ActivityManagerService源码分析（一）

来源：互联网发布：php二次开发工具编辑：程序博客网时间：2024/06/05 14:31

前言：

AMS是Android系统服务中很重要的一个，他负责四大组件的启动、切换、调度、生命周期的管理等等，接下来我们根据AMS的启动来分析AMS的源码

1. SystemServer启动AMS

ActivityManagerService是在SystemServer.java中启动并注册的：

private void startBootstrapServices() {        ......        // 启动AMS，见小节2.1        mActivityManagerService = mSystemServiceManager.startService(                ActivityManagerService.Lifecycle.class).getService();        // 设置AMS        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);        //安装App安装器        mActivityManagerService.setInstaller(installer);        ......        // 电源管理已经开启，在AMS中初始化PM，见小节3        Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "InitPowerManagement");        mActivityManagerService.initPowerManagement();        Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);        ......        // 设置应用实例，在系统进程开始的时候，见小节4        mActivityManagerService.setSystemProcess();        ......    }

看源码可以看到（我没有贴出来），startBootstrapServices中启动并注册了很多其他的服务，比如：PowerManagerService，DisplayManagerService，LightsService，PackageManagerService，UserManagerService，SensorService(native)，这写服务彼此之间有依赖，所以都放在startBootstrapServices方法里面

2. 注册并启动

2.1 startService

文件：SystemServiceManager.java

    public <T extends SystemService> T startService(Class<T> serviceClass) {        try {            final String name = serviceClass.getName();            Slog.i(TAG, "Starting " + name);            Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);            // 创建服务            if (!SystemService.class.isAssignableFrom(serviceClass)) {                throw new RuntimeException("Failed to create " + name                        + ": service must extend " + SystemService.class.getName());            }            final T service;            try {                Constructor<T> constructor = serviceClass.getConstructor(Context.class);                service = constructor.newInstance(mContext);            } catch (InstantiationException ex) {                throw new RuntimeException("Failed to create service " + name                        + ": service could not be instantiated", ex);            } catch (IllegalAccessException ex) {                throw new RuntimeException("Failed to create service " + name                        + ": service must have a public constructor with a Context argument", ex);            } catch (NoSuchMethodException ex) {                throw new RuntimeException("Failed to create service " + name                        + ": service must have a public constructor with a Context argument", ex);            } catch (InvocationTargetException ex) {                throw new RuntimeException("Failed to create service " + name                        + ": service constructor threw an exception", ex);            }            // 注册            mServices.add(service);            // 开始服务            try {                service.onStart();            } catch (RuntimeException ex) {                throw new RuntimeException("Failed to start service " + name                        + ": onStart threw an exception", ex);            }            return service;        } finally {            Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);        }    }

可以看出这方法的作用是创建并且开始一个服务，但是这个服务的类必须是SystemService的子类，于是我们需要传入带有ActivityManagerService的Lifecycle

2.2 Lifecycle

文件：SystemServiceManager.java

    public static final class Lifecycle extends SystemService {        private final ActivityManagerService mService;        public Lifecycle(Context context) {            super(context);            // 构建一个新的AMS，见小节2.3            mService = new ActivityManagerService(context);        }        @Override        public void onStart() {            // 开始服务，2.1中的service.onStart()调用的就是它，见小节2.4            mService.start();        }        public ActivityManagerService getService() {            return mService;        }    }

