Android ActivityManagerService--
2023-10-26 本文已影响0人
DarcyZhou
本文转自：
本文基于Android 11.0源码分析
前言
ActivityManagerService简称AMS，负责管理四大组件的生命周期以及应用程序进程调度，其中Activity相关实际上由ATMS负责。它有自己的IActivityManager.aidl、ActivityManagerInternal，属于server/am目录下。
ActivityTaskManagerService简称ATMS，负责管理Activities和Activity相关容器（Task，Stacks，Display），也有自己的IActivityTaskManager.aidl、ActivityManagerInternal，在server/wm目录下。
AMS和ATMS启动流程，如下面所示：
AMS01.PNG
1.SystemServer启动
SystemServer是Zygote第一个Fork的进程，这里只分析SystemServer启动流程中AMS相关的逻辑，启动流程可以分为如下几个步骤：
- 初始化SystemContext；
- 创建SystemServiceManage对象，用来启动后面的服务；
- 启动系统服务，共分为三种系统服务：系统引导服务（Boot Service）、核心服务（Core Service）和其他服务（Other Service）；
- 在引导服务（Boot Service）中启动ATMS和AMS服务；
- 在其他服务（Other Service）中完成AMS的最后工作systemReady。
// frameworks/base/services/java/com/android/server/SystemServer.java
public static void main(String[] args) {
new SystemServer().run();
}
//--------------
private void run() {
...
// Initialize the system context.
createSystemContext();// 1.初始化 System Context
// Call per-process mainline module initialization.
ActivityThread.initializeMainlineModules();
// 2.创建SystemServiceManager对象，用来启动后面的服务
mSystemServiceManager = new SystemServiceManager(mSystemContext);
mSystemServiceManager.setStartInfo(mRuntimeRestart,
mRuntimeStartElapsedTime, mRuntimeStartUptime);
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
...
//3.启动服务
try {
t.traceBegin("StartServices");
startBootstrapServices(t); // 启动引导服务
startCoreServices(t); // 启动核心服务
startOtherServices(t); // 启动其他服务
} catch (Throwable ex) {
...
}
下面对这三个过程逐步分析。
1.1 初始化System Context
在SystemServer的run()方法中，在启动AMS之前，调用了createSystemContext()方法，主要用来是初始化 System Context和SystemUI Context，并设置主题。
当SystemServer调用createSystemContext()完毕后，完成以下两个内容：
- 得到了一个ActivityThread对象，它代表当前进程 (此时为系统进程) 的主线程；
- 得到了一个Context对象，对于SystemServer而言，它包含的Application运行环境与framework-res.apk有关。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void createSystemContext() {
//1.创建ActivityThread对象
ActivityThread activityThread = ActivityThread.systemMain();
//2.获取system context
mSystemContext = activityThread.getSystemContext();
//3.设置系统主题
mSystemContext.setTheme(DEFAULT_SYSTEM_THEME);
//4.获取systemui context
final Context systemUiContext = activityThread.getSystemUiContext();
//5.设置systemUI 主题
systemUiContext.setTheme(DEFAULT_SYSTEM_THEME);
}
1.1.1 systemMain()
systemMain函数主要作用是： 创建ActivityThread对象，然后调用该对象的attach函数。
// frameworks/base/core/java/android/app/ActivityThread.java
public static ActivityThread systemMain() {
// The system process on low-memory devices do not get to use hardware
// accelerated drawing, since this can add too much overhead to the
// process.
if (!ActivityManager.isHighEndGfx()) {
ThreadedRenderer.disable(true);
} else {
ThreadedRenderer.enableForegroundTrimming();
}
// 1.创建ActivityThread对象
ActivityThread thread = new ActivityThread();
// 2.调用attach方法
thread.attach(true, 0);
return thread;
}
（1）创建ActivityThread对象
ActivityThread是Android Framework中一个非常重要的类，它代表一个应用进程的主线程，其职责就是调度及执行在该线程中运行的四大组件。 注意到此处的ActivityThread创建于SystemServer进程中。
由于SystemServer中也运行着一些系统APK，例如framework-res.apk、SettingsProvider.apk等，因此也可以认为SystemServer是一个特殊的应用进程。
AMS负责管理和调度进程，因此AMS需要通过Binder机制和应用进程通信。 为此，Android提供了一个IApplicationThread接口，该接口定义了AMS和应用进程之间的交互函数。
ActivityThread的构造函数比较简单，获取ResourcesManager的单例对象，比较关键的是它的成员变量：
// frameworks/base/core/java/android/app/ActivityThread.java
public final class ActivityThread extends ClientTransactionHandler {
...
//定义了AMS与应用通信的接口，拿到ApplicationThread的对象
final ApplicationThread mAppThread = new ApplicationThread();
//拥有自己的looper，说明ActivityThread确实可以代表事件处理线程
final Looper mLooper = Looper.myLooper();
//H继承Handler，ActivityThread中大量事件处理依赖此Handler
final H mH = new H();
//用于保存该进程的ActivityRecord
final ArrayMap<IBinder, ActivityClientRecord> mActivities = new ArrayMap<>();
//用于保存进程中的Service
final ArrayMap<IBinder, Service> mServices = new ArrayMap<>();
用于保存进程中的Application
final ArrayList<Application> mAllApplications
= new ArrayList<Application>();
//构造函数
@UnsupportedAppUsage
ActivityThread() {
mResourcesManager = ResourcesManager.getInstance();
}
}
（2）调用attach()方法
对于系统进程而言，ActivityThread的attach函数最重要的工作就是创建了Instrumentation、Application和Context。
// frameworks/base/core/java/android/app/ActivityThread.java
private void attach(boolean system, long startSeq) {
sCurrentActivityThread = this;
mSystemThread = system;
//系统进程system为true
if (!system) {
// 应用进程处理流程
} else {
// Don't set application object here -- if the system crashes,
// we can't display an alert, we just want to die die die.
android.ddm.DdmHandleAppName.setAppName("system_process",
UserHandle.myUserId());
try {
//系统进程的处理流程，该情况只在SystemServer中处理
//1.创建Instrumentation
mInstrumentation = new Instrumentation();
mInstrumentation.basicInit(this);
//2.创建系统Context
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
//3.创建Application
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
...
