Android11 AMS的出生地到此一游
2024-05-28 17:07:57
目录
一、出生地：
SystemServer.run()方法：
Systemserver.startBootstarpServices(t)方法：
二、SystemServiceManger
SystemServiceManager.startService的流程
ActivityTaskManagerService.Lifecycle
SystemService.publishBinderService
SystemServiceManager.startService时序图：
三、ActivityManagerService启动流程
ActivityManagerService的启动时序图：
四、ActivityManagerService在启动之后还做了什么
五、AMS和ATMS的接口简介
Activity管理：
Stack管理:
Task管理：
初始化操作
Configuration和Orientation
状态监听
角色图：
问题：
查看android 源码最方便的就是https://cs.android.com/ 只不过需要翻墙。
AMS是android非常复杂的一个类，要想细致的研究它，有些时候不可能面面俱到。我认为有时候就像观赏风景一样，一座山很大，要想一下子都观赏完是不可能的。走走停停，走马观花，然后再重要的景点上驻足，在墙上写上“到此一游”。
我们要学习ActivityManagerService那就先从它是怎么出生的开始吧。
一、出生地：
AMS的出生地在SystemServer的main()方法，可以查看frameworks/base/services/java/com/android/server/SystemServer.java
Code block1:
/*** The main entry point from zygote.*/public static void main(String[] args) {new SystemServer().run();}SystemServer.run()方法：
SystemServer.run()方法有200行。把主要的代码粘在下面：
Code block2:
private void run() {TimingsTraceAndSlog t = new TimingsTraceAndSlog();try {t.traceBegin("InitBeforeStartServices");// Record the process start information in sys props.SystemProperties.set(SYSPROP_START_COUNT, String.valueOf(mStartCount));......// Start services.try {t.traceBegin("StartServices");startBootstrapServices(t);// code snippet 1startCoreServices(t);startOtherServices(t);} catch (Throwable ex) {Slog.e("System", "******************************************");Slog.e("System", "************ Failure starting system services", ex);throw ex;} finally {t.traceEnd(); // StartServices}......}Systemserver.startBootstarpServices(t)方法：
Code block3:
/*** Starts the small tangle of critical services that are needed to get the system off the* ground. These services have complex mutual dependencies which is why we initialize them all* in one place here. Unless your service is also entwined in these dependencies, it should be* initialized in one of the other functions.*/private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {t.traceBegin("startBootstrapServices");......// Activity manager runs the show.t.traceBegin("StartActivityManager");// TODO: Might need to move after migration to WM.ActivityTaskManagerService atm = mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();//code snippet 2mActivityManagerService = ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);//code snippet 3mActivityManagerService.setSystemServiceManager(mSystemServiceManager);mActivityManagerService.setInstaller(installer);......}到现在为至，出场的角色有：
- SystemServiceManger
- ActivityTaskManagerService
- ActivityTaskManagerService.Lifecycle
- ActivityManagerService
- ActivityManagerService.Lifecycle
在code snippet2中SystemServiceManger首先登场，调用了其startService方法，参数为ActivityTaskManagerService.Lifecycle
二、SystemServiceManger
看一下SystemServiceManger的类的主要代码：
Code block4:
/*** Manages creating, starting, and other lifecycle events of* {@link com.android.server.SystemService system services}.** {@hide}*/
public class SystemServiceManager {// Services that should receive lifecycle events.private final ArrayList<SystemService> mServices = new ArrayList<SystemService>();//code snippet 4/*** Publish the service so it is accessible to other services and apps.** @param name the name of the new service* @param service the service object*/protected final void publishBinderService(@NonNull String name, @NonNull IBinder service) {publishBinderService(name, service, false);}/*** Starts a service by class name.** @return The service instance.*/public SystemService startService(String className) {//code snippet 5final Class<SystemService> serviceClass = loadClassFromLoader(className,this.getClass().getClassLoader());return startService(serviceClass);}/*** Creates and starts a system service. The class must be a subclass of* {@link com.android.server.SystemService}.** @param serviceClass A Java class that implements the SystemService interface.* @return The service instance, never null.* @throws RuntimeException if the service fails to start.*/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);// Create the service.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);//code snippet 6service = 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);}startService(service);//code snippet 7return service;} finally {Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);}}public void startService(@NonNull final SystemService service) {// Register it.mServices.add(service);// Start it.long time = SystemClock.elapsedRealtime();try {service.onStart();//code snippet 8} catch (RuntimeException ex) {throw new RuntimeException("Failed to start service " + service.getClass().getName()+ ": onStart threw an exception", ex);}warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");}
