核心類

Framework中有一個類SystemActivityMonitoringService專門用于監控Activity堆棧變化，屬于隱藏Api，應用側無法調用。此類位于

packages/services/Car/service/src/com/android/car/SystemActivityMonitoringService.java

方法

void registerTaskStackListener(in ITaskStackListener listener);

void registerProcessObserver(in IProcessObserver observer);

這兩個方法都位于AMS中，不對應用開放

SystemActivityMonitoringService中init調用

    @Overridepublic void init() {// Monitoring both listeners are necessary as there are cases where one listener cannot// monitor activity change.try {mAm.registerProcessObserver(mProcessObserver);mAm.registerTaskStackListener(mTaskListener);} catch (RemoteException e) {Log.e(CarLog.TAG_AM, "cannot register activity monitoring", e);throw new RuntimeException(e);}updateTasks();}

?ProcessObserver

void onForegroundActivitiesChanged(int pid, int uid, boolean foregroundActivities) //前臺Activity發生改變

void onForegroundServicesChanged(int pid, int uid, int fgServiceTypes) //前臺服務發生變化

   private class ProcessObserver extends IProcessObserver.Stub {@Overridepublic void onForegroundActivitiesChanged(int pid, int uid, boolean foregroundActivities) {if (Log.isLoggable(CarLog.TAG_AM, Log.INFO)) {Log.i(CarLog.TAG_AM,String.format("onForegroundActivitiesChanged uid %d pid %d fg %b",uid, pid, foregroundActivities));}mHandler.requestForegroundActivitiesChanged(pid, uid, foregroundActivities);}@Overridepublic void onForegroundServicesChanged(int pid, int uid, int fgServiceTypes) {}@Overridepublic void onProcessDied(int pid, int uid) {mHandler.requestProcessDied(pid, uid);}}

TaskListener

onTaskCreated 應用被創建，首次被拉起至前臺；

onTaskRemoved 應用進程被移除

onTaskMovedToFront 應用從后臺切換至前臺

    private class TaskListener extends TaskStackListener {@Overridepublic void onTaskStackChanged() {if (Log.isLoggable(CarLog.TAG_AM, Log.INFO)) {Log.i(CarLog.TAG_AM, "onTaskStackChanged");}mHandler.requestUpdatingTask();}}