一.ActivityManagerService(AMS) 启动过程分析

在SystemServer启动ActivityManagerService

如果想了解SystemServer启动过程可以看这篇文章：

frameworks\base\services\java\com\android\server\SystemServer.java        // Activity manager runs the show.        traceBeginAndSlog("StartActivityManager");        mActivityManagerService = mSystemServiceManager.startService(                ActivityManagerService.Lifecycle.class).getService();        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);        mActivityManagerService.setInstaller(installer);

frameworks\base\services\core\java\com\android\server\am\ActivityManagerService.java

public class ActivityManagerService extends IActivityManager.Stub        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {    /** All system services */    SystemServiceManager mSystemServiceManager;        /** Run all ActivityStacks through this */    //管理Activity    final ActivityStackSupervisor mStackSupervisor;        final ActivityStarter mActivityStarter;        final TaskChangeNotificationController mTaskChangeNotificationController;    final InstrumentationReporter mInstrumentationReporter = new InstrumentationReporter();    final ArrayList
     
       mActiveInstrumentation = new ArrayList<>();        // Whether we should use SCHED_FIFO for UI and RenderThreads.    private boolean mUseFifoUiScheduling = false;     //Broadcast 广播 ，前台广播队列和后台广播队列    BroadcastQueue mFgBroadcastQueue;    BroadcastQueue mBgBroadcastQueue;        // Convenient for easy iteration over the queues. Foreground is first    // so that dispatch of foreground broadcasts gets precedence.    final BroadcastQueue[] mBroadcastQueues = new BroadcastQueue[2];    BroadcastStats mLastBroadcastStats;    BroadcastStats mCurBroadcastStats;    BroadcastQueue broadcastQueueForIntent(Intent intent) {        final boolean isFg = (intent.getFlags() & Intent.FLAG_RECEIVER_FOREGROUND) != 0;        if (DEBUG_BROADCAST_BACKGROUND) Slog.i(TAG_BROADCAST,                "Broadcast intent " + intent + " on "                + (isFg ? "foreground" : "background") + " queue");        return (isFg) ? mFgBroadcastQueue : mBgBroadcastQueue;    }    //Activity 堆栈    /**     * The last resumed activity. This is identical to the current resumed activity most     * of the time but could be different when we're pausing one activity before we resume     * another activity.     */    private ActivityRecord mLastResumedActivity;    /**     * If non-null, we are tracking the time the user spends in the currently focused app.     */    private AppTimeTracker mCurAppTimeTracker;        //ANR ？ 最后个ANR状态，难道可以记录app发生ANR的？    /**     * Dump of the activity state at the time of the last ANR. Cleared after     * {@link WindowManagerService#LAST_ANR_LIFETIME_DURATION_MSECS}     */    String mLastANRState;        //Service 和 Provider 管理    final ActiveServices mServices;    final ProviderMap mProviderMap;        //存放系统数据目录    // TODO: Move creation of battery stats service outside of activity manager service.    File dataDir = Environment.getDataDirectory();    File systemDir = new File(dataDir, "system");    systemDir.mkdirs();    mBatteryStatsService = new BatteryStatsService(systemDir, mHandler);    //应用权限管理    mAppOpsService = mInjector.getAppOpsService(new File(systemDir, "appops.xml"), mHandler);            //AcitivityManager 添加进来        ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);                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));                }                ServiceManager.addService("permission", new PermissionController(this));                ServiceManager.addService("processinfo", new ProcessInfoService(this));        //最后 使用Watchdog监控    Watchdog.getInstance().addMonitor(this);    Watchdog.getInstance().addThread(mHandler);    }
     

   从上面截取的一些代码片段，我们能了解到， AMS创建过程 涉及到Android 四大组件管理的初始化工作。并且ActivityManagerService extends IActivityManager.Stub，所以可知AcitivityManagerService与AcitivityManager之间通信也是使用binder机制。

    进ActivityManager 里面看看

//与ActivityManagerService里的ServiceManager.addService(Context.ACTIVITY_SERVICE, this, true);对应。@SystemService(Context.ACTIVITY_SERVICE)public class ActivityManager {    ...}

 

二.ActivityManager和ActivityManagerService关系

如果想了解Activity是如果通过ActivityManager调用ActivityManagerService的过程可以看下这篇文章.

ActivityManager（frameworks/base/core/java/android/app/ActivityManager.java）

ActivityManager 是客户端用来管理系统中正在运行的所有Activity.

上层APP通过ActivityManager使用binder机制传递信息给AMS，由AMS去完成交互和调度工作后通过binder机制返回给ActivityManager，把结果在返回给上层app。

一张图了解ActivityManager和ActivityManagerService在整个Android系统通信过程中位置。

 

 

 

 

参考：

[1]https://www.cnblogs.com/bastard/p/5770573.html