java - UpdateHandler，只有当触发器为真时才做一件事，Android

Question

我有一个处理程序，它每 5 秒在每次位置更新时接收一条消息。从位置我可以请求用户正在移动的当前城市。然后我想下载一些数据一次并且仅当城市发生变化时。我怎样才能意识到这一点？

Handler myViewUpdateHandler = new Handler(){

    public void handleMessage(Message msg) {
            switch (msg.what) {
            case UPDATE_LOCATION:
                mc.animateTo(geosenseo.getCurrentPoint());  
                mapView.invalidate();

                    //a async task sets the currentCity field   

               if(trigger && (currentCity != "")){
                   firstCity = currentCity;
                   trigger = false;
               }

               if((currentCity != "") && (firstCity != "")){
                   if(firstCity != currentCity){
                       //download only when city changes
                       trigger = true;
                   } 
               }

           }

            super.handleMessage(msg);
    }
};

如您所见，我玩过 vars。有任何想法吗？谢谢

Answer 1

这有助于...将字符串与 equals 和以下 if 语句进行比较

if(!currentCity.equals("")){
    if(!firstCity.equals(currentCity)){
      firstCity = currentCity;
    }
}