error: No resource identifier found for attribute 'layout_with' in package 'android'

在Graphical Layout(就是main.xml旁边那个视图)

"button" does not set the required layout_width attribute:

 (1) Set to "wrap_content"

 (2) Set to "match_parent"

You must supply a layout_width attribute.

原来敲成android:layout_with="wrap_content" 漏了个d ,应为android:layout_width="wrap_content"