styles.xml

<resources>

    <!--
        Base application theme, dependent on API level. This theme is replaced
        by AppBaseTheme from res/values-vXX/styles.xml on newer devices.

    -->
    <style name="AppBaseTheme" parent="android:Theme.Holo.Light.NoActionBar.Fullscreen">
        <!--
            Theme customizations available in newer API levels can go in
            res/values-vXX/styles.xml, while customizations related to
            backward-compatibility can go here.

        -->
    </style>

    <!-- Application theme. -->
    <style name="AppTheme" parent="AppBaseTheme">
        <!-- All customizations that are NOT specific to a particular API-level can go here. -->
    </style>
    <!-- style for auto ratio ImageView -->
    <declare-styleable name="AutoRatioImageView">

        <!-- -ratio 高/宽 -->
        <attr name="ratio" format="float" />
        <attr name="prefer" format="integer" />
    </declare-styleable>

</resources>