Send data via Bluetooth in Android

Question

Here is the code I used to send data via Bluetooth, It works well if I click the button, but I can't use it if I directly call the function sendData(String...) without clicking button.

I am trying to change clicking button to using voice recognization.

It works well if I use

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Log.d(TAG, "In onCreate()");

    setContentView(R.layout.main);

    btnOn = (Button) findViewById(R.id.btnOn);
    btnOff = (Button) findViewById(R.id.btnOff);

    btAdapter = BluetoothAdapter.getDefaultAdapter();
    checkBTState();

    btnOn.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
        sendData("a");
        Toast msg = Toast.makeText(getBaseContext(),
            "You have clicked On", Toast.LENGTH_SHORT);
        msg.show();
      }
    });

    btnOff.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
        sendData("b");
        Toast msg = Toast.makeText(getBaseContext(),
            "You have clicked Off", Toast.LENGTH_SHORT);
        msg.show();
      }
    });}

But if I move the sendData outside, it doesn't work

btnOff.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
      }
    });
sendData("b");

Here is the full Code

import java.io.IOException;
import java.io.OutputStream;
import java.util.UUID;
import java.util.concurrent.TimeUnit;
import com.example.ledonoff.R;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import android.widget.Toast;
import android.speech.RecognizerIntent;

import java.util.ArrayList;
import java.util.Locale;
import android.content.ActivityNotFoundException;

public class LEDOnOff extends Activity {
  private static final String TAG = "LEDOnOff";

  Button btnOn, btnOff, btnSpeak;
  public   String cmd = "none";
    private final int SPEECH_RECOGNITION_CODE = 1;
  private static final int REQUEST_ENABLE_BT = 1;
  private BluetoothAdapter btAdapter = null;
  private BluetoothSocket btSocket = null;
  private OutputStream outStream = null;
  private TextView textout;
  // Well known SPP UUID
  private static final UUID MY_UUID =
      UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

  // Insert your bluetooth devices MAC address
  private static String address = "98:D3:32:10:91:1F";

  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    Log.d(TAG, "In onCreate()");

    setContentView(R.layout.main);

    btnOn = (Button) findViewById(R.id.btnOn);
    btnOff = (Button) findViewById(R.id.btnOff);
    btnSpeak = (Button) findViewById(R.id.btnSpeak);
    textout = (TextView) findViewById(R.id.textout);

    btAdapter = BluetoothAdapter.getDefaultAdapter();
    checkBTState();

    btnOn.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
        sendData("a");
        Toast msg = Toast.makeText(getBaseContext(),
            "You have clicked On", Toast.LENGTH_SHORT);
        msg.show();
      }
    });

    btnOff.setOnClickListener(new OnClickListener() {
      public void onClick(View v) {
        sendData("b");
        Toast msg = Toast.makeText(getBaseContext(),
            "You have clicked Off", Toast.LENGTH_SHORT);
        msg.show();
      }
    });

      btnSpeak.setOnClickListener(new OnClickListener() {
          public void onClick(View v) {
            startSpeechToText();

          }
      });

  }




    /**
     * Start speech to text intent. This opens up Google Speech Recognition API dialog box to listen the speech input.
     * */
    private void startSpeechToText() {
        Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
        intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault());
        intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
                RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
        intent.putExtra(RecognizerIntent.EXTRA_PROMPT,
                "Speak something...");
        try {
            startActivityForResult(intent, SPEECH_RECOGNITION_CODE);
        } catch (ActivityNotFoundException a) {
            Toast.makeText(getApplicationContext(),
                    "Sorry! Speech recognition is not supported in this device.",
                    Toast.LENGTH_SHORT).show();
        }
    }
    /**
     * Callback for speech recognition activity
     * */
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case SPEECH_RECOGNITION_CODE: {
                if (resultCode == RESULT_OK && null != data) {
                    ArrayList<String> result = data
                            .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);
                    String text = result.get(0);
                    textout.setText(text); 

                }


              break;


            }
        }
    }

    public String VoiceFilter(String str_voice_input){


        if(str_voice_input.contains("on") ){sendData("a"); //TEST SENDING DATA
          return "a" ;
        }

        if(str_voice_input.contains("off") ){sendData("b"); //TEST SENDING DATA
          return "b" ;
        }

      return "c";


    }

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

    Log.d(TAG, "...In onResume - Attempting client connect...");

    // Set up a pointer to the remote node using it's address.
    BluetoothDevice device = btAdapter.getRemoteDevice(address);

    // Two things are needed to make a connection:
    //   A MAC address, which we got above.
    //   A Service ID or UUID.  In this case we are using the
    //     UUID for SPP.
    try {
      btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
    } catch (IOException e) {
      errorExit("Fatal Error", "In onResume() and socket create failed: " + e.getMessage() + ".");
    }

    // Discovery is resource intensive.  Make sure it isn't going on
    // when you attempt to connect and pass your message.
    btAdapter.cancelDiscovery();

    // Establish the connection.  This will block until it connects.
    Log.d(TAG, "...Connecting to Remote...");
    try {
      btSocket.connect();
      Log.d(TAG, "...Connection established and data link opened...");
    } catch (IOException e) {
      try {
        btSocket.close();
      } catch (IOException e2) {
        errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
      }
    }

    // Create a data stream so we can talk to server.
    Log.d(TAG, "...Creating Socket...");

    try {
      outStream = btSocket.getOutputStream();
    } catch (IOException e) {
      errorExit("Fatal Error", "In onResume() and output stream creation failed:" + e.getMessage() + ".");
    }
  }

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

    Log.d(TAG, "...In onPause()...");

    if (outStream != null) {
      try {
        outStream.flush();
      } catch (IOException e) {
        errorExit("Fatal Error", "In onPause() and failed to flush output stream: " + e.getMessage() + ".");
      }
    }

    try     {
      btSocket.close();
    } catch (IOException e2) {
      errorExit("Fatal Error", "In onPause() and failed to close socket." + e2.getMessage() + ".");
    }
  }

  private void checkBTState() {
    // Check for Bluetooth support and then check to make sure it is turned on

    // Emulator doesn't support Bluetooth and will return null
    if(btAdapter==null) { 
      errorExit("Fatal Error", "Bluetooth Not supported. Aborting.");
    } else {
      if (btAdapter.isEnabled()) {
        Log.d(TAG, "...Bluetooth is enabled...");
      } else {
        //Prompt user to turn on Bluetooth
        Intent enableBtIntent = new Intent(btAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
      }
    }
  }

  private void errorExit(String title, String message){
    Toast msg = Toast.makeText(getBaseContext(),
        title + " - " + message, Toast.LENGTH_SHORT);
    msg.show();
    finish();
  }

  private void sendData(String message) {
    byte[] msgBuffer = message.getBytes();

    Log.d(TAG, "...Sending data: " + message + "...");

    try {
      outStream.write(msgBuffer);
    } catch (IOException e) {
      String msg = "In onResume() and an exception occurred during write: " + e.getMessage();
      if (address.equals("00:00:00:00:00:00")) 
        msg = msg + ".\n\nUpdate your server address from 00:00:00:00:00:00 to the correct address on line 37 in the java code";
      msg = msg +  ".\n\nCheck that the SPP UUID: " + MY_UUID.toString() + " exists on server.\n\n";

      errorExit("Fatal Error", msg);       
    }
  }
}

Answer 1

Are you trying to execute sendData("b") in OnCreate() method? Because if so it won't work as the connection is not established with other device yet. Try running it in onResume() after the connection is established. Starting transmission immediately after establishing connection may cause in initial data loss, so create a thread and wait for a second and start communicating.