uidStr = parser.getAttributeValue(null, "uid");if (uidStr == null) {Slog.w(TAG, "<assign-permission> without uid at "+ parser.getPositionDescription());XmlUtils.skipCurrentTag(parser);continue;}int uid = Process.getUidForName(uidStr);perm = perm.intern();HashSet<String> perms = mSystemPermissions.get(uid);if (perms == null) {perms = new HashSet<String>();mSystemPermissions.put(uid, perms);}perms.add(perm);XmlUtils.skipCurrentTag(parser);} else if ("library".equals(name)) {String lname = parser.getAttributeValue(null, "name");String lfile = parser.getAttributeValue(null, "file");if (lname == null) {} else if (lfile == null) {} else {mSharedLibraries.put(lname, new SharedLibraryEntry(lfile, null));}XmlUtils.skipCurrentTag(parser);continue;} else if ("feature".equals(name)) {String fname = parser.getAttributeValue(null, "name");if (fname == null) {} else {FeatureInfo fi = new FeatureInfo();fi.name = fname;mAvailableFeatures.put(fname, fi);}XmlUtils.skipCurrentTag(parser);continue;} else {XmlUtils.skipCurrentTag(parser);continue;}}permReader.close();} catch (XmlPullParserException e) {Slog.w(TAG, "Got execption parsing permissions.", e);} catch (IOException e) {Slog.w(TAG, "Got execption parsing permissions.", e);}}

首先来看处理feature这个tag的代码，在fname中保存feature的名字，然后创建一个FeatureInfo，并把fname和FeatureInfo保存到mAvailableFeatures这个HashMap中。接着来看处理permission tag，首先读出permission的name，然后调用readPermission去处理后面的group信息：

    void readPermission(XmlPullParser parser, String name)throws IOException, XmlPullParserException {name = name.intern();BasePermission bp = mSettings.mPermissions.get(name);if (bp == null) {bp = new BasePermission(name, null, BasePermission.TYPE_BUILTIN);mSettings.mPermissions.put(name, bp);}int outerDepth = parser.getDepth();int type;while ((type=parser.next()) != XmlPullParser.END_DOCUMENT&& (type != XmlPullParser.END_TAG|| parser.getDepth() > outerDepth)) {if (type == XmlPullParser.END_TAG|| type == XmlPullParser.TEXT) {continue;}String tagName = parser.getName();if ("group".equals(tagName)) {String gidStr = parser.getAttributeValue(null, "gid");if (gidStr != null) {int gid = Process.getGidForName(gidStr);bp.gids = appendInt(bp.gids, gid);} else {Slog.w(TAG, "<group> without gid at "+ parser.getPositionDescription());}}XmlUtils.skipCurrentTag(parser);}}

在readPermission中首先构造BasePermission对象，并把name和BasePermission一起添加到Settings的mPermissions这个HashMap中。Android管理权限的机制其实就是对应相应的permission，用一个gid号来描述，当一个应用程序请求这个permission的时候，就把这个gid号添加到对应的application中去。Process.getGidForName方法通过JNI调用getgrnam系统函数去获取相应的组名称所对应的gid号，并把它添加到BasePermission对象的gids数组中。再来看处理assign-permission这个tag的代码，首先读出permission的名字和uid，保存在perm和uidStr中，Process.getUidForName方法通过JNI调用getpwnam系统函数获取相应的用户名所对应的uid号，并把刚解析的permission名添加到HashSet当中，最后把上面的uid和hashset添加到mSystemPermissions这个数组中。最后来看处理library这个tag的代码，这里把解析处理的library名字和路径保存在mSharedLibraries这个hashMap中。再回到PMS的构造函数中，接着往下来看：

            mRestoredSettings = mSettings.readLPw(this, sUserManager.getUsers(false),mSdkVersion, mOnlyCore);String customResolverActivity = Resources.getSystem().getString(R.string.config_customResolverActivity);if (TextUtils.isEmpty(customResolverActivity)) {customResolverActivity = null;} else {mCustomResolverComponentName = ComponentName.unflattenFromString(customResolverActivity);}long startTime = SystemClock.uptimeMillis();int scanMode = SCAN_MONITOR | SCAN_NO_PATHS | SCAN_DEFER_DEX | SCAN_BOOTING;if (mNoDexOpt) {Slog.w(TAG, "Running ENG build: no pre-dexopt!");scanMode |= SCAN_NO_DEX;}final HashSet<String> alreadyDexOpted = new HashSet<String>();String bootClassPath = System.getProperty("java.boot.class.path");if (bootClassPath != null) {String[] paths = splitString(bootClassPath, ':');for (int i=0; i<paths.length; i++) {alreadyDexOpted.add(paths[i]);}} else {Slog.w(TAG, "No BOOTCLASSPATH found!");}boolean didDexOpt = false;if (mSharedLibraries.size() > 0) {Iterator<SharedLibraryEntry> libs = mSharedLibraries.values().iterator();while (libs.hasNext()) {String lib = libs.next().path;if (lib == null) {continue;}try {if (dalvik.system.DexFile.isDexOptNeeded(lib)) {alreadyDexOpted.add(lib);mInstaller.dexopt(lib, Process.SYSTEM_UID, true);didDexOpt = true;}} catch (FileNotFoundException e) {Slog.w(TAG, "Library not found: " + lib);} catch (IOException e) {Slog.w(TAG, "Cannot dexopt " + lib + "; is it an APK or JAR? "+ e.getMessage());}}}