}从SystemServiceManager的命令就能猜到，它是一个管理类，用于管理SystemService的。从类的注释“Manages creating, starting, and other lifecycle events of system services”就能明白了，它控制system service的生命周期事情。
在code snippet 4中可以看到有一个名叫mServicesArrayList存了管理的所有System service。
SystemServiceManager.startService的流程
现在，我们来说说SystemServiceManager.startService的流程：
- 在code block3的code snippet2开始mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class)
- 再调到code block4的code snippet5的startService方法
- code block4的code snippet6的Constructor<T> constructor = serviceClass.getConstructor(Context.class)；和service = constructor.newInstance(mContext);
- 这一步运行了ActivityTaskManagerService.Lifecycle.class的构造，并实例化得到一个名为service的SystemService
- 调用startService(service)在code snippet 8高用service.onStart(),即ActivityTaskManagerService.Lifecycle的onStart()
ActivityTaskManagerService.Lifecycle
从上面的流程看，有必要看一下ActivityTaskManagerService.Lifecycle的代码：
Code block5:
/*** System service for managing activities and their containers (task, stacks, displays,... ).** {@hide}*/
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {private void start() {//code snippet 11LocalServices.addService(ActivityTaskManagerInternal.class, mInternal);}public static final class Lifecycle extends SystemService {private final ActivityTaskManagerService mService;public Lifecycle(Context context) {super(context);mService = new ActivityTaskManagerService(context);}@Overridepublic void onStart() {publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService);//code snippet 9mService.start();//code snippet 10}public ActivityTaskManagerService getService() {return mService;}}}上面SystemServiceManager.startService流程最后调到了ActivityTaskManagerService.Lifecycle的onStart()。
ActivityTaskManagerService.Lifecycle的onStart()调到了code snippet 9 publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService);和code snippet 10的mService.start();
code snippet 10的mService.start()比较要理解，调了外部类ActivityTaskManagerService的start方法。
publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService)的作用是什么呢？
SystemService.publishBinderService
咱们来主要看一下publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService)的作用：
Code block 6:
/*** The base class for services running in the system process. Override and implement* the lifecycle event callback methods as needed.* <p>* The lifecycle of a SystemService:* </p><ul>* <li>The constructor is called and provided with the system {@link Context}* to initialize the system service.* <li>{@link #onStart()} is called to get the service running. The service should* publish its binder interface at this point using* {@link #publishBinderService(String, IBinder)}. It may also publish additional* local interfaces that other services within the system server may use to access* privileged internal functions.* <li>Then {@link #onBootPhase(int)} is called as many times as there are boot phases* until {@link #PHASE_BOOT_COMPLETED} is sent, which is the last boot phase. Each phase* is an opportunity to do special work, like acquiring optional service dependencies,* waiting to see if SafeMode is enabled, or registering with a service that gets* started after this one.* </ul><p>* NOTE: All lifecycle methods are called from the system server's main looper thread.* </p>** {@hide}*/
@SystemApi(client = Client.SYSTEM_SERVER)
public abstract class SystemService {/*** Publish the service so it is accessible to other services and apps.** @param name the name of the new service* @param service the service object*/protected final void publishBinderService(@NonNull String name, @NonNull IBinder service) {publishBinderService(name, service, false);}/*** Publish the service so it is accessible to other services and apps.** @param name the name of the new service* @param service the service object* @param allowIsolated set to true to allow isolated sandboxed processes* to access this service* @param dumpPriority supported dump priority levels as a bitmask** @hide*/protected final void publishBinderService(String name, IBinder service,boolean allowIsolated, int dumpPriority) {ServiceManager.addService(name, service, allowIsolated, dumpPriority);}}从上面的代码可以看出最后把service 添加到了ServiceManager里了。
