you would get the desired reason why the design is not visible, please do that and update your question :)

CodePudding user response：

In newer versions of Android Studio, there's been a issue, XML will not be shown until you fix all the bugs available in your code.

Solutions

1. Downgrade your Android Studio to BumbleBee. By this, xml will be shown if error still exists in code.
2. Fix issues illustrated by android studio. You can find issues by clicking red error icon on top-right side of xml page.