这里首先调用Settings的readLPw函数去解析packages.xml和packages-backup.xml保存的安装列表信息，并把解析的pakcages信息添加到相应的数据结构中，这里我们先假设这是第一次开机，所有packages.xml和packages-backup.xml文件都还不存在。所以Settings的readLPw函数会直接返回。接着把boot class path里面的文件添加到alreadyDexOpted这个HashSet中，因为它们在zygote启动时已经进过Dex优化了。接着扫描mSharedLibraries中的文件，这些文件是在解析platfrom.xml中的library tag添加进来的，如果它们需要做dex优化，则调用Installd的的dexopt方法，关于installd的调用流程，我们后面在安装apk的时候再来分析。接着来看PMS的构造函数：

            File frameworkDir = new File(Environment.getRootDirectory(), "framework");alreadyDexOpted.add(frameworkDir.getPath() + "/framework-res.apk");alreadyDexOpted.add(frameworkDir.getPath() + "/core-libart.jar");String[] frameworkFiles = frameworkDir.list();if (frameworkFiles != null) {for (int i=0; i<frameworkFiles.length; i++) {File libPath = new File(frameworkDir, frameworkFiles[i]);String path = libPath.getPath();if (alreadyDexOpted.contains(path)) {continue;}if (!path.endsWith(".apk") && !path.endsWith(".jar")) {continue;}try {if (dalvik.system.DexFile.isDexOptNeeded(path)) {mInstaller.dexopt(path, Process.SYSTEM_UID, true);didDexOpt = true;}} catch (FileNotFoundException e) {Slog.w(TAG, "Jar not found: " + path);} catch (IOException e) {Slog.w(TAG, "Exception reading jar: " + path, e);}}}if (didDexOpt) {File dalvikCacheDir = new File(dataDir, "dalvik-cache");String[] files = dalvikCacheDir.list();if (files != null) {for (int i=0; i<files.length; i++) {String fn = files[i];if (fn.startsWith("data@app@")|| fn.startsWith("data@app-private@")) {Slog.i(TAG, "Pruning dalvik file: " + fn);(new File(dalvikCacheDir, fn)).delete();}}}}

这里扫描所有的/system/framework下面除framework-res以外的apk和jar包(因为framework-res只有resource文件)，然后依次对它们做Dex优化。在上面如果有对文件做过Dex优化，就要去删除dalvi-cache下面所有的dex文件，以防止cache文件和现在的文件不相符。接着来看PMS的构造函数：

            mFrameworkInstallObserver = new AppDirObserver(frameworkDir.getPath(), OBSERVER_EVENTS, true, false);mFrameworkInstallObserver.startWatching();scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR| PackageParser.PARSE_IS_PRIVILEGED,scanMode | SCAN_NO_DEX, 0);// Collected privileged system packages.File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");mPrivilegedInstallObserver = new AppDirObserver(privilegedAppDir.getPath(), OBSERVER_EVENTS, true, true);mPrivilegedInstallObserver.startWatching();scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR| PackageParser.PARSE_IS_PRIVILEGED, scanMode, 0);// Collect ordinary system packages.File systemAppDir = new File(Environment.getRootDirectory(), "app");mSystemInstallObserver = new AppDirObserver(systemAppDir.getPath(), OBSERVER_EVENTS, true, false);mSystemInstallObserver.startWatching();scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);// Collect all vendor packages.File vendorAppDir = new File("/vendor/app");mVendorInstallObserver = new AppDirObserver(vendorAppDir.getPath(), OBSERVER_EVENTS, true, false);mVendorInstallObserver.startWatching();scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);if (DEBUG_UPGRADE) Log.v(TAG, "Running installd update commands");mInstaller.moveFiles();

这里首先会/system/framework、/system/priv-app、/system/app、/vendor/app四个目录建立AppDirObserver去监听它们的add、delete等操作，AppDirObserver是继承于FileObserver，它的底层是通过linux内核的inotify机制实现的。接着调用scanDirLI去扫描上面的四个目录。我们来看一下AppDirObserver的架构：

接着来看scanDirLI的代码：

    private void scanDirLI(File dir, int flags, int scanMode, long currentTime) {String[] files = dir.list();int i;for (i=0; i<files.length; i++) {File file = new File(dir, files[i]);if (!isPackageFilename(files[i])) {continue;}PackageParser.Package pkg = scanPackageLI(file,flags|PackageParser.PARSE_MUST_BE_APK, scanMode, currentTime, null);if (pkg == null && (flags & PackageParser.PARSE_IS_SYSTEM) == 0 &&mLastScanError == PackageManager.INSTALL_FAILED_INVALID_APK) {Slog.w(TAG, "Cleaning up failed install of " + file);file.delete();}}}

