feat: US-007~010 实现年月视图共享元素转场动画

- 引入 SharedTransitionLayout + AnimatedContent 管理月/年视图切换
- 使用 sharedBounds + rememberSharedContentState 标记共享元素
- 转场动画 400ms，FastOutSlowInEasing
- 添加 compose-animation 依赖支持 SharedTransition API

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gradle/libs.versions.toml

@@ -24,6 +24,7 @@ androidx-lifecycle-viewmodelCompose = { module = "androidx.lifecycle:lifecycle-v
 androidx-lifecycle-runtimeCompose = { module = "androidx.lifecycle:lifecycle-runtime-compose", version.ref = "androidx-lifecycle" }
 compose-bom = { module = "androidx.compose:compose-bom", version.ref = "composeBom" }
 compose-runtime = { module = "androidx.compose.runtime:runtime" }
+compose-animation = { module = "androidx.compose.animation:animation" }
 compose-foundation = { module = "androidx.compose.foundation:foundation" }
 compose-material3 = { module = "androidx.compose.material3:material3" }
 compose-ui = { module = "androidx.compose.ui:ui" }

shared/build.gradle.kts

@@ -45,6 +45,7 @@ dependencies {
 
     implementation(libs.compose.runtime)
     implementation(libs.compose.foundation)
+    implementation(libs.compose.animation)
     implementation(libs.compose.material3)
     implementation(libs.compose.ui)
     implementation(libs.compose.uiToolingPreview)

shared/src/main/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -1,14 +1,19 @@
 package plus.rua.project.ui
 
+import androidx.compose.animation.AnimatedContent
 import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.animation.EnterTransition
 import androidx.compose.animation.ExitTransition
+import androidx.compose.animation.SharedTransitionLayout
 import androidx.compose.animation.core.FastOutSlowInEasing
 import androidx.compose.animation.core.tween
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
+import androidx.compose.animation.ExperimentalSharedTransitionApi
 import androidx.compose.animation.scaleIn
 import androidx.compose.animation.scaleOut
+import androidx.compose.animation.togetherWith
+import androidx.compose.ui.graphics.TransformOrigin
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
@@ -50,7 +55,6 @@ import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.draw.clipToBounds
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.TransformOrigin
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.onSizeChanged
@@ -70,13 +74,14 @@ import kotlin.math.abs
 import kotlin.time.Clock
 
 /**
- * 日历主界面，包含月/周视图切换、折叠动画和年视图缩放转场。
+ * 日历主界面，包含月/周视图切换、折叠动画和年视图共享元素转场。
  *
  * 折叠时日历从月视图收缩为周视图（1行），BottomCard 同步上移填充空间。
- * 通过左下角 FAB 菜单切换月/年视图，以当前月为锚点缩放转场。
+ * 通过左下角 FAB 菜单切换月/年视图，使用 SharedTransitionLayout 实现共享元素转场。
  *
  * @param modifier 外部布局修饰符
  */
+@OptIn(ExperimentalSharedTransitionApi::class)
 @Composable
 fun CalendarMonthView(
     modifier: Modifier = Modifier,
@@ -139,10 +144,8 @@ fun CalendarMonthView(
         }
     }
 
-    // 年视图锚点缩放：当前月在 4×3 网格中的归一化位置
-    val anchorPivotX = ((currentMonth - 1) % 3 + 0.5f) / 3f
-    val anchorPivotY = ((currentMonth - 1) / 3 + 0.5f) / 4f
-
+    SharedTransitionLayout {
+        val sharedScope = this
         Box(
             modifier = modifier
                 .fillMaxSize()
@@ -152,21 +155,30 @@ fun CalendarMonthView(
                     screenWidthPx = size.width
                 }
         ) {
-        // 月视图层：仅在非年视图时渲染，年视图激活时立即移除。
-        if (!viewModel.isYearView) {
+            AnimatedContent(
+                targetState = viewModel.isYearView,
+                label = "month_year_transition",
+                transitionSpec = {
+                    fadeIn(tween(300, easing = FastOutSlowInEasing)) togetherWith
+                        fadeOut(tween(300, easing = FastOutSlowInEasing))
+                },
+                modifier = Modifier.fillMaxSize()
+            ) { isYearView ->
+                with(sharedScope) {
+                if (!isYearView) {
                     composeTraceBeginSection("MonthView:Compose")
                     val layoutReady = rowHeightPx > 0
                     Box(
                         modifier = Modifier
                             .fillMaxSize()
-                    .graphicsLayer {
-                        val monthProgress = 1f - viewModel.yearViewProgress
-                        val scale = lerp(0.3f, 1f, monthProgress)
-                        scaleX = scale
-                        scaleY = scale
-                        alpha = if (layoutReady) monthProgress.coerceIn(0f, 1f) else 0f
-                        transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
+                            .sharedBounds(
+                                sharedContentState = rememberSharedContentState(key = "month_content"),
+                                animatedVisibilityScope = this@AnimatedContent,
+                                boundsTransform = { _, _ ->
+                                    tween(400, easing = FastOutSlowInEasing)
                                 }
+                            )
+                            .alpha(if (layoutReady) 1f else 0f)
                     ) {
                         Column(
                             modifier = Modifier
@@ -205,22 +217,18 @@ fun CalendarMonthView(
                         }
                     }
                     composeTraceEndSection()
-        }
-
-        // 年视图层：标题固定，HorizontalPager 只包裹网格。
-        if (viewModel.isYearView) {
-            val yearProgress = viewModel.yearViewProgress
+                } else {
                     composeTraceBeginSection("YearView:Compose")
                     Column(
                         modifier = Modifier
                             .fillMaxSize()
-                    .graphicsLayer {
-                        val scale = lerp(3.3f, 1f, yearProgress)
-                        scaleX = scale
-                        scaleY = scale
-                        alpha = yearProgress.coerceIn(0f, 1f)
-                        transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
+                            .sharedBounds(
+                                sharedContentState = rememberSharedContentState(key = "month_content"),
+                                animatedVisibilityScope = this@AnimatedContent,
+                                boundsTransform = { _, _ ->
+                                    tween(400, easing = FastOutSlowInEasing)
                                 }
+                            )
                             .padding(horizontal = HORIZONTAL_PADDING_DP.dp)
                     ) {
                         YearHeader(
@@ -271,6 +279,8 @@ fun CalendarMonthView(
                     }
                     composeTraceEndSection()
                 }
+                }
+            }
 
             // FAB 浮动按钮
         FloatingActionButton(
@@ -358,6 +368,7 @@ fun CalendarMonthView(
         }
     }
 }
+}
 
 @Composable
 private fun MenuIcon(color: Color, modifier: Modifier = Modifier) {