你应该给形状添加角":

you should add "corners" to the shape:

 <?xml version="1.0" encoding="UTF-8"?> 
<shape xmlns:android="http://schemas.android.com/apk/res/android"> 
<solid android:color="#ffffffff"/>    

<stroke android:width="3dp"
        android:color="#ff000000"
        />

<padding android:left="1dp"
         android:top="1dp"
         android:right="1dp"
         android:bottom="1dp"
         /> 

<corners android:radius="7dp"/>