Java 更新始终位于顶部的Android视图

我想创建一个更新其内容并定期显示在窗口顶部的视图。我发现了一个在窗口顶部创建视图的示例（）。该活动将生成一个UI，如果我按下启动服务按钮，视图将显示其文本。但是当视图创建后，它不会更新其内容。我试图添加简单的代码来计算视图更新的次数，但它不起作用。如何定期更改视图的内容？我应该在服务中添加循环代码吗？我需要你的建议，谢谢

1.AlwaysOnTopActivity.java

public class AlwaysOnTopActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    findViewById(R.id.start).setOnClickListener(this);  //start button  
    findViewById(R.id.end).setOnClickListener(this);    //stop button       
}

@Override
public void onClick(View v) {
    int view = v.getId();
    if(view == R.id.start)
        startService(new Intent(this, AlwaysOnTopService.class));   
    else
        stopService(new Intent(this, AlwaysOnTopService.class));    
}

}

2.AlwaysOnTopService.java

public class AlwaysOnTopService extends Service {
private TextView tv;                                            
@Override
public IBinder onBind(Intent arg0) { return null; }

@Override
public void onCreate() {
    super.onCreate();

    tv = new TextView(this);        //creating view
    tv.setText("This view is always on top.");
    tv.setTextSize(TypedValue.COMPLEX_UNIT_SP, 18);
    tv.setTextColor(Color.BLUE);


    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
        WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY, //to always on top
        WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,//for touch event
        PixelFormat.TRANSLUCENT);                                                   

    WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);    
    wm.addView(tv, params);//We must configure the permission in the manifest
}

@Override
public void onDestroy() {
    super.onDestroy();
    if(tv != null)      //terminating the view
    {
        ((WindowManager) getSystemService(WINDOW_SERVICE)).removeView(tv);
        tv = null;
    }
}

---

}

按说明使用

LocalBroadcastManager

。在

onReceive

方法中更新用户界面