scanDirLI调用scanPackageLI依次扫描并解析上面四个目录的目录下所有的apk文件：

    private PackageParser.Package scanPackageLI(File scanFile,int parseFlags, int scanMode, long currentTime, UserHandle user) {mLastScanError = PackageManager.INSTALL_SUCCEEDED;String scanPath = scanFile.getPath();parseFlags |= mDefParseFlags;PackageParser pp = new PackageParser(scanPath);//首先解析出一个Package对象final PackageParser.Package pkg = pp.parsePackage(scanFile,scanPath, mMetrics, parseFlags);PackageSetting ps = null;PackageSetting updatedPkg;synchronized (mPackages) {String oldName = mSettings.mRenamedPackages.get(pkg.packageName);if (pkg.mOriginalPackages != null && pkg.mOriginalPackages.contains(oldName)) {ps = mSettings.peekPackageLPr(oldName);}if (ps == null) {ps = mSettings.peekPackageLPr(pkg.packageName);}updatedPkg = mSettings.getDisabledSystemPkgLPr(ps != null ? ps.name : pkg.packageName);if (DEBUG_INSTALL && updatedPkg != null) Slog.d(TAG, "updatedPkg = " + updatedPkg);}if (updatedPkg != null && (parseFlags&PackageParser.PARSE_IS_SYSTEM) != 0) {//与update app相关的}if (updatedPkg != null) {parseFlags |= PackageParser.PARSE_IS_SYSTEM;}if (!collectCertificatesLI(pp, ps, pkg, scanFile, parseFlags)) {Slog.w(TAG, "Failed verifying certificates for package:" + pkg.packageName);return null;}//处理system与非system的app同名的问题boolean shouldHideSystemApp = false;if (updatedPkg == null && ps != null&& (parseFlags & PackageParser.PARSE_IS_SYSTEM_DIR) != 0 && !isSystemApp(ps)) {if (compareSignatures(ps.signatures.mSignatures, pkg.mSignatures)!= PackageManager.SIGNATURE_MATCH) {if (DEBUG_INSTALL) Slog.d(TAG, "Signature mismatch!");deletePackageLI(pkg.packageName, null, true, null, null, 0, null, false);ps = null;} else {if (pkg.mVersionCode < ps.versionCode) {shouldHideSystemApp = true;} else {InstallArgs args = createInstallArgs(packageFlagsToInstallFlags(ps),ps.codePathString, ps.resourcePathString, ps.nativeLibraryPathString);synchronized (mInstallLock) {args.cleanUpResourcesLI();}}}}if ((parseFlags & PackageParser.PARSE_IS_SYSTEM_DIR) == 0) {if (ps != null && !ps.codePath.equals(ps.resourcePath)) {parseFlags |= PackageParser.PARSE_FORWARD_LOCK;}}String codePath = null;String resPath = null;if ((parseFlags & PackageParser.PARSE_FORWARD_LOCK) != 0) {if (ps != null && ps.resourcePathString != null) {resPath = ps.resourcePathString;} else {}} else {resPath = pkg.mScanPath;}codePath = pkg.mScanPath;setApplicationInfoPaths(pkg, codePath, resPath);//PackageParser.Package scannedPkg = scanPackageLI(pkg, parseFlags, scanMode| SCAN_UPDATE_SIGNATURE, currentTime, user);if (shouldHideSystemApp) {synchronized (mPackages) {grantPermissionsLPw(pkg, true);mSettings.disableSystemPackageLPw(pkg.packageName);}}return scannedPkg;}

scanPackageLI首先调用PackageParser的parsePackage去解析扫描的文件，注意这里有两个parsePackage函数，但它们的参数不同，我们来看以File为第一个参数的parsePackage方法：

    public Package parsePackage(File sourceFile, String destCodePath,DisplayMetrics metrics, int flags) {mParseError = PackageManager.INSTALL_SUCCEEDED;mArchiveSourcePath = sourceFile.getPath();XmlResourceParser parser = null;AssetManager assmgr = null;Resources res = null;boolean assetError = true;try {assmgr = new AssetManager();int cookie = assmgr.addAssetPath(mArchiveSourcePath);if (cookie != 0) {res = new Resources(assmgr, metrics, null);assmgr.setConfiguration(0, 0, null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,Build.VERSION.RESOURCES_SDK_INT);parser = assmgr.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);assetError = false;} else {Slog.w(TAG, "Failed adding asset path:"+mArchiveSourcePath);}} catch (Exception e) {Slog.w(TAG, "Unable to read AndroidManifest.xml of "+ mArchiveSourcePath, e);}if (assetError) {if (assmgr != null) assmgr.close();mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_MANIFEST;return null;}String[] errorText = new String[1];Package pkg = null;Exception errorException = null;try {// XXXX todo: need to figure out correct configuration.pkg = parsePackage(res, parser, flags, errorText);} catch (Exception e) {errorException = e;mParseError = PackageManager.INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION;}parser.close();assmgr.close();pkg.mPath = destCodePath;pkg.mScanPath = mArchiveSourcePath;pkg.mSignatures = null;return pkg;}

首先从apk文件中打开AndroidManifest.xml文件，然后调用以Resources为第一个参数的parsePackage方法，这个函数比较长，主要就是解析AndroidManifest.xml文件，建立一个Package对象，大概类图如下。最后设置Package对象的mPath和mScanPath为当前APK所在的全路径名。

我们以Mms这个应用的Manifest文件来看分析解析后的结果，首先来看Mms的AndroidManifest.xml文件(这里只截取了一部分)

