@Override
protected void onServiceConnected() {
    Call call = getSinchServiceInterface().getCall(mCallId);
    if (call != null) {
        call.addCallListener(new SinchCallListener());
        TextView remoteUser = (TextView) findViewById(R.id.remoteUser);
        remoteUser.setText(call.getRemoteUserId());

    } else {
        Log.e(TAG, "Started with invalid callId, aborting");
        finish();
    }
}

private void answer() {
    mAudioPlayer.stopRingtone();
    Call call = getSinchServiceInterface().getCall(mCallId);
    if (call != null) {
        call.answer();
        Intent intent = new Intent(this, CallScreenActivity.class);
        intent.putExtra(SinchService.CALL_ID, mCallId);
        startActivity(intent);
    } else {
        finish();
    }
}

private void stop() {
    mAudioPlayer.stopRingtone();
    Call call = getSinchServiceInterface().getCall(mCallId);
    if (call != null) {
        call.hangup();
    }
    finish();
}