是否有可能为一个标注图形绘制9个补丁?

I'm trying to make a callout graphic in Android. I'm not married to the idea of using a 9-patch-drawable, but I think it's the right way to go. I'm essentially trying to make a button with a little nub at the bottom. I'd like the nub to be centered regardless of the size of the content. Here are some example graphics showing what look I'm going for:I'm trying to make a callout graphic in Android