Android中凹下去的分割线

布局文件中添加以下代码：

    <RelativeLayout
        android:background="#222222"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <View
            android:id="@+id/view1"
            android:background="@drawable/shape_line_top"
            android:layout_centerInParent="true"
            android:layout_width="match_parent"
            android:layout_height="1dp"/>
        <View
            android:id="@+id/view2"
            android:layout_below="@+id/view1"
            android:background="@drawable/shape_line_bottom"
            android:layout_centerInParent="true"
            android:layout_width="match_parent"
            android:layout_height="1dp"/>
    </RelativeLayout>

shape_line_top.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:endColor="#363636"
        android:startColor="#000000"
        android:type="linear"
        android:angle="90"/>
</shape>

shape_line_bottom.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:endColor="#000000"
        android:startColor="#363636"
        android:type="linear"
        android:angle="90"/>
</shape>

实际上就是两条渐变线组合起来的效果，shape_line_top颜色浅到深的线，shape_line_bottom由深到浅的线。