PackageManagerService初始化

PackageManagerService初始化

前言

在接触了framework一段时间后，对于Android的各大服务都有了一定的了解，之前我在做应用的时候就一直好奇，应用商店这类程序究竟是怎么写的，怎么实现的。最后发现了PKMS这个东西。PKMS，其实是Android最主要的核心服务之一，界面的跳转，广播的发送，服务的启动，应用的安装以及卸载一系列Android的基础操作都离不开PKMS的帮助，我们可以把PKMS看成我们Android系统的管家，PKMS会对manifest进行解析，提取其中的组件信息，权限等一系列的有用信息进行保存，为我们之后的操作做准备。看到这有没有一种恍然大悟的感觉，估计没有。你啥都没写呢，你让我悟啥？这就是咱们为什么要把四大组件，权限这些东西在manifest里注册的原因。你注册了，安装的时候才能解析到，跳转的时候才能匹配到，系统才知道往哪跳啊。是不是很有道理，你品，你细品。。。

PKMS的成员

PKMS是一个很庞大的集团，老总呢就是PackageManagerService.java。真正的业务功能的实现都是老总来亲自做的（你要问，这么大的公司为啥全是老板干活，还缺人不。额，我也在找这种公司，找到记得联系我一下）。这就包括，应用的安装啊卸载啊这些。我们客户端，其实相当于集团的业务员，他们去帮集团拉业务，最后给老总发邮件写清楚业务的内容（binder），然后老总做完后告诉他们，他们在把结果呈现在用户面前。
分析一下上图中的成员：
PackageManagerService：Android的核心服务，用来实现功能。
IPackageManager：其实是binder，用来进行客户端与pkms之间的通信。
PackageManager：abstract类，实现在ApplicationPackageManager。
ApplicationPackageManager:PackageManager的实现类，我们在API的中getPackageManager()，实际上就是得到的ApplicationPackageManager的对象。

    @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;
    }

上证据，是不是不骗人。这个类包含pkms提供给客户端的全部方法，其中一部分api是隐藏的api，应用无法调用。（不许抬杠，和我说我用反射啊，源码环境下编译啊，我能拿到别的pkms的隐藏方法，那不算）。
简单来说pkms就是上述的成员结构，当然其中包含的通讯步骤十分的复杂，这些都会在之后的博客介绍binder的时候进行介绍，还有应用的安装和卸载也会单独开一篇博客。

PKMS初始化

正文来了，初始化究竟在哪里进行，我们又在初始化的时候做了些什么事？
frameworks/base/services/java/com/android/server/SystemServer.java

    private void run() {
        ......
        // Start services.
        try {
            traceBeginAndSlog("StartServices");
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
            SystemServerInitThreadPool.shutdown();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        } finally {
            traceEnd();
        }
        ......
    }

private void startBootstrapServices() {
       ......
        // Start the package manager.
        if (!mRuntimeRestart) {
            MetricsLogger.histogram(null, "boot_package_manager_init_start",
                    (int) SystemClock.elapsedRealtime());
        }
        traceBeginAndSlog("StartPackageManagerService");
        mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
                mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
        mFirstBoot = mPackageManagerService.isFirstBoot();
        mPackageManager = mSystemContext.getPackageManager();
        traceEnd();
        if (!mRuntimeRestart && !isFirstBootOrUpgrade()) {
            MetricsLogger.histogram(null, "boot_package_manager_init_ready",
                    (int) SystemClock.elapsedRealtime());
        }
    ......  
    }

private void startOtherServices() {
      if (!mOnlyCore) {
                Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "UpdatePackagesIfNeeded");
                try {
                    mPackageManagerService.updatePackagesIfNeeded();
                } catch (Throwable e) {...}
            }

      ...

      try {
            mPackageManagerService.systemReady();//PMS ok
      } catch (Throwable e) {
            reportWtf("making Package Manager Service ready", e);
      }
    }
}

SystemServer其实是调到了PackageManagerService的main()方法。
我们继续看PackageManagerService。
/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java

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

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

我们继续看package的构造方法。ServiceManager.addService(“package”, m);提一句这个方法把，将创造好的服务注册到ServiceManager，我们调用的时候也是从ServiceManager获取到这个它，大概理解一下把，与本章我主要想讲的内容不同，与binder相关。

