Q:

Android removing navigation menu item highlighting

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. 
Is it some kind of overlay? I've think I've covered all possible states in drawer_items.xml.
How do I prevent this behaviour?
activity_main.xml
<android.support.design.widget.NavigationView
  .
  .
  android:background="@drawable/drawer_items"
  .
  app:menu="@menu/activity_main_drawer" />

drawer_items.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@color/grey" android:state_activated="true" />
  <item android:drawable="@color/grey" android:state_selected="true" />
  <item android:drawable="@color/grey" android:state_focused="true"  />
  <item android:drawable="@color/grey" android:state_pressed="true" />
  <item android:drawable="@color/grey" android:state_checked="true" />
  <item android:drawable="@color/grey" />
</selector>

activity_main_drawer.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

    <group android:checkableBehavior="single"
           android:id="@+id/arbitrary_id_1">
      <item
        android:id="@+id/nav_refresh"
        android:icon="@drawable/ic_refresh_24dp"
        android:title="Try Again/Refresh" />
    </group>

    <group android:checkableBehavior="single"
           android:id="@+id/arbitrary_id_2">
      <item
        android:id="@+id/nav_back"
        android:icon="@drawable/ic_fast_rewind_24dp"
        android:title="Go Back" />
    </group>

    <group android:checkableBehavior="single"
           android:id="@+id/arbitrary_id_3">
      <item
        android:id="@+id/nav_3" />
    </group>

</menu>

A:

Maybe you can use something like this,
to prevent item from changing its color when clicked, you can try to change in activity_main_drawer.xml:
<group android:checkableBehavior="single">

to
<group android:checkableBehavior="none">

Or you can do this way:
<group android:checkableBehavior="single">
    ...
    <item
        android:id="@+id/item_one"
        android:icon="@drawable/ic_item_one"
        android:title="Item One"/>
    ...
  </group>

To: 
<item>
    <menu>
      ...
      <item
        android:id="@+id/item_one"
        android:icon="@drawable/ic_item_one"
        android:title="Item One"/>
      ...
    </menu>
  </item> 

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A:

So the NavigationView is highlighted based on the colorControlHighlight property. You could create a theme for your drawer and make it transparent:
<style name="Drawer" parent="Theme.AppCompat.Light">
    <item name="colorControlHighlight">#0000</item>
</style>

<android.support.design.widget.NavigationView
    ...
    android:theme="@style/Drawer" />

