1

I below is my code for receiving Multicast Wifi Data on android. I am using runnables like below to update the GUI but i found thatsome packets are missing. I am using this code to receive count down message but the count down is not continious. I dont know whether packets are lost due to the style of GUI updating or due to some other problem. request you all to give suggestions.

    package com.example.cdttiming;

    public class MainActivity extends Activity
    {
        EditText time;
        String s;
        Button button;
     InetAddress ia = null;

         byte[] bmessage = new byte[1500];
         DatagramPacket dp = new DatagramPacket(bmessage, bmessage.length);
         MulticastSocket ms = null;
        @Override

        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);     

            time = (EditText) findViewById(R.id.et_time);
        try 
            {
            WifiManager wm = (WifiManager)getSystemService(Context.WIFI_SERVICE); 
            //wm.setWifiEnabled(true);      
            WifiManager.MulticastLock multicastLock = wm.createMulticastLock("multicastLock");
            multicastLock.setReferenceCounted(true);        
            multicastLock.acquire();      

            ia = InetAddress.getByName("226.1.1.1");    
            try {
                ms = new MulticastSocket(4321);
                } catch (IOException e) {
                e.printStackTrace();
                }
            try {
                ms.joinGroup(ia);
                } catch (IOException e) {
                e.printStackTrace();
                }

            ms.setReuseAddress(true);


            }
               catch (UnknownHostException e)
                {
                e.printStackTrace();

                }
                catch (IOException e) 
                 {
                    e.printStackTrace();
                 }     
         }

        public void startProgress(View view) {
        Runnable runnable = new Runnable() {
              @Override
              public void run() {

            while(true)
                {
                 try
                 {
                      ms.receive(dp);
              s = new String(dp.getData(),0,dp.getLength()); 
                                         }
                 catch (UnknownHostException e)
                    {
                    e.printStackTrace();

                    }
                   catch (IOException e) 
                    {
                      e.printStackTrace();
                    }     


                   time.post(new Runnable() {
                    @Override
                    public void run() {
                        time.setText(s);

                    }
                  });
               }  // while
              }
            };
            new Thread(runnable).start();
          }

        @Override
         public boolean onCreateOptionsMenu(Menu menu)
        {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }   
    }
4

1 回答 1

1

您无权访问主 UI 线程。这就是为什么您不能将文本设置为 UI 视图元素的原因。

访问 UI 线程的方法很少 1) 使用 Activity.runOnUiThread()

this.runOnUiThread( new Runnable() { @Override
                    public void run() {
                        time.setText(s);

                    } })

2）我想在你的情况下最好使用 Handler 对象，它是你的工作线程和主 UI 线程之间的桥梁

         private Handler handler = new Handler(){
                 @Override
                 public void handleMessage(Message message) {
                     switch (message.what) {
                         case SET_TEXT:{
                             time.setText(s);
                         }break;
     }
...
handler.sendEmptyMessage(SET_TEXT);
于 2013-07-23T17:18:50.103 回答