年月视图切换时立即移除源视图，仅对目标视图播放缩放动画

之前月↔年切换使用交叉淡入：两层同时合成，源视图渐隐、目标视图渐显。
现改为单向过渡：先翻转 isYearView 让源视图立刻从合成中移除，
withFrameNanos 等一帧后再启动目标视图的 scale/alpha 动画，避免抖动。

shared/src/commonMain/kotlin/plus/rua/project/CalendarViewModel.kt

@@ -88,22 +88,26 @@ class CalendarViewModel(
 
     /**
      * 切换年视图。仅在展开态可用。
+     *
+     * 切换瞬间立即翻转 isYearView，让对应方向的目标视图立刻接管渲染，
+     * 当前视图被直接移除；动画只作用在目标视图的 scale/alpha 上。
      */
     fun toggleYearView() {
         if (isCollapsed) return
         yearViewJob?.cancel()
         yearViewJob = coroutineScope.launch {
             if (isYearView) {
+                // 年 → 月：先切换状态让月视图开始合成，再等一帧避免首帧抖动
+                isYearView = false
+                withFrameNanos { }
                 _yearViewAnimatable.animateTo(
                     0f, tween(400, easing = FastOutSlowInEasing)
                 )
-                isYearView = false
             } else {
+                // 月 → 年：先切换状态让年视图开始合成
                 yearViewYear = selectedDate.year
                 isYearView = true
                 _yearViewAnimatable.snapTo(0f)
-                // 等待一帧让年视图先完成首次合成与布局，
-                // 避免首次进入年视图时动画时间被合成开销吞掉。
                 withFrameNanos { }
                 _yearViewAnimatable.animateTo(
                     1f, tween(400, easing = FastOutSlowInEasing)
@@ -120,12 +124,13 @@ class CalendarViewModel(
         val date = if (yearViewYear == today.year && today.month.number == month) today
         else LocalDate(yearViewYear, month, 1)
         selectedDate = date
+        isYearView = false
         yearViewJob?.cancel()
         yearViewJob = coroutineScope.launch {
+            withFrameNanos { }
             _yearViewAnimatable.animateTo(
                 0f, tween(400, easing = FastOutSlowInEasing)
             )
-            isYearView = false
         }
     }
 

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

@@ -168,13 +168,15 @@ fun CalendarMonthView(
     val anchorPivotX = ((currentMonth - 1) % 3 + 0.5f) / 3f
     val anchorPivotY = ((currentMonth - 1) / 3 + 0.5f) / 4f
 
-    // 月视图层缩放：从 1f 缩小到 ~0.3f（年网格单格 vs 月视图大小比）
+    // 过渡进度：0=目标视图刚出现，1=目标视图完全到位。
-    val monthScale = 1f - yearProgress * 0.7f
+    // 月→年时 yearProgress 从 0→1，年→月时从 1→0，因此用 isYearView 同步翻转方向。
-    val monthAlpha = (1f - yearProgress * 1.4f).coerceIn(0f, 1f)
+    val transitionProgress = if (viewModel.isYearView) yearProgress else 1f - yearProgress
+    val targetAlpha = transitionProgress.coerceIn(0f, 1f)
 
-    // 年视图层缩放：从 ~3.3f 放大到 1f
+    // 月视图层缩放：从 0.3f（年网格单格大小）放大到 1f
-    val yearScale = lerp(3.3f, 1f, yearProgress)
+    val monthScale = lerp(0.3f, 1f, transitionProgress)
-    val yearAlpha = ((yearProgress - 0.2f) / 0.8f).coerceIn(0f, 1f)
+    // 年视图层缩放：从 3.3f（月视图被放大到一格那么大的反向比例）缩小到 1f
+    val yearScale = lerp(3.3f, 1f, transitionProgress)
 
     Box(
         modifier = modifier
@@ -185,16 +187,28 @@ fun CalendarMonthView(
                 screenHeightPx = size.height
             }
     ) {
-        // 月视图层
+        // 月视图层：仅在非年视图时渲染，年视图激活时立即移除。
-        Column(
+        if (!viewModel.isYearView) {
+            val dragRangeMinPx = with(density) { DRAG_RANGE_MIN_DP.dp.toPx() }
+            val dragRangePx = if (effectiveRowHeightPx > 0) {
+                maxOf((effectiveWeeks - 1) * effectiveRowHeightPx.toFloat(), dragRangeMinPx)
+            } else {
+                dragRangeMinPx
+            }
+
+            Box(
                 modifier = Modifier
                     .fillMaxSize()
                     .graphicsLayer {
                         scaleX = monthScale
                         scaleY = monthScale
-                    alpha = monthAlpha
+                        alpha = targetAlpha
                         transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
                     }
+            ) {
+                Column(
+                    modifier = Modifier
+                        .fillMaxSize()
                         .padding(horizontal = HORIZONTAL_PADDING_DP.dp)
                 ) {
                     MonthHeader(
@@ -270,8 +284,21 @@ fun CalendarMonthView(
                     }
                 }
 
-        // 年视图层：HorizontalPager 支持左右滑动切年
+                if (cardHeightPx > 0) {
-        if (viewModel.isYearView || yearProgress > 0.01f) {
+                    BottomCard(
+                        viewModel = viewModel,
+                        dragRangePx = dragRangePx,
+                        modifier = Modifier
+                            .fillMaxWidth()
+                            .height(with(density) { cardHeightPx.toDp() })
+                            .align(Alignment.BottomCenter)
+                    )
+                }
+            }
+        }
+
+        // 年视图层：仅在年视图激活时渲染；HorizontalPager 支持左右滑动切年。
+        if (viewModel.isYearView) {
             HorizontalPager(
                 state = yearPagerState,
                 beyondViewportPageCount = 1,
@@ -281,7 +308,7 @@ fun CalendarMonthView(
                     .graphicsLayer {
                         scaleX = yearScale
                         scaleY = yearScale
-                        alpha = yearAlpha
+                        alpha = targetAlpha
                         transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
                     }
                     .padding(horizontal = HORIZONTAL_PADDING_DP.dp)
@@ -312,26 +339,5 @@ fun CalendarMonthView(
                 )
             }
         }
-
-        // BottomCard：年视图时隐藏
-        if (yearProgress < 0.01f) {
-            val dragRangeMinPx = with(density) { DRAG_RANGE_MIN_DP.dp.toPx() }
-            val dragRangePx = if (effectiveRowHeightPx > 0) {
-                maxOf((effectiveWeeks - 1) * effectiveRowHeightPx.toFloat(), dragRangeMinPx)
-            } else {
-                dragRangeMinPx
-            }
-
-            if (cardHeightPx > 0) {
-                BottomCard(
-                    viewModel = viewModel,
-                    dragRangePx = dragRangePx,
-                    modifier = Modifier
-                        .fillMaxWidth()
-                        .height(with(density) { cardHeightPx.toDp() })
-                        .align(Alignment.BottomCenter)
-                )
-            }
-        }
     }
 }