I added some deps to build.gradle, then the preview buttons on the top-right appeared. But next time I started Android Studio, those buttons only appeared for a short time, then disappeared after loading completed.

What I've tried that doesn't help:

• File - Settings - Editor - UI Tools: disasble and enable the options.
• Build - Clean Project, then Make Project
• File - Invalidate Caches - Just restart

What finally solve the problem：

• File - Invalidate Caches - Invalidate and Restart