351 lines
12 KiB
C#
351 lines
12 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Windows;
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using System.Windows.Controls;
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using System.Windows.Media;
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using System.Windows.Media.Animation;
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using System.Windows.Threading;
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using Melskin.Assists;
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using Melskin.Extensions;
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namespace Melskin.Controls;
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/// <summary>
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/// 锚点
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/// </summary>
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[TemplatePart(Name = "PART_AnchorList", Type = typeof(ListBox))]
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[TemplatePart(Name = "PART_ContentScroller", Type = typeof(ScrollViewer))]
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public class Anchor : ContentControl
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{
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#region 私有字段
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private ListBox? anchorList;
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private ScrollViewer? contentScroller;
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// 扫描防抖
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private DispatcherTimer? scanDebounceTimer;
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// 缓存锚点映射
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private readonly Dictionary<string, UIElement?> anchorElements = new();
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// 标志位：是否正在通过代码设置选中项（防止触发滚动）
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private bool isInternalSelectionChange;
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// 标志位：是否正在执行点击导航导致的自动滚动（防止滚动时频繁更新高亮）
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private bool isAutoScrolling;
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// 动画中介器（复用实例以便取消动画）
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private readonly ScrollViewerOffsetMediator mediator = new();
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#endregion
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static Anchor()
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{
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DefaultStyleKeyProperty.OverrideMetadata(typeof(Anchor), new FrameworkPropertyMetadata(typeof(Anchor)));
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}
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/// <inheritdoc />
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public override void OnApplyTemplate()
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{
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base.OnApplyTemplate();
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UnbindEvents();
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scanDebounceTimer?.Stop();
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anchorList = GetTemplateChild("PART_AnchorList") as ListBox;
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contentScroller = GetTemplateChild("PART_ContentScroller") as ScrollViewer;
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if (anchorList != null && contentScroller != null)
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{
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// 初始化中介器关联
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mediator.ScrollViewer = contentScroller;
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BindEvents();
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InitializeScanTimer();
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// 延迟一点以等待布局完成
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contentScroller.Loaded += RequestScan;
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}
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}
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private void UnbindEvents()
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{
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if (anchorList != null) anchorList.SelectionChanged -= AnchorList_SelectionChanged;
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if (contentScroller != null)
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{
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contentScroller.ScrollChanged -= ContentScroller_ScrollChanged;
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contentScroller.SizeChanged -= RequestScan;
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if (contentScroller.Content is FrameworkElement fe) fe.LayoutUpdated -= RequestScan;
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}
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}
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private void BindEvents()
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{
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if (anchorList != null) anchorList.SelectionChanged += AnchorList_SelectionChanged;
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if (contentScroller == null) return;
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contentScroller.ScrollChanged += ContentScroller_ScrollChanged;
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contentScroller.SizeChanged += RequestScan;
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if (contentScroller.Content is FrameworkElement fe) fe.LayoutUpdated += RequestScan;
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}
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private void InitializeScanTimer()
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{
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scanDebounceTimer = new DispatcherTimer(DispatcherPriority.ContextIdle, Dispatcher)
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{
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Interval = TimeSpan.FromMilliseconds(150)
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};
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scanDebounceTimer.Tick += (_, _) =>
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{
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scanDebounceTimer.Stop();
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ScanAnchors();
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};
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}
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#region 逻辑处理
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private void RequestScan(object? sender, EventArgs e)
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{
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scanDebounceTimer?.Stop();
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scanDebounceTimer?.Start();
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}
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private void ScanAnchors()
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{
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if (contentScroller == null || anchorList == null) return;
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anchorElements.Clear();
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// 查找所有锚点
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// 注意：这里假设 Melskin.Extensions 的 FindVisualChildren 工作正常
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var anchorUiElements = contentScroller.FindVisualChildren<UIElement>()
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.Where(el => VisualTreeHelper.GetParent(el) != null &&
