title: Android removing navigation menu item highlighting
body: <p>When you click a menu item in my navigation drawer, it becomes slightly darker and remains that way until another item is clicked. I'm trying to keep it the same colour no matter what state it's in. </p>
  
  <p>Is it some kind of overlay? I've think I've covered all possible states in drawer_items.xml.<br>
  How do I prevent this behaviour?</p>
  
  <p><strong>activity_main.xml</strong></p>
  
  <pre><code>&lt;android.support.design.widget.NavigationView
    .
    .
    android:background="@drawable/drawer_items"
    .
    app:menu="@menu/activity_main_drawer" /&gt;
  </code></pre>
  
  <p><strong>drawer_items.xml</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;selector xmlns:android="http://schemas.android.com/apk/res/android"&gt;
    &lt;item android:drawable="@color/grey" android:state_activated="true" /&gt;
    &lt;item android:drawable="@color/grey" android:state_selected="true" /&gt;
    &lt;item android:drawable="@color/grey" android:state_focused="true"  /&gt;
    &lt;item android:drawable="@color/grey" android:state_pressed="true" /&gt;
    &lt;item android:drawable="@color/grey" android:state_checked="true" /&gt;
    &lt;item android:drawable="@color/grey" /&gt;
  &lt;/selector&gt;
  </code></pre>
  
  <p><strong>activity_main_drawer.xml</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;menu xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;group android:checkableBehavior="single"
             android:id="@+id/arbitrary_id_1"&gt;
        &lt;item
          android:id="@+id/nav_refresh"
          android:icon="@drawable/ic_refresh_24dp"
          android:title="Try Again/Refresh" /&gt;
      &lt;/group&gt;
  
      &lt;group android:checkableBehavior="single"
             android:id="@+id/arbitrary_id_2"&gt;
        &lt;item
          android:id="@+id/nav_back"
          android:icon="@drawable/ic_fast_rewind_24dp"
          android:title="Go Back" /&gt;
      &lt;/group&gt;
  
      &lt;group android:checkableBehavior="single"
             android:id="@+id/arbitrary_id_3"&gt;
        &lt;item
          android:id="@+id/nav_3" /&gt;
      &lt;/group&gt;
  
  &lt;/menu&gt;
  </code></pre>