It's not that visible on the gif, you can only see it when going back from Irene.
When going from UsersListScreen to UserDetailsScreen everything works fine. The sequence is as follows:
startElement from previous screen is goneendElement calls onElementRegistered and hides itself (by using alpha = 0)transition is set to SharedElementTransition.WaitingForEndElementPosition and invalidateTransitionsOverlay() is called.SharedElementTransitionsOverlay reads that transition and draws SharedElementTransitionPlaceholder of startElement for a brief moment until endElement will be positioned and we can launch the real transition.endElement calls onElementPositioned.transition is set to SharedElementTransition.InProgress and invalidateTransitionsOverlay() is called.SharedElementTransitionsOverlay reads and draws the real transition from startElement to endElement
Steps 2, 3 and 4 are done in the same pass (frame?). endElement hides itself, but at the same time we already have a placeholder of startElement drawn by SharedElementTransitionsOverlay.
When going from UserDetailsScreen to UsersListScreen there is one difference though. It looks like AdapterList (that is used on UsersListScreen) never disposes its list items, even when it's gone (#1, https://issuetracker.google.com/issues/150174792). I believe it causes it to be positioned "instantly"(?). The sequence is as follows:
startElement from previous screen is goneendElement calls onElementRegistered and hides itself (by using alpha = 0)transition is set to SharedElementTransition.WaitingForEndElementPosition and invalidateTransitionsOverlay() is called.- DIFFERENT: NOT HAPPENING
- DIFFERENT:
endElement calls onElementPositioned in the same pass as 2 and 3. SharedElementTransitionsOverlay had no chance to refresh, so we have missed frame.
transition is set to SharedElementTransition.InProgress and invalidateTransitionsOverlay() is called.SharedElementTransitionsOverlay reads and draws the real transition from startElement to endElement
It's not that visible on the gif, you can only see it when going back from Irene.
When going from
UsersListScreentoUserDetailsScreeneverything works fine. The sequence is as follows:startElementfrom previous screen is goneendElementcallsonElementRegisteredand hides itself (by usingalpha = 0)transitionis set toSharedElementTransition.WaitingForEndElementPositionandinvalidateTransitionsOverlay()is called.SharedElementTransitionsOverlayreads that transition and drawsSharedElementTransitionPlaceholderofstartElementfor a brief moment untilendElementwill be positioned and we can launch the real transition.endElementcallsonElementPositioned.transitionis set toSharedElementTransition.InProgressandinvalidateTransitionsOverlay()is called.SharedElementTransitionsOverlayreads and draws the real transition fromstartElementtoendElementSteps 2, 3 and 4 are done in the same pass (frame?).
endElementhides itself, but at the same time we already have a placeholder ofstartElementdrawn bySharedElementTransitionsOverlay.When going from
UserDetailsScreentoUsersListScreenthere is one difference though. It looks likeAdapterList(that is used onUsersListScreen) never disposes its list items, even when it's gone (#1, https://issuetracker.google.com/issues/150174792). I believe it causes it to be positioned "instantly"(?). The sequence is as follows:startElementfrom previous screen is goneendElementcallsonElementRegisteredand hides itself (by usingalpha = 0)transitionis set toSharedElementTransition.WaitingForEndElementPositionandinvalidateTransitionsOverlay()is called.endElementcallsonElementPositionedin the same pass as 2 and 3.SharedElementTransitionsOverlayhad no chance to refresh, so we have missed frame.transitionis set toSharedElementTransition.InProgressandinvalidateTransitionsOverlay()is called.SharedElementTransitionsOverlayreads and draws the real transition fromstartElementtoendElement