}
- Instrumentation
Instrumentation是Android中的一个工具类，当该类被启用时，它将优先于应用中其它的类被初始化。 此时，系统先创建它，再通过它创建其它组件。
mInstrumentation = new Instrumentation();
mInstrumentation.basicInit(this);
- Context
Context是Android中的一个抽象类，用于维护应用运行环境的全局信息。通过Context可以访问应用的资源和类，甚至进行系统级的操作，例如启动Activity、发送广播等。
ActivityThread的attach函数中，通过下面的代码创建出系统应用对应的Context：
ContextImpl context = ContextImpl.createAppContext(this, getSystemContext().mPackageInfo);
- Application
Android中Application类用于保存应用的全局状态。在ActivityThread中，针对系统进程，通过下面的代码创建了初始的Application：
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
1.1.2 getSystemContext()
再回到createSystemContext()方法中初始化SystemContext的过程中，到getSystemContext()方法，该方法主要是创建并返回System Context。
// frameworks/base/services/java/com/android/server/SystemServer.java
public ContextImpl getSystemContext() {
synchronized (this) {
if (mSystemContext == null) {
//调用ContextImpl的静态函数createSystemContext()
mSystemContext = ContextImpl.createSystemContext(this);
}
return mSystemContext;
}
}
这里直接调用了ContextImpl中的静态方法：
// frameworks/base/core/java/android/app/ContextImpl.java
static ContextImpl createSystemContext(ActivityThread mainThread) {
//创建LoadedApk类，代表一个加载到系统中的APK
//注意此时的LoadedApk只是一个空壳
//PKMS还没有启动，无法得到有效的ApplicationInfo
LoadedApk packageInfo = new LoadedApk(mainThread);
//拿到ContextImpl的对象
ContextImpl context = new ContextImpl(null, mainThread, packageInfo, null, null, null, null,
0, null, null);
//初始化资源信息
context.setResources(packageInfo.getResources());
context.mResources.updateConfiguration(context.mResourcesManager.getConfiguration(),
context.mResourcesManager.getDisplayMetrics());
context.mIsSystemOrSystemUiContext = true;
return context;
}
createSystemContext()的内容就是创建一个LoadedApk，然后初始化一个ContextImpl对象。 创建的LoadApk对应packageName为”android”，也就是framwork-res.apk。 由于该APK仅供SystemServer进程使用，因此创建的Context被定义为System Context。
现在该LoadedApk还没有得到framwork-res.apk实际的信息。当PKMS启动，完成对应的解析后，AMS将重新设置这个LoadedApk。
1.1.3 getSystemUiContext()
这个方法是用来获取SystemUi的Context，具体流程与getSystemContext()方法类似。
// frameworks/base/services/java/com/android/server/SystemServer.java
public ContextImpl getSystemUiContext() {
synchronized (this) {
if (mSystemUiContext == null) {
mSystemUiContext = ContextImpl.createSystemUiContext(getSystemContext());
}
return mSystemUiContext;
}
}
然后再调用ContextImpl的createSystemUiContext()方法：
// frameworks/base/core/java/android/app/ContextImpl.java
static ContextImpl createSystemUiContext(ContextImpl systemContext, int displayId) {
final LoadedApk packageInfo = systemContext.mPackageInfo;
// 创建context
ContextImpl context = new ContextImpl(null, systemContext.mMainThread, packageInfo, null,
null, null, null, 0, null, null);
context.setResources(createResources(null, packageInfo, null, displayId, null,
packageInfo.getCompatibilityInfo(), null));
context.updateDisplay(displayId);
context.mIsSystemOrSystemUiContext = true;
return context;
}
1.2 创建SystemServiceManager
再回到SystemServer启动的run()方法中，在调用createSystemContext()方法初始化System Context后，就是创建SystemServiceManager对象。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void run() {
...
//1.创建SystemServiceManager对象
mSystemServiceManager = new SystemServiceManager(mSystemContext);
mSystemServiceManager.setStartInfo(mRuntimeRestart,
mRuntimeStartElapsedTime, mRuntimeStartUptime);
//2.启动SystemServiceManager服务
LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);
...
}
1.2.1 SystemServiceManager()
SystemServiceManager对象主要用于管理SystemService的创建、启动等生命周期，SystemService 类是一个抽象类。
// frameworks/base/services/core/java/com/android/server/SystemServiceManager.java
public class SystemServiceManager {
...
private final Context mContext;
private final ArrayList<SystemService> mServices = new ArrayList<SystemService>();
...
SystemServiceManager(Context context) {
mContext = context;
}
public SystemService startService(String className) {
//通过反射根据类名，拿到类对象
final Class<SystemService> serviceClass = loadClassFromLoader(className,
this.getClass().getClassLoader());
return startService(serviceClass);
}
//------------------------
private static Class<SystemService> loadClassFromLoader(String className,
ClassLoader classLoader) {
try {
return (Class<SystemService>) Class.forName(className, true, classLoader);
} catch (ClassNotFoundException ex) {
...
}
//------------------------
public <T extends SystemService> T startService(Class<T> serviceClass) {
try {
final String name = serviceClass.getName();
...
final T service;
try {
Constructor<T> constructor = serviceClass.getConstructor(Context.class);
service = constructor.newInstance(mContext);
} catch (InstantiationException ex) {
...
startService(service);
return 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(); //调用各个服务中的onStart()方法完成服务启动
} catch (RuntimeException ex) {
throw new RuntimeException("Failed to start service " + service.getClass().getName()
+ ": onStart threw an exception", ex);
}
warnIfTooLong(SystemClock.elapsedRealtime() - time, service, "onStart");
}
...
