<ImageView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:adjustViewBounds="true"
    android:scaleType="fitXY"
    android:src="@drawable/res_version_bg" />

<!-- Set this to true if you want the ImageView to adjust its bounds
     to preserve the aspect ratio of its drawable. -->

如果希望ImageView调整其边界，请将此设置为true 以保持其可拉伸的长宽比

<attr name="adjustViewBounds" format="boolean" />

把图片按比例扩大/缩小到View的宽度，显示在View的上部分位置
 android:scaleType="fitXY"