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，每5秒收到一次关于每个位置更新的消息。从我可以请求当前城市的位置，用户正在进入。然后我想下载一些数据，只有当城市发生变化时。我怎么能意识到这一点？

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);
    }
};

就像你可以看到我玩过vars一样。有任何想法吗？感谢

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;
    }
}