Java – Unknown warning icon – Android Studio

This is my simple_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="false">
        <shape android:shape="rectangle">
            <solid android:color="@android:color/white" />
        </shape>
    </item>
    <item android:state_pressed="true">
        <shape android:shape="rectangle">
            <solid android:color="@android:color/darker_gray" />
        </shape>
    </item>
</selector>

What is the reason behind the warning icon and what am I doing wrong?

I’m using Android Studio v1.4.1.

This is not a bug in the code you wrote. This means that Android Studio cannot display thumbnails for a given drawable”
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