<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.android.mms"><original-package android:name="com.android.mms" /><uses-permission android:name="android.permission.RECEIVE_MMS" /><uses-permission android:name="android.permission.SEND_SMS" /><!-- System apps can access the  receiver through intent--><permission android:name="android.permission.MMS_SEND_OUTBOX_MSG"android:protectionLevel="signatureOrSystem"android:label="@string/label_mms_send_outbox_msg"android:description="@string/desc_mms_send_outbox_msg"/><application android:name="MmsApp"android:label="@string/app_label"android:icon="@mipmap/ic_launcher_smsmms"android:taskAffinity="android.task.mms"android:allowTaskReparenting="true"><activity android:name=".ui.ConversationList"android:label="@string/app_label"android:configChanges="orientation|screenSize|keyboardHidden"android:theme="@style/MmsHoloTheme"android:uiOptions="splitActionBarWhenNarrow"android:launchMode="singleTop"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /><category android:name="android.intent.category.DEFAULT" /><category android:name="android.intent.category.APP_MESSAGING" /></intent-filter><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="vnd.android.cursor.dir/mms" /></intent-filter><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="vnd.android-dir/mms-sms" /></intent-filter></activity><activity android:name=".ui.ComposeMessageActivity"android:configChanges="orientation|screenSize|keyboardHidden"android:windowSoftInputMode="stateHidden|adjustResize"android:theme="@style/MmsHoloTheme"android:parentActivityName=".ui.ConversationList"android:launchMode="singleTop" ><intent-filter><action android:name="android.intent.action.VIEW" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="vnd.android-dir/mms-sms" /></intent-filter><intent-filter><action android:name="android.intent.action.VIEW" /><action android:name="android.intent.action.SENDTO" /><category android:name="android.intent.category.DEFAULT" /><category android:name="android.intent.category.BROWSABLE" /><data android:scheme="sms" /><data android:scheme="smsto" /></intent-filter><intent-filter><action android:name="android.intent.action.VIEW" /><action android:name="android.intent.action.SENDTO" /><category android:name="android.intent.category.DEFAULT" /><category android:name="android.intent.category.BROWSABLE" /><data android:scheme="mms" /><data android:scheme="mmsto" /></intent-filter><intent-filter><action android:name="android.intent.action.SEND" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="image/*" /></intent-filter><intent-filter><action android:name="android.intent.action.SEND" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="text/plain" /></intent-filter><intent-filter><action android:name="android.intent.action.SEND_MULTIPLE" /><category android:name="android.intent.category.DEFAULT" /><data android:mimeType="image/*" /></intent-filter></activity><receiver android:name=".transaction.PushReceiver"android:permission="android.permission.BROADCAST_WAP_PUSH"><intent-filter><action android:name="android.provider.Telephony.WAP_PUSH_DELIVER" /><data android:mimeType="application/vnd.wap.mms-message" /></intent-filter></receiver><receiver android:name=".transaction.SmsReceiver"><intent-filter><action android:name="android.intent.action.BOOT_COMPLETED" /></intent-filter><intent-filter><action android:name="com.android.mms.transaction.MESSAGE_SENT" /><!-- TODO Do a better data match here. --><data android:scheme="content" /></intent-filter><intent-filter><action android:name="android.intent.action.SEND_MESSAGE" /></intent-filter></receiver><provider android:name="SuggestionsProvider"android:exported="true"android:readPermission="android.permission.READ_SMS"android:authorities="com.android.mms.SuggestionsProvider" ><path-permissionandroid:pathPrefix="/search_suggest_query"android:readPermission="android.permission.GLOBAL_SEARCH" /><path-permissionandroid:pathPrefix="/search_suggest_shortcut"android:readPermission="android.permission.GLOBAL_SEARCH" /></provider><service android:name=".ui.NoConfirmationSendService"android:permission="android.permission.SEND_RESPOND_VIA_MESSAGE"android:exported="true" ><intent-filter><action android:name="android.intent.action.RESPOND_VIA_MESSAGE" /><category android:name="android.intent.category.DEFAULT" /><data android:scheme="sms" /><data android:scheme="smsto" /></intent-filter></service></application>
</manifest>

上面的AndroidManifest.xml文件中定义了2个Activity，2个receiver，1个service和1个provider，我们来看进过parsePackage得到的Package对象如下：

接着回到scanPackageLI方法，解析完AndroidManifest.xml文件后，再来检查是否是更新的APK，如果更新的APK版本比以前的版本还有低，则直接返回；如果更新的APK版本比以前的版本高，则去删除之前的APK以及resource文件。若不是更新APK，并且当前package是系统app，但之前安装了非系统的app，这里首先比较签名，如果签名不一致，则直接删除当前package；若签名文件一致，则首先比较当前package和之前的版本号，如果当前版本号比较新，则直接删除之前的APK以及resource文件。最后调用scanPackageLI方法让把当前package的信息归入到PMS中的数据结构：

    private PackageParser.Package scanPackageLI(PackageParser.Package pkg,int parseFlags, int scanMode, long currentTime, UserHandle user) {File scanFile = new File(pkg.mScanPath);mScanningPath = scanFile;if ((parseFlags&PackageParser.PARSE_IS_SYSTEM) != 0) {pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SYSTEM;}if ((parseFlags&PackageParser.PARSE_IS_PRIVILEGED) != 0) {pkg.applicationInfo.flags |= ApplicationInfo.FLAG_PRIVILEGED;}if (mCustomResolverComponentName != null &&mCustomResolverComponentName.getPackageName().equals(pkg.packageName)) {setUpCustomResolverActivity(pkg);}if (pkg.packageName.equals("android")) {synchronized (mPackages) {if (mAndroidApplication != null) {mLastScanError = PackageManager.INSTALL_FAILED_DUPLICATE_PACKAGE;return null;}mPlatformPackage = pkg;pkg.mVersionCode = mSdkVersion;mAndroidApplication = pkg.applicationInfo;if (!mResolverReplaced) {mResolveActivity.applicationInfo = mAndroidApplication;mResolveActivity.name = ResolverActivity.class.getName();mResolveActivity.packageName = mAndroidApplication.packageName;mResolveActivity.processName = "system:ui";mResolveActivity.launchMode = ActivityInfo.LAUNCH_MULTIPLE;mResolveActivity.flags = ActivityInfo.FLAG_EXCLUDE_FROM_RECENTS;mResolveActivity.theme = com.android.internal.R.style.Theme_Holo_Dialog_Alert;mResolveActivity.exported = true;mResolveActivity.enabled = true;mResolveInfo.activityInfo = mResolveActivity;mResolveInfo.priority = 0;mResolveInfo.preferredOrder = 0;mResolveInfo.match = 0;mResolveComponentName = new ComponentName(mAndroidApplication.packageName, mResolveActivity.name);}}}File destCodeFile = new File(pkg.applicationInfo.sourceDir);File destResourceFile = new File(pkg.applicationInfo.publicSourceDir);SharedUserSetting suid = null;PackageSetting pkgSetting = null;if (!isSystemApp(pkg)) {// Only system apps can use these features.pkg.mOriginalPackages = null;pkg.mRealPackage = null;pkg.mAdoptPermissions = null;}// writersynchronized (mPackages) {if ((parseFlags&PackageParser.PARSE_IS_SYSTEM_DIR) == 0) {if (!updateSharedLibrariesLPw(pkg, null)) {return null;}}if (pkg.mSharedUserId != null) {suid = mSettings.getSharedUserLPw(pkg.mSharedUserId, 0, true);if (suid == null) {Slog.w(TAG, "Creating application package " + pkg.packageName+ " for shared user failed");mLastScanError = PackageManager.INSTALL_FAILED_INSUFFICIENT_STORAGE;return null;}if (DEBUG_PACKAGE_SCANNING) {if ((parseFlags & PackageParser.PARSE_CHATTY) != 0)Log.d(TAG, "Shared UserID " + pkg.mSharedUserId + " (uid=" + suid.userId+ "): packages=" + suid.packages);}}

