title: Adding EditText alongside RadioButton
body: <p>I have a custom <code>DialogPreference</code> subclass in which I would like to have a <code>RadioGroup</code> with three radio buttons.  The first two are vanilla <code>RadioButton</code> components with titles, but for the third I would like to place an <code>EditText</code> directly to the right of it so I can enter a custom value when that button is selected.</p>
  
  <p>I have tried putting the third button into a horizontal <code>LinearLayout</code> along with the <code>EditText</code> but then the third button does not participate in the parent <code>RadioGroup</code> anymore. </p>
  
  <pre><code>&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="match_parent"&gt;
      &lt;RadioGroup
              android:id="@+id/lactate_radio"
              android:layout_width="match_parent"
              android:layout_height="wrap_content" &gt;
  
          &lt;RadioButton
                  android:id="@+id/lactate_default_value"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="@string/lactate_default_value"/&gt;
  
          &lt;RadioButton
                  android:id="@+id/lactate_calibrated_value"
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:text="@string/lactate_calibrated_value" /&gt;
          &lt;LinearLayout android:orientation="horizontal"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"&gt;
              &lt;RadioButton
                      android:id="@+id/lactate_custom_value"
                      android:layout_width="wrap_content"
                      android:layout_height="wrap_content"
                      android:text="@string/lactate_custom_value"/&gt;
  
              &lt;EditText
                      android:id="@+id/lactate_custom_value_edit_text"
                      android:layout_width="match_parent"
                      android:layout_height="wrap_content"/&gt;
  
          &lt;/LinearLayout&gt;
      &lt;/RadioGroup&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/VrLu2.png" alt="Screenshot of custom DialogPreference"></p>
  
  <p>I have also tried adding this <code>LinearLayout</code> programmatically but still had the same behavior.  Is there any way to do this, perhaps by explicitly telling the parent <code>RadioGroup</code> about the third button or by somehow positioning the <code>EditText</code> appropriately without using a horizontal <code>LinearLayout</code>?  Otherwise, I think I'll have to write a <code>RadioButton</code> subclass which ought to be a real party!</p>