Cannot lower case button text in android studio

You could add android:textAllCaps="false" to the button.

The button text might be transformed to uppercase by your app's theme that applies to all buttons. Check themes / styles files for setting the attribute android:textAllCaps.

<style name="AppTheme" parent="AppBaseTheme">
    <item name="android:buttonStyle">@style/Button</item>
</style>

<style name="Button" parent="Widget.AppCompat.Button">
    <item name="android:textAllCaps">false</item>
</style>