title: Values are not displaying on TextView
body: <p>I have a couple issues with a math program im currently working on im trying to make a delete button so the user can remove any mistake made and also i want to append("0") but it does nothing when i press both buttons. When i append values from 1-9 it displays it but wierdly it does nothing when pressing delete and one. answer is a TextView. Any ideas would be appreciated.</p>
  
  <pre><code>        case R.id.delete:
              answer.append("");
              break;
          case R.id.zero:
              answer.append("0");
              break;
  </code></pre>