    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) {
            Slog.w(TAG, "**** ro.build.version.sdk not set!");
        }

        mContext = context;

        mPermissionReviewRequired = context.getResources().getBoolean(
                R.bool.config_permissionReviewRequired);

        mFactoryTest = factoryTest;
        mOnlyCore = onlyCore;
        mMetrics = new DisplayMetrics();
        mSettings = new Settings(mPackages);
        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);

        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;
        }

        mInstaller = installer;
        mPackageDexOptimizer = new PackageDexOptimizer(installer, mInstallLock, context,
                "*dexopt*");
        mDexManager = new DexManager(this, mPackageDexOptimizer, installer, mInstallLock);
        mMoveCallbacks = new MoveCallbacks(FgThread.get().getLooper());

        mOnPermissionChangeListeners = new OnPermissionChangeListeners(
                FgThread.get().getLooper());

        getDefaultDisplayMetrics(context, mMetrics);

        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "get system config");
        SystemConfig systemConfig = SystemConfig.getInstance();
        mGlobalGids = systemConfig.getGlobalGids();
        mSystemPermissions = systemConfig.getSystemPermissions();
        mAvailableFeatures = systemConfig.getAvailableFeatures();
        Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);

        mProtectedPackages = new ProtectedPackages(mContext);

        synchronized (mInstallLock) {
        // writer
        synchronized (mPackages) {
            mHandlerThread = new ServiceThread(TAG,
                    Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
            mHandlerThread.start();
            mHandler = new PackageHandler(mHandlerThread.getLooper());
            mProcessLoggingHandler = new ProcessLoggingHandler();
            Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);

            mDefaultPermissionPolicy = new DefaultPermissionGrantPolicy(this);
            mInstantAppRegistry = new InstantAppRegistry(this);

            File dataDir = Environment.getDataDirectory();
            mAppInstallDir = new File(dataDir, "app");
            mAppLib32InstallDir = new File(dataDir, "app-lib");
            mAsecInternalPath = new File(dataDir, "app-asec").getPath();
            mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
            sUserManager = new UserManagerService(context, this,
                    new UserDataPreparer(mInstaller, mInstallLock, mContext, mOnlyCore), mPackages);

            // Propagate permission configuration in to package manager.
            ArrayMap<String, SystemConfig.PermissionEntry> permConfig
                    = systemConfig.getPermissions();
            for (int i=0; i<permConfig.size(); i++) {
                SystemConfig.PermissionEntry perm = permConfig.valueAt(i);
                BasePermission bp = mSettings.mPermissions.get(perm.name);
                if (bp == null) {
                    bp = new BasePermission(perm.name, "android", BasePermission.TYPE_BUILTIN);
                    mSettings.mPermissions.put(perm.name, bp);
                }
                if (perm.gids != null) {
                    bp.setGids(perm.gids, perm.perUser);
                }
            }

            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);
            }

            mFoundPolicyFile = SELinuxMMAC.readInstallPolicy();

            Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "read user settings");
            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
            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);
                }
            }

            if (mFirstBoot) {
                requestCopyPreoptedFiles();
            }

            String customResolverActivity = Resources.getSystem().getString(
                    R.string.config_customResolverActivity);
            if (TextUtils.isEmpty(customResolverActivity)) {
                customResolverActivity = null;
            } else {
                mCustomResolverComponentName = ComponentName.unflattenFromString(
                        customResolverActivity);
            }

            long startTime = SystemClock.uptimeMillis();

            EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_SYSTEM_SCAN_START,
                    startTime);

            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!");
            }

            File frameworkDir = new File(Environment.getRootDirectory(), "framework");

            final VersionInfo ver = mSettings.getInternalVersion();
            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
            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.
            mIsPreNUpgrade = mIsUpgrade && ver.sdkVersion < Build.VERSION_CODES.N;

            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
            if (mPromoteSystemApps) {
                Iterator<PackageSetting> pkgSettingIter = mSettings.mPackages.values().iterator();
                while (pkgSettingIter.hasNext()) {
                    PackageSetting ps = pkgSettingIter.next();
                    if (isSystemApp(ps)) {
                        mExistingSystemPackages.add(ps.name);
                    }
                }
            }

            mCacheDir = preparePackageParserCache(mIsUpgrade);

