Android AMS启动详解

 //frameworks/base/services/java/corri/android/server/SystemServer.java

//该方法主要启动服务 ActivityManagerService，PowerManagerService，LightsService，DisplayManagerService，PackageManagerService，UserManagerService。
//设置 ActivityManagerService，启动传感器服务。
startBootstrapServices(); // 启动引导服务

//该方法主要
//启动服务 BatteryService 用于统计电池电量，需要 LightService。
//启动服务 UsageStatsService，用于统计应用使用情况。
//启动服务 WebViewUpdateService。
startCoreServices(); // 启动核心服务

//该方法主要启动服务 InputManagerService，WindowManagerService。
//等待 ServiceManager，SurfaceFlinger启动完成，然后显示启动界面。
//启动服务 StatusBarManagerService，
//准备好 window, power, package, display 服务：
//	- WindowManagerService.systemReady()
//	- PowerManagerService.systemReady()
//	- PackageManagerService.systemReady()
//	- DisplayManagerService.systemReady()
startOtherServices(); // 启动其他服务

 //frameworks/base/services/java/corri/android/server/SystemServer.java
 private void startBootstrapServices() {
 	...
 //这里会将ATMS注册到ServiceManager中，然后调用ATMS的start方法。
 ActivityTaskManagerService atm = mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();
 //重点方法1。 注册AMS服务，并返回对应的对象信息
 mActivityManagerService = ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);
 mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
 //设置app安装器
 mActivityManagerService.setInstaller(installer);
 ...
 //重点方法2。 向ServiceManager中注册Binder服务
 mActivityManagerService.setSystemProcess();
 }

// 
	public static ActivityManagerService startService(SystemServiceManager ssm, ActivityTaskManagerService atm) {
  sAtm = atm;
  //调用SM的startService方法。创建AMS实例，并启动AMS
  return ssm.startService(ActivityManagerService.Lifecycle.class).getService();
 }

//frameworks/base/services/core/java/com/android/server/SystemServiceManager.java
		public SystemService startService(String className) {
 final Class<SystemService> serviceClass;
 serviceClass = (Class<SystemService>)Class.forName(className);
 return startService(serviceClass);
 }

 @SuppressWarnings("unchecked")
 public <T extends SystemService> T startService(Class<T> serviceClass) {
 try {
  final String name = serviceClass.getName();
  final T service;
  try {
  //反射构造函数
  Constructor<T> constructor = serviceClass.getConstructor(Context.class);
  //创建服务
  service = constructor.newInstance(mContext);
  ...
  //启动服务
  startService(service);
  return service;
 } finally {
  Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
 }
 }

 public void startService(@NonNull final SystemService service) {
 // Register it.
 //注册到ServiceManager列表中
 mServices.add(service);
 //调用服务对应的onStart方法
 service.onStart();
 }

 public static final class Lifecycle extends SystemService {
 private final ActivityTaskManagerService mService;
 public Lifecycle(Context context) {
  super(context);
  //创建AMS对象
  mService = new ActivityManagerService(context, sAtm);
 }
 @Override
 public void onStart() {
  //调用AMS的start方法
  mService.start();
 }

 public ActivityManagerService getService() {
  //返回了AMS实例
  return mService;
 }
 }

 //构造方法，
 public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {
 //获取系统的ActivityThread
 mSystemThread = ActivityThread.currentActivityThread();
 //创建一个ServiceThread用来处理AMS接收到的命令
 mHandlerThread = new ServiceThread(TAG,THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
 mHandlerThread.start();
 mHandler = new MainHandler(mHandlerThread.getLooper());
 mUiHandler = mInjector.getUiHandler(this);
 //低内存监控
 mLowMemDetector = new LowMemDetector(this);
 //初始化广播队列。这里包含了前台广播，后台广播等
 mFgBroadcastQueue = new BroadcastQueue(this, mHandler, "foreground", foreConstants, false);
 mBgBroadcastQueue = new BroadcastQueue(this, mHandler, "background", backConstants, true);
 mOffloadBroadcastQueue = new BroadcastQueue(this, mHandler, "offload", offloadConstants, true);
 mBroadcastQueues[0] = mFgBroadcastQueue;
 mBroadcastQueues[1] = mBgBroadcastQueue;
 mBroadcastQueues[2] = mOffloadBroadcastQueue;
 //用于保存注册的Service
 mServices = new ActiveServices(this);
 //map，用于保存注册的ContentProvider
 mProviderMap = new ProviderMap(this);
 mPackageWatchdog = PackageWatchdog.getInstance(mUiContext);
 mAppErrors = new AppErrors(mUiContext, this, mPackageWatchdog);

