title: How to reset radio_button.setButtonDrawable(null)
body: <p>I want to toggle the appearance of circle of the radio button. I am able to make it disappear by setting radio_btn.setButtonDrawable(null) but I don't know how to bring it back.</p>
  
  <pre><code>    rbGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener()
      {
          public void onCheckedChanged(RadioGroup group, int checkedId) {
              checkAnswerRadio();
          }
      });
  
  private void checkAnswerRadio(){
     rb1.setButtonDrawable(null);
  }
  </code></pre>