title: Dial digits (1 or 2) when call active/answered from custom Default Dialer in Android programmatically?
body: <p><br><br>Im making a <b>Default Dialer App</b> in Android replacing built-in phone dialer. Everything is working fine, call is attending as well as rejecting.
  <br><br>But when the call attends: When suppose operator asks to press  <b>"1"</b>  for this and <b>"2"</b> for this. <br><br> How can I send these <b>(1 or 2)</b> commands to operator programmatically without interrupting my custom calling screen and without going out of my custom call screen. <br><br>Things I have tried for pressing button 3: <br><br>   <b>Intent intent = Intent(Intent.ACTION_CALL, Uri.parse("tel://3"))<br>
  startActivity(intent)</b> <br><br> But the above code prompt me a dialog <b>"Unable to make conference call."</b><br><br>Thank you.</p>