hey guys i have two doubts regarding silver app bar
1) i want the bottom section to be autosize according to the content
2) like in twitter or insta on the profile page once we scroll down the tab bar pins to the top and we can scroll the post but how can i pinn the tab bar to the top here after the app bar collapses becoz once i scroll down again the app bar reopens and the available space for tab bar decrease which makes the experience bad