在res/drawable目录下穿件shape的xml来实现圆角矩形效果。代码如下：

    <?xml version="1.0" encoding="utf-8"?>  
    <shape xmlns:android="http://schemas.android.com/apk/res/android"  
        android:shape="rectangle" >  
      
        <corners  
            android:bottomLeftRadius="8dp"  
            android:bottomRightRadius="8dp"  
            android:topLeftRadius="8dp"  
            android:topRightRadius="8dp" />  
      
        <gradient  
            android:angle="45"  
            android:centerColor="#CCFFDD"  
            android:endColor="#CCCCCC"  
            android:startColor="#CCCCCC" />  
      
        <padding  
            android:bottom="7dp"  
            android:left="7dp"  
            android:right="7dp"  
            android:top="7dp" />  
      
    </shape>  

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
        xmlns:tools="http://schemas.android.com/tools"  
        android:layout_width="match_parent"  
        android:layout_height="match_parent"  
        android:paddingBottom="@dimen/activity_vertical_margin"  
        android:paddingLeft="@dimen/activity_horizontal_margin"  
        android:paddingRight="@dimen/activity_horizontal_margin"  
        android:paddingTop="@dimen/activity_vertical_margin"  
        tools:context=".MainActivity" >  
      
        <Button  
            android:id="@+id/button1"  
            android:layout_width="140dp"  
            android:layout_height="60dp"  
            android:layout_alignParentTop="true"  
            android:layout_centerHorizontal="true"  
            android:background="@drawable/button"  
            android:text="设置Shape的形状" />  
      
        <LinearLayout  
            android:layout_width="200dp"  
            android:layout_height="100dp"  
            android:layout_alignParentLeft="true"  
            android:layout_alignParentRight="true"  
            android:layout_below="@+id/button1"  
            android:layout_marginTop="71dp"  
           <span style="color:#ff0000;"> android:background="@drawable/button"</span>  
            android:orientation="vertical" >  
      
        </LinearLayout>  
      
    </RelativeLayout>