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!string.IsNullOrEmpty(ControlAssist.GetAnchorHeaderText(el)))
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.ToList();
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foreach (var element in anchorUiElements)
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{
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anchorElements[ControlAssist.GetAnchorHeaderText(element)] = element;
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}
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var newNames = anchorElements.Keys.ToList();
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var currentNames = anchorList.ItemsSource?.Cast<string>().ToList() ?? new List<string>();
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if (!currentNames.SequenceEqual(newNames))
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{
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// 保持当前选中的项（如果在列表中还存在）
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var oldSelection = anchorList.SelectedItem;
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isInternalSelectionChange = true;
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anchorList.ItemsSource = newNames;
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if (oldSelection != null && newNames.Contains(oldSelection))
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{
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anchorList.SelectedItem = oldSelection;
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}
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isInternalSelectionChange = false;
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}
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// 初始扫描后更新一次高亮
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UpdateHighlight();
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}
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/// <summary>
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/// 用户点击列表项触发
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/// </summary>
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private void AnchorList_SelectionChanged(object sender, SelectionChangedEventArgs e)
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{
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// 如果是代码设置的选中（如滚动触发的高亮更新），则不执行滚动逻辑，防止死循环
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if (isInternalSelectionChange) return;
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if (e.AddedItems.Count == 0) return;
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if (e.AddedItems[0] is string selectedAnchorName &&
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anchorElements.TryGetValue(selectedAnchorName, out var targetElement))
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{
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// 标记为自动滚动，暂停高亮更新
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isAutoScrolling = true;
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ScrollToElement(targetElement);
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}
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}
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private void ScrollToElement(UIElement? targetElement)
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{
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if (contentScroller == null || targetElement == null) return;
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try
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{
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// 获取目标相对位置
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var transform = targetElement.TransformToVisual(contentScroller);
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var position = transform.Transform(new Point(0, 0));
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// 目标 offset = 当前 offset + 相对位置
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var currentOffset = contentScroller.VerticalOffset;
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var targetOffset = currentOffset + position.Y;
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// 边界检查
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if (targetOffset < 0) targetOffset = 0;
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if (targetOffset > contentScroller.ScrollableHeight) targetOffset = contentScroller.ScrollableHeight;
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// 如果距离很短，直接跳过去，不动画（可选优化）
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if (Math.Abs(targetOffset - currentOffset) < 2.0)
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{
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contentScroller.ScrollToVerticalOffset(targetOffset);
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isAutoScrolling = false;
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return;
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}
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// 停止旧动画
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mediator.BeginAnimation(ScrollViewerOffsetMediator.VerticalOffsetProperty, null);
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// 确保 Mediator 的起始值与当前 ScrollViewer 一致
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// 这一步很重要，否则动画可能会从上一次动画结束的位置开始跳变
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mediator.VerticalOffset = currentOffset;
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var animation = new DoubleAnimation(
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currentOffset,
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targetOffset,
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new Duration(TimeSpan.FromMilliseconds(400))) // 建议400-500ms
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{
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EasingFunction = new CubicEase { EasingMode = EasingMode.EaseOut }
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};
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animation.Completed += (_, _) =>
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{
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isAutoScrolling = false;
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// 动画结束后强制校准一次高亮，防止浮点误差导致的选中项错误
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UpdateHighlight();
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};
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mediator.BeginAnimation(ScrollViewerOffsetMediator.VerticalOffsetProperty, animation);
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}
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catch (Exception)
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{
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isAutoScrolling = false;
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}
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}
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private void ContentScroller_ScrollChanged(object sender, ScrollChangedEventArgs e)
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{
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// 如果是点击导航导致的滚动，不要更新高亮，以免列表项乱跳
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if (isAutoScrolling) return;
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// 只有垂直滚动才处理
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if (Math.Abs(e.VerticalChange) > 0)
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{
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UpdateHighlight();
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}
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}
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private void UpdateHighlight()
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{