}
在SystemServiceManager中都是通过反射创建SystemService中对象的，而且在 startService(@NonNull final SystemService service)方法中，会将SystemService添加到mServices 中，并调用 onStart() 方法。
1.2.2 addService()
回到《1.2 创建SystemServiceManager》中，在创建完SystemServiceManager对象后，会调用addService()方法：
// frameworks/base/core/java/com/android/server/LocalServices.java
public final class LocalServices {
private LocalServices() {}
private static final ArrayMap<Class<?>, Object> sLocalServiceObjects =
new ArrayMap<Class<?>, Object>();
//返回实现指定接口的本地服务实例对象
@SuppressWarnings("unchecked")
public static <T> T getService(Class<T> type) {
synchronized (sLocalServiceObjects) {
return (T) sLocalServiceObjects.get(type);
}
}
//将指定接口的服务实例添加到本地服务的全局注册表中
public static <T> void addService(Class<T> type, T service) {
synchronized (sLocalServiceObjects) {
if (sLocalServiceObjects.containsKey(type)) {
throw new IllegalStateException("Overriding service registration");
}
sLocalServiceObjects.put(type, service);
}
}
//删除服务实例，只能在测试中使用
@VisibleForTesting
public static <T> void removeServiceForTest(Class<T> type) {
synchronized (sLocalServiceObjects) {
sLocalServiceObjects.remove(type);
}
}
}
1.3 启动核心服务
回到《1.SystemServer启动》中，在处理完SystemServiceManager对象后，回去启动三个服务，这里只关注核心服务启动：startBootstrapServices()。
在该方法中启动引导服务，在其中启动了ATM和AMS服务，通过AMS安装Installer、初始化Power，设置系统进程等。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
//1.启动ActivityTaskManagerService服务，简称ATMS
//Android10新引入功能，用来管理Activity的启动、调度等功能
ActivityTaskManagerService atm = mSystemServiceManager.startService(
ActivityTaskManagerService.Lifecycle.class).getService();
//2.启动服务 ActivityManagerService，简称AMS
mActivityManagerService = ActivityManagerService.Lifecycle.startService(
mSystemServiceManager, atm);
//3.把ssm和installer赋值给ActivityManagerService
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
mActivityManagerService.setInstaller(installer);
//4\. 利用atm，获取WindowManagerGlobalLock
mWindowManagerGlobalLock = atm.getGlobalLock();
t.traceEnd();
//5.初始化PowerManager
mActivityManagerService.initPowerManagement();
//6.设置系统进程
mActivityManagerService.setSystemProcess();
...
}
到这里SystemServer已经开启去启动服务了，这篇文档关注的ATMS和AMS的启动过程在下面作详细的分析。
2.ActivityTaskMangerService启动过程
ActivityTaskManagerService简称ATM，Android10中引入新功能,用来管理Activity的启动、调度等功能。紧接上面的流程，在SystemServer在startBootstrapServices()方法中会去启动ATMS：
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices() {
...
//启动ATMS
ActivityTaskManagerService atm = mSystemServiceManager.startService(
ActivityTaskManagerService.Lifecycle.class).getService();
...
}
从《1.2.1 SystemServiceManager()》中，可以知道SystemServiceManager.startService()最终调用的是启动对象中的onStart方法，因此ATM启动，这里最终会调用ActivityTaskManagerService.Lifecycle.onStart()来启动ATMS服务：
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
//静态内部类，继承SystemService，说明它是一个系统service
public static final class Lifecycle extends SystemService {
private final ActivityTaskManagerService mService;
public Lifecycle(Context context) {
// 这个context是SystemServiceManager传递过来的系统上下文，
// 即ContextImpl.getSystemContext()返回的实例
super(context);
//1.创建ActivityTaskManagerService对象
mService = new ActivityTaskManagerService(context);
}
@Override
public void onStart() {
//有SystemService调用ServiceManager.addService()加入到servicemanager进程中管理
publishBinderService(Context.ACTIVITY_TASK_SERVICE, mService);
//2.启动ATMS服务
mService.start();
}
@Override
public void onUnlockUser(int userId) {
synchronized (mService.getGlobalLock()) {
mService.mStackSupervisor.onUserUnlocked(userId);
}
}
@Override
public void onCleanupUser(int userId) {
synchronized (mService.getGlobalLock()) {
mService.mStackSupervisor.mLaunchParamsPersister.onCleanupUser(userId);
}
}
// 返回的是new的ActivityTaskManagerService实例，SystemSever中使用
// SystemServiceManager.startService()后调用的getService()就是调用该方法
public ActivityTaskManagerService getService() {
return mService;
}
}
2.1 创建ActivityTaskManagerService
ActivityTaskManagerService简称ATMS，Android10新引入功能，用来管理Activity的启动、调度等功能。
Android 10中把原先在AMS中activity的管理移动到ATMS中，从Android 10的代码路径可以看出，管理Activity的ATMS被放入到的wm路径中，这个路径原先归WindowManagerService控制，谷歌的目的也是希望在将来把activity和window融合在一起，减少冗余代码以及AMS和WMS的协调工作。
- ATMS的路径为：frameworks/base/services/core/java/com/android/server/wm
- AMS的路径为：frameworks/base/services/core/java/com/android/server/am
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
final Context mUiContext;
final ActivityThread mSystemThread;
final ActivityTaskManagerInternal mInternal;
//ActivityStackSupervisor 是ATM中用来管理Activity启动和调度的核心类
ActivityStackSupervisor mStackSupervisor;
//Activity 容器的根节点
RootWindowContainer mRootWindowContainer;
//WMS 负责窗口的管理
WindowManagerService mWindowManager;
//这是我们目前认为是"Home" Activity的过程
WindowProcessController mHomeProcess;
public ActivityTaskManagerService(Context context) {
//拿到System Context
mContext = context;
mFactoryTest = FactoryTest.getMode();
//取出的是ActivityThread的静态变量sCurrentActivityThread
//这意味着mSystemThread与SystemServer中的ActivityThread一致
mSystemThread = ActivityThread.currentActivityThread();
//拿到System UI Context
mUiContext = mSystemThread.getSystemUiContext();
mLifecycleManager = new ClientLifecycleManager();
//拿到LocalService的对象
mInternal = new LocalService();
GL_ES_VERSION = SystemProperties.getInt("ro.opengles.version", GL_ES_VERSION_UNDEFINED);
mWindowOrganizerController = new WindowOrganizerController(this);
mTaskOrganizerController = mWindowOrganizerController.mTaskOrganizerController;
}
}
在ActivityTaskManagerService的构造方法中初始化了ActivityThread实例，它的使用会在之后慢慢展开，此处给出ActivityThread的官方解释：它管理应用程序进程中主线程的执行、调度和执行activities、broadcasts和其他ActivityManagerService请求的其他操作。
2.2 ActivityTaskManagerService.start()
该方法在启动ActivityTaskManagerService时会被调用，在Lifecycle.onStart()中调用了该start()。
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
private void start() {
LocalServices.addService(ActivityTaskManagerInternal.class, mInternal);
}
mInternal是创建的LocalService对象，它是ActivityTaskManagerService的内部类，继承了ActivityTaskManagerInternal的抽象类。这里的addService()方法会将ActivityTaskManagerInternal添加到本地服务的全局注册表中。
Activity Task manager的本地系统服务接口，只能在system server进程中使用。它的接口定义如下：
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerInternal.java
public abstract class ActivityTaskManagerInternal {
public interface ScreenObserver {
void onAwakeStateChanged(boolean isAwake);
void onKeyguardStateChanged(boolean isShowing);
}
public abstract void registerScreenObserver(ScreenObserver observer);
public abstract ComponentName getHomeActivityForUser(int userId);
public abstract int startActivitiesAsPackage(String packageName,
int userId, Intent[] intents, Bundle bOptions);
public abstract int startActivityAsUser(IApplicationThread caller, String callingPackage,
Intent intent, @Nullable Bundle options, int userId);
public abstract boolean isSleeping();
public abstract boolean isShuttingDown();
public abstract boolean shuttingDown(boolean booted, int timeout);
public abstract void enableScreenAfterBoot(boolean booted);
public final class ActivityTokens {
private final @NonNull IBinder mActivityToken;
private final @NonNull IBinder mAssistToken;
private final @NonNull IApplicationThread mAppThread;
...
