ActivityManager m = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE );
    List<RunningTaskInfo> runningTaskInfoList =  m.getRunningTasks(10);
    Iterator<RunningTaskInfo> itr = runningTaskInfoList.iterator();
    while(itr.hasNext())
    {
        RunningTaskInfo runningTaskInfo = (RunningTaskInfo)itr.next();
        int id = runningTaskInfo.id;
        CharSequence desc= runningTaskInfo.description;
        String topActivity = runningTaskInfo.topActivity.getShortClassName();
        int numOfActivities = runningTaskInfo.numActivities;
    }

注意:您必须在清单文件中指定 android.permission.GET_TASKS 权限.

Note: You have to specify android.permission.GET_TASKS permission in Manifest file.