Android 消息机制

  //在主线程中定义一个Handler
  private Handler handler=new Handler(){
      //这个方法是在主线程中执行的
      @Override
      public void handleMessage(Message msg) {
         tv_result.setText(msg.obj.toString());
      }
  };

    Message msg=new Message();
    msg.obj=content;
    handler.sendMessage(msg);//发消息

    Message msg=new Message();
    msg.what=REQUESTEXCEPTION;
    handler.sendMessage(msg);

    @Override
    public void handleMessage(Message msg) {
        switch (msg.what){
            case REQUESTSUCCESS: //请求成功
                tv_result.setText(msg.obj.toString());
                break;
            case REQUESTNOTFIND: //目标资源不存在
                Toast.makeText(MainActivity.this, "目标资源不存在", Toast.LENGTH_SHORT).show();
                break;
            case REQUESTEXCEPTION: //异常
                Toast.makeText(MainActivity.this, "服务器忙 请稍等。。。", Toast.LENGTH_SHORT).show();
        }
    }