}
public abstract Intent getHomeIntent();
public abstract boolean startHomeActivity(int userId, String reason);
...
}
3.ActivityManagerService启动过程
SystemServer中startBootstrapServices()方法启动ATMS后，紧接就是去启动AMS。在Android 10的版本中，Activity的管理和调度移到ATMS中，AMS负责 service,broadcast,provider的管理和调度。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices() {
...
//启动AMS
mActivityManagerService = ActivityManagerService.Lifecycle.startService(
mSystemServiceManager, atm);
...
}
从《1.2.1 SystemServiceManager()》中，可以知道SystemServiceManager.startService()最终调用的是启动对象中的onStart方法，因此AMS启动，这里最终会调用ActivityTaskManagerService.Lifecycle.onStart()来启动AMS服务：
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public static final class Lifecycle extends SystemService {
private final ActivityManagerService mService;
private static ActivityTaskManagerService sAtm;
public Lifecycle(Context context) {
super(context);
//1.创建ActivityManagerService，得到对象，传入ATM的对象
mService = new ActivityManagerService(context, sAtm);
}
public static ActivityManagerService startService(
SystemServiceManager ssm, ActivityTaskManagerService atm) {
sAtm = atm;
return ssm.startService(ActivityManagerService.Lifecycle.class).getService();
}
@Override
public void onStart() {
//2.启动AMS服务
mService.start();
}
@Override
public void onBootPhase(int phase) {
mService.mBootPhase = phase;
if (phase == PHASE_SYSTEM_SERVICES_READY) {
mService.mBatteryStatsService.systemServicesReady();
mService.mServices.systemServicesReady();
} else if (phase == PHASE_ACTIVITY_MANAGER_READY) {
mService.startBroadcastObservers();
} else if (phase == PHASE_THIRD_PARTY_APPS_CAN_START) {
mService.mPackageWatchdog.onPackagesReady();
}
}
@Override
public void onCleanupUser(int userId) {
mService.mBatteryStatsService.onCleanupUser(userId);
}
public ActivityManagerService getService() {
return mService;
}
}
3.1 创建ActivityManagerService
Activity的管理和调度放入到ATMS中执行，AMS中保留service，broadcast，provider的管理和调度。构造函数初始化主要工作就是初始化一些变量，供之后的service，broadcast，provider的管理和调度。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
...
public ActivityManagerService(Context systemContext, ActivityTaskManagerService atm) {
LockGuard.installLock(this, LockGuard.INDEX_ACTIVITY);
mInjector = new Injector(systemContext);
//系统上下文，由systemserver进程创建的，ContextImpl.getSystemContext()得到的
mContext = systemContext;
mFactoryTest = FactoryTest.getMode();
//取出的是ActivityThread的静态变量sCurrentActivityThread
//这意味着mSystemThread与SystemServer中的ActivityThread一致
mSystemThread = ActivityThread.currentActivityThread();
mUiContext = mSystemThread.getSystemUiContext();
Slog.i(TAG, "Memory class: " + ActivityManager.staticGetMemoryClass());
//mHandler和mUiHandler初始化
mHandlerThread = new ServiceThread(TAG,
THREAD_PRIORITY_FOREGROUND, false /*allowIo*/);
mHandlerThread.start();
//处理AMS中消息的主力
mHandler = new MainHandler(mHandlerThread.getLooper());
//UiHandler对应于Android中的UiThreads
mUiHandler = mInjector.getUiHandler(this);
//mProcStartHandler初始化
mProcStartHandlerThread = new ServiceThread(TAG + ":procStart",
THREAD_PRIORITY_FOREGROUND, false /* allowIo */);
mProcStartHandlerThread.start();
mProcStartHandler = new Handler(mProcStartHandlerThread.getLooper());
...
//创建 BroadcastQueue 前台广播对象，处理超时时长是 10s
mFgBroadcastQueue = new BroadcastQueue(this, mHandler,
"foreground", foreConstants, false);
//创建 BroadcastQueue 后台广播对象，处理超时时长是 60s
mBgBroadcastQueue = new BroadcastQueue(this, mHandler,
"background", backConstants, true);
//创建 BroadcastQueue 分流广播对象，处理超时时长是 60s
mOffloadBroadcastQueue = new BroadcastQueue(this, mHandler,
"offload", offloadConstants, true);
mBroadcastQueues[0] = mFgBroadcastQueue;
mBroadcastQueues[1] = mBgBroadcastQueue;
mBroadcastQueues[2] = mOffloadBroadcastQueue;
// 创建 ActiveServices 对象，用于管理 ServiceRecord 对象
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.
//初始化BatteryStatsService
mBatteryStatsService = new BatteryStatsService(systemContext, systemDir,
BackgroundThread.get().getHandler());
mBatteryStatsService.getActiveStatistics().readLocked();
mBatteryStatsService.scheduleWriteToDisk();
mOnBattery = DEBUG_POWER ? true
: mBatteryStatsService.getActiveStatistics().getIsOnBattery();
mBatteryStatsService.getActiveStatistics().setCallback(this);
...
mTrackingAssociations = "1".equals(SystemProperties.get("debug.track-associations"));
mIntentFirewall = new IntentFirewall(new IntentFirewallInterface(), mHandler);
//持有atm引用,并调用其initialize()
mActivityTaskManager = atm;
mActivityTaskManager.initialize(mIntentFirewall, mPendingIntentController,
DisplayThread.get().getLooper());
//获取其local service对象
mAtmInternal = LocalServices.getService(ActivityTaskManagerInternal.class);
...
