Android create a “flat button”

You can use the style="?android:attr/borderlessButtonStyle on your Button as follows:

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextGoesHere"
style="?android:attr/borderlessButtonStyle"
/>

BorderlessButtonStyle

Style for buttons without an explicit border, often used in groups.

Also you can use those Flat Buttons