年视图标题固定 + 交叉淡入淡出 + 移除 fadeIn/fadeOut

年视图标题行从 HorizontalPager 内移到外部，左右滑动时标题不随 pager 滚动。
年份切换时标题文字用垂直滑动动画（与 MonthHeader 一致，移除 fadeIn/fadeOut）。
月/年视图左右滑动改为交叉淡入淡出，修复原实现中间全白的问题。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -41,6 +41,7 @@ import androidx.compose.runtime.setValue
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.draw.clipToBounds
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Color
@@ -331,12 +332,9 @@ fun CalendarMonthView(
             }
         }
 
-        // 年视图层：仅在年视图激活时渲染；HorizontalPager 支持左右滑动切年。
+        // 年视图层：标题固定，HorizontalPager 只包裹网格。
         if (viewModel.isYearView) {
-            HorizontalPager(
+            Column(
-                state = yearPagerState,
-                beyondViewportPageCount = 1,
-                flingBehavior = PagerDefaults.flingBehavior(state = yearPagerState),
                 modifier = Modifier
                     .fillMaxSize()
                     .graphicsLayer {
@@ -346,31 +344,51 @@ fun CalendarMonthView(
                         transformOrigin = TransformOrigin(anchorPivotX, anchorPivotY)
                     }
                     .padding(horizontal = HORIZONTAL_PADDING_DP.dp)
-            ) { page ->
+            ) {
-                val pageYear = viewModel.selectedDate.year + (page - START_PAGE)
+                YearHeader(
-                YearGridView(
+                    year = viewModel.yearViewYear,
-                    year = pageYear,
-                    selectedMonth = if (pageYear == currentYear) currentMonth else 0,
-                    today = today,
-                    onMonthClick = { month ->
-                        viewModel.selectMonthFromYearView(month)
-                        @Suppress("DEPRECATION") // monthNumber 无替代 API
-                        val targetPage = yearMonthToPage(
-                            viewModel.yearViewYear, month,
-                            today.year, today.month.number
-                        )
-                        if (targetPage != pagerState.currentPage) {
-                            coroutineScope.launch { pagerState.scrollToPage(targetPage) }
-                        }
-                    },
                     onYearChange = { newYear ->
-                        val offset = newYear - pageYear
+                        val offset = newYear - viewModel.yearViewYear
                         val targetPage = yearPagerState.currentPage + offset
                         if (targetPage != yearPagerState.currentPage) {
                             coroutineScope.launch { yearPagerState.animateScrollToPage(targetPage) }
                         }
                     }
                 )
+                HorizontalPager(
+                    state = yearPagerState,
+                    beyondViewportPageCount = 1,
+                    flingBehavior = PagerDefaults.flingBehavior(state = yearPagerState),
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .weight(1f)
+                ) { page ->
+                    val pageOffset = abs(yearPagerState.currentPageOffsetFraction)
+                    val isCurrentPage = page == yearPagerState.currentPage
+                    val crossFadeAlpha = if (isCurrentPage) {
+                        1f - pageOffset
+                    } else {
+                        pageOffset
+                    }
+                    val pageYear = viewModel.selectedDate.year + (page - START_PAGE)
+                    YearGridView(
+                        year = pageYear,
+                        selectedMonth = if (pageYear == currentYear) currentMonth else 0,
+                        today = today,
+                        onMonthClick = { month ->
+                            viewModel.selectMonthFromYearView(month)
+                            @Suppress("DEPRECATION") // monthNumber 无替代 API
+                            val targetPage = yearMonthToPage(
+                                viewModel.yearViewYear, month,
+                                today.year, today.month.number
+                            )
+                            if (targetPage != pagerState.currentPage) {
+                                coroutineScope.launch { pagerState.scrollToPage(targetPage) }
+                            }
+                        },
+                        modifier = Modifier.alpha(crossFadeAlpha)
+                    )
+                }
             }
         }
 

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

@@ -72,7 +72,12 @@ fun CalendarPager(
         modifier = modifier
     ) { page ->
         val pageOffset = abs(pagerState.currentPageOffsetFraction)
-        val alpha = 1f - pageOffset.coerceIn(0f, 0.3f) / 0.3f
+        val isCurrentPage = page == pagerState.currentPage
+        val alpha = if (isCurrentPage) {
+            1f - pageOffset
+        } else {
+            pageOffset
+        }
         val (year, month) = pageToYearMonth(page, initialYear, initialMonth)
         CalendarMonthPage(
             year = year,

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

@@ -2,8 +2,6 @@ package plus.rua.project.ui
 
 import androidx.compose.animation.AnimatedContent
 import androidx.compose.animation.core.tween
-import androidx.compose.animation.fadeIn
-import androidx.compose.animation.fadeOut
 import androidx.compose.animation.slideInVertically
 import androidx.compose.animation.slideOutVertically
 import androidx.compose.animation.togetherWith
@@ -52,11 +50,11 @@ fun MonthHeader(
             targetState = Pair(year, month),
             transitionSpec = {
                 if (targetState.second > initialState.second) {
-                    slideInVertically(tween(250)) { -it } + fadeIn(tween(250)) togetherWith
+                    slideInVertically(tween(250)) { -it } togetherWith
-                            slideOutVertically(tween(250)) { it } + fadeOut(tween(250))
+                            slideOutVertically(tween(250)) { it }
                 } else {
-                    slideInVertically(tween(250)) { it } + fadeIn(tween(250)) togetherWith
+                    slideInVertically(tween(250)) { it } togetherWith
-                            slideOutVertically(tween(250)) { -it } + fadeOut(tween(250))
+                            slideOutVertically(tween(250)) { -it }
                 }
             }
         ) { (y, m) ->
@@ -70,11 +68,11 @@ fun MonthHeader(
             targetState = weekNumber,
             transitionSpec = {
                 if (targetState > initialState) {
-                    slideInVertically(tween(250)) { -it } + fadeIn(tween(250)) togetherWith
+                    slideInVertically(tween(250)) { -it } togetherWith
-                            slideOutVertically(tween(250)) { it } + fadeOut(tween(250))
+                            slideOutVertically(tween(250)) { it }
                 } else {
-                    slideInVertically(tween(250)) { it } + fadeIn(tween(250)) togetherWith
+                    slideInVertically(tween(250)) { it } togetherWith
-                            slideOutVertically(tween(250)) { -it } + fadeOut(tween(250))
+                            slideOutVertically(tween(250)) { -it }
                 }
             },
             modifier = Modifier