可以看出Lifecycle是继承SystemService的，并且在构造里构建了AMS，接下来我们来看看AMS的构建函数

2.3 AMS的构建函数

    public ActivityManagerService(Context systemContext) {        mContext = systemContext;        mFactoryTest = FactoryTest.getMode();        mSystemThread = ActivityThread.currentActivityThread();        Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());        // 创建一个mHandlerThread线程，默认名是：ActivityManager        mHandlerThread = new ServiceThread(TAG,                android.os.Process.THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);        mHandlerThread.start();        // 创建一个基于ActivityManager线程的Handler        mHandler = new MainHandler(mHandlerThread.getLooper());        // 创建一个UiHandler线程        mUiHandler = new UiHandler();        // 用单例的方式创建一个名叫ActivityManager:kill的线程，并且创建一个killHandler        if (sKillHandler == null) {            sKillThread = new ServiceThread(TAG + ":kill",                    android.os.Process.THREAD_PRIORITY_BACKGROUND, true /* allowIo */);            sKillThread.start();            // 用于杀死进程            sKillHandler = new KillHandler(sKillThread.getLooper());        }        // 构建一个可以延时10秒的前台广播队列        mFgBroadcastQueue = new BroadcastQueue(this, mHandler,                "foreground", BROADCAST_FG_TIMEOUT, false);        // 构建一个可以延时60秒的普通广播队列        mBgBroadcastQueue = new BroadcastQueue(this, mHandler,                "background", BROADCAST_BG_TIMEOUT, true);        mBroadcastQueues[0] = mFgBroadcastQueue;        mBroadcastQueues[1] = mBgBroadcastQueue;        mServices = new ActiveServices(this);        mProviderMap = new ProviderMap(this);        mAppErrors = new AppErrors(mContext, this);        // 新建一个data/system目录        File dataDir = Environment.getDataDirectory();        File systemDir = new File(dataDir, "system");        systemDir.mkdirs();        // 创建一个BatteryStatsService类        mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);        // 把最新的数据写入硬盘        mBatteryStatsService.scheduleWriteToDisk();        mOnBattery = DEBUG_POWER ? true                : mBatteryStatsService.getActiveStatistics().getIsOnBattery();        mBatteryStatsService.getActiveStatistics().setCallback(this);        // 创建进程统计服务类，并新建一个data/system/procstats目录        mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));        // 创建一个应用权限检查类，新建一个data/system/appops.xml文件，并注册对应的回调接口        mAppOpsService = new AppOpsService(new File(systemDir, "appops.xml"), mHandler);        mAppOpsService.startWatchingMode(AppOpsManager.OP_RUN_IN_BACKGROUND, null,                new IAppOpsCallback.Stub() {                    @Override public void opChanged(int op, int uid, String packageName) {                        if (op == AppOpsManager.OP_RUN_IN_BACKGROUND && packageName != null) {                            if (mAppOpsService.checkOperation(op, uid, packageName)                                    != AppOpsManager.MODE_ALLOWED) {                                runInBackgroundDisabled(uid);                            }                        }                    }                });        mGrantFile = new AtomicFile(new File(systemDir, "urigrants.xml"));        // 创建多用户控制器，user 0是第一个，同时也是唯一开机过程中运行的用户        mUserController = new UserController(this);        // 获取OpenGL版本，如果没有找到，则默认为0        GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version",            ConfigurationInfo.GL_ES_VERSION_UNDEFINED);        mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));        // 设置系统的一些默认配置信息        mConfiguration.setToDefaults();        mConfiguration.setLocales(LocaleList.getDefault());        mConfigurationSeq = mConfiguration.seq = 1;        // 初始化进程CPU跟踪器        mProcessCpuTracker.init();        // 解析/data/system/packages-compat.xml文件，当设备屏幕大小不满足APK所需要的大小，        // 则从packages-compat.xml都去尺寸，用兼容的方式运行        mCompatModePackages = new CompatModePackages(this, systemDir, mHandler);        // 根据AMS传入规则，过滤一些Intent        mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);        // 用来管理Activity栈        mStackSupervisor = new ActivityStackSupervisor(this);        // 解释怎样启动Activity        mActivityStarter = new ActivityStarter(this, mStackSupervisor);        // 管理最近任务列表        mRecentTasks = new RecentTasks(this, mStackSupervisor);        //创建一个统计进程使用CPU情况的线程，名叫CpuTracker        mProcessCpuThread = new Thread("CpuTracker") {            @Override            public void run() {                while (true) {                    try {                        try {                            synchronized(this) {                                final long now = SystemClock.uptimeMillis();                                long nextCpuDelay = (mLastCpuTime.get()+MONITOR_CPU_MAX_TIME)-now;                                long nextWriteDelay = (mLastWriteTime+BATTERY_STATS_TIME)-now;                                //Slog.i(TAG, "Cpu delay=" + nextCpuDelay                                //        + ", write delay=" + nextWriteDelay);                                if (nextWriteDelay < nextCpuDelay) {                                    nextCpuDelay = nextWriteDelay;                                }                                if (nextCpuDelay > 0) {                                    mProcessCpuMutexFree.set(true);                                    this.wait(nextCpuDelay);                                }                            }                        } catch (InterruptedException e) {                        }                        updateCpuStatsNow();                    } catch (Exception e) {                        Slog.e(TAG, "Unexpected exception collecting process stats", e);                    }                }            }        };        // watchdog添加对AMS的监控        Watchdog.getInstance().addMonitor(this);        Watchdog.getInstance().addThread(mHandler);        ......

