Fix popBackStack() animation #6

massivemadness · Feb 2, 2023 · 7bb0d11 · 7bb0d11
1 parent 14f6285
commit 7bb0d11
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Showing 2 changed files with 36 additions and 9 deletions.
diff --git a/fragula-compose/src/main/kotlin/com/fragula2/compose/FragulaNavHost.kt b/fragula-compose/src/main/kotlin/com/fragula2/compose/FragulaNavHost.kt
@@ -111,11 +111,13 @@ fun FragulaNavHost(
             animDurationMs = animDurationMs,
             elevation = elevation,
             offsetProvider = { parallaxOffset },
+            systemBackProvider = { swipeBackNavigator.systemBack.value != null },
             positionChanger = { position, positionOffset, positionOffsetPixels ->
                 onPageScrolled(position, positionOffset, positionOffsetPixels)
                 parallaxOffset = positionOffset
             },
-            scrollFinished = { swipeBackNavigator.markTransitionComplete(backStackEntry) },
+            onScrollCancelled = { swipeBackNavigator.slideOut = it == SwipeState.SLIDE_OUT },
+            onScrollFinished = { swipeBackNavigator.markTransitionComplete(backStackEntry) },
             modifier = modifier.fillMaxSize(),
         ) {
             NavHostContent(saveableStateHolder, backStackEntry)
@@ -144,8 +146,10 @@ private fun SwipeableBox(
     animDurationMs: Int,
     elevation: Dp,
     offsetProvider: () -> Float,
+    systemBackProvider: () -> Boolean,
     positionChanger: (Int, Float, Int) -> Unit,
-    scrollFinished: () -> Unit,
+    onScrollCancelled: (SwipeState) -> Unit,
+    onScrollFinished: () -> Unit,
     modifier: Modifier = Modifier,
     content: @Composable () -> Unit,
 ) {
@@ -177,13 +181,13 @@ private fun SwipeableBox(
                 pageStart -> {
                     pointerPosition = pageStart
                     swipeState = SwipeState.FOLLOW_POINTER
-                    scrollFinished()
+                    onScrollFinished()
                 }
                 pageEnd -> {
                     pointerPosition = pageStart
                     swipeState = SwipeState.FOLLOW_POINTER
                     navController.popBackStack()
-                    scrollFinished()
+                    onScrollFinished()
                 }
             }
         }
@@ -196,16 +200,17 @@ private fun SwipeableBox(
             val positionOffsetPixels = (pageEnd * (1.0f - positionOffset)).toInt()
             val positionActual = if (scrollPosition > pageStart) position - 1 else position
             positionChanger(positionActual, positionOffset, positionOffsetPixels)
+
+            if (systemBackProvider()) { // system back button
+                swipeState = SwipeState.SLIDE_OUT
+            }
         }
 
-        DisposableEffect(position) {
+        LaunchedEffect(position) {
             if (animateSlideIn) {
                 animateSlideIn = false
                 swipeState = SwipeState.SLIDE_IN
             }
-            onDispose {
-                // TODO popBackStack animation
-            }
         }
 
         val applyScrim by remember {
@@ -237,6 +242,7 @@ private fun SwipeableBox(
                             pointerPosition < pageEnd / 2 -> SwipeState.SLIDE_IN
                             else -> SwipeState.FOLLOW_POINTER
                         }
+                        onScrollCancelled(swipeState)
                     }
                 },
             ).graphicsLayer {

diff --git a/fragula-compose/src/main/kotlin/com/fragula2/compose/SwipeBackNavigator.kt b/fragula-compose/src/main/kotlin/com/fragula2/compose/SwipeBackNavigator.kt
@@ -1,6 +1,7 @@
 package com.fragula2.compose
 
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.navigation.*
 import androidx.navigation.compose.rememberNavController
@@ -28,8 +29,10 @@ fun rememberSwipeBackNavigator(): SwipeBackNavigator {
 @Navigator.Name("swipeable")
 class SwipeBackNavigator : Navigator<SwipeBackNavigator.Destination>() {
 
+    internal val systemBack = mutableStateOf<Pair<NavBackStackEntry, Boolean>?>(null)
     internal val transitionsInProgress get() = state.transitionsInProgress
     internal val backStack get() = state.backStack
+    internal var slideOut = false
 
     override fun navigate(
         entries: List<NavBackStackEntry>,
@@ -46,7 +49,25 @@ class SwipeBackNavigator : Navigator<SwipeBackNavigator.Destination>() {
     }
 
     override fun popBackStack(popUpTo: NavBackStackEntry, savedState: Boolean) {
-        state.popWithTransition(popUpTo, savedState)
+        when {
+            slideOut -> {
+                state.popWithTransition(
+                    popUpTo = popUpTo,
+                    saveState = savedState,
+                )
+                slideOut = false
+            }
+            systemBack.value == null -> {
+                systemBack.value = popUpTo to savedState
+            }
+            systemBack.value != null -> {
+                state.popWithTransition(
+                    popUpTo = systemBack.value?.first ?: return,
+                    saveState = systemBack.value?.second ?: return,
+                )
+                systemBack.value = null
+            }
+        }
     }
 
     internal fun markTransitionComplete(entry: NavBackStackEntry) {