public void plus3(View v) {
        switch (v.getId()) {
            case R.id.button:
                TextView score = (TextView) findViewById(R.id.textView3);
                String s = score.toString();
                int x = Integer.parseInt(s);
                x += 3;
                score.setText("" + x);
                break;
            case R.id.button2:
                TextView scoreB = (TextView) findViewById(R.id.textView4);
                String sB = scoreB.toString();
                int xB = Integer.parseInt(sB);
                xB += 3;
                scoreB.setText("" + xB);
                break;
        }
    }
}

//Вызов в вью кнопки:
        android:onClick="plus3"