SystemServiceManager.startService时序图：
三、ActivityManagerService启动流程
从Code block3的code snippet 3的代码mActivityManagerService = ActivityManagerService.Lifecycle.startService( mSystemServiceManager, atm); 其中参数atm是上面分析提到的已经启动的ActivityTaskManagerService。
来看一下ActivityManagerService.Lifecycle.startService的代码：
Code block7:
public class ActivityManagerService extends IActivityManager.Stubimplements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {//code snippet 24// Note: This method is invoked on the main thread but may need to attach various// handlers to other threads. So take care to be explicit about the looper.public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {LockGuard.installLock(this, LockGuard.INDEX_ACTIVITY);mInjector = new Injector(systemContext);mContext = systemContext;mFactoryTest = FactoryTest.getMode();mSystemThread = ActivityThread.currentActivityThread();mUiContext = mSystemThread.getSystemUiContext();Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());mHandlerThread = new ServiceThread(TAG,THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);mHandlerThread.start();mHandler = new MainHandler(mHandlerThread.getLooper());mUiHandler = mInjector.getUiHandler(this);mProcStartHandlerThread = new ServiceThread(TAG + ":procStart",THREAD_PRIORITY_FOREGROUND, false /* allowIo */);mProcStartHandlerThread.start();mProcStartHandler = new Handler(mProcStartHandlerThread.getLooper());mConstants = new ActivityManagerConstants(mContext, this, mHandler);final ActiveUids activeUids = new ActiveUids(this, true /* postChangesToAtm */);mPlatformCompat = (PlatformCompat) ServiceManager.getService(Context.PLATFORM_COMPAT_SERVICE);mProcessList = mInjector.getProcessList(this);mProcessList.init(this, activeUids, mPlatformCompat);mLowMemDetector = new LowMemDetector(this);mOomAdjuster = new OomAdjuster(this, mProcessList, activeUids);// Broadcast policy parametersfinal BroadcastConstants foreConstants = new BroadcastConstants(Settings.Global.BROADCAST_FG_CONSTANTS);foreConstants.TIMEOUT = BROADCAST_FG_TIMEOUT;final BroadcastConstants backConstants = new BroadcastConstants(Settings.Global.BROADCAST_BG_CONSTANTS);backConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;final BroadcastConstants offloadConstants = new BroadcastConstants(Settings.Global.BROADCAST_OFFLOAD_CONSTANTS);offloadConstants.TIMEOUT = BROADCAST_BG_TIMEOUT;// by default, no "slow" policy in this queueoffloadConstants.SLOW_TIME = Integer.MAX_VALUE;mEnableOffloadQueue = SystemProperties.getBoolean("persist.device_config.activity_manager_native_boot.offload_queue_enabled", false);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;mServices = new ActiveServices(this);mProviderMap = new ProviderMap(this);mPackageWatchdog = PackageWatchdog.getInstance(mUiContext);mAppErrors = new AppErrors(mUiContext, this, mPackageWatchdog);final File systemDir = SystemServiceManager.ensureSystemDir();// TODO: Move creation of battery stats service outside of activity manager service.mBatteryStatsService = new BatteryStatsService(systemContext, systemDir,BackgroundThread.get().getHandler());mBatteryStatsService.getActiveStatistics().readLocked();mBatteryStatsService.scheduleWriteToDisk();mOnBattery = DEBUG_POWER ? true: mBatteryStatsService.getActiveStatistics().getIsOnBattery();mBatteryStatsService.getActiveStatistics().setCallback(this);mOomAdjProfiler.batteryPowerChanged(mOnBattery);mProcessStats = new ProcessStatsService(this, new File(systemDir, "procstats"));mAppOpsService = mInjector.getAppOpsService(new File(systemDir, "appops.xml"), mHandler);mUgmInternal = LocalServices.getService(UriGrantsManagerInternal.class);mUserController = new UserController(this);mPendingIntentController = new PendingIntentController(mHandlerThread.getLooper(), mUserController, mConstants);if (SystemProperties.getInt("sys.use_fifo_ui", 0) != 0) {mUseFifoUiScheduling = true;}mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);mActivityTaskManager = atm;mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController,DisplayThread.get().getLooper());mAtmInternal = LocalServices.getService(ActivityTaskManagerInternal.class);mProcessCpuThread = new Thread("CpuTracker") {@Overridepublic void run() {synchronized (mProcessCpuTracker) {mProcessCpuInitLatch.countDown();mProcessCpuTracker.init();}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);}}}};mHiddenApiBlacklist = new HiddenApiSettings(mHandler, mContext);Watchdog.getInstance().addMonitor(this);Watchdog.getInstance().addThread(mHandler);// bind background threads to little cores// this is expected to fail inside of framework tests because apps can't touch cpusets directly// make sure we've already adjusted system_server's internal view of itself firstupdateOomAdjLocked(OomAdjuster.OOM_ADJ_REASON_NONE);try {Process.setThreadGroupAndCpuset(BackgroundThread.get().getThreadId(),Process.THREAD_GROUP_SYSTEM);Process.setThreadGroupAndCpuset(mOomAdjuster.mCachedAppOptimizer.mCachedAppOptimizerThread.getThreadId(),Process.THREAD_GROUP_SYSTEM);} catch (Exception e) {Slog.w(TAG, "Setting background thread cpuset failed");}mInternal = new LocalService();mPendingStartActivityUids = new PendingStartActivityUids(mContext);}public static final class Lifecycle extends SystemService {private final ActivityManagerService mService;private static ActivityTaskManagerService sAtm;public Lifecycle(Context context) {super(context);mService = new ActivityManagerService(context, sAtm);}public static ActivityManagerService startService(SystemServiceManager ssm, ActivityTaskManagerService atm) {sAtm = atm;return ssm.startService(ActivityManagerService.Lifecycle.class).getService();//code snippet 11}@Overridepublic void onStart() {mService.start();}}ActivityManagerService.Lifecycle.startService方法传进来两个参数：1个是ssm,即SystemServiceManager；1个是atm，即ActivityTaskManagerService。
看到code snippet11的ssm。startService是不是很熟悉了。它就是上面分析的SystemServiceManager.startService的流程。
那么现在ActivityManagerService的启动流程就清晰了：
- 由SystemServiceManager启动，启动过程调用ActivityManagerService.Lifecycle的构造方法并实例化
- 在ActivityManagerService.Lifecycle的构造方法里new了ActivityManagerService。这时把一个ActivityTaskManagerService实例传给了ActivityManagerService。构造方法请看上面的Code block7的code snippet24。
- 调用ActivityManagerService.Lifecycle的onStart()方法。进而调到了ActivityManagerService的start()方法。
ActivityManagerService start方法：
Code block8:
public class ActivityManagerService extends IActivityManager.Stubimplements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {private void start() {removeAllProcessGroups();mProcessCpuThread.start();mBatteryStatsService.publish();mAppOpsService.publish();Slog.d("AppOps", "AppOpsService published");LocalServices.addService(ActivityManagerInternal.class, mInternal);mActivityTaskManager.onActivityManagerInternalAdded();mPendingIntentController.onActivityManagerInternalAdded();// Wait for the synchronized block started in mProcessCpuThread,// so that any other access to mProcessCpuTracker from main thread// will be blocked during mProcessCpuTracker initialization.try {mProcessCpuInitLatch.await();} catch (InterruptedException e) {Slog.wtf(TAG, "Interrupted wait during start", e);Thread.currentThread().interrupt();throw new IllegalStateException("Interrupted wait during start");}}
}ActivityManagerService的启动时序图：
四、ActivityManagerService在启动之后还做了什么
还是从SystemServer的startBootstrapServices()方法开始看：
Code block9:
/*** Starts the small tangle of critical services that are needed to get the system off the* ground. These services have complex mutual dependencies which is why we initialize them all* in one place here. Unless your service is also entwined in these dependencies, it should be* initialized in one of the other functions.*/private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {ActivityTaskManagerService atm = mSystemServiceManager.startService(ActivityTaskManagerService.Lifecycle.class).getService();mActivityManagerService = ActivityManagerService.Lifecycle.startService(mSystemServiceManager, atm);mActivityManagerService.setSystemServiceManager(mSystemServiceManager);//code snippet 12mActivityManagerService.setInstaller(installer);//code snippet 13// Power manager needs to be started early because other services need it.