Commit ab6e7dc5 authored by Mugurell's avatar Mugurell Committed by Sebastian Kaspari
Browse files

Fix 4827 - Use ktx doOnPreDraw() to restore HomeFragment's layout 

The previous solution would result in a crash because the passed in
viewTreeObserver that would trigger onPreDraw would be invalid.
The proposed solution is simpler and ensures we'll always use the right
viewTreeObserver.

`FragmentPreDrawManager` is general enough that can be used by other Fragments
also, so I've added it to the `utils` package.
parent 115833c7

app/src/main/java/org/mozilla/fenix/home/HomeFragment.kt

+10 −14
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ import org.mozilla.fenix.mvi.getManagedEmitter 
import org.mozilla.fenix.onboarding.FenixOnboarding

import org.mozilla.fenix.settings.SupportUtils

import org.mozilla.fenix.share.ShareTab

import org.mozilla.fenix.utils.FragmentPreDrawManager

import org.mozilla.fenix.utils.allowUndo



@SuppressWarnings("TooManyFunctions", "LargeClass")
@@ -182,11 +183,14 @@ class HomeFragment : Fragment(), AccountObserver { 
        val activity = activity as HomeActivity

        activity.themeManager.applyStatusBarTheme(activity)



        postponeEnterTransition()

        TransitionPreDrawListener(

            fragment = this,

            viewTreeObserver = sessionControlComponent.view.viewTreeObserver,

            restoreLayoutState = {

        return view

    }



    @SuppressWarnings("LongMethod")

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

        super.onViewCreated(view, savedInstanceState)



        FragmentPreDrawManager(this).execute {

            val homeViewModel: HomeScreenViewModel by activityViewModels()

            homeViewModel.layoutManagerState?.also { parcelable ->

                sessionControlComponent.view.layoutManager?.onRestoreInstanceState(parcelable)
@@ -194,14 +198,6 @@ class HomeFragment : Fragment(), AccountObserver { 
            homeLayout?.progress = homeViewModel.motionLayoutProgress

            homeViewModel.layoutManagerState = null

        }

        )



        return view

    }



    @SuppressWarnings("LongMethod")

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

        super.onViewCreated(view, savedInstanceState)



        setupHomeMenu()

app/src/main/java/org/mozilla/fenix/home/TransitionPreDrawListener.kt→app/src/main/java/org/mozilla/fenix/utils/FragmentPreDrawManager.kt

+36 −0
Original line number Diff line number Diff line
@@ -2,48 +2,32 @@ 
 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */



package org.mozilla.fenix.home

package org.mozilla.fenix.utils



import android.view.ViewTreeObserver

import androidx.core.view.doOnPreDraw

import androidx.fragment.app.Fragment

import androidx.lifecycle.Lifecycle

import androidx.lifecycle.LifecycleObserver

import androidx.lifecycle.OnLifecycleEvent

import androidx.lifecycle.lifecycleScope

import kotlinx.coroutines.delay

import kotlinx.coroutines.launch



class TransitionPreDrawListener(

    private val fragment: Fragment,

    private val viewTreeObserver: ViewTreeObserver,

    private val restoreLayoutState: () -> Unit

) : ViewTreeObserver.OnPreDrawListener, LifecycleObserver {



/**

 * Helper class that allows executing code immediately before [Fragment]s View being drawn.

 */

class FragmentPreDrawManager(

    private val fragment: Fragment

) {

    init {

        fragment.viewLifecycleOwner.lifecycle.addObserver(this)

    }



    @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)

    fun onCreateView() {

        viewTreeObserver.addOnPreDrawListener(this)

    }



    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)

    fun onDestroyView() {

        viewTreeObserver.removeOnPreDrawListener(this)

        fragment.postponeEnterTransition()

    }



    override fun onPreDraw(): Boolean {

        if (fragment.view != null) {

    fun execute(code: () -> Unit) {

        fragment.view?.doOnPreDraw {

            fragment.viewLifecycleOwner.lifecycleScope.launch {

                delay(ANIM_SCROLL_DELAY)

                restoreLayoutState()

                code()

                fragment.startPostponedEnterTransition()

            }.invokeOnCompletion {

                viewTreeObserver.removeOnPreDrawListener(this)

            }

        }

        return true

    }



    companion object {