Threading issue in android

Question

I am working on an application in android. And I am trying to update data to UI from the background thread. However, it doesn't work for some reasons. Can any one splot the error or suggest any better solution? I used Thread to read data from the bluetooth socket and update the UI with RunOntheUI. Here is the code:

socket = belt.createRfcommSocketToServiceRecord(UUID_SECURE);
            socket.connect();

                   stream = socket.getInputStream();
                    //  final int intch;
                       Thread timer2 = new Thread() { // Threads - do multiple things
                            public void run() {
                                try {

                                   // read data from input stream if the end has not been reached
                                   while ((intch = stream.read()) != -1) {

                                       byte ch = (byte) intch;
                                       b1.append(ByteToHexString(ch) +"/");
                                        decoder.Decode(b1.toString());  
                                        runOnUiThread(new Runnable() {
                                            public void run()
                                            {
// update the uI

                                        hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
                                            }
                                        });
                                        Thread.sleep(1000);
                                   }
                                } catch (Exception e) {
                                       e.printStackTrace();
                                   } 
                                }};

                                timer2.start();

score 1 · Answer 1 · answered Jul 03 '12 at 20:40

use

Your_Current_Activity.this.runOnUiThread(new Runnable() {
            @Override
            public void run() {
             hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
           }
       });

instead of

runOnUiThread(new Runnable() {
      public void run()
      {
      // update the uI
      hRMonitor.SetHeartRateValue((int) decoder.GetHeartRate());
      }
   });

score 0 · Answer 2 · edited May 23 '17 at 12:20

No. You MUST NOT do that. Never use another thread to update UI Thread, because UI Thread is not thread-safe, it means : when you update your UI Thread, UI Thread doesn't stop working for you do some stuff.

And Android has a machism for this work. This is Asyntask : it will create another thread and when need, it will has safe way to update UI Thread. If you want to more detail, Asyntask will drop a message to message queue of UI Thread.

Here is another link of my post about different Thread, Handler and Asyntask. Asyntask

Hope this help :)

Threading issue in android

2 Answers2