            // Set flag to monitor and not change apk file paths when
            // scanning install directories.
            int scanFlags = SCAN_BOOTING | SCAN_INITIAL;

            if (mIsUpgrade || mFirstBoot) {
                scanFlags = scanFlags | SCAN_FIRST_BOOT_OR_UPGRADE;
            }

            // Collect vendor 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.
            scanDirTracedLI(new File(VENDOR_OVERLAY_DIR), mDefParseFlags
                    | PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR
                    | PackageParser.PARSE_TRUSTED_OVERLAY, scanFlags | SCAN_TRUSTED_OVERLAY, 0);

            mParallelPackageParserCallback.findStaticOverlayPackages();

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

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

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

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

            // Collect all vendor packages.
            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
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

            // Collect all OEM packages.
            final File oemAppDir = new File(Environment.getOemDirectory(), "app");
            scanDirTracedLI(oemAppDir, mDefParseFlags
                    | PackageParser.PARSE_IS_SYSTEM
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanFlags, 0);

            // Prune any system packages that no longer exist.
            final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<String>();
            if (!mOnlyCore) {
                Iterator<PackageSetting> psit = mSettings.mPackages.values().iterator();
                while (psit.hasNext()) {
                    PackageSetting ps = psit.next();

                    /*
                     * If this is not a system app, it can't be a
                     * disable system app.
                     */
                    if ((ps.pkgFlags & ApplicationInfo.FLAG_SYSTEM) == 0) {
                        continue;
                    }

                    /*
                     * If the package is scanned, it's not erased.
                     */
                    final PackageParser.Package scannedPkg = mPackages.get(ps.name);
                    if (scannedPkg != null) {
                        /*
                         * 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.
                         */
                        if (mSettings.isDisabledSystemPackageLPr(ps.name)) {
                            logCriticalInfo(Log.WARN, "Expecting better updated system app for "
                                    + ps.name + "; removing system app.  Last known codePath="
                                    + ps.codePathString + ", installStatus=" + ps.installStatus
                                    + ", versionCode=" + ps.versionCode + "; scanned versionCode="
                                    + scannedPkg.mVersionCode);
                            removePackageLI(scannedPkg, true);
                            mExpectingBetter.put(ps.name, ps.codePath);
                        }

                        continue;
                    }

                    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 {
                        final PackageSetting disabledPs = mSettings.getDisabledSystemPkgLPr(ps.name);
                        if (disabledPs.codePath == null || !disabledPs.codePath.exists()) {
                            possiblyDeletedUpdatedSystemApps.add(ps.name);
                        }
                    }
                }
            }

            //look for any incomplete package installations
            ArrayList<PackageSetting> deletePkgsList = mSettings.getListOfIncompleteInstallPackagesLPr();
            for (int i = 0; i < deletePkgsList.size(); i++) {
                // Actual deletion of code and data will be handled by later
                // reconciliation step
                final String packageName = deletePkgsList.get(i).name;
                logCriticalInfo(Log.WARN, "Cleaning up incompletely installed app: " + packageName);
                synchronized (mPackages) {
                    mSettings.removePackageLPw(packageName);
                }
            }

            //delete tmp files
            deleteTempPackageFiles();

            // Remove any shared userIDs that have no associated packages
            mSettings.pruneSharedUsersLPw();

            if (!mOnlyCore) {
                EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
                        SystemClock.uptimeMillis());
                scanDirTracedLI(mAppInstallDir, 0, scanFlags | SCAN_REQUIRE_KNOWN, 0);

                scanDirTracedLI(mDrmAppPrivateInstallDir, mDefParseFlags
                        | PackageParser.PARSE_FORWARD_LOCK,
                        scanFlags | SCAN_REQUIRE_KNOWN, 0);

                /**
                 * Remove disable package settings for any updated system
                 * apps that were removed via an OTA. If they're not a
                 * previously-updated app, remove them completely.
                 * Otherwise, just revoke their system-level permissions.
                 */
                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; it's data will be wiped";
                        // Actual deletion of code and data will be handled by later
                        // reconciliation step
                    } 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;
                    }
                    logCriticalInfo(Log.WARN, msg);
                }

                /**
                 * Make sure all system apps that we expected to appear on
                 * the userdata partition actually showed up. If they never
                 * appeared, crawl back and revive the system version.
                 */
                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");

