将0（零）附加到grep匹配引用(Appending 0 (zero) to a grep match reference)

 你使用带有插图的图层列表，以避免内圈从外圈潜伏，如下所示： 
 
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <stroke
                android:width="4dp"
                android:color="@android:color/holo_red_dark" />
        </shape>
    </item>
    <item>
        <inset android:inset="4dp">
            <shape android:shape="oval">
                <stroke
                    android:width="4dp"
                    android:color="@android:color/holo_green_dark" />
            </shape>
        </inset>
    </item>
</layer-list>
 
 您可以像这样设置按钮的大小和背景： 
 
<Button
    android:id="@+id/button"
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:background="@drawable/red_green" />
 
 它看起来像这样： 
 
  

You use a layer list with insets in order to avoid the inner circle to lurk out from the outer circle, like this:
 
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape android:shape="oval">
            <stroke
                android:width="4dp"
                android:color="@android:color/holo_red_dark" />
        </shape>
    </item>
    <item>
        <inset android:inset="4dp">
            <shape android:shape="oval">
                <stroke
                    android:width="4dp"
                    android:color="@android:color/holo_green_dark" />
            </shape>
        </inset>
    </item>
</layer-list>
 
You set the size and background of the button like this:
 
<Button
    android:id="@+id/button"
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:background="@drawable/red_green" />
 
It then looks like this: