public class MainActivity extends Activity implements AudioManager.OnAudioFocusChangeListener
{

Button receive,remove;
AudioManager audioManager;

@Override
public void onAudioFocusChange(int focusState)
{
    // TODO: Implement this method

    switch(focusState){

        case AudioManager.AUDIOFOCUS_GAIN:
            showToast("Gain");  //this line not executed after pressing the button receive
            break;

        case AudioManager.AUDIOFOCUS_LOSS:
            showToast("Loss");
            break;

        case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
            showToast("Loss can duck");
            break;

        case audioManager.AUDIOFOCUS_LOSS_TRANSIENT:
            showToast("Lost transient");
            break;
    }

}

private void showToast(String msg)
{
    // TODO: Implement this method

    Toast.makeText(this,msg,Toast.LENGTH_SHORT).show();

}

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

    receive=(Button)findViewById(R.id.receive);
    remove=(Button)findViewById(R.id.remove);

    receive.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view)
            {
                // TODO: Implement this method

                requestAudioFocus();

            }
    });

    remove.setOnClickListener(new View.OnClickListener(){

            @Override
            public void onClick(View view)
            {
                // TODO: Implement this method

                removeAudioFocus();

            }

    });

}

private boolean requestAudioFocus(){

    audioManager=(AudioManager)getSystemService(AUDIO_SERVICE);

    int res=audioManager.requestAudioFocus(this,AudioManager.STREAM_MUSIC,audioManager.AUDIOFOCUS_GAIN);

    if(res == audioManager.AUDIOFOCUS_REQUEST_GRANTED){
        return true;
    }
    return false;
}

private boolean removeAudioFocus() {

    return AudioManager.AUDIOFOCUS_REQUEST_GRANTED == audioManager.abandonAudioFocus(this);
}
}