// Native daemons may be watching for it to be registered so it must be ready// to handle incoming binder calls immediately (including being able to verify// the permissions for those calls).mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);// Now that the power manager has been started, let the activity manager// initialize power management features.mActivityManagerService.initPowerManagement();//code snippet 14// Set up the Application instance for the system process and get started.mActivityManagerService.setSystemProcess();//code snippet 15if (SystemProperties.getInt("persist.sys.displayinset.top", 0) > 0) {// DisplayManager needs the overlay immediately.mActivityManagerService.updateSystemUiContext();//code snippet 16LocalServices.getService(DisplayManagerInternal.class).onOverlayChanged();}}在SystemServer的startBootstrapServices()方法中，在ActivityManagerService启动之后顺序执行了：
- code snippet12: mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
- code snippet13: mActivityManagerService.setInstaller(installer);
- code snippet14: mActivityManagerService.initPowerManagement();
- code snippet15: mActivityManagerService.setSystemProcess();
- code snippet16: if (SystemProperties.getInt("persist.sys.displayinset.top", 0) > 0) mActivityManagerService.updateSystemUiContext();
接着是SystemServer的startCoreServices()方法：
Code block10:
/*** Starts some essential services that are not tangled up in the bootstrap process.*/private void startCoreServices(@NonNull TimingsTraceAndSlog t) {mSystemServiceManager.startService(UsageStatsService.class);mActivityManagerService.setUsageStatsManager(LocalServices.getService(UsageStatsManagerInternal.class));//code snippet 17}在SystemServer的startCoreServices()方法中，只有一个调用：
- code snippet17: mActivityManagerService.setUsageStatsManager(LocalServices.getService(UsageStatsManagerInternal.class));
然后是SystemServer的startOtherServices()方法：
Code block11:
/*** Starts a miscellaneous grab bag of stuff that has yet to be refactored and organized.*/private void startOtherServices(@NonNull TimingsTraceAndSlog t) {mActivityManagerService.installSystemProviders();//code snippet 18wm = WindowManagerService.main(context, inputManager, !mFirstBoot, mOnlyCore,new PhoneWindowManager(), mActivityManagerService.mActivityTaskManager);ServiceManager.addService(Context.WINDOW_SERVICE, wm, /* allowIsolated= */ false,DUMP_FLAG_PRIORITY_CRITICAL | DUMP_FLAG_PROTO);mActivityManagerService.setWindowManager(wm);//code snippet 19if (safeMode) {mActivityManagerService.enterSafeMode();//code snippet 20}// Emit any pending system_server WTFssynchronized (SystemService.class) {if (sPendingWtfs != null) {mActivityManagerService.schedulePendingSystemServerWtfs(sPendingWtfs);//code snippet 21sPendingWtfs = null;}}if (safeMode) {mActivityManagerService.showSafeModeOverlay();//code snippet 22}// We now tell the activity manager it is okay to run third party// code. It will call back into us once it has gotten to the state// where third party code can really run (but before it has actually// started launching the initial applications), for us to complete our// initialization.mActivityManagerService.systemReady(() -> {//code snippet 23Slog.i(TAG, "Making services ready");mSystemServiceManager.startBootPhase(t, SystemService.PHASE_ACTIVITY_MANAGER_READY);try {mActivityManagerService.startObservingNativeCrashes();} catch (Throwable e) {reportWtf("observing native crashes", e);}// No dependency on Webview preparation in system server. But this should// be completed before allowing 3rd partyfinal String WEBVIEW_PREPARATION = "WebViewFactoryPreparation";Future<?> webviewPrep = null;if (!mOnlyCore && mWebViewUpdateService != null) {webviewPrep = SystemServerInitThreadPool.submit(() -> {Slog.i(TAG, WEBVIEW_PREPARATION);TimingsTraceAndSlog traceLog = TimingsTraceAndSlog.newAsyncLog();ConcurrentUtils.waitForFutureNoInterrupt(mZygotePreload, "Zygote preload");mZygotePreload = null;mWebViewUpdateService.prepareWebViewInSystemServer();}, WEBVIEW_PREPARATION);}if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_AUTOMOTIVE)) {mSystemServiceManager.startService(CAR_SERVICE_HELPER_SERVICE_CLASS);}try {startSystemUi(context, windowManagerF);} catch (Throwable e) {reportWtf("starting System UI", e);}// Enable airplane mode in safe mode. setAirplaneMode() cannot be called// earlier as it sends broadcasts to other services.