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" />

Style

If many view use the same attribute,we can change it to astyle

<Button
        android:id="@+id/btBTB"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:background="@drawable/orange_custom_button_background"
        android:padding="5dp"
        android:text="@string/ant_terminator"
        android:textColor="@color/textColor" />

change to a style

in styles.xml

<style name="OrangeButton">
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:layout_margin">10dp</item>
        <item name="android:background">@drawable/orange_custom_button_background</item>
        <item name="android:padding">5dp</item>
        <item name="android:textColor">@color/textColor</item>
    </style>

After apply

<Button
        android:id="@+id/btBTB"
        style="@style/OrangeButton"
        android:text="@string/ant_terminator" />