Android多线程UI更新

我试图运行与外部设备的UDP连接。我希望它每3秒向设备发送一条消息并阅读响应。我创建了3个类：主，发送者和接收者。我为发送者和接收者打开一个Runnable，让他们在继续之前休眠3秒。Android多线程UI更新

我的问题是，当我按下屏幕上的按钮时，发送和接收的消息，但它们没有在我的屏幕上更新，因为更新行不在循环中。我如何告诉它每3秒更新一次屏幕？读取消息并显示它的代码是：

textViewState.setText（udpReceive.receivedMessage）;

代码

public class MainActivity extends AppCompatActivity { 

public static TextView textViewState; 
public static Context context; 

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

    textViewState = (TextView) findViewById(R.id.textView); 
    context = getApplicationContext(); 

} 

public void buttonConnect(View v) { 

    (new Thread(new udpSender())).start(); 

    (new Thread(new udpReceive())).start(); 

    textViewState.setText(udpReceive.receivedMessage); 

} 


}

类发送消息：

public class udpSender implements Runnable { 


public void run() { 

    while (true) { 

     String messageStr = "Hello Android!"; 
     int server_port = 8888; 
     DatagramSocket s = null; 
     try { 
      s = new DatagramSocket(); 
     } catch (SocketException e) { 
      e.printStackTrace(); 
     } 
     InetAddress local = null; 
     try { 
      local = InetAddress.getByName("192.168.43.159"); 
     } catch (UnknownHostException e) { 
      e.printStackTrace(); 
     } 
     int msg_length = messageStr.length(); 
     byte[] message = messageStr.getBytes(); 

     DatagramPacket p = new DatagramPacket(message, msg_length, local, server_port); 
     try { 
      s.send(p); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

     try { 
      Thread.sleep(3000); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 

    } 
} 
}

类从UDP

public class udpReceive implements Runnable { 

private static final int MAX_UDP_DATAGRAM_LEN = 100; 
private static final int UDP_SERVER_PORT = 8888; 
public static String receivedMessage; 

public void run() { 


    while (true) { 
     String message; 
     byte[] lmessage = null; 
     lmessage = new byte[MAX_UDP_DATAGRAM_LEN]; 
     DatagramPacket packet = null; 

     DatagramSocket socket = null; 
     try { 
      packet = new DatagramPacket(lmessage, lmessage.length); 
      socket = new DatagramSocket(UDP_SERVER_PORT); 
      socket.receive(packet); 
      message = new String(lmessage, 0, packet.getLength()); 
      receivedMessage = message; 
     } catch (SocketException e) { 
      e.printStackTrace(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } finally { 
      if (socket != null) { 
       socket.close(); 
      } 
     } 
     try { 
      Thread.sleep(3000); 
     } catch (InterruptedException e) { 
      e.printStackTrace(); 
     } 
    } 
} 
}

来源

2017-07-30 yspede

使用Handler to g o回到主线程，然后你可以更新你的TextView – MohammedAlSafwan

我发现同时基于你的答案:)谢谢

MainActivity类别的解决方案：

public static Handler UIHandler; 

static { 
    UIHandler = new Handler(Looper.getMainLooper()); 
} 

public static void runOnUI(Runnable runnable) { 
    UIHandler.post(runnable); 
}

接收类

MainActivity.runOnUI(new Runnable() { 
    public void run() { 
     MainActivity.textViewState.setText(message_received); 
    } 
});

来源

2017-07-31 15:05:56 yspede

收到消息，在任何类，它是在另一个线程，尝试这样做

Handler handler = new Handler(getActivity().getMainLooper()); 

handler.post(new Runnable(){ 
     // your TextView goes here 
})

来源

2017-07-30 15:15:11 MohammedAlSafwan

只有UI线程（主线程）可以访问UI元素

// Your message receiving class 
... 
message = new String(lmessage, 0, packet.getLength()); 
final String message_received = new String(lmessage, 0, packet.getLength()); 
... 

MainActivity.context.runOnUiThread(new Runnable() { 
    @Override 
    public void run() { 
     MainActivity.textViewState.setText(message_received); 
    } 
}); 
...

来源

2017-07-30 15:18:34 KnightMobile

Android多线程UI更新

回答

相关问题