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

@@ -1,5 +1,10 @@
 package plus.rua.project.ui
 
+import androidx.compose.animation.AnimatedContent
+import androidx.compose.animation.core.tween
+import androidx.compose.animation.slideInVertically
+import androidx.compose.animation.slideOutVertically
+import androidx.compose.animation.togetherWith
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
@@ -31,16 +36,12 @@ import kotlinx.datetime.plus
 private val WEEKDAY_LABELS = listOf("一", "二", "三", "四", "五", "六", "日")
 
 /**
- * 年度网格视图，显示 4×3 精简月历网格，支持年份切换。
+ * 年视图 4×3 月历网格。
- *
- * 每格显示一个精简版月历（月份标题 + 星期行 + 日期数字网格），
- * 选中月份高亮，点击进入该月。
  *
  * @param year 显示的年份
  * @param selectedMonth 当前选中月份（1-12）
  * @param today 今天的日期
  * @param onMonthClick 月份点击回调
- * @param onYearChange 年份切换回调
  * @param modifier 外部布局修饰符
  */
 @Composable
@@ -49,49 +50,12 @@ fun YearGridView(
     selectedMonth: Int,
     today: LocalDate,
     onMonthClick: (Int) -> Unit,
-    onYearChange: (Int) -> Unit,
     modifier: Modifier = Modifier
 ) {
     Column(
         modifier = modifier.fillMaxSize(),
         horizontalAlignment = Alignment.CenterHorizontally
     ) {
-        // 年份导航行
-        Row(
-            modifier = Modifier
-                .fillMaxWidth()
-                .padding(vertical = 8.dp),
-            verticalAlignment = Alignment.CenterVertically
-        ) {
-            Text(
-                text = "‹",
-                fontSize = 24.sp,
-                fontWeight = FontWeight.Bold,
-                color = MaterialTheme.colorScheme.primary,
-                modifier = Modifier
-                    .clip(CircleShape)
-                    .clickable { onYearChange(year - 1) }
-                    .padding(horizontal = 16.dp, vertical = 8.dp)
-            )
-            Box(modifier = Modifier.weight(1f), contentAlignment = Alignment.Center) {
-                Text(
-                    text = "${year}年",
-                    style = MaterialTheme.typography.titleLarge,
-                    fontWeight = FontWeight.Bold
-                )
-            }
-            Text(
-                text = "›",
-                fontSize = 24.sp,
-                fontWeight = FontWeight.Bold,
-                color = MaterialTheme.colorScheme.primary,
-                modifier = Modifier
-                    .clip(CircleShape)
-                    .clickable { onYearChange(year + 1) }
-                    .padding(horizontal = 16.dp, vertical = 8.dp)
-            )
-        }
-
         // 4×3 月历网格
         Column(
             modifier = Modifier
@@ -244,3 +208,67 @@ private fun generateMiniMonthDays(year: Int, month: Int): List<MiniDayData> {
         )
     }
 }
+
+/**
+ * 年视图标题栏，显示年份文字和左右导航箭头。
+ *
+ * 年份切换时文字有垂直滑动过渡动画，方向由新旧年份大小决定。
+ *
+ * @param year 当前年份
+ * @param onYearChange 年份切换回调
+ * @param modifier 外部布局修饰符
+ */
+@Composable
+fun YearHeader(
+    year: Int,
+    onYearChange: (Int) -> Unit,
+    modifier: Modifier = Modifier
+) {
+    Row(
+        modifier = modifier
+            .fillMaxWidth()
+            .padding(vertical = 8.dp),
+        verticalAlignment = Alignment.CenterVertically
+    ) {
+        Text(
+            text = "‹",
+            fontSize = 24.sp,
+            fontWeight = FontWeight.Bold,
+            color = MaterialTheme.colorScheme.primary,
+            modifier = Modifier
+                .clip(CircleShape)
+                .clickable { onYearChange(year - 1) }
+                .padding(horizontal = 16.dp, vertical = 8.dp)
+        )
+        Box(modifier = Modifier.weight(1f), contentAlignment = Alignment.Center) {
+            AnimatedContent(
+                targetState = year,
+                transitionSpec = {
+                    if (targetState > initialState) {
+                        slideInVertically(tween(250)) { -it } togetherWith
+                            slideOutVertically(tween(250)) { it }
+                    } else {
+                        slideInVertically(tween(250)) { it } togetherWith
+                            slideOutVertically(tween(250)) { -it }
+                    }
+                }
+            ) { y ->
+                Text(
+                    text = "${y}年",
+                    style = MaterialTheme.typography.titleLarge,
+                    fontWeight = FontWeight.Bold
+                )
+            }
+        }
+        Text(
+            text = "›",
+            fontSize = 24.sp,
+            fontWeight = FontWeight.Bold,
+            color = MaterialTheme.colorScheme.primary,
+            modifier = Modifier
+                .clip(CircleShape)
+                .clickable { onYearChange(year + 1) }
+                .padding(horizontal = 16.dp, vertical = 8.dp)
+        )
+    }
+}