深入分析AMS启动流程

private void startBootstrapServices() {        // Activity manager runs the show.     mActivityManagerService = mSystemServiceManager.startService(                ActivityManagerService.Lifecycle.class).getService();     mActivityManagerService.setSystemProcess();……     mActivityManagerService.installSystemProviders();……     mActivityManagerService.systemReady(new Runnable() {            @Override            public void run() {                Slog.i(TAG, "Making services ready");                mSystemServiceManager.startBootPhase(                        SystemService.PHASE_ACTIVITY_MANAGER_READY);                try {                    mActivityManagerService.startObservingNativeCrashes();                } catch (Throwable e) {                    reportWtf("observing native crashes", e);                }

public ActivityManagerService(Context systemContext) {//系统的context        mContext = systemContext;    //获得系统的ActivityThread        mSystemThread = ActivityThread.currentActivityThread();    //创建一个HandlerThread用来处理AMS接收的命令        mHandlerThread = new ServiceThread(TAG,                android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);        mHandlerThread.start();        mHandler = new MainHandler(mHandlerThread.getLooper());        mUiHandler = new UiHandler();    //初始化广播的队列        mFgBroadcastQueue = new BroadcastQueue(this, mHandler,                "foreground", BROADCAST_FG_TIMEOUT, false);        mBgBroadcastQueue = new BroadcastQueue(this, mHandler,                "background", BROADCAST_BG_TIMEOUT, true);        mBroadcastQueues[0] = mFgBroadcastQueue;        mBroadcastQueues[1] = mBgBroadcastQueue;    //初始化Service相关的容器        mServices = new ActiveServices(this);    //初始化Provider相关的Map，里面保存了注册的ContentProvider        mProviderMap = new ProviderMap(this);        //初始化并创建data/system/目录        File dataDir = Environment.getDataDirectory();        File systemDir = new File(dataDir, "system");        systemDir.mkdirs();    //初始化电量统计服务相关的信息        mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);        mBatteryStatsService.getActiveStatistics().readLocked();        mBatteryStatsService.scheduleWriteToDisk();        mOnBattery = DEBUG_POWER ? true                : mBatteryStatsService.getActiveStatistics().getIsOnBattery();        mBatteryStatsService.getActiveStatistics().setCallback(this);    //初始化系统统计服务，用于统计系统的运行信息        mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));        mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"), mHandler);        mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml"));        //创建系统的第一个user,userID为0，该用户具有管理员权限        mStartedUsers.put(UserHandle.USER_OWNER, new UserState(UserHandle.OWNER, true));        mUserLru.add(UserHandle.USER_OWNER);        updateStartedUserArrayLocked();    //获取opengle的版本        GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version",            ConfigurationInfo.GL_ES_VERSION_UNDEFINED);        //初始化字体语言等配置信息        mConfiguration.setToDefaults();        mConfiguration.setLocale(Locale.getDefault());     ……;        mRecentTasks = new RecentTasks(this);    //初始化StackSupervisor,该类是Activity启动和调度的核心类        mStackSupervisor = new ActivityStackSupervisor(this, mRecentTasks);        mTaskPersister = new TaskPersister(systemDir, mStackSupervisor, mRecentTasks);

   private void start() {        mProcessCpuThread.start();        mBatteryStatsService.publish(mContext);        LocalServices.addService(ActivityManagerInternal.class, new LocalService());    }

