title: Button onClick attribute is none if activity written in Kotlin
body: <p>Follow this tutorial:  <a href="https://developer.android.com/training/basics/firstapp/starting-activity.html" rel="noreferrer">Android - Start Another Activity</a> if I made <code>MainActivity.java</code> button <code>OnClick</code> attribute has the <code>sendMessage()</code> method.</p>
  
  <p>But if I made <code>MainActivity.kt</code> button <code>OnClick</code> attribute has nothing to show, just a <code>none</code>.</p>
  
  <p>Is this an Android Studio 3 bug or I missed something for Kotlin?</p>
  
  <p>Java mainActivity:</p>
  
  <pre><code>public class MainActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
      }
  
      /** Called when the user taps the Send button */
      public void sendMessage(View view) {
          // Do something in response to button
      }
  
  }
  </code></pre>
  
  <p>Kotlin mainActivity:</p>
  
  <pre><code>class MainActivity : AppCompatActivity() {
  
      override fun onCreate(savedInstanceState: Bundle?) {
          super.onCreate(savedInstanceState)
          setContentView(R.layout.activity_main)
      }
  
      /** Called when the user taps the Send button  */
      fun sendMessage(view: View) {
          // Do something in response to button
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/6nB3U.png" rel="noreferrer"><img src="https://i.stack.imgur.com/6nB3U.png" alt="OnClick attribute"></a></p>
  
  <p>XML layout (Java and Kotlin project are the same)</p>
  
  <pre><code>    &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context="ir.bigbang.vahid.myapplication.MainActivity"&gt;
  
      &lt;Button
          android:id="@+id/button"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Button"
          tools:layout_editor_absoluteX="148dp"
          tools:layout_editor_absoluteY="81dp" /&gt;
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>