refactor: 优化 FAB 共享元素转场动画

app/src/main/kotlin/cn/super12138/todo/ui/navigation/TopNavigation.kt

@@ -2,6 +2,7 @@ package cn.super12138.todo.ui.navigation
 
 import androidx.compose.animation.ExperimentalAnimationApi
 import androidx.compose.animation.SharedTransitionLayout
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Modifier
 import androidx.navigation3.runtime.NavKey
@@ -22,28 +23,9 @@ import cn.super12138.todo.ui.pages.settings.SettingsMain
 import cn.super12138.todo.ui.pages.tasks.TasksPage
 import cn.super12138.todo.ui.theme.fadeThrough
 import cn.super12138.todo.ui.theme.materialSharedAxisX
+import cn.super12138.todo.ui.theme.veilFade
 import cn.super12138.todo.ui.viewmodels.MainViewModel
 
-
-private const val INITIAL_OFFSET_FACTOR = 0.10f
-
-private fun settingsTransition() = NavDisplay.transitionSpec {
-    materialSharedAxisX(
-        initialOffsetX = { (it * INITIAL_OFFSET_FACTOR).toInt() },
-        targetOffsetX = { -(it * INITIAL_OFFSET_FACTOR).toInt() }
-    )
-} + NavDisplay.popTransitionSpec {
-    materialSharedAxisX(
-        initialOffsetX = { -(it * INITIAL_OFFSET_FACTOR).toInt() },
-        targetOffsetX = { (it * INITIAL_OFFSET_FACTOR).toInt() }
-    )
-} + NavDisplay.predictivePopTransitionSpec {
-    materialSharedAxisX(
-        initialOffsetX = { -(it * INITIAL_OFFSET_FACTOR).toInt() },
-        targetOffsetX = { (it * INITIAL_OFFSET_FACTOR).toInt() }
-    )
-}
-
 @OptIn(ExperimentalAnimationApi::class)
 @Composable
 fun TopNavigation(
@@ -55,7 +37,33 @@ fun TopNavigation(
         backStack.removeLast()
     }
 
-//    val veilColor = MaterialTheme.colorScheme.surfaceDim
+    val veilColor = MaterialTheme.colorScheme.surfaceDim
+    fun editorTransition() = NavDisplay.transitionSpec {
+        veilFade(veilColor)
+    } + NavDisplay.popTransitionSpec {
+        veilFade(veilColor)
+    } + NavDisplay.predictivePopTransitionSpec {
+        veilFade(veilColor)
+    }
+
+    val initialOffestFactor = 0.10f
+    fun settingsTransition() = NavDisplay.transitionSpec {
+        materialSharedAxisX(
+            initialOffsetX = { (it * initialOffestFactor).toInt() },
+            targetOffsetX = { -(it * initialOffestFactor).toInt() }
+        )
+    } + NavDisplay.popTransitionSpec {
+        materialSharedAxisX(
+            initialOffsetX = { -(it * initialOffestFactor).toInt() },
+            targetOffsetX = { (it * initialOffestFactor).toInt() }
+        )
+    } + NavDisplay.predictivePopTransitionSpec {
+        materialSharedAxisX(
+            initialOffsetX = { -(it * initialOffestFactor).toInt() },
+            targetOffsetX = { (it * initialOffestFactor).toInt() }
+        )
+    }
+
     SharedTransitionLayout {
         NavDisplay(
             backStack = backStack.backStack,
@@ -88,7 +96,7 @@ fun TopNavigation(
                     )
                 }
 
-                entry<TodoScreen.Editor.Add> {
+                entry<TodoScreen.Editor.Add>(metadata = editorTransition()) {
                     TodoAddPage(
                         onSave = {
                             viewModel.addTodo(it)
@@ -98,7 +106,7 @@ fun TopNavigation(
                     )
                 }
 
