How to check bluetooth connection state with paired device in Android

Question

I develop an bluetooth app which will connect to a paired device and send a message, but I have to test connection before. I've tried many options, but nothing works in good way. So could you send me any example of code which can do it? I made an thread, but I can't get an good state of connection to build an "if" function. Here is the code:

package com.example.szukacz;

import java.lang.reflect.Method;
import java.util.Set;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;


public class MainActivity extends Activity {
    LinearLayout sparowaneUrzadzenia;

    public void lokalizowanie() {
    Intent intencja = new Intent(this, Lokalizator.class);
    startActivity(intencja);

    }

    public void parowanie(View v) {
        Intent intencja = new Intent(this, Parowanie.class);
        startActivity(intencja);

    }

    boolean isRunning;

    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            String status = (String)msg.obj;
            if(status == "polaczony") {
                alarm();
                showToast("prawda, zwraca" + status);
            } else {
                showToast("wykonanie x, zwraca: " + status);
            };
        }
    };

    public void alarm() {
        showToast("Alarm!!!");
    }


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

        sparowaneUrzadzenia = (LinearLayout) findViewById(R.id.listaUrzadzenGlowna);

        pokazSparowane();



    }

    public void onStop() {
        super.onStop();
        isRunning = false;
    }

    public void onStart() {
        super.onStart();
        Thread testPolaczen = new Thread(new Runnable() {
            public void run() {
                try {
                    for(int i = 0; i < 1000000; i++) {
                        Thread.sleep(5000);
                        testujPolaczenia();
                        int stan = 0;
                        String status = Integer.toString(stan);

                        Message msg = handler.obtainMessage(1, (String)status);

                        if(isRunning == true) {
                            handler.sendMessage(msg);
                        }
                    }
                } catch (Throwable t) {
                    // watek stop
                }
            }
        });
        isRunning = true;
        testPolaczen.start();
    }

    private void testujPolaczenia() {

    }

    public void pokazSparowane(){
        /*
         * Wyświetlanie listy sparowanych urządzeń .
         * */
        Log.d("INFO","Sparowane dla tego urzÄ…dzenia");
        BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();  
        if (pairedDevices.size() > 0) { 
            for (BluetoothDevice device : pairedDevices) {              
                Log.d("INFO",device.getName()+" - "+device.getAddress());

                // dodawanie urzadzen do listy
                Button urzadzenie = new Button(getApplicationContext());
                urzadzenie.setText(device.getName());
            //  urzadzenie.setTextColor(0xffffff); //jak ustawic na czarny kolor napsisów ?

                urzadzenie.setOnClickListener(new OnClickListener() {           

                      @Override
                      public void onClick(View v) 
                      {
                          showToast("klik");
                          lokalizowanie();

                      }    
                    });

                sparowaneUrzadzenia.addView(urzadzenie);
            }
        } else {
            showToast("brak sparowanych urzadzen");
        }
    }



    @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;
    }
    private void showToast(String message) {
        Toast.makeText(getApplicationContext(), message, Toast.LENGTH_SHORT).show();
    }

    @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);
    }


}

thanks!

Solution 1

I faced the same problem as I am working on an app which may use TTS while it is running. I think there is no way to check if there is any bluetooth device connected by the BluetoothAdapter class immediately except creating a broadcast receiver and monitor the changes of status of bluetooth.

After scratching my head for a few hours, I found a quite subtle way to solve this problem. I tried, it works pretty well for me.

AudioManager audioManager = (AudioManager) getApplicationContext.getSystemService(Context.AUDIO_SERVICE);
if (audioManager.isBluetoothA2dpOn()) {
   //audio is currently being routed to bluetooth -> bluetooth is connected
}

Source: http://developer.android.com/training/managing-audio/audio-output.html

Solution 2

I think it's to late for answer to your question but I think can helps somebody :

If you use Thread you have to create a BroadcastReceiver in your main activity on create :

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_digital_metrix_connexion);
     BroadcastReceiver bState = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if(action.equals(BluetoothAdapter.ACTION_CONNECTION_STATE_CHANGED))
            {
                int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                        BluetoothAdapter.ERROR);
                switch (state)
                {
                    case BluetoothAdapter.ACTION_ACL_CONNECTED:
                    {
                        //Do something you need here
                        System.out.println("Connected");
                        break;
                    }
                    default:
                        System.out.println("Default");
                        break;
                }
            }
        }
    };
}

BluetoothAdapter.STATE_CONNECTED is one state over many, for exemple it's possible to check if device connecting or disconnecting thanks to BluetoothAdapter.ACTION_ACL_DISCONNECTED or BluetoothAdapter.ACTION_ACL_DISCONNECTED_REQUEST .

After, you have to create a filter in your thread class or in you main activity if you don't use thread :

IntentFilter filter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);

This filter check the bluetoothadapter state.

And now you have to register your filter so if you use thread pass context in parameter of your thread like this context.registerReceiver(bState,filter); or in your main Activity : registerReceiver(bState,filter);

If you have any question don't hesitate to ask me.

Hope I helps you somebody.