Bug: bad transformation on list when going back to it

[AndroidDeveloperLB]

Check the video that's attached:

device-2019-12-07-140719.zip

[tunjid]

@AndroidDeveloperLB thanks for pointing out the issue! It happens when the shared element transition starts before the recyclerview scrolls to make sure the item is in the proper place. I should fixe this by postponing the transition, I just haven't gotten around to it yet.

[AndroidDeveloperLB]

Please show in code why it occurs, and how you fix it.
I want to see if I can learn from it.

[tunjid]

@AndroidDeveloperLB it is fixed in the linked PR. Since there is a shared element transition between fragments, in onCreateView I call postponeEnterTransition() to make sure the image has been loaded with Picasso before the transition runs.

Also, since the user may be returning to an image that is offscreen, I use scrollToPosition() to make sure the image shows fully on the screen for animating.

Sometimes, the image will have loaded before the RecyclerView has scrolled (Image was cached). To fix this, I need to wait till the RecyclerView has scrolled before starting the transition. The fix is to call view?.doOnLayout to start the transition after the RecyclerView has scrolled.

Thanks again for pointing out the bug!

    override fun onDoggoImageLoaded(doggo: Doggo) {
        if (doggo == Doggo.transitionDoggo) view?.doOnLayout { startPostponedEnterTransition() }
    }

[AndroidDeveloperLB]

And this fixed it? can you please show a video?

[tunjid]

@AndroidDeveloperLB sorry I missed this, yes it did fix it. I can't quite record a video right now, but you can run it to verify.

[AndroidDeveloperLB]

OK tried now.
Seems to still has an issue:
The RecyclerView scrolls while I'm on the new screen.

See attached video:
2020-02-12_23-30-34.zip