//加入Watchdog的监控
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 first
updateOomAdjLocked(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);
}
3.2 ActivityManagerService.start()
该方法主要工作有：
- 启动CPU监控线程，在启动CPU监控线程之前，首先将进程复位；
- 注册电池状态服务和权限管理服务。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
private void start() {
//1.移除所有的进程组
removeAllProcessGroups();
//启动 CPU 监控线程
mProcessCpuThread.start();
//2.注册电池状态和权限管理服务
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");
}
}
4.AMS设置SystemServiceManager和Installer
继续回到《1.3 启动核心服务》中，在启动完ATMS和AMS后，会去设置SystemServiceManager和Installer：
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
...
//3.把ssm和installer赋值给ActivityManagerService
mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
mActivityManagerService.setInstaller(installer);
...
}
这里回去调用AMS中对应的方法：
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback, ActivityManagerGlobalLock {
...
public void setSystemServiceManager(SystemServiceManager mgr) {
mSystemServiceManager = mgr;
}
public void setInstaller(Installer installer) {
mInstaller = installer;
}
...
}
这里只是简单地将两个对象保存到AMS中，后续会用到。
5.获取ATMS的全局Lock
继续回到《1.3 启动核心服务》中：
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
...
//4\. 利用atm，获取WindowManagerGlobalLock
mWindowManagerGlobalLock = atm.getGlobalLock();
...
}
继续调用ATMS中的方法：
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
final WindowManagerGlobalLock mGlobalLock = new WindowManagerGlobalLock();
...
public WindowManagerGlobalLock getGlobalLock() {
return mGlobalLock;
}
}
----------------
// frameworks/base/services/core/java/com/android/server/wm/WindowManagerGlobalLock.java
public class WindowManagerGlobalLock {
}
6.AMS.initPowerManagement()
继续回到《1.3 启动核心服务》中：
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
...
//5.初始化PowerManager
mActivityManagerService.initPowerManagement();
...
}
调用AMS中的方法：
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback, ActivityManagerGlobalLock {
...
public void initPowerManagement() {
mActivityTaskManager.onInitPowerManagement();
mBatteryStatsService.initPowerManagement();
// AMS持有PowerMManagerInternal service引用
mLocalPowerManager = LocalServices.getService(PowerManagerInternal.class);
}
...
}
ATMS同AMS一样，也持有PowerManagerInternal service引用，ATMS.onInitPowerManagement()如下：
// /frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public class ActivityTaskManagerService extends IActivityTaskManager.Stub {
public void onInitPowerManagement() {
synchronized (mGlobalLock) {
mTaskSupervisor.initPowerManagement();
final PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
//持有PowerManagerInternal service引用
mPowerManagerInternal = LocalServices.getService(PowerManagerInternal.class);
mVoiceWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "*voice*");
mVoiceWakeLock.setReferenceCounted(false);
}
}
...
}
继续initPowerManagement()方法：
// /frameworks/base/services/core/java/com/android/server/am/BatteryStatsService.java
public final class BatteryStatsService extends IBatteryStats.Stub
implements PowerManagerInternal.LowPowerModeListener,
BatteryStatsImpl.PlatformIdleStateCallback,
BatteryStatsImpl.MeasuredEnergyRetriever,
Watchdog.Monitor {
public void initPowerManagement() {
//持有PowerManagerInternal service引用,并注册低电量模式监听
final PowerManagerInternal powerMgr = LocalServices.getService(PowerManagerInternal.class);
powerMgr.registerLowPowerModeObserver(this);
synchronized (mStats) {
mStats.notePowerSaveModeLocked(
powerMgr.getLowPowerState(ServiceType.BATTERY_STATS).batterySaverEnabled,
SystemClock.elapsedRealtime(), SystemClock.uptimeMillis(), true);
}
(new WakeupReasonThread()).start();
}
7.AMS.setSystemProcess()
继续回到《1.3 启动核心服务》中：
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startBootstrapServices(@NonNull TimingsTraceAndSlog t) {
...
//6.设置系统进程
mActivityManagerService.setSystemProcess();
...
}
该方法主要业务：
- 把AMS作为name = activity添加到systemserver进程中管理；
- 注册procstats服务（进程状态），meminfo服务（内存信息），gfxinfo服务（图像信息），dbinfo服务（数据库信息），cpuinfo服务（cup信息），permission服务（权限控制信息），processinfo服务（进程信息），cacheinfo服务（cache信息）注册到systemserver进程中进行管理；
- 获取package=“android”的ApplicationInfo，为ActivityThread安装相关system application信息；
- 为systemserver 主进程开辟一个ProcessRecord来维护进程的相关信息。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void setSystemProcess() {
try {
//1.注册一些服务到ServiceManager：
//包括 activity、procstats、meminfo、gfxinfo、dbinfo、permission、processinfo
//把AMS注册到systemserver进程中管理:activity
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:procstats
ServiceManager.addService(ProcessStats.SERVICE_NAME, mProcessStats);
//注册内存信息服务:meminfo
ServiceManager.addService("meminfo", new MemBinder(this), /* allowIsolated= */ false,
DUMP_FLAG_PRIORITY_HIGH);
//注册图像信息服务和数据库信息服务：gfxinfo，dbinfo
ServiceManager.addService("gfxinfo", new GraphicsBinder(this));
ServiceManager.addService("dbinfo", new DbBinder(this));
if (MONITOR_CPU_USAGE) {
//注册cupinfo服务到systemserver进程中，CUP信息
ServiceManager.addService("cpuinfo", new CpuBinder(this),
/* allowIsolated= */ false, DUMP_FLAG_PRIORITY_CRITICAL);
}
//注册权限服务、进程信息服务、缓存信息服务：permission，processinfo，cacheinfo
ServiceManager.addService("permission", new PermissionController(this));
ServiceManager.addService("processinfo", new ProcessInfoService(this));
ServiceManager.addService("cacheinfo", new CacheBinder(this));
//2.通过解析framework-res.apk里的AndroidManifest.xml获得ApplicationInfo
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
//3.为ActivityThread 安装 system application相关信息,
//将framework-res.apk对应的ApplicationInfo安装到LoadedApk中的mApplicationInfo
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
//4.为systemserver主进程开辟一个ProcessRecord来维护进程的相关信息
synchronized (this) {
ProcessRecord app = mProcessList.newProcessRecordLocked(info, info.processName,
false,
0,
new HostingRecord("system"));
app.setPersistent(true);//设置进程常驻
app.pid = MY_PID;//为ProcessRecord赋值当前进程ID，即system_server进程ID
app.getWindowProcessController().setPid(MY_PID);
app.maxAdj = ProcessList.SYSTEM_ADJ;
app.makeActive(mSystemThread.getApplicationThread(), mProcessStats);
addPidLocked(app);//将ProcessRecord放到mPidSelfLocked里统一管理
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);
}
// Start watching app ops after we and the package manager are up and running.
