Android：蓝牙监听线程正在阻止UI线程

Question

my ListeningThread is freezing the UI thread of the Barometer activity although it shouldn't. I have no idea why this is happening. Help needed :)

This is my ListeningThread:

public class ListeningThread extends Thread {

String TAG = "bluetoothThread";

private final BluetoothServerSocket bluetoothServerSocket;
BluetoothAdapter bl;

public ListeningThread(BluetoothAdapter bluetoothAdapter, String appName) {
    BluetoothServerSocket temp = null;
    bl = bluetoothAdapter;
    try {
        temp = bluetoothAdapter.listenUsingRfcommWithServiceRecord(appName, Constants.MY_UUID_SECURE);
    } catch (IOException e) {
        e.printStackTrace();
    }
    bluetoothServerSocket = temp;
}

public void start() {
    Log.d(TAG, "ListeningThread running");
    BluetoothSocket bluetoothSocket;
    //This will block while listening until a BluetoothSocket is returned or an exception occurs
    while (true) {
        try {
            bluetoothSocket = bluetoothServerSocket.accept();
            Log.d(TAG, "ListeningThread connected");
        } catch (IOException e) {
            break;
        }
        // If a connection is accepted
        if (bluetoothSocket != null) {

            // Manage the connection in a separate thread

            try {
                bluetoothServerSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            break;
        }
    }
}

// Cancel the listening socket and terminate the thread
public void cancel() {
    try {
        bluetoothServerSocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
}

And this is the activity using the thread and freezing:

public class BarometerActivity extends AppCompatActivity {

BluetoothAdapter bluetoothAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_barometer);
    if (SingletonBluetoothAdapter.bluetoothAdapter == null) {
        SingletonBluetoothAdapter.bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    }
    bluetoothAdapter = SingletonBluetoothAdapter.bluetoothAdapter;

    ListeningThread t = new ListeningThread(bluetoothAdapter, getString(R.string.app_name));
    t.start();
}

}

I am sure the problem is somewhere in the run-method of the thread. I tried to surround this method with a comment and then everything runs fine.

Answer 1

You should put the while(true) code inside the method public void run() . Not in the public void start() as documented here https://docs.oracle.com/javase/tutorial/essential/concurrency/runthread.html