这里的mCustomResolverComponentName默认是空，采用framework是本身的ResolverActivity去解析intent。mAndroidApplication在Android系统中只有一个这样的application，就是framework-res.apk，它的packageName是"android"。然后在mResolveActivity和mResolveInfo保存ResolverActivity的信息，ResolverActivity用于在启动Activity的时候，如果有多个activity符合条件，弹出对话框给用户选择，这部分我们在以后分析AcitivityManagerService的时候再来分析。如果在Manifest中指定了ShareUserId，则首先获取一个关联的SharedUserSetting对象：

    SharedUserSetting getSharedUserLPw(String name,int pkgFlags, boolean create) {SharedUserSetting s = mSharedUsers.get(name);if (s == null) {if (!create) {return null;}s = new SharedUserSetting(name, pkgFlags);s.userId = newUserIdLPw(s);Log.i(PackageManagerService.TAG, "New shared user " + name + ": id=" + s.userId);// < 0 means we couldn't assign a userid; fall out and return// s, which is currently nullif (s.userId >= 0) {mSharedUsers.put(name, s);}}return s;}

在开始PMS的构造函数里面我们知道，系统会首先添加一系列的sysem的user id到mSharedUsers，所以如果能够从mSharedUsers获得到就直接返回；如果不能，则首先构造一个SharedUserSetting，并指派一个没有使用的APPLICATION UID，当然APPLICATION UID的值是在FIRST_APPLICATION_UID到LAST_APPLICATION_UID之间。最后把创建的SharedUserSetting添加到mSharedUsers和mUserIds数组当中。接着来看scanPackageLI函数：

            PackageSetting origPackage = null;String realName = null;if (pkg.mOriginalPackages != null) {//关于应用命名和更新的代码}pkgSetting = mSettings.getPackageLPw(pkg, origPackage, realName, suid, destCodeFile,destResourceFile, pkg.applicationInfo.nativeLibraryDir,pkg.applicationInfo.flags, user, false);if (pkgSetting == null) {Slog.w(TAG, "Creating application package " + pkg.packageName + " failed");mLastScanError = PackageManager.INSTALL_FAILED_INSUFFICIENT_STORAGE;return null;}if (pkgSetting.origPackage != null) {pkg.setPackageName(origPackage.name);String msg = "New package " + pkgSetting.realName+ " renamed to replace old package " + pkgSetting.name;reportSettingsProblem(Log.WARN, msg);mTransferedPackages.add(origPackage.name);pkgSetting.origPackage = null;}if (realName != null) {mTransferedPackages.add(pkg.packageName);}if (mSettings.isDisabledSystemPackageLPr(pkg.packageName)) {pkg.applicationInfo.flags |= ApplicationInfo.FLAG_UPDATED_SYSTEM_APP;}if (mFoundPolicyFile) {SELinuxMMAC.assignSeinfoValue(pkg);}pkg.applicationInfo.uid = pkgSetting.appId;pkg.mExtras = pkgSetting;if (!verifySignaturesLP(pkgSetting, pkg)) {if ((parseFlags&PackageParser.PARSE_IS_SYSTEM_DIR) == 0) {return null;}pkgSetting.signatures.mSignatures = pkg.mSignatures;if (pkgSetting.sharedUser != null) {if (compareSignatures(pkgSetting.sharedUser.signatures.mSignatures,pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {Log.w(TAG, "Signature mismatch for shared user : " + pkgSetting.sharedUser);mLastScanError = PackageManager.INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES;return null;}}String msg = "System package " + pkg.packageName+ " signature changed; retaining data.";reportSettingsProblem(Log.WARN, msg);}

关于应用程序改名和更新的代码我们这里先忽略，首先来看构造PackageSetting的方法：

    PackageSetting getPackageLPw(PackageParser.Package pkg, PackageSetting origPackage,String realName, SharedUserSetting sharedUser, File codePath, File resourcePath,String nativeLibraryPathString, int pkgFlags, UserHandle user, boolean add) {final String name = pkg.packageName;PackageSetting p = getPackageLPw(name, origPackage, realName, sharedUser, codePath,resourcePath, nativeLibraryPathString, pkg.mVersionCode, pkgFlags,user, add, true /* allowInstall */);return p;}private PackageSetting getPackageLPw(String name, PackageSetting origPackage,String realName, SharedUserSetting sharedUser, File codePath, File resourcePath,String nativeLibraryPathString, int vc, int pkgFlags,UserHandle installUser, boolean add, boolean allowInstall) {PackageSetting p = mPackages.get(name);if (p != null) {//更新apk相关}if (p == null) {if (origPackage != null) {//更新apk相关} else {p = new PackageSetting(name, realName, codePath, resourcePath,nativeLibraryPathString, vc, pkgFlags);p.setTimeStamp(codePath.lastModified());p.sharedUser = sharedUser;if ((pkgFlags&ApplicationInfo.FLAG_SYSTEM) == 0) {List<UserInfo> users = getAllUsers();if (users != null && allowInstall) {//多用户的部分}}}if (sharedUser != null) {p.appId = sharedUser.userId;} else {//更新系统apk相关}if (add) {// Finish adding new package by adding it and updating shared// user preferencesaddPackageSettingLPw(p, name, sharedUser);}} else {//多用户的部分}return p;}