 //创建 /data/system目录
 final File systemDir = SystemServiceManager.ensureSystemDir();
 //创建进程统计服务，保存在/data/system/proccstats目录中。
 mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));
 //赋值ATM，并进行初始化
 mActivityTaskManager = atm;
 mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController, DisplayThread.get().getLooper());
 //CPU追踪器进程
 mProcessCpuThread = new Thread("CpuTracker") {
  @Override
  public void run() {
  ...
  }
 };

 }

 private void start() {
 	 //移除所有的进程组
 removeAllProcessGroups();
 //启动CpuTracker线程
 mProcessCpuThread.start();
 //启动电池统计服务，能够统计具体的应用的电池消耗，从而来进行一定的电量统计
 mBatteryStatsService.publish();
 //创建LocalService，并添加到LocalServices列表中
 LocalServices.addService(ActivityManagerInternal.class, new LocalService());
 mActivityTaskManager.onActivityManagerInternalAdded();
 mUgmInternal.onActivityManagerInternalAdded();
 mPendingIntentController.onActivityManagerInternalAdded();
 }

 public void setSystemProcess() {
 try {
 	//注册ActivityService服务
  ServiceManager.addService(Context.ACTIVITY_SERVICE, this, /* allowIsolated= */ true,
   DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PRIORITY_NORMAL | DUMP_FLAG_PROTO);
  //注册进程状态服务
  ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
  //注册内存Binder
  ServiceManager.addService("meminfo", new MemBinder(this), /* allowIsolated= */ false,DUMP_FLAG_PRIORITY_HIGH);
  //注册图像Binder
  ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
  //注册SQLite DB binder
  ServiceManager.addService("dbinfo", new DbBinder(this));
  if (MONITOR_CPU_USAGE) {
  	//注册CPU使用情况的Binder
  ServiceManager.addService("cpuinfo", new CpuBinder(this),/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
  }
  //注册权限控制Binder
  ServiceManager.addService("permission", new PermissionController(this));
  //注册进程管理Binder
  ServiceManager.addService("processinfo", new ProcessInfoService(this));
  //获取“android”应用的ApplicationInfo，并装载到mSystemThread
  ApplicationInfo info = mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
  mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
  //创建ProcessRecord维护进程的相关信息
  synchronized (this) {
  ProcessRecord app = mProcessList.newProcessRecordLocked(info, info.processName,...);
  app.setPersistent(true);
  app.pid = MY_PID;
  app.getWindowProcessController().setPid(MY_PID);
  app.maxAdj = ProcessList.SYSTEM_ADJ;
  app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
  mPidsSelfLocked.put(app);
  mProcessList.updateLruProcessLocked(app, false, null);
  updateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);
  }
 } catch (PackageManager.NameNotFoundException e) {
  throw new RuntimeException(
   "Unable to find android system package", e);
 }
 }

 private void startOtherServices() {
  //注册系统的ContentProvider信息
  mActivityManagerService.installSystemProviders();
 
  mActivityManagerService.setWindowManager(wm);
  	mActivityManagerService.systemReady(() -> {
  ......//goingCallback
  }, BOOT_TIMINGS_TRACE_LOG);
 }

 mActivityManagerService.systemReady(() -> {
  try {
  //启动NativeCrash的监测
  mActivityManagerService.startObservingNativeCrashes();
  } catch (Throwable e) {
  reportWtf("observing native crashes", e);
  }
  if (!mOnlyCore && mWebViewUpdateService != null) {
  webviewPrep = SystemServerInitThreadPool.get().submit(() -> {
   //启动WebView相关
   mWebViewUpdateService.prepareWebViewInSystemServer();
  }, WEBVIEW_PREPARATION);
  }

  try {
  //启动systemUI
  startSystemUi(context, windowManagerF);
  } catch (Throwable e) {
  reportWtf("starting System UI", e);
  }
  ...
 }