Bluetooth IOException : Bluetooth is off

Question

I tried to make a Bluetooth Connection between an Android Smartphone and a Mindstorms NXT. The Smartphone is a Sony Xperia Zl with Android 5.1.1. The App should send the NXT a Number and the NXT should recieve it with a running Programm. This is my current Source Code:

package com.mona.projektkurs;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.UUID;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;


public class MainActivity extends Activity {

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

@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;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}



 private BluetoothAdapter adapter;
   private BluetoothDevice device = null;
   private BluetoothSocket BTsocket=null;

public void enableBt(){
    adapter = BluetoothAdapter.getDefaultAdapter();
    if(!adapter.isEnabled()){
        adapter.enable();
        connection();
    }else{
        Toast.makeText(getApplicationContext(),"Error1" , Toast.LENGTH_LONG).show();
    }
}

public void connection(){
    device = adapter.getRemoteDevice("00:16:53:1B:1D:C5");
    try{
         BTsocket = device.createRfcommSocketToServiceRecord(UUID
                  .fromString("00001101-0000-1000-8000-00805F9B34FB"));
         BTsocket.connect();
         messageWrite();
    }catch(IOException e){
        Toast.makeText(getApplicationContext(), "Error2"+e.toString(), Toast.LENGTH_LONG).show();
    }
}

public void messageWrite(){
    if(BTsocket != null){
        try{
             OutputStreamWriter out = new OutputStreamWriter(BTsocket.getOutputStream());
             out.write((byte)0x80); // no respond
             out.write((byte)0x09); // MessageWrite
             out.write((byte)0x03); // Inbox (0-9)
             out.write((byte)0x02); // MessageSize
             out.write((byte)0x49); // Data ("1" == 0x49 ASCII Code)
             out.write((byte)0x00); // Null termination (/0)
             BTsocket.close();
        }catch(IOException f){
            Toast.makeText(getApplicationContext(), "Error3"+f.toString(), Toast.LENGTH_LONG).show();


    }
        }
    }

}

Bluetooth is successfully enabled but the Errorhandler throws an IO.Exception: Bluetooth is off. The MAC-Adress is proven. The Bluetooth Connection can be established with a Commercial App successfully.

Any Ideas?

Answer 1

Did you add bluetooth permission in manifest ?