关于PackageSetting结构可以看文章最开始的类图。在新建一个PackageSetting对象后，首先将得到的系统的uid值赋给applicationInfo.uid ，这就是当前APK以后运行时的UID了。然后就做数字签名验证，这里主要是对于更新APK来做验证。在做完数字签名验证后，还需要检查当前APK是否提供providers与系统已有的providers冲突，如果冲突，则提示安装失败。接着来看scanPackageLI函数：

        synchronized (mPackages) {// We don't expect installation to fail beyond this point,if ((scanMode&SCAN_MONITOR) != 0) {mAppDirs.put(pkg.mPath, pkg);}// Add the new setting to mSettingsmSettings.insertPackageSettingLPw(pkgSetting, pkg);// Add the new setting to mPackagesmPackages.put(pkg.applicationInfo.packageName, pkg);// Make sure we don't accidentally delete its data.final Iterator<PackageCleanItem> iter = mSettings.mPackagesToBeCleaned.iterator();while (iter.hasNext()) {PackageCleanItem item = iter.next();if (pkgName.equals(item.packageName)) {iter.remove();}}// Take care of first install / last update times.if (currentTime != 0) {if (pkgSetting.firstInstallTime == 0) {pkgSetting.firstInstallTime = pkgSetting.lastUpdateTime = currentTime;} else if ((scanMode&SCAN_UPDATE_TIME) != 0) {pkgSetting.lastUpdateTime = currentTime;}} else if (pkgSetting.firstInstallTime == 0) {// We need *something*.  Take time time stamp of the file.pkgSetting.firstInstallTime = pkgSetting.lastUpdateTime = scanFileTime;} else if ((parseFlags&PackageParser.PARSE_IS_SYSTEM_DIR) != 0) {if (scanFileTime != pkgSetting.timeStamp) {// A package on the system image has changed; consider this// to be an update.pkgSetting.lastUpdateTime = scanFileTime;}}// Add the package's KeySets to the global KeySetManagerKeySetManager ksm = mSettings.mKeySetManager;try {ksm.addSigningKeySetToPackage(pkg.packageName, pkg.mSigningKeys);if (pkg.mKeySetMapping != null) {for (Map.Entry<String, Set<PublicKey>> entry : pkg.mKeySetMapping.entrySet()) {if (entry.getValue() != null) {ksm.addDefinedKeySetToPackage(pkg.packageName,entry.getValue(), entry.getKey());}}}} catch (NullPointerException e) {Slog.e(TAG, "Could not add KeySet to " + pkg.packageName, e);} catch (IllegalArgumentException e) {Slog.e(TAG, "Could not add KeySet to malformed package" + pkg.packageName, e);}

首先调用Settings的insertPackageSettingLPw将pkgSetting对象加入到Settings中的mPackages这个HashMap中。在insertPackageSettingLPw方法中，首先将Package中的一些信息赋予给PackageSetting，然后调用addPackageSettingLPw方法将PackageSetting对象添加到mPackages中，并将PackageSetting加入到SharedUserSetting中的packages这个HashSet中。接着将pkg对象加入到PMS的mPackages这个HashMap中，保存在mPackages中信息会被后面很多地方使用到。最后对apk的安装或者更新时间做相应的更新。接着来看scanPackageLI函数：

