在Fragment里面，上下文不能使MainActivity.this  只能是getActivity() ;

ToastUtils.show(getActivity(),"请求成功");

Handler机制的简单代码

private Handler handler = new Handler(){

        @Override

        public void handleMessage(Message msg) {

                if (msg.what == 1){

                        getWeatherData();

                }

        }

};

调用

handler.sendEmptyMessageDelayed(1,5000);

5s执行一次。