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 (getAppOpsManager().checkOpNoThrow(op, uid, packageName)
!= AppOpsManager.MODE_ALLOWED) {
runInBackgroundDisabled(uid);
}
}
}
});
final int[] cameraOp = {AppOpsManager.OP_CAMERA};
mAppOpsService.startWatchingActive(cameraOp, new IAppOpsActiveCallback.Stub() {
@Override
public void opActiveChanged(int op, int uid, String packageName, boolean active) {
cameraActiveChanged(uid, active);
}
});
}
7.1 getApplicationInfo()
这里会通过PackageManagerService.java的getApplicationInfo()方法去获取Application的信息：
//2.通过解析framework-res.apk里的AndroidManifest.xml获得ApplicationInfo
ApplicationInfo info = mContext.getPackageManager().getApplicationInfo(
"android", STOCK_PM_FLAGS | MATCH_SYSTEM_ONLY);
获取package="android"的ApplicationInfo，为ActivityThread安装相关system application信息；在后边的章节中介绍了AMS的这个mSystemThread，这个实际上是systemserver进程的主线程，所以此处是在systemserver进程中安装了framework-res.apk，（之后系统还会安装SettingsProvider.apk）。
此处安装的是framework-res.apk。因为只有该apk的AndroidManifest.xml中package="android"且是SYSTEM_UID，如下：
// frameworks/base/core/res/AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="android" coreApp="true" android:sharedUserId="android.uid.system"
android:sharedUserLabel="@string/android_system_label">
<!-- ================================================ -->
<!-- Special broadcasts that only the system can send -->
<!-- ================================================ -->
<eat-comment />
7.2 installSystemApplicationInfo()
这里会通过ActivityThread.java的installSystemApplicationInfo()方法安装system application的信息：
//3.为ActivityThread安装 system application相关信息,
//将framework-res.apk对应的ApplicationInfo安装到LoadedApk中的mApplicationInfo
mSystemThread.installSystemApplicationInfo(info, getClass().getClassLoader());
继续调用ActivityThread.java中的方法：
// frameworks/base/core/java/android/app/ActivityThread.java
public void installSystemApplicationInfo(ApplicationInfo info, ClassLoader classLoader) {
synchronized (this) {
getSystemContext().installSystemApplicationInfo(info, classLoader);
getSystemUiContext().installSystemApplicationInfo(info, classLoader);
// give ourselves a default profiler
mProfiler = new Profiler();
}
}
8.AMS.systemReady()
经过上面的分析，已经梳理出了AMS和ATMS的启动过程。这里再回到《1.SystemServer启动》中，在SystemServer的run()方法中，在调用startBootstrapServices()启动完AMS和ATMS服务后，会在startOtherServices()中启动完其他的服务之后，调用AMS的systemReady()方法去作一些准备工作。
AMS的systemReady处理分为三个阶段：
-
阶段1：主要是调用一些关键服务的初始化函数， 然后杀死那些没有FLAG_PERSISTENT却在AMS启动完成前已经存在的进程， 同时获取一些配置参数。 需要注意的是，由于只有Java进程才会向AMS注册，而一般的Native进程不会向AMS注册，因此此处杀死的进程是Java进程。
-
阶段2：执行goingCallback的处理，主要的工作就是通知一些服务可以进行systemReady、systemRunning相关的工作，并进行启动服务或应用进程的工作。
-
阶段3：启动Home Activity，当启动结束，并发送ACTION_BOOT_COMPLETED广播时，AMS的启动过程告一段落。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startOtherServices() {
mActivityManagerService.systemReady(() -> {xxxxxgoingCallbackxxx, BOOT_TIMINGS_TRACE_LOG);
}
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
阶段1：关键服务的初始化
阶段2：goingCallback处理
阶段3：启动Home Activity，完成AMS启动
}
8.1 systemReady阶段1
主要是调用一些关键服务的初始化函数， 然后杀死那些没有FLAG_PERSISTENT却在AMS启动完成前已经存在的进程， 同时获取一些配置参数。 需要注意的是，由于只有Java进程才会向AMS注册，而一般的Native进程不会向AMS注册，因此此处杀死的进程是Java进程。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback, @NonNull TimingsTraceAndSlog t) {
t.traceBegin("PhaseActivityManagerReady");
mSystemServiceManager.preSystemReady();
synchronized(this) {
//第一次进入mSystemReady 为false，不走该流程
if (mSystemReady) {
// If we're done calling all the receivers, run the next "boot phase" passed in
// by the SystemServer
if (goingCallback != null) {
goingCallback.run();
}
t.traceEnd(); // PhaseActivityManagerReady
return;
}
t.traceBegin("controllersReady");
mLocalDeviceIdleController =
LocalServices.getService(DeviceIdleInternal.class);
//这一部分主要是调用一些关键服务SystemReady相关的函数，
//进行一些等待AMS初始完，才能进行的工作
mActivityTaskManager.onSystemReady();
// Make sure we have the current profile info, since it is needed for security checks.
mUserController.onSystemReady();
mAppOpsService.systemReady();
mProcessList.onSystemReady();
mSystemReady = true;
t.traceEnd();
}
try {
sTheRealBuildSerial = IDeviceIdentifiersPolicyService.Stub.asInterface(
ServiceManager.getService(Context.DEVICE_IDENTIFIERS_SERVICE))
.getSerial();
} catch (RemoteException e) {}
t.traceBegin("killProcesses");
ArrayList<ProcessRecord> procsToKill = null;
synchronized(mPidsSelfLocked) {
//mPidsSelfLocked中保存当前正在运行的所有进程的信息
for (int i=mPidsSelfLocked.size()-1; i>=0; i--) {
ProcessRecord proc = mPidsSelfLocked.valueAt(i);
//在AMS启动完成前，如果没有FLAG_PERSISTENT标志的进程已经启动了，
//就将这个进程加入到procsToKill中
if (!isAllowedWhileBooting(proc.info)){
if (procsToKill == null) {
procsToKill = new ArrayList<ProcessRecord>();
}
procsToKill.add(proc);
}
}
}
//收集已经启动的进程并杀死，排除persistent常驻进程
synchronized(this) {
//利用removeProcessLocked关闭procsToKill中的进程
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);
mProcessList.removeProcessLocked(proc, true, false,
ApplicationExitInfo.REASON_OTHER,
ApplicationExitInfo.SUBREASON_SYSTEM_UPDATE_DONE,
"system update done");
}
}
// Now that we have cleaned up any update processes, we
// are ready to start launching real processes and know that
// we won't trample on them any more.