-                entry<TodoScreen.Editor.Edit> { editorArgs ->
+                entry<TodoScreen.Editor.Edit>(metadata = editorTransition()) { editorArgs ->
                     TodoEditPage(
                         toDo = editorArgs.toDo,
                         onSave = {

app/src/main/kotlin/cn/super12138/todo/ui/pages/editor/TodoEditorPage.kt

@@ -53,10 +53,13 @@ fun SharedTransitionScope.TodoAddPage(
     onNavigateUp: () -> Unit
 ) = TodoEditorPage(
     toDo = null,
-    modifier = modifier.sharedBounds(
-        sharedContentState = rememberSharedContentState(key = Constants.KEY_TODO_FAB_TRANSITION),
-        animatedVisibilityScope = LocalNavAnimatedContentScope.current
-    ),
+    modifier = modifier
+        .sharedBounds(
+            sharedContentState = rememberSharedContentState(key = Constants.KEY_TODO_FAB_TRANSITION),
+            animatedVisibilityScope = LocalNavAnimatedContentScope.current,
+            resizeMode = SharedTransitionScope.ResizeMode.RemeasureToBounds
+        )
+        .skipToLookaheadSize(), // 这个修饰符必须放后面
     onSave = onSave,
     onDelete = {},
     onNavigateUp = onNavigateUp
@@ -76,13 +79,14 @@ fun SharedTransitionScope.TodoEditPage(
         animatedVisibilityScope = LocalNavAnimatedContentScope.current,
         resizeMode = SharedTransitionScope.ResizeMode.RemeasureToBounds
     ),
+        //TODO: 没想好加不加 .skipToLookaheadSize(),
     onSave = onSave,
     onDelete = onDelete,
     onNavigateUp = onNavigateUp
 )
 
 @Composable
-fun TodoEditorPage(
+fun SharedTransitionScope.TodoEditorPage(
     modifier: Modifier = Modifier,
     toDo: TodoEntity? = null,
     onSave: (TodoEntity) -> Unit,

app/src/main/kotlin/cn/super12138/todo/ui/pages/tasks/TasksPage.kt

@@ -27,7 +27,6 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.style.TextAlign
-import androidx.compose.ui.zIndex
 import androidx.navigation3.ui.LocalNavAnimatedContentScope
 import cn.super12138.todo.R
 import cn.super12138.todo.constants.Constants
@@ -87,7 +86,8 @@ fun SharedTransitionScope.TasksPage(
                 modifier = Modifier
                     .sharedBounds(
                         sharedContentState = rememberSharedContentState(key = Constants.KEY_TODO_FAB_TRANSITION),
-                        animatedVisibilityScope = animatedVisibilityScope
+                        animatedVisibilityScope = animatedVisibilityScope,
+                        resizeMode = SharedTransitionScope.ResizeMode.RemeasureToBounds
                     )
                     .animateFloatingActionButton(
                         visible = !inSelectedMode,

app/src/main/kotlin/cn/super12138/todo/ui/theme/Motion.kt

@@ -3,6 +3,7 @@ package cn.super12138.todo.ui.theme
 import androidx.compose.animation.ContentTransform
 import androidx.compose.animation.EnterTransition
 import androidx.compose.animation.ExitTransition
+import androidx.compose.animation.ExperimentalAnimationApi
 import androidx.compose.animation.core.FastOutLinearInEasing
 import androidx.compose.animation.core.FastOutSlowInEasing
 import androidx.compose.animation.core.LinearOutSlowInEasing
@@ -12,6 +13,9 @@ import androidx.compose.animation.fadeOut
 import androidx.compose.animation.scaleIn
 import androidx.compose.animation.slideInHorizontally
 import androidx.compose.animation.slideOutHorizontally
+import androidx.compose.animation.unveilIn
+import androidx.compose.animation.veilOut
+import androidx.compose.ui.graphics.Color
 
 /**
  * 来自：https://github.com/Ashinch/ReadYou/blob/main/app/src/main/java/me/ash/reader/ui/motion/MaterialSharedAxis.kt
@@ -114,4 +118,37 @@ fun fadeThroughOut(
         durationMillis = durationMillis,
         easing = FastOutLinearInEasing
     )
-)
+)
+
+fun veilFade(
+    initialColor: Color,
+    durationMillis: Int = 200
+): ContentTransform = ContentTransform(
+    veilFadeIn(
+        initialColor = initialColor,
+        durationMillis = durationMillis
+    ),
+    veilFadeOut(
+        initialColor = initialColor,
+        durationMillis = durationMillis
+    )
+)
+
+@OptIn(ExperimentalAnimationApi::class)
+fun veilFadeIn(
+    initialColor: Color,
+    durationMillis: Int = DefaultMotionDuration,
+): EnterTransition =
+    fadeIn(
+    ) + unveilIn(
+        initialColor = initialColor
+    )
+
+@OptIn(ExperimentalAnimationApi::class)
+fun veilFadeOut(
+    initialColor: Color,
+    durationMillis: Int = DefaultMotionDuration,
+): ExitTransition =
+    fadeOut() + veilOut(
+        targetColor = initialColor
+    )