public void setSystemProcess() {        try {    //将AMS注册到ServiceManager中            ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);    //注册其他服务到ServiceMananger中            ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);            ServiceManager.addService("meminfo", new MemBinder(this));            ServiceManager.addService("gfxinfo", new GraphicsBinder(this));            ServiceManager.addService("dbinfo", new DbBinder(this));            if (MONITOR_CPU_USAGE) {                ServiceManager.addService("cpuinfo", new CpuBinder(this));            }    //注册权限服务到ServiceMananger中            ServiceManager.addService("permission", new PermissionController(this));            ServiceManager.addService("processinfo", new ProcessInfoService(this));    //从PMS中查询包名为android的application,即framework-res的Application信息            ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(                    "android", STOCK_PM_FLAGS);        //将application信息配置到开始创建的activityThread中            mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());            synchronized (this) {        //创建了一个ProcessRecord对象，该对象中保存着系统ongoing服务的进程信息                ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);                app.persistent = true;                app.pid = MY_PID;                app.maxAdj = ProcessList.SYSTEM_ADJ;                app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);                synchronized (mPidsSelfLocked) {        然后将系统进程的processRecord对象也添加到mPidsSelfLocked集合中，和普通应用的进程一样，接收AMS的管理调度                    mPidsSelfLocked.put(app.pid, app);                }        //更细进程管理的调度信息                updateLruProcessLocked(app, false, null);                updateOomAdjLocked();            }

public void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {        synchronized (this) {            getSystemContext().installSystemApplicationInfo(info, classLoader);        }    }

void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {        mPackageInfo.installSystemApplicationInfo(info, classLoader);    }

public final void installSystemProviders() {        List<ProviderInfo> providers;        synchronized (this) {            //找到名称为”System”的进程，就是上一步创建的processRecord对象            ProcessRecord app = mProcessNames.get("system", Process.SYSTEM_UID);            //找到所有和system进程相关的ContentProvider            providers = generateApplicationProvidersLocked(app);            if (providers != null) {                for (int i=providers.size()-1; i>=0; i--) {                    ProviderInfo pi = (ProviderInfo)providers.get(i);                    //再次确认进程为system的provider,把不是该进程provider移除                    if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) == 0) {                        Slog.w(TAG, "Not installing system proc provider " + pi.name                                + ": not system .apk");                        providers.remove(i);                    }                }            }        }        if (providers != null) {            //把provider安装到系统的ActivityThread中            mSystemThread.installSystemProviders(providers);        }        mCoreSettingsObserver = new CoreSettingsObserver(this);    }

private final List<ProviderInfo> generateApplicationProvidersLocked(ProcessRecord app) {        List<ProviderInfo> providers = null;        try {            //调用PMS根据进程ID和进程名称来查询Provider            ParceledListSlice<ProviderInfo> slice = AppGlobals.getPackageManager().                queryContentProviders(app.processName, app.uid,                        STOCK_PM_FLAGS | PackageManager.GET_URI_PERMISSION_PATTERNS);            providers = slice != null ? slice.getList() : null;        } catch (RemoteException ex) {        }        int userId = app.userId;        if (providers != null) {            int N = providers.size();            for (int i=0; i<N; i++) {                ProviderInfo cpi =                    (ProviderInfo)providers.get(i);               ……                ComponentName comp = new ComponentName(cpi.packageName, cpi.name);           //从AMS管理的contentProvider列表中查询对应的provider     ContentProviderRecord cpr = mProviderMap.getProviderByClass(comp, userId);                if (cpr == null) {                    //如果AMS的Provider列表中没有对应的Provider实例，就根据查询的provider信息，创建一个对象保存到队列中                    cpr = new ContentProviderRecord(this, cpi, app.info, comp, singleton);                    mProviderMap.putProviderByClass(comp, cpr);                }               //同时将provider保存到processRecord对象的pubProviders列表中                app.pubProviders.put(cpi.name, cpr);                ……            }        }        return providers;    }

private void installContentProviders(            Context context, List<ProviderInfo> providers) {         ……        for (ProviderInfo cpi : providers) {            //通过installProvider方法把provider封装成一个ContentProviderHolder对象，有利于进程间传输            IActivityManager.ContentProviderHolder cph = installProvider(context, null, cpi,                    false /*noisy*/, true /*noReleaseNeeded*/, true /*stable*/);            if (cph != null) {                cph.noReleaseNeeded = true;                results.add(cph);            }        }        try {            //将上面得到的contentProviderHolder对象发布到AMS服务，getApplicationThread代表本地进程的一个binder对象，binder对象可跨进程传输，它在AMS中对应一个ProcessRecord.            ActivityManagerNative.getDefault().publishContentProviders(                getApplicationThread(), results);       ……    }

