title: Android launch phone call application
body: <p>What I'm wanna achieve is to create a button whenever there is an CALL_STATE_OFFHOOK (active call) phone call it can be clicked to open the native phone call application on the phone.
  So that user can go back to the call.</p>
  
  <p>What I've tried :</p>
  
  <pre><code> Intent i = new Intent(Intent.ACTION_PICK, ContactsContract.Contacts.CONTENT_URI);
   Intent i = new Intent(Intent.ACTION_VIEW, ContactsContract.Contacts.CONTENT_URI);
   Intent i = new Intent(Intent.ACTION_DIAL, null);
   Intent i = new Intent(Intent.ACTION_VIEW, CallLog.Calls.CONTENT_URI);
   Intent i = new Intent(Intent.ACTION_CALL_BUTTON);
  </code></pre>
  
  <p>and none of these can achieve my goal.</p>
  
  <p>Is there any ways I could actually open the phone activity or phone intent etc. ?</p>