                        int reparseFlags = mDefParseFlags;
                        if (FileUtils.contains(privilegedAppDir, scanFile)) {
                            reparseFlags = PackageParser.PARSE_IS_SYSTEM
                                    | PackageParser.PARSE_IS_SYSTEM_DIR
                                    | PackageParser.PARSE_IS_PRIVILEGED;
                        } else if (FileUtils.contains(systemAppDir, scanFile)) {
                            reparseFlags = PackageParser.PARSE_IS_SYSTEM
                                    | PackageParser.PARSE_IS_SYSTEM_DIR;
                        } else if (FileUtils.contains(vendorAppDir, scanFile)) {
                            reparseFlags = PackageParser.PARSE_IS_SYSTEM
                                    | PackageParser.PARSE_IS_SYSTEM_DIR;
                        } else if (FileUtils.contains(oemAppDir, scanFile)) {
                            reparseFlags = PackageParser.PARSE_IS_SYSTEM
                                    | PackageParser.PARSE_IS_SYSTEM_DIR;
                        } else {
                            Slog.e(TAG, "Ignoring unexpected fallback path " + scanFile);
                            continue;
                        }

                        mSettings.enableSystemPackageLPw(packageName);

                        try {
                            scanPackageTracedLI(scanFile, reparseFlags, scanFlags, 0, null);
                        } catch (PackageManagerException e) {
                            Slog.e(TAG, "Failed to parse original system package: "
                                    + e.getMessage());
                        }
                    }
                }
            }
            mExpectingBetter.clear();

            // 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 filter
                        continue;
                    }
                    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);
                }
            }
            mDeferProtectedFilters = false;
            mProtectedFilters.clear();

            // Now that we know all of the shared libraries, update all clients to have
            // the correct library paths.
            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.
                adjustCpuAbisForSharedUserLPw(setting.packages, null /*scannedPackage*/);
            }

            // Now that we know all the packages we are keeping,
            // read and update their last usage times.
            mPackageUsage.read(mPackages);
            mCompilerStats.read();

            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.
            int updateFlags = UPDATE_PERMISSIONS_ALL;
            if (ver.sdkVersion != mSdkVersion) {
                Slog.i(TAG, "Platform changed from " + ver.sdkVersion + " to "
                        + mSdkVersion + "; regranting permissions for internal storage");
                updateFlags |= UPDATE_PERMISSIONS_REPLACE_PKG | UPDATE_PERMISSIONS_REPLACE_ALL;
            }
            updatePermissionsLPw(null, null, StorageManager.UUID_PRIVATE_INTERNAL, updateFlags);
            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.
            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 start
            final 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(() -> {
                BootTimingsTraceLog traceLog = new BootTimingsTraceLog("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).
            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,
                                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
            mExistingSystemPackages.clear();
            mPromoteSystemApps = false;

            // All the changes are done during package scanning.
            ver.databaseVersion = Settings.CURRENT_DATABASE_VERSION;

            // can downgrade to reader
            Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "write settings");
            mSettings.writeLPr();
            Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);

            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;
            }

            mInstallerService = new PackageInstallerService(context, this);
            final Pair<ComponentName, String> instantAppResolverComponent =
                    getInstantAppResolverLPr();
            if (instantAppResolverComponent != null) {
                if (DEBUG_EPHEMERAL) {
                    Slog.d(TAG, "Set ephemeral resolver: " + instantAppResolverComponent);
                }
                mInstantAppResolverConnection = new EphemeralResolverConnection(
                        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);
        } // 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);

        Trace.traceBegin(TRACE_TAG_PACKAGE_MANAGER, "loadFallbacks");
        FallbackCategoryProvider.loadFallbacks();
        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);

        // Expose private service for system components to use.
        LocalServices.addService(PackageManagerInternal.class, new PackageManagerInternalImpl());
        Trace.traceEnd(TRACE_TAG_PACKAGE_MANAGER);
    }

这个构造方法我也不知道到底有几百行了，看其中的重点就可以。
主要做了下面这几件事：

1、 添加一些用户id，如system、phone等;

2、 建立并启动PackageHandler消息循环，用于处理apk安装请求如adbinstall packageinstaller安装apk时就会发送消息;

3、 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;

4、 检查/data/system/packages.xml是否存在，里面记录了系统的ppermission,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innotify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,int,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。