public final void publishContentProviders(IApplicationThread caller,            List<ContentProviderHolder> providers) {           ……            //根据调用者的进程得到相应的processRecord对象，就是系统进程的ProcessRecord            final ProcessRecord r = getRecordForAppLocked(caller);           ……            final int N = providers.size();            for (int i = 0; i < N; i++) {                //ActivityThread客户端传过来的provider src                ContentProviderHolder src = providers.get(i);                //根据src provider name得到一开始保存的进程中保存的ProciderRecord                ContentProviderRecord dst = r.pubProviders.get(src.info.name);                if (dst != null) {                    ComponentName comp = new ComponentName(dst.info.packageName, dst.info.name);                    //按类将它保存在mProviderMap中                    mProviderMap.putProviderByClass(comp, dst);                    String names[] = dst.info.authority.split(";");                    for (int j = 0; j < names.length; j++) {                        //按authority保存在mProviderMap中                        mProviderMap.putProviderByName(names[j], dst);                    }                   ……                    }

public void systemReady(final Runnable goingCallback) {        synchronized(this) {            //初始化Doze模式的controller            mLocalDeviceIdleController                    = LocalServices.getService(DeviceIdleController.LocalService.class);        //重置RecentTasks            mRecentTasks.clear();            mRecentTasks.addAll(mTaskPersister.restoreTasksLocked());            mRecentTasks.cleanupLocked(UserHandle.USER_ALL);            mTaskPersister.startPersisting();            ……            //设置systemReady为true            mSystemReady = true;        }        ArrayList<ProcessRecord> procsToKill = null;        //收集那些在AMS之前启动的进程        synchronized(mPidsSelfLocked) {            for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {                ProcessRecord proc = mPidsSelfLocked.valueAt(i);                if (!isAllowedWhileBooting(proc.info)){                    if (procsToKill == null) {                        procsToKill = new ArrayList<ProcessRecord>();                    }                    procsToKill.add(proc);                }            }        }       //将那些在AMS之前启动的进程杀死，有的进程不能再AMS之前启动        synchronized(this) {            if (procsToKill != null) {                for (int i=procsToKill.size()-1; i>=0; i--) {                    ProcessRecord proc = procsToKill.get(i);                    Slog.i(TAG, "Removing system update proc: " + proc);                    removeProcessLocked(proc, true, false, "system update done");                }            }        }        //从settingsProvider的设置总初始化部分变量        retrieveSettings();        //调用callback方法，该方法在systemServer代码中实现        if (goingCallback != null) goingCallback.run();                    //查询那些persistent为1的application,并启动他们所在的进程                    List apps = AppGlobals.getPackageManager().                        getPersistentApplications(STOCK_PM_FLAGS);                    if (apps != null) {                        int N = apps.size();                        int i;                        for (i=0; i<N; i++) {                            ApplicationInfo info                                = (ApplicationInfo)apps.get(i);                            if (info != null &&                                    !info.packageName.equals("android")) {                                addAppLocked(info, false, null /* ABI override */);                            }            }            //启动HomeActivity，也就是launcher程序            mBooting = true;            startHomeActivityLocked(mCurrentUserId, "systemReady");           ……        }    }

try {                    //ams开始监听native层的crash信息                    mActivityManagerService.startObservingNativeCrashes();                } catch (Throwable e) {                    reportWtf("observing native crashes", e);                }                //初始化webVew                WebViewFactory.prepareWebViewInSystemServer();                try {                    //启动systemUI                    startSystemUi(context);                } catch (Throwable e) {                    reportWtf("starting System UI", e);                }                try {                    //调用其他服务的systemready方法                    if (networkScoreF != null) networkScoreF.systemReady();                } catch (Throwable e) {                    reportWtf("making Network Score Service ready", e);                }