/**
 * 管理应用程序进程中主线程的执行、调度和执行活动、广播以及活动管理器请求的其他操作。
 *
 * {@hide}
 */
public final class ActivityThread extends ClientTransactionHandler {
    public static void main(String[] args) {
  // 将主线程设置为 Looper 线程 , 开启 Looper , 用于配合 H 处理消息 
        Looper.prepareMainLooper();
  // 创建 ActivityThread 实例对象 
        ActivityThread thread = new ActivityThread();
        // 绑定
        thread.attach(false, startSeq);
  // 开始无限循环 , 处理 Handler 消息 
        Looper.loop();
        throw new RuntimeException("Main thread loop unexpectedly exited");
    }
}

/**
 * 管理应用程序进程中主线程的执行、调度和执行活动、广播以及活动管理器请求的其他操作。
 *
 * {@hide}
 */
public final class ActivityThread extends ClientTransactionHandler {
    private void attach(boolean system, long startSeq) {
        sCurrentActivityThread = this;
        mSystemThread = system;
        if (!system) {
            RuntimeInit.setApplicationObject(mAppThread.asBinder());
            // 通过 Binder 机制获取 AMS 
            final IActivityManager mgr = ActivityManager.getService();
            try {
                // 调用 AMS 的 attachApplication 方法 , 为 ActivityThread 绑定 ApplicationThread 
                mgr.attachApplication(mAppThread, startSeq);
            } catch (RemoteException ex) {
                throw ex.rethrowFromSystemServer();
            }
        }
    }
}

public class ActivityManagerService extends IActivityManager.Stub
        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
    @Override
    public final void attachApplication(IApplicationThread thread) {
        synchronized (this) {
            int callingPid = Binder.getCallingPid();
            final long origId = Binder.clearCallingIdentity();
            attachApplicationLocked(thread, callingPid);
            Binder.restoreCallingIdentity(origId);
        }
    }
    // 为 ApplicationThread 绑定 Application 主方法
    private final boolean attachApplicationLocked(IApplicationThread thread,
            int pid) {
        try {
            checkTime(startTime, "attachApplicationLocked: immediately before bindApplication");
            mStackSupervisor.mActivityMetricsLogger.notifyBindApplication(app);
    // 在此处为 ActivityThread 绑定 Application , 此时又回到 ActivityThread
            if (app.instr != null) {
                thread.bindApplication(processName, appInfo, providers,
                        app.instr.mClass,
                        profilerInfo, app.instr.mArguments,
                        app.instr.mWatcher,
                        app.instr.mUiAutomationConnection, testMode,
                        mBinderTransactionTrackingEnabled, enableTrackAllocation,
                        isRestrictedBackupMode || !normalMode, app.persistent,
                        new Configuration(getGlobalConfiguration()), app.compat,
                        getCommonServicesLocked(app.isolated),
                        mCoreSettingsObserver.getCoreSettingsLocked(),
                        buildSerial);
            } else {
                thread.bindApplication(processName, appInfo, providers, null, profilerInfo,
                        null, null, null, testMode,
                        mBinderTransactionTrackingEnabled, enableTrackAllocation,
                        isRestrictedBackupMode || !normalMode, app.persistent,
                        new Configuration(getGlobalConfiguration()), app.compat,
                        getCommonServicesLocked(app.isolated),
                        mCoreSettingsObserver.getCoreSettingsLocked(),
                        buildSerial);
            }
        } catch (Exception e) {
        }
        return true;
    }
}

/**
 * 管理应用程序进程中主线程的执行、调度和执行活动、广播以及活动管理器请求的其他操作。
 *
 * {@hide}
 */
public final class ActivityThread extends ClientTransactionHandler {
    private class ApplicationThread extends IApplicationThread.Stub {
  // 为 ActivityThread 绑定 Application 
        public final void bindApplication(String processName, ApplicationInfo appInfo,
                List<ProviderInfo> providers, ComponentName instrumentationName,
                ProfilerInfo profilerInfo, Bundle instrumentationArgs,
                IInstrumentationWatcher instrumentationWatcher,
                IUiAutomationConnection instrumentationUiConnection, int debugMode,
                boolean enableBinderTracking, boolean trackAllocation,
                boolean isRestrictedBackupMode, boolean persistent, Configuration config,
                CompatibilityInfo compatInfo, Map services, Bundle coreSettings,
                String buildSerial, boolean autofillCompatibilityEnabled) {
            // 此处在所有数据就位后 , 发送了一个 H.BIND_APPLICATION 消息
            sendMessage(H.BIND_APPLICATION, data);
        }
    }
}