如何知道主屏幕是否有焦点

Question

我正在开发一个Android应用程序，它在后台运行一个服务，只有当用户在主屏幕上运行时才会运行。我遵循了这个类似的answer，但总是需要点击这个方法来得到答案。我使用以下代码。

    @Override
    public void onStart(Intent intent, int startId) {
        // TODO Auto-generated method stub
        super.onStart(intent, startId);
        task = new TimerTask() {

            @Override
            public void run() {
                detect();
            }
        };
        Timer timer = new Timer();
        timer.schedule(task, 0, 1000);
    }

    void detect(){
        ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
        taskInfo = am.getRunningTasks(1);
        ComponentName currentTask = taskInfo.get(0).topActivity;

        final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
        mainIntent.addCategory(Intent.CATEGORY_HOME);
        mPackageManager = getPackageManager();

        List<ResolveInfo> appList = mPackageManager.queryIntentActivities(mainIntent, 0);
        for(int i = 0; i < appList.size(); i++) {
            ResolveInfo apl = appList.get(i);
            if(currentTask.getPackageName().equals(apl.activityInfo.packageName)) {
                Log.e(TAG, "ONHOMESCREEN");
            }
        }
    }

BroadcastReceiver是否有任何解决方案可以通过Intent接收主屏幕是否在焦点上？

请帮助......