//至此系统准备完毕
mProcessesReady = true;
}
...
mUgmInternal.onSystemReady();
...
}
}
8.2 systemReady阶段2
执行goingCallback的处理，主要的工作就是通知一些服务可以进行systemReady相关的工作，并进行启动服务或应用进程的工作。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback, TimingsTraceLog traceLog) {
...
//1.调用参数传入的runnable对象，SystemServer中有具体的定义,参考[4.7.2.1]
if (goingCallback != null) goingCallback.run();
...
//调用所有系统服务的onStartUser接口
if (bootingSystemUser) {
mSystemServiceManager.startUser(t, currentUserId);
}
synchronized (this) {
//2.启动persistent为1的application所在的进程
startPersistentApps(PackageManager.MATCH_DIRECT_BOOT_AWARE);
// Start up initial activity.
mBooting = true;
...
}
8.2.1 goingCallback.run()
监控Native的crash，启动WebView，执行一些服务的systemReady 和systemRunning方法。
// frameworks/base/services/java/com/android/server/SystemServer.java
private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
...
mActivityManagerService.systemReady(() -> {
...
try {
//1.监控Native的crash
mActivityManagerService.startObservingNativeCrashes();
} catch (Throwable e) {
reportWtf("observing native crashes", e);
}
t.traceEnd();
// No dependency on Webview preparation in system server. But this should
// be completed before allowing 3rd party
final String WEBVIEW_PREPARATION = "WebViewFactoryPreparation";
Future<?> webviewPrep = null;
if (!mOnlyCore && mWebViewUpdateService != null) {
webviewPrep = SystemServerInitThreadPool.submit(() -> {
Slog.i(TAG, WEBVIEW_PREPARATION);
TimingsTraceAndSlog traceLog = TimingsTraceAndSlog.newAsyncLog();
traceLog.traceBegin(WEBVIEW_PREPARATION);
ConcurrentUtils.waitForFutureNoInterrupt(mZygotePreload, "Zygote preload");
mZygotePreload = null;
//2.启动WebView
mWebViewUpdateService.prepareWebViewInSystemServer();
traceLog.traceEnd();
}, WEBVIEW_PREPARATION);
}
...
try {
//3.启动systemUI
startSystemUi(context, windowManagerF);
} catch (Throwable e) {
reportWtf("starting System UI", e);
}
//4.执行一系列服务的systemReady方法
networkManagementF.systemReady();
ipSecServiceF.systemReady();
networkStatsF.systemReady();
connectivityF.systemReady();
networkPolicyF.systemReady(networkPolicyInitReadySignal);
...
mSystemServiceManager.startBootPhase(t, SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
...
//5.执行一系列服务的systemRunning方法
locationF.systemRunning();
countryDetectorF.systemRunning();
networkTimeUpdaterF.systemRunning();
inputManagerF.systemRunning();
telephonyRegistryF.systemRunning();
mediaRouterF.systemRunning();
mmsServiceF.systemRunning();
...
}
这里继续看一下startSystemUi()方法，启动systemUI服务，服务名称”com.android.systemui/.SystemUIService”：
// frameworks/base/services/java/com/android/server/SystemServer.java
private static void startSystemUi(Context context, WindowManagerService windowManager) {
PackageManagerInternal pm = LocalServices.getService(PackageManagerInternal.class);
Intent intent = new Intent();
intent.setComponent(pm.getSystemUiServiceComponent());//获取SystemUI的Component
intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);
//Slog.d(TAG, "Starting service: " + intent);
context.startServiceAsUser(intent, UserHandle.SYSTEM);//启动SystemUI服务
windowManager.onSystemUiStarted();
}
8.2.2 AMS.startPersistentApps()
该方法用于启动persistent为1的application所在的进程：
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
void startPersistentApps(int matchFlags) {
if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL) return;
synchronized (this) {
try {
//从PKMS中得到persistent为1的ApplicationInfo
final List<ApplicationInfo> apps = AppGlobals.getPackageManager()
.getPersistentApplications(STOCK_PM_FLAGS | matchFlags).getList();
for (ApplicationInfo app : apps) {
//由于framework-res.apk已经由系统启动，所以此处不再启动它
if (!"android".equals(app.packageName)) {
addAppLocked(app, null, false, null /* ABI override */,
ZYGOTE_POLICY_FLAG_BATCH_LAUNCH);
}
}
} catch (RemoteException ex) {
}
}
}
8.3 systemReady阶段3
启动Home Activity，当启动结束，并发送ACTION_BOOT_COMPLETED广播时，AMS的启动过程告一段落。
// frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
public void systemReady(final Runnable goingCallback, @NonNull TimingsTraceAndSlog t) {
...
if (bootingSystemUser) {
t.traceBegin("startHomeOnAllDisplays");
//1.通过ATM，启动Home Activity
mAtmInternal.startHomeOnAllDisplays(currentUserId, "systemReady");
t.traceEnd();
}
...
//2.发送一些广播消息
try {
//2.1 system发送广播 ACTION_USER_STARTED = "android.intent.action.USER_STARTED";
Intent intent = new Intent(Intent.ACTION_USER_STARTED);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY
| Intent.FLAG_RECEIVER_FOREGROUND);
intent.putExtra(Intent.EXTRA_USER_HANDLE, currentUserId);
broadcastIntentLocked(null, null, null, intent,
null, null, 0, null, null, null, OP_NONE,
null, false, false, MY_PID, SYSTEM_UID, callingUid, callingPid,
currentUserId);
//2.2 system发送广播 ACTION_USER_STARTING= "android.intent.action.USER_STARTING";
intent = new Intent(Intent.ACTION_USER_STARTING);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
intent.putExtra(Intent.EXTRA_USER_HANDLE, currentUserId);
broadcastIntentLocked(null, null, null, intent, null,
new IIntentReceiver.Stub() {
@Override
public void performReceive(Intent intent, int resultCode,
String data, Bundle extras, boolean ordered, boolean sticky,
int sendingUser) {}
}, 0, null, null, new String[] {INTERACT_ACROSS_USERS}, OP_NONE, null,
true, false, MY_PID, SYSTEM_UID, callingUid, callingPid,
UserHandle.USER_ALL);
} catch (Throwable e) {
Slog.wtf(TAG, "Failed sending first user broadcasts", e);
} finally {
Binder.restoreCallingIdentity(ident);
...
