使用如下style即可:
"@style/Widget.MaterialComponents.Button.UnelevatedButton"
对应的style源码定义如下:
<style name="Widget.MaterialComponents.Button.UnelevatedButton">
<item name="android:stateListAnimator" ns2:ignore="NewApi">@animator/mtrl_btn_unelevated_state_list_anim</item>
<item name="elevation">0dp</item>
</style>