这个方法会在main thread中被唤醒，但是它需要通过各个handers和其他thread通信，所以要注意明确looper。该构造函数，里面是初始化一些变量，及创建了一些线程，大部分我都进行了注释。

2.4 start

文件：ActivityManagerService.java

    private void start() {        // 移除所有的进程组        Process.removeAllProcessGroups();        // 开始监控进程的CPU使用情况        mProcessCpuThread.start();        // 注册电池统计服务        mBatteryStatsService.publish(mContext);        // 注册应用权限检测服务        mAppOpsService.publish(mContext);        Slog.d("AppOps", "AppOpsService published");        // 注册LocalService服务        LocalServices.addService(ActivityManagerInternal.class, new LocalService());    }

启动ProcessCpuThread，注册电池统计服务，应用权限检测服务和LocalService，其中LocalService继承了ActivityManagerInternal。
小结：创建AMS，启动AMS

3. 初始化PM

3. initPowerManagement

文件：ActivityManagerService.java

    public void initPowerManagement() {        // Activity堆栈管理器和电池统计服务初始化PM        mStackSupervisor.initPowerManagement();        mBatteryStatsService.initPowerManagement();        mLocalPowerManager = LocalServices.getService(PowerManagerInternal.class);        PowerManager pm = (PowerManager)mContext.getSystemService(Context.POWER_SERVICE);        mVoiceWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "*voice*");        // 该唤醒锁为不计数锁，即无论acquire()多少次，一次release()就可以解锁        mVoiceWakeLock.setReferenceCounted(false);    }

小结：这主要是在AMS中初始化PM

4. 设置应用实例

4.1 setSystemProcess

文件：ActivityManagerService.java

    public void setSystemProcess() {        try {            // 以下都是想ServiceManager注册服务            ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true); // 注册AMS自己            ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats); // 注册进程统计服务            ServiceManager.addService("meminfo", new MemBinder(this)); // 注册内存信息的服务            ServiceManager.addService("gfxinfo", new GraphicsBinder(this)); // 注册输出渲染信息的服务            ServiceManager.addService("dbinfo", new DbBinder(this)); // 注册输出数据库信息的服务            // MONITOR_CPU_USAGE默认为true            if (MONITOR_CPU_USAGE) {                ServiceManager.addService("cpuinfo", new CpuBinder(this)); // 输出进程使用CPU的情况            }            ServiceManager.addService("permission", new PermissionController(this)); // 注册权限管理            ServiceManager.addService("processinfo", new ProcessInfoService(this)); // 注册进程信息            // 查询名为android的应用信息            ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(                    "android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);            // 调用installSystemApplicationInfo ，见小节4.2            mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());            //             synchronized (this) {                // 创建一个ProcessRecord对象 ，见小节4.5                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) {                    mPidsSelfLocked.put(app.pid, app);                }                updateLruProcessLocked(app, false, null);                updateOomAdjLocked();            }        } catch (PackageManager.NameNotFoundException e) {            throw new RuntimeException(                    "Unable to find android system package", e);        }    }