}
}
8.3.1 ATMS.startHomeOnAllDisplays()
该方法用于启动Home Activity：
// frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
public boolean startHomeOnAllDisplays(int userId, String reason) {
synchronized (mGlobalLock) {
// 调用RootWindowContainer的startHomeOnAllDisplays()，最终到startHomeOnDisplay()
return mRootWindowContainer.startHomeOnAllDisplays(userId, reason);
}
}
调用RootWindowContainer的startHomeOnAllDisplays()方法：
// frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java
boolean startHomeOnAllDisplays(int userId, String reason) {
boolean homeStarted = false;
for (int i = getChildCount() - 1; i >= 0; i--) {
final int displayId = getChildAt(i).mDisplayId;
homeStarted |= startHomeOnDisplay(userId, reason, displayId);
}
return homeStarted;
}
boolean startHomeOnDisplay(int userId, String reason, int displayId) {
return startHomeOnDisplay(userId, reason, displayId, false /* allowInstrumenting */,
false /* fromHomeKey */);
}
boolean startHomeOnDisplay(int userId, String reason, int displayId, boolean allowInstrumenting,
boolean fromHomeKey) {
// Fallback to top focused display or default display if the displayId is invalid.
if (displayId == INVALID_DISPLAY) {
final ActivityStack stack = getTopDisplayFocusedStack();
displayId = stack != null ? stack.getDisplayId() : DEFAULT_DISPLAY;
}
final DisplayContent display = getDisplayContent(displayId);
boolean result = false;
for (int tcNdx = display.getTaskDisplayAreaCount() - 1; tcNdx >= 0; --tcNdx) {
final TaskDisplayArea taskDisplayArea = display.getTaskDisplayAreaAt(tcNdx);
result |= startHomeOnTaskDisplayArea(userId, reason, taskDisplayArea,
allowInstrumenting, fromHomeKey);
}
return result;
}
boolean startHomeOnTaskDisplayArea(int userId, String reason, TaskDisplayArea taskDisplayArea,
boolean allowInstrumenting, boolean fromHomeKey) {
// Fallback to top focused display area if the provided one is invalid.
if (taskDisplayArea == null) {
final ActivityStack stack = getTopDisplayFocusedStack();
taskDisplayArea = stack != null ? stack.getDisplayArea()
: getDefaultTaskDisplayArea();
}
Intent homeIntent = null;
ActivityInfo aInfo = null;
if (taskDisplayArea == getDefaultTaskDisplayArea()) {
homeIntent = mService.getHomeIntent();
//根据intent中携带的ComponentName，利用PKMS得到ActivityInfo
aInfo = resolveHomeActivity(userId, homeIntent);
} else if (shouldPlaceSecondaryHomeOnDisplayArea(taskDisplayArea)) {
Pair<ActivityInfo, Intent> info = resolveSecondaryHomeActivity(userId, taskDisplayArea);
aInfo = info.first;
homeIntent = info.second;
}
if (aInfo == null || homeIntent == null) {
return false;
}
if (!canStartHomeOnDisplayArea(aInfo, taskDisplayArea, allowInstrumenting)) {
return false;
}
// Updates the home component of the intent.
homeIntent.setComponent(new ComponentName(aInfo.applicationInfo.packageName, aInfo.name));
homeIntent.setFlags(homeIntent.getFlags() | FLAG_ACTIVITY_NEW_TASK);
// Updates the extra information of the intent.
if (fromHomeKey) {
homeIntent.putExtra(WindowManagerPolicy.EXTRA_FROM_HOME_KEY, true);
mWindowManager.cancelRecentsAnimation(REORDER_KEEP_IN_PLACE, "startHomeActivity");
}
// Update the reason for ANR debugging to verify if the user activity is the one that
// actually launched.
final String myReason = reason + ":" + userId + ":" + UserHandle.getUserId(
aInfo.applicationInfo.uid) + ":" + taskDisplayArea.getDisplayId();
//启动Home Activity--Luncher
mService.getActivityStartController().startHomeActivity(homeIntent, aInfo, myReason,
taskDisplayArea);
return true;
}
这里的mService就是ActivityTaskManagerService，通过getActivityStartController()获取到ActivityStartController对象，然后再调用该对象的startHomeActivity()方法：
// frameworks/base/services/core/java/com/android/server/wm/ActivityStartController.java
void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason,
TaskDisplayArea taskDisplayArea) {
final ActivityOptions options = ActivityOptions.makeBasic();
options.setLaunchWindowingMode(WINDOWING_MODE_FULLSCREEN);
if (!ActivityRecord.isResolverActivity(aInfo.name)) {
// The resolver activity shouldn't be put in home stack because when the foreground is
// standard type activity, the resolver activity should be put on the top of current
// foreground instead of bring home stack to front.
options.setLaunchActivityType(ACTIVITY_TYPE_HOME);
}
final int displayId = taskDisplayArea.getDisplayId();
options.setLaunchDisplayId(displayId);
options.setLaunchTaskDisplayArea(taskDisplayArea.mRemoteToken
.toWindowContainerToken());
// The home activity will be started later, defer resuming to avoid unneccerary operations
// (e.g. start home recursively) when creating home stack.
mSupervisor.beginDeferResume();
final ActivityStack homeStack;
try {
// Make sure home stack exists on display area.
homeStack = taskDisplayArea.getOrCreateRootHomeTask(ON_TOP);
} finally {
mSupervisor.endDeferResume();
}
mLastHomeActivityStartResult = obtainStarter(intent, "startHomeActivity: " + reason)
.setOutActivity(tmpOutRecord)
.setCallingUid(0)
.setActivityInfo(aInfo)
.setActivityOptions(options.toBundle())
.execute();
mLastHomeActivityStartRecord = tmpOutRecord[0];
if (homeStack.mInResumeTopActivity) {
// If we are in resume section already, home activity will be initialized, but not
// resumed (to avoid recursive resume) and will stay that way until something pokes it
// again. We need to schedule another resume.
mSupervisor.scheduleResumeTopActivities();
}
}
这里就分析到这，后面的详细分析后续另外单独分析。
至此，AMS和ATMS的启动流程分析完毕。
