Android studio grid layout don't show any view : I have a grid layout that is a child of another layout (like frame layout or constraint layout ) . I drag and drop views on it like button or image view but it didn't show !! . How can i fix this problem ? 
[pic1][1]


[pic2][2]


  [1]: https://i.stack.imgur.com/xYbyQ.png
  [2]: https://i.stack.imgur.com/YN8Ws.png