title: bad operand types for binary operator +
body: <p>I need a large number up to 20 digits and I'm using bigint. It gives me this error(bad operand types for binary operator +) on line below. </p>
  
  <pre><code>BigInteger t = new BigInteger(my_number.getText().toString());
                  my_number.setText(String.valueOf(t+1));
  </code></pre>