Android bluetooth application process killed

Question

I'm very new with programming for android. I have two classes : main and btmanager. When i try to test my app on phone, all I get is a information that procees was killed. What am I doing wrong ?

Code implementation :

Main class :

public class MainActivity extends Activity {

BluetoothAdapter bluetooth = BluetoothAdapter.getDefaultAdapter();

Btmanager manager;


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

    if (bluetooth == null)
    {
        Toast.makeText(this, "Bluetooth is not enabled on this device", Toast.LENGTH_LONG).show();
        System.exit(0);
    }


}

@Override
public void onStart()
{
    super.onStart();

    if (!bluetooth.isEnabled()) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, 2);
    }

    manager.run();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}




public void closeApp (View view)
{
    System.exit(0);
}
}

Btmanager class :

public class Btmanager extends Thread {

private final BluetoothSocket mmSocket;
private final BluetoothDevice mmDevice;
public static final UUID myUUID = UUID.fromString("0x1101");
BluetoothAdapter bluetooth = BluetoothAdapter.getDefaultAdapter();

public Btmanager(BluetoothDevice device) {
    // Use a temporary object that is later assigned to mmSocket,
    // because mmSocket is final
    BluetoothSocket tmp = null;
    mmDevice = device;

    // Get a BluetoothSocket to connect with the given BluetoothDevice
    try {
        // MY_UUID is the app's UUID string, also used by the server code
        tmp = device.createRfcommSocketToServiceRecord(myUUID);
    } catch (IOException e) { }
    mmSocket = tmp;
}

public void run() {
    // Cancel discovery because it will slow down the connection
    bluetooth.cancelDiscovery();

    try {
        // Connect the device through the socket. This will block
        // until it succeeds or throws an exception
        mmSocket.connect();
    } catch (IOException connectException) {
        // Unable to connect; close the socket and get out
        try {
            mmSocket.close();
        } catch (IOException closeException) { }
        return;
    }

}

/** Will cancel an in-progress connection, and close the socket */
public void cancel() {
    try {
        mmSocket.close();
    } catch (IOException e) { }
}

Answer 1

2 problems I see in your code:

1. You don't instantiate the Btmanager object, it is still null when you call run. (Will cause a NullPointerException - your app will crash).
2. You call the run method instead of the start method of the Btmanager. If you want the code in the run method to run in a new thread, you have to call start. Calling run will cause it to run in the same thread. This blocks your UI thread which may cause your app to crash, if it blocks for too long.