Place that can apply style(theme)

in Manifest

application

activity



in the layout file

example:
<android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:layout_alignParentTop="true"
            android:layout_alignParentLeft="true"

            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" />