title: how to add a button value to edittext
body: <p>l have 3 buttons and 1 edittext</p>
  
  <pre><code>   &lt;Button
        android:id="@+id/button1" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="1" /&gt;
    &lt;Button
        android:id="@+id/button2" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="2" /&gt;
    &lt;Button
        android:id="@+id/button3" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="3" /&gt;
    &lt;EditText
      android:id="@+id/display" android:layout_width="match_parent"
      android:layout_height="wrap_content" android:text="@string/result" /&gt;
  </code></pre>
  
  <p>when i click on android emulator <em>button 1</em> the text value of <em>1</em> should display in <strong><em>edittext</em></strong> how can do this</p>