            int N = pkg.providers.size();StringBuilder r = null;int i;for (i=0; i<N; i++) {PackageParser.Provider p = pkg.providers.get(i);p.info.processName = fixProcessName(pkg.applicationInfo.processName,p.info.processName, pkg.applicationInfo.uid);mProviders.addProvider(p);p.syncable = p.info.isSyncable;if (p.info.authority != null) {String names[] = p.info.authority.split(";");p.info.authority = null;for (int j = 0; j < names.length; j++) {if (j == 1 && p.syncable) {p = new PackageParser.Provider(p);p.syncable = false;}if (!mProvidersByAuthority.containsKey(names[j])) {mProvidersByAuthority.put(names[j], p);if (p.info.authority == null) {p.info.authority = names[j];} else {p.info.authority = p.info.authority + ";" + names[j];}} else {PackageParser.Provider other = mProvidersByAuthority.get(names[j]);}}}if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(p.info.name);}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Providers: " + r);}N = pkg.services.size();r = null;for (i=0; i<N; i++) {PackageParser.Service s = pkg.services.get(i);s.info.processName = fixProcessName(pkg.applicationInfo.processName,s.info.processName, pkg.applicationInfo.uid);mServices.addService(s);if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(s.info.name);}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Services: " + r);}N = pkg.receivers.size();r = null;for (i=0; i<N; i++) {PackageParser.Activity a = pkg.receivers.get(i);a.info.processName = fixProcessName(pkg.applicationInfo.processName,a.info.processName, pkg.applicationInfo.uid);mReceivers.addActivity(a, "receiver");if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(a.info.name);}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Receivers: " + r);}N = pkg.activities.size();r = null;for (i=0; i<N; i++) {PackageParser.Activity a = pkg.activities.get(i);a.info.processName = fixProcessName(pkg.applicationInfo.processName,a.info.processName, pkg.applicationInfo.uid);mActivities.addActivity(a, "activity");if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(a.info.name);}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Activities: " + r);}N = pkg.permissionGroups.size();r = null;for (i=0; i<N; i++) {PackageParser.PermissionGroup pg = pkg.permissionGroups.get(i);PackageParser.PermissionGroup cur = mPermissionGroups.get(pg.info.name);if (cur == null) {mPermissionGroups.put(pg.info.name, pg);if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(pg.info.name);}} else {Slog.w(TAG, "Permission group " + pg.info.name + " from package "+ pg.info.packageName + " ignored: original from "+ cur.info.packageName);if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append("DUP:");r.append(pg.info.name);}}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Permission Groups: " + r);}N = pkg.permissions.size();r = null;for (i=0; i<N; i++) {PackageParser.Permission p = pkg.permissions.get(i);HashMap<String, BasePermission> permissionMap =p.tree ? mSettings.mPermissionTrees: mSettings.mPermissions;p.group = mPermissionGroups.get(p.info.group);if (p.info.group == null || p.group != null) {BasePermission bp = permissionMap.get(p.info.name);if (bp == null) {bp = new BasePermission(p.info.name, p.info.packageName,BasePermission.TYPE_NORMAL);permissionMap.put(p.info.name, bp);}if (bp.perm == null) {if (bp.sourcePackage != null&& !bp.sourcePackage.equals(p.info.packageName)) {if (isSystemApp(p.owner)) {Slog.i(TAG, "New decl " + p.owner + " of permission  "+ p.info.name + " is system");bp.sourcePackage = null;}}if (bp.sourcePackage == null|| bp.sourcePackage.equals(p.info.packageName)) {BasePermission tree = findPermissionTreeLP(p.info.name);if (tree == null|| tree.sourcePackage.equals(p.info.packageName)) {bp.packageSetting = pkgSetting;bp.perm = p;bp.uid = pkg.applicationInfo.uid;if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(p.info.name);}} else {}} else {}} else if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append("DUP:");r.append(p.info.name);}if (bp.perm == p) {bp.protectionLevel = p.info.protectionLevel;}} else {}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Permissions: " + r);}N = pkg.instrumentation.size();r = null;for (i=0; i<N; i++) {PackageParser.Instrumentation a = pkg.instrumentation.get(i);a.info.packageName = pkg.applicationInfo.packageName;a.info.sourceDir = pkg.applicationInfo.sourceDir;a.info.publicSourceDir = pkg.applicationInfo.publicSourceDir;a.info.dataDir = pkg.applicationInfo.dataDir;a.info.nativeLibraryDir = pkg.applicationInfo.nativeLibraryDir;mInstrumentation.put(a.getComponentName(), a);if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {if (r == null) {r = new StringBuilder(256);} else {r.append(' ');}r.append(a.info.name);}}if (r != null) {if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Instrumentation: " + r);}if (pkg.protectedBroadcasts != null) {N = pkg.protectedBroadcasts.size();for (i=0; i<N; i++) {mProtectedBroadcasts.add(pkg.protectedBroadcasts.get(i));}}pkgSetting.setTimeStamp(scanFileTime);}return pkg;}

上面的代码比较长，但功能却比较简单，就是将前面从AndroidManifest里面Parse出来的providers、services、receivers、activities、permissionGroups、permissions和instrumentation添加到PMS的相应数据结构中。providers保存在ProviderIntentResolver对象中；services保存在ServiceIntentResolver对象中；receivers和activities保存在ActivityIntentResolver中；permissionGroups、permissions和permissions保存在HashMap中。ProviderIntentResolver、ServiceIntentResolver和ActivityIntentResolver都是继承于IntentResolver，它们的类图关系如下：

到这里，我们就把scanDirLI介绍完了，依次扫描完/system/framework、/system/priv-app、/system/app、/vendor/app这四个目录下面所有的APK文件，并解析成一个个Package对象，并把他们加入到PMS和Settings中的一些数据结构中。接着回到PMS的构造函数来分析：

            final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<String>();if (!mOnlyCore) {Iterator<PackageSetting> psit = mSettings.mPackages.values().iterator();while (psit.hasNext()) {PackageSetting ps = psit.next();if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) == 0) {continue;}final PackageParser.Package scannedPkg = mPackages.get(ps.name);if (scannedPkg != null) {if (mSettings.isDisabledSystemPackageLPr(ps.name)) {Slog.i(TAG, "Expecting better updatd system app for " + ps.name+ "; removing system app");removePackageLI(ps, true);}continue;}if (!mSettings.isDisabledSystemPackageLPr(ps.name)) {psit.remove();String msg = "System package " + ps.name+ " no longer exists; wiping its data";reportSettingsProblem(Log.WARN, msg);removeDataDirsLI(ps.name);} else {final PackageSetting disabledPs = mSettings.getDisabledSystemPkgLPr(ps.name);if (disabledPs.codePath == null || !disabledPs.codePath.exists()) {possiblyDeletedUpdatedSystemApps.add(ps.name);}}}}

上面的代码主要是处理在mSettings中保存了的System app，但在在刚刚的scanDirLI并没有找到对应的APK，这里分三种情况：一是在mSettings中有保存，刚刚的scanDirLI也有找到，这里判断它是否被disable的APK，如果是，说明这个apk是通过OTA升级后更新了的，所以清除相应的数据结构；二是在mSettings中有保存，但刚刚的scanDirLI没有找到对应的APK，并且不是被disable的APK就直接删除相应的数据结构；三是在mSettings中有保存，但刚刚的scanDirLI没有找到对应的APK，并且是被disable的APK，就通过查看它的codePath是否存在来判断它是否有可能被更新或者删除，并添加到possiblyDeletedUpdatedSystemApps链表里。接着来看PMS的构造函数：

            ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();for(int i = 0; i < deletePkgsList.size(); i++) {//clean up herecleanupInstallFailedPackage(deletePkgsList.get(i));}deleteTempPackageFiles();mSettings.pruneSharedUsersLPw();if (!mOnlyCore) {EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,SystemClock.uptimeMillis());mAppInstallObserver = new AppDirObserver(mAppInstallDir.getPath(), OBSERVER_EVENTS, false, false);mAppInstallObserver.startWatching();scanDirLI(mAppInstallDir, 0, scanMode, 0);mDrmAppInstallObserver = new AppDirObserver(mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false, false);mDrmAppInstallObserver.startWatching();scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,scanMode, 0);for (String deletedAppName : possiblyDeletedUpdatedSystemApps) {PackageParser.Package deletedPkg = mPackages.get(deletedAppName);mSettings.removeDisabledSystemPackageLPw(deletedAppName);String msg;if (deletedPkg == null) {msg = "Updated system package " + deletedAppName+ " no longer exists; wiping its data";removeDataDirsLI(deletedAppName);} else {msg = "Updated system app + " + deletedAppName+ " no longer present; removing system privileges for "+ deletedAppName;deletedPkg.applicationInfo.flags &= ~ApplicationInfo.FLAG_SYSTEM;PackageSetting deletedPs = mSettings.mPackages.get(deletedAppName);deletedPs.pkgFlags &= ~ApplicationInfo.FLAG_SYSTEM;}reportSettingsProblem(Log.WARN, msg);}} else {mAppInstallObserver = null;mDrmAppInstallObserver = null;}

首先去删除安装不完整的APK文件及其数据，然后清除安装的temp文件，并清除在mSharedUsers没有被使用的ShareUserSettins。接着去扫描/data/app和/data/app-private两个目录中的所有APK文件，并建立对应的FileObserver。最后处理通过OTA更新或者删除的APK文件。来看PMS构造函数的最后一部分：

            updateAllSharedLibrariesLPw();final boolean regrantPermissions = mSettings.mInternalSdkPlatform!= mSdkVersion;if (regrantPermissions) Slog.i(TAG, "Platform changed from "+ mSettings.mInternalSdkPlatform + " to " + mSdkVersion+ "; regranting permissions for internal storage");mSettings.mInternalSdkPlatform = mSdkVersion;updatePermissionsLPw(null, null, UPDATE_PERMISSIONS_ALL| (regrantPermissions? (UPDATE_PERMISSIONS_REPLACE_PKG|UPDATE_PERMISSIONS_REPLACE_ALL): 0));if (!mRestoredSettings && !onlyCore) {mSettings.readDefaultPreferredAppsLPw(this, 0);}mSettings.writeLPr();Runtime.getRuntime().gc();} // synchronized (mPackages)} // synchronized (mInstallLock)}

这一部分的代码量虽然很少，却做了比较多的事情，首先调用updateAllSharedLibrariesLPw为所有需要使用ShareLibrary的package找到对应的ShareLibrary路径，并把这些路径保存在package的usesLibraryFiles数组中。接着调用updatePermissionsLPw为需要使用权限的APK分配对应的权限：

    private void updatePermissionsLPw(String changingPkg,PackageParser.Package pkgInfo, int flags) {Iterator<BasePermission> it = mSettings.mPermissionTrees.values().iterator();while (it.hasNext()) {final BasePermission bp = it.next();if (bp.packageSetting == null) {bp.packageSetting = mSettings.mPackages.get(bp.sourcePackage);}}it = mSettings.mPermissions.values().iterator();while (it.hasNext()) {final BasePermission bp = it.next();if (bp.type == BasePermission.TYPE_DYNAMIC) {if (bp.packageSetting == null && bp.pendingInfo != null) {final BasePermission tree = findPermissionTreeLP(bp.name);if (tree != null && tree.perm != null) {bp.packageSetting = tree.packageSetting;bp.perm = new PackageParser.Permission(tree.perm.owner,new PermissionInfo(bp.pendingInfo));bp.perm.info.packageName = tree.perm.info.packageName;bp.perm.info.name = bp.name;bp.uid = tree.uid;}}}if (bp.packageSetting == null) {bp.packageSetting = mSettings.mPackages.get(bp.sourcePackage);}if (bp.packageSetting == null) {Slog.w(TAG, "Removing dangling permission: " + bp.name+ " from package " + bp.sourcePackage);it.remove();} else if (changingPkg != null && changingPkg.equals(bp.sourcePackage)) {if (pkgInfo == null || !hasPermission(pkgInfo, bp.name)) {Slog.i(TAG, "Removing old permission: " + bp.name+ " from package " + bp.sourcePackage);flags |= UPDATE_PERMISSIONS_ALL;it.remove();}}}if ((flags&UPDATE_PERMISSIONS_ALL) != 0) {for (PackageParser.Package pkg : mPackages.values()) {if (pkg != pkgInfo) {grantPermissionsLPw(pkg, (flags&UPDATE_PERMISSIONS_REPLACE_ALL) != 0);}}}}

updatePermissionsLPw中首先对mPermissionTrees和mPermissions两个Map中的permission的一些信息进行赋值，然后调用grantPermissionsLPw为每个package分配权限，Android分配权限其实就是分配对应的gid号。在grantPermissionsLPw有一系列的判断条件，如果请求分配的权限被允许，就会将对应的gid号码加入到GrantedPermissions的gids数组当中。回到PMS的构造函数函数，最后调用readDefaultPreferredAppsLPw去设置对于处理Intent默认的Activity信息，关于这部分，我们在ActivityMangerService中再来介绍。在PMS构造函数的最后调用mSettings.writeLPr将所有的package、permission、ShareUserID等信息全部写到/data/system/packages.xml中。到这里PMS的构造函数就介绍完了。

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