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if (anchorElements.Count == 0 || anchorList == null || contentScroller == null) return;
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// 获取 Viewport 的信息
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//double viewportTop = 0;
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//double viewportHeight = contentScroller.ViewportHeight;
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double scrollOffset = contentScroller.VerticalOffset;
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double scrollHeight = contentScroller.ScrollableHeight;
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string? bestMatch = null;
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// 策略1：如果已经滚动到底部，直接选中最后一个
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// 使用一个小的容差 (1.0)
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if (scrollOffset >= scrollHeight - 1.0 && scrollHeight > 0)
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{
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bestMatch = anchorElements.Keys.LastOrDefault();
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}
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else
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{
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// 策略2：寻找当前视口中最靠上的元素
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// 也就是：Top 值 <= 某个阈值（比如 ViewportHeight 的 1/3 或一个固定像素值）的最后一个元素
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// 我们寻找所有 "Top < 20px" 的元素，取其中位置最大的一个（最靠近顶部的）
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// 解释：如果元素A的Top是 -100，元素B的Top是 -10，元素C的Top是 50。
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// 我们认为A和B都已经滚过去了，B是当前“激活”的块。
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double threshold = 20.0; // 20像素的宽容度，解决刚好停在边缘的问题
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foreach (var kvp in anchorElements)
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{
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var element = kvp.Value;
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if (element == null || !element.IsVisible) continue;
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try
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{
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// 获取元素相对于 ScrollViewer 可视区域左上角的坐标
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var transform = element.TransformToVisual(contentScroller);
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var position = transform.Transform(new Point(0, 0));
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var top = position.Y;
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// 核心逻辑：
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// 只要元素的 Top 小于等于 阈值，它就是候选者。
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// 因为字典通常是按顺序扫描生成的，后面的元素会覆盖前面的 bestMatch
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if (top <= threshold)
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{
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bestMatch = kvp.Key;
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}
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else
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{
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// 因为是顺序排列，一旦遇到 Top > threshold 的，说明后面的都在视口下面了，可以直接停止
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// 除非你的布局不是垂直线性的，否则这样效率最高
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break;
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}
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}
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catch
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{
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// 忽略异常
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}
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}
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// 如果没有任何元素满足条件（比如第一个元素都在下面），则选中第一个
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if (bestMatch == null)
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{
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bestMatch = anchorElements.Keys.FirstOrDefault();
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}
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}
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// 更新 ListBox 选中项
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if (bestMatch != null && (string?)anchorList.SelectedItem != bestMatch)
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{
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// 标记为内部变更，防止触发 AnchorList_SelectionChanged 里的 ScrollToElement
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isInternalSelectionChange = true;
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anchorList.SelectedItem = bestMatch;
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anchorList.ScrollIntoView(bestMatch); // 确保左侧列表也跟随滚动
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isInternalSelectionChange = false;
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}
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}
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#endregion
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}
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/// <summary>
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/// 辅助类保持不变，但建议确保它能复用
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/// </summary>
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internal class ScrollViewerOffsetMediator : Animatable
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{
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public ScrollViewer? ScrollViewer
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{
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get => (ScrollViewer)GetValue(ScrollViewerProperty);
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set => SetValue(ScrollViewerProperty, value);
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}
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public static readonly DependencyProperty ScrollViewerProperty =
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DependencyProperty.Register(nameof(ScrollViewer), typeof(ScrollViewer), typeof(ScrollViewerOffsetMediator), new PropertyMetadata(null));
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public double VerticalOffset
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{
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get => (double)GetValue(VerticalOffsetProperty);
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set => SetValue(VerticalOffsetProperty, value);
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}
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public static readonly DependencyProperty VerticalOffsetProperty =
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DependencyProperty.Register(nameof(VerticalOffset), typeof(double), typeof(ScrollViewerOffsetMediator), new PropertyMetadata(0.0, OnVerticalOffsetChanged));
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private static void OnVerticalOffsetChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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{
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if (d is ScrollViewerOffsetMediator mediator && mediator.ScrollViewer != null)
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{
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mediator.ScrollViewer.ScrollToVerticalOffset((double)e.NewValue);
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}
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}
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protected override Freezable CreateInstanceCore() => new ScrollViewerOffsetMediator();
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} |