Android API 21 changes my custom button background

Question

I am testing out my app for API21 on Android! Unfortunately, my buttons seem weird - there is some kind of background color added. The background images did not change - they are completely transparent except for the border. (The different text and size is due to the screenshot).

Here you see the buttons before and since API 21: http://imgur.com/9EEcl0o,yVEnJkI#0

I already tried android:elevation="0dp" and android:background="@android:color/transparent". Anybody knows why my buttons change? Thank you very much!

layout.xml:

<Button android:id="@+id/sm_achievements_btn"
    android:layout_width="fill_parent"
    android:layout_height="0dp"
    android:layout_weight="1.1"   
    android:background="@drawable/menu_btn_selector"
    android:onClick="showAchievements"
    android:text="@string/sm_achievements_btn"
    android:padding="@dimen/padding_std"
    android:layout_marginTop="@dimen/margin_small"
    android:textColor="@color/button_text"
    android:textSize="@dimen/text_xlarge"
    style="@style/lbm_button"/>

menu_btn_selector.xml:

<item android:drawable="@drawable/menu_button"
 android:state_pressed="false"/>

style.xml:

<style name="lbm_button" parent="android:Theme.Holo.Light">
    <item name="android:textAllCaps">false</item>
</style>

Answer 1

Material buttons have a default stateListAnimator that provides state-based elevation (e.g. 0dp when disabled, 1dp when enabled). You can clear it by setting android:stateListAnimator="@null" in your style or directly on the Button.

Here is what that would look like on your button XML:

<Button android:id="@+id/sm_achievements_btn"
    ...
    android:textAllCaps="false"
    android:stateListAnimator="@null" />

Also, you're using the wrong parent for your button style. You should never set a theme as the parent for a widget style. Regardless, here is what that should look like if you prefer that route:

<Button android:id="@+id/sm_achievements_btn"
    ...
    style="@style/MyButtonStyle" />

<style name="MyButtonStyle" parent="android:Widget.Material.Light.Button">
    <item name="android:textAllCaps">false</item>
    <item name="android:stateListAnimator">@null</item>
</style>