效果如下：

默认.png

选中.png

代码：

switch_track.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="true">
        <shape>
            <size android:width="38dp" android:height="18dp" />
            <corners android:radius="10dp" />
            <solid android:color="#0c0c0c" />
        </shape>
    </item>

    <item>
        <shape>
            <size android:width="38dp" android:height="18dp" />
            <corners android:radius="10dp" />
            <solid android:color="#a0a0a0" />
        </shape>
    </item>
</selector>

switch_thumb.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_checked="true">
        <shape>
            <size android:width="18dp" android:height="18dp" />
            <corners android:radius="10dp" />
            <solid android:color="#ffffff" />
            <stroke android:width="2dp" android:color="#0c0c0c" />
        </shape>
    </item>

    <item>
        <shape>
            <size android:width="18dp" android:height="18dp" />
            <corners android:radius="10dp" />
            <solid android:color="#ffffff" />
            <stroke android:width="2dp" android:color="#a0a0a0" />
        </shape>
    </item>
</selector>

使用：

<Switch
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:thumb="@drawable/switch_thumb"
    android:track="@drawable/switch_track" />