// TODO: This may actually be too late if radio firmware already started leaking// RF before the respective services start. However, fixing this requires changes// to radio firmware and interfaces.if (safeMode) {t.traceBegin("EnableAirplaneModeInSafeMode");try {connectivityF.setAirplaneMode(true);} catch (Throwable e) {reportWtf("enabling Airplane Mode during Safe Mode bootup", e);}t.traceEnd();}t.traceBegin("MakeNetworkManagementServiceReady");try {if (networkManagementF != null) {networkManagementF.systemReady();}} catch (Throwable e) {reportWtf("making Network Managment Service ready", e);}CountDownLatch networkPolicyInitReadySignal = null;if (networkPolicyF != null) {networkPolicyInitReadySignal = networkPolicyF.networkScoreAndNetworkManagementServiceReady();}t.traceEnd();t.traceBegin("MakeIpSecServiceReady");try {if (ipSecServiceF != null) {ipSecServiceF.systemReady();}} catch (Throwable e) {reportWtf("making IpSec Service ready", e);}t.traceEnd();t.traceBegin("MakeNetworkStatsServiceReady");try {if (networkStatsF != null) {networkStatsF.systemReady();}} catch (Throwable e) {reportWtf("making Network Stats Service ready", e);}t.traceEnd();t.traceBegin("MakeConnectivityServiceReady");try {if (connectivityF != null) {connectivityF.systemReady();}} catch (Throwable e) {reportWtf("making Connectivity Service ready", e);}t.traceEnd();t.traceBegin("MakeNetworkPolicyServiceReady");try {if (networkPolicyF != null) {networkPolicyF.systemReady(networkPolicyInitReadySignal);}} catch (Throwable e) {reportWtf("making Network Policy Service ready", e);}t.traceEnd();// Wait for all packages to be preparedmPackageManagerService.waitForAppDataPrepared();// It is now okay to let the various system services start their// third party code...t.traceBegin("PhaseThirdPartyAppsCanStart");// confirm webview completion before starting 3rd partyif (webviewPrep != null) {ConcurrentUtils.waitForFutureNoInterrupt(webviewPrep, WEBVIEW_PREPARATION);}mSystemServiceManager.startBootPhase(t, SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);t.traceEnd();t.traceBegin("StartNetworkStack");try {// Note : the network stack is creating on-demand objects that need to send// broadcasts, which means it currently depends on being started after// ActivityManagerService.mSystemReady and ActivityManagerService.mProcessesReady// are set to true. Be careful if moving this to a different place in the// startup sequence.NetworkStackClient.getInstance().start();} catch (Throwable e) {reportWtf("starting Network Stack", e);}t.traceEnd();t.traceBegin("StartTethering");try {// TODO: hide implementation details, b/146312721.ConnectivityModuleConnector.getInstance().startModuleService(TETHERING_CONNECTOR_CLASS,PERMISSION_MAINLINE_NETWORK_STACK, service -> {ServiceManager.addService(Context.TETHERING_SERVICE, service,false /* allowIsolated */,DUMP_FLAG_PRIORITY_HIGH | DUMP_FLAG_PRIORITY_NORMAL);});} catch (Throwable e) {reportWtf("starting Tethering", e);}t.traceEnd();t.traceBegin("MakeCountryDetectionServiceReady");try {if (countryDetectorF != null) {countryDetectorF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying CountryDetectorService running", e);}t.traceEnd();t.traceBegin("MakeNetworkTimeUpdateReady");try {if (networkTimeUpdaterF != null) {networkTimeUpdaterF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying NetworkTimeService running", e);}t.traceEnd();t.traceBegin("MakeInputManagerServiceReady");try {// TODO(BT) Pass parameter to input managerif (inputManagerF != null) {inputManagerF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying InputManagerService running", e);}t.traceEnd();t.traceBegin("MakeTelephonyRegistryReady");try {if (telephonyRegistryF != null) {telephonyRegistryF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying TelephonyRegistry running", e);}t.traceEnd();t.traceBegin("MakeMediaRouterServiceReady");try {if (mediaRouterF != null) {mediaRouterF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying MediaRouterService