4.2 installSystemApplicationInfo

文件：ActivityThread.java

    public void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {        synchronized (this) {            // 看SystemService中创建的ContextIml的installSystemApplicationInfo，见小节4.3            getSystemContext().installSystemApplicationInfo(info, classLoader);            // give ourselves a default profiler            mProfiler = new Profiler();        }    }

4.3 ContextIml.installSystemApplicationInfo

文件：ContextImpl.java

    void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {        // 调用的是LoadeApk里面的installSystemApplicationInfo，见小节4.4        mPackageInfo.installSystemApplicationInfo(info, classLoader);    }

4.4 LoadeApk.installSystemApplicationInfo

文件：LoadeApk.java

    void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {        // 断言只有packageName为android才能使用        assert info.packageName.equals("android");        mApplicationInfo = info;        mClassLoader = classLoader;    }

将ApplicationInfo加入到LoadeApk中，因为SystemService创建LoadeApk时，PKMS并没有完成对手机中文件的解析

4.5 AMS进程管理

文件：ActivityManagerService.java

            ......            synchronized (this) {                // 调用进程管理函数，见4.6                ProcessRecord app = newProcessRecordLocked(info, info.processName, false, 0);                app.persistent = true;                app.pid = MY_PID;                app.maxAdj = ProcessList.SYSTEM_ADJ;                // 将SystemServer对应的ApplicationThread保存到ProcessRecord中                app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);                synchronized (mPidsSelfLocked) {                    // 根据ProcessRecord的pid，将ProcessRecord存在mPidsSelfLocked中                    mPidsSelfLocked.put(app.pid, app);                }                updateLruProcessLocked(app, false, null);                updateOomAdjLocked();            }            ......

4.6 newProcessRecordLocked

文件：ActivityManagerService.java

    final ProcessRecord newProcessRecordLocked(ApplicationInfo info, String customProcess,            boolean isolated, int isolatedUid) {        String proc = customProcess != null ? customProcess : info.processName;        BatteryStatsImpl stats = mBatteryStatsService.getActiveStatistics();        final int userId = UserHandle.getUserId(info.uid);        int uid = info.uid;        // isolated为false        if (isolated) {            ......        }        // 创建一个进程记录对象，见小节4.7        final ProcessRecord r = new ProcessRecord(stats, info, proc, uid);        // 判断是否为常驻的进程        if (!mBooted && !mBooting                && userId == UserHandle.USER_SYSTEM                && (info.flags & PERSISTENT_MASK) == PERSISTENT_MASK) {            r.persistent = true;        }        // 将ProcessRecord保存在AMS里的mProcessNames里        addProcessNameLocked(r);        return r;    }

4.7 ProcessRecord

文件：ProcessRecord.java

    ProcessRecord(BatteryStatsImpl _batteryStats, ApplicationInfo _info,            String _processName, int _uid) {        mBatteryStats = _batteryStats;        info = _info;        isolated = _info.uid != _uid;        uid = _uid;        userId = UserHandle.getUserId(_uid);        processName = _processName;        pkgList.put(_info.packageName, new ProcessStats.ProcessStateHolder(_info.versionCode));        maxAdj = ProcessList.UNKNOWN_ADJ;        curRawAdj = setRawAdj = ProcessList.INVALID_ADJ;        curAdj = setAdj = verifiedAdj = ProcessList.INVALID_ADJ;        persistent = false;        removed = false;        lastStateTime = lastPssTime = nextPssTime = SystemClock.uptimeMillis();    }

这主要是保存一些ProcessRecord里面的属性。
小结：第四节的主要作用就是将一些服务注册到ServiceManger中，包括AMS自己；然后将framework-res-.apk中applicationInfo信息加入到SystemServeice生成的LoadedApk中，同时构建SystemService对应的ProcessRecord，最后通过addProcessNameLocked(r)来把SystemService加入AMS的管理中来。

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