How to use MaterialFadeThrough Transition as StackTransactionModifier?

[wman1980]

Hi,

very nice library!

Currently I am asking myself how to implement MaterialFadeThrough-Transition during a stack-change?

I was able to implement a Cross-Fade Transition by using stackTransactionModifier of MultiStackNavigator like this
this.stackTransactionModifier = { setCustomAnimations( R.anim.fade_in, R.anim.fade_out, R.anim.fade_in, R.anim.fade_out ) }

But how to do this by using a MaterialFadeThrough Transition?

[tunjid]

Hi @wman1980, thanks for checking out the library. MainActivity has an example of this using an extension:

navigator.stackTransactionModifier = navigator.materialFadeThroughTransition()

The full implementation is:

fun MultiStackNavigator.materialFadeThroughTransition(): FragmentTransaction.(Int) -> Unit = fade@{ index ->
    val rootFragmentManager = current?.activity?.supportFragmentManager ?: return@fade

    rootFragmentManager.findFragmentByTag(activeIndex.toString())?.apply {
        enterTransition = null
        if (exitTransition !is MaterialFadeThrough) exitTransition = MaterialFadeThrough().setDuration(300)
    }
    rootFragmentManager.findFragmentByTag(index.toString())?.apply {
        exitTransition = null
        if (enterTransition !is MaterialFadeThrough) enterTransition = MaterialFadeThrough().setDuration(300)
    }
}

[wman1980]

ahh, that is awesome!

I just forgot about the supportFragmentManager and the index.

Thanks a lot!

[wman1980]

Hi @tunjid,

I have a follow up question.

If I add some Transition.TransitionListener to that code above to listen to start and end events for each transition. Do you have an idea how I could pass these events to my active and target fragment?

Currently the fragment returned by findFragmentByTag is a StackFragment and it does not offer a lot to me because everything is internal ...

I first though I could just add this listener within my active/target fragment, but there the transition is null. So is there actually a way to get these transitions from my active/target fragment?

Thanks

[tunjid]

@wman1980 MultistackNavigator.current and MultistackNavigator.previous should give you you a reference to your Fragment in your Transtion.Listener. Do you have a snippet of what you're trying to achieve with the listener?

[wman1980]

Actually I have a WebView within android and the webview "flickers/blinks" if a transition (MaterialSharedAxis.X) is started. My plan to prevent that was to create a bitmap snapshot and put that snapshot in front of the webview on transition start and remove that snapshot on transition end. But unfortunately I just discovered that onDestroyView of my fragment is called before onTransitionStart e.g. during a returnTransition. Damn android!

[wman1980]

ok, I worked around my issue by creating a snapshot onPause within my fragment. Sorry to spam with unrelated stuff and thanks for your response.