running", e);}t.traceEnd();t.traceBegin("MakeMmsServiceReady");try {if (mmsServiceF != null) {mmsServiceF.systemRunning();}} catch (Throwable e) {reportWtf("Notifying MmsService running", e);}t.traceEnd();t.traceBegin("IncidentDaemonReady");try {// TODO: Switch from checkService to getService once it's always// in the build and should reliably be there.final IIncidentManager incident = IIncidentManager.Stub.asInterface(ServiceManager.getService(Context.INCIDENT_SERVICE));if (incident != null) {incident.systemRunning();}} catch (Throwable e) {reportWtf("Notifying incident daemon running", e);}t.traceEnd();if (mIncrementalServiceHandle != 0) {t.traceBegin("MakeIncrementalServiceReady");setIncrementalServiceSystemReady(mIncrementalServiceHandle);t.traceEnd();}}, t);}
SystemServer的startOtherServices()方法中的调用顺序为：
- code snippet 18：mActivityManagerService.installSystemProviders();
- code snippet 19：mActivityManagerService.setWindowManager(wm);
- code snippet 20：if (safeMode) mActivityManagerService.enterSafeMode();
- code snippet 21：if (sPendingWtfs != null) mActivityManagerService.schedulePendingSystemServerWtfs(sPendingWtfs);
- code snippet 22：if (safeMode) mActivityManagerService.enterSafeMode();
- code snippet 23：mActivityManagerService.systemReady(() -> {
五、AMS和ATMS的接口简介
在AMS构造方法中，传进来一个参数为ActivityTaskManagerService atm。
从ActivityTaskManagerService的类注释System service for managing activities and their containers (task, stacks, displays,... ).可以清楚的看出:它是一个系统服务，用来管理activitys和它们的容器（如task, stacks, displays）
再从ActivityManagerService里找找ActivityTaskManagerService的使用：
Activity管理：
mActivityTaskManager.startActivity();
mActivityTaskManager.startActivityAsUser();
mActivityTaskManager.startActivityAndWait();
mActivityTaskManager.startActivityFromRecents();
mActivityTaskManager.startRecentsActivity();
mActivityTaskManager.finishActivity
Stack管理:
mActivityTaskManager.setFocusedStack(stackId);
mActivityTaskManager.removeStack(stackId);
mActivityTaskManager.registerTaskStackListener(listener);//Sets the task stack listener that gets callbacks when a task stack changes.
Task管理：
mActivityTaskManager.getTasks(maxNum);
mActivityTaskManager.setTaskResizeable(taskId, resizeableMode);
mActivityTaskManager.resizeTask(taskId, bounds, resizeMode);
mActivityTaskManager.getTaskBounds(taskId);
mActivityTaskManager.removeTask(taskId);
mActivityTaskManager.moveTaskToFront(appThread, callingPackage, taskId, flags, bOptions);
mActivityTaskManager.moveActivityTaskToBack(token, nonRoot);
mActivityTaskManager.moveTaskToStack(taskId, stackId, toTop);
mActivityTaskManager.positionTaskInStack(taskId, stackId, position);
mActivityTaskManager.getTaskForActivity(token, onlyRoot);
mActivityTaskManager.isTopOfTask(token);
初始化操作
mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController,DisplayThread.get().getLooper());
详见ActivityManagerService构造方法
mActivityTaskManager.installSystemProviders();
mActivityTaskManager.setActivityController(controller, imAMonkey);
mActivityTaskManager.setPackageScreenCompatMode(packageName, mode);
详见ActivityManagerService.setPackageScreenCompatMode()
Configuration和Orientation
mActivityTaskManager.setRequestedOrientation(token, requestedOrientation);
详见ActivityManagerService.setRequestedOrientation()
mActivityTaskManager.updateConfiguration(values);
状态监听
mActivityTaskManager.onActivityManagerInternalAdded();
详见ActivityManagerService.start()
mActivityTaskManager.onScreenAwakeChanged(isAwake);
在AMS的setWindowManager(WindowManagerService wm) 方法把WindowManagerService设置给了变量 mWindowManager。
WindowManagerService在AMS的使用不多：
public void setWindowManager(WindowManagerService wm) {synchronized (this) {mWindowManager = wm;mWmInternal = LocalServices.getService(WindowManagerInternal.class);mActivityTaskManager.setWindowManager(wm);}}在AMS的setWindowManager方法直接又传给了ActivityTaskManagerService
从当前AMS出生地这个视角，能看到这些。能看出来在AMS使用最多的是ActivityTaskManagerService。AMS的很多接口功能直接是ActivityTaskManagerService实现的。
这篇文章的目的是从一个视角整理类的设计理念，功能和类之前的关联，达到在脑子里有一个整体的架构。因此不去研究各个方法的具体实现。
角色图：
下面针对上面的分析画一个角色图：
问题：
从上面的角色图可以看到三个概念：
- Task
- Stack
- WindowManager
要想研究明白Android的Activity和Window管理，接下来肯定要花些时间研究一下：
- ActivityTaskManagerService
- 什么是Task
- 什么是Stack
- Window的管理
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