WPF自定义控件之列表滑动特效 PowerListBox
列表控件是应用程序中常见的控件之一，对其做一些绚丽的视觉特效，可以让软件增色不少。
本人网上看过一个视频，是windows phone 7系统上的一个App的列表滚动效果，效果非常炫
现在在WPF上用ListBox重现此效果
首先我们来分析一下，这种实时滚动的效果是如何实现的，有哪些步骤
1.获取ListBox模板内部的ScrollViewer和ItemsPanel
2.监听ScrollViewer的滚动事件ScrollChange, 获取ItemsPanel的布局方向
3.在滚动事件发生时计算当前可视化区域中的第一项和最后一项，这是此滑动效果的核心算法所在，算法的效率决定了滑动效果的流畅性
4.根据滚动的方向和布局的方向依次对指定的Item做动画效果。
重写ListBoxItem
public class PowerListBoxItem : ListBoxItem
声明构造函数并赋初始值
static PowerListBoxItem()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(PowerListBoxItem), new FrameworkPropertyMetadata(typeof(PowerListBoxItem)));
}
public PowerListBoxItem()
{
ItemStatus = ItemStatusEnum.Out; //默认Item状态为"退出"
duration = new TimeSpan(0, 0, 0, 0, 300);
//easingFunction = new PowerEase() { EasingMode = EasingMode.EaseIn, Power = 4 };
easingFunction = new CircleEase() { EasingMode = EasingMode.EaseInOut };
}
定义PowerListBoxItem的成员属性
/// <summary>
/// PowerListBoxItem模板中的内容控件
/// </summary>
private FrameworkElement contentControl;
/// <summary>
/// 动画间隔时间
/// </summary>
private TimeSpan duration;
private IEasingFunction easingFunction; //动画缓动函数
private IList<AnimationModel> DownInAnimationList; //定义Item从下往上运动的动画内容集合
private IList<AnimationModel> UpInAnimationList; //定义Item从上往下运动的动画内容集合
/// <summary>
/// 项枚举状态，指明Item运动的方向
/// </summary>
internal enum ItemStatusEnum
{
UpIn, DownIn, RightIn, LeftIn, Out
}
private ItemStatusEnum _itemStatus;
internal ItemStatusEnum ItemStatus
{
get { return _itemStatus; }
set
{
if (_itemStatus == value) //状态相同时不再刷新状态
return;
_itemStatus = value;
PlayAnimation(); //执行动画
}
}
重写ListBox
[StyleTypedProperty(Property = "ItemContainerStyle", StyleTargetType = typeof(PowerListBoxItem))]
public class PowerListBox : ListBox
{
static PowerListBox()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(PowerListBox), new FrameworkPropertyMetadata(typeof(PowerListBox)));
}
public PowerListBox()
{
DefaultStyleKey = typeof(PowerListBox);
}
}
protected override DependencyObject GetContainerForItemOverride()
{
return new PowerListBoxItem(); //指定PowerListBox的项为PowerListBoxItem
}
protected override bool IsItemItsOwnContainerOverride(object item)
{
return item is PowerListBoxItem;
}
定义PowerList的成员属性
/// <summary>
/// ListBox内部的滚动试图
/// </summary>
private ScrollViewer _scrollView;
/// <summary>
/// 容器的布局方向
/// </summary>
private Orientation _panelOrientation;
/// <summary>
/// 当前可视化视图的第一项
/// </summary>
private int firstVisibleIndex;
/// <summary>
/// 当前可视化视图的最后一项
/// </summary>
private int lastVisibleIndex;
/// <summary>
/// 上次滚动时可视化视图的第一项
/// </summary>
private int oldFirstVisibleIndex;
/// <summary>
/// 上次滚动时可视化视图的最后一项
/// </summary>
private int oldLastVisibleIndex;
/// <summary>
/// 标识，是否已找到第一项
/// </summary>
private bool isFindFirst;
/// <summary>
/// 当前累计已遍历过的Item高度或宽度的值，用于寻找第一项和最后一项
/// </summary>
private double cumulativeNum;
获取PowerListBox内部的ScrollViewer和ItemsPanel，并监听滚动事件
public override void OnApplyTemplate()
{
_scrollView = VisualHelper.FindFirstVisualChild<ScrollViewer>(this);
if (_scrollView == null)
return;
_scrollView.CanContentScroll = false; //不按Item为步长滚动
_scrollView.PanningMode = PanningMode.Both;
_scrollView.ScrollChanged += _scrollView_ScrollChanged; //监听滚动事件
var panel = this.ItemsPanel.LoadContent(); //读取布局容器
if (panel is StackPanel)
_panelOrientation = (panel as StackPanel).Orientation;
else if (panel is VirtualizingPanel)
_panelOrientation = (panel as VirtualizingStackPanel).Orientation;
base.OnApplyTemplate();
}
private void _scrollView_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
//Console.WriteLine("itemCount:{0} VerticalOffset:{1} ViewportHeight:{2} ContentVerticalOffset:{3}",
//Items.Count, _scrollView.VerticalOffset, _scrollView.ViewportHeight, _scrollView.ContentVerticalOffset);
//每次滚动时都计算当前可视化区域的首尾项
calculationIndex();
refreshItemStatus(); //刷新Item状态
}
计算可视化区域的第一项和最后一项
private void calculationIndex()
{
oldFirstVisibleIndex = firstVisibleIndex;
oldLastVisibleIndex = lastVisibleIndex;
isFindFirst = false;
if (_panelOrientation == Orientation.Vertical)
{
cumulativeNum = 0.0;
for (int i = 0; i < Items.Count; i++)
{
var _item = this.ItemContainerGenerator.ContainerFromIndex(i) as PowerListBoxItem;
cumulativeNum += _item.ActualHeight + _item.Margin.Top + _item.Margin.Bottom;
//遍历Items, 累计Item高度，第一个超过滚动条垂直偏移量的Item就是当前可视化区域中的第一项
if (!isFindFirst && cumulativeNum >= _scrollView.VerticalOffset)
{
firstVisibleIndex = i;
isFindFirst = true;
}
//累计Item高度超过滚动条垂直偏移量和滚动区显示高度的和，就是当前可视化区域的最后一项
if (cumulativeNum >= (_scrollView.VerticalOffset + _scrollView.ViewportHeight))
{
lastVisibleIndex = i;
break;
}
}
}
}
确定当前可视化区域的首尾项之后，刷新Item的状态
private void refreshItemStatus()
{
Console.WriteLine("firstIndex: {0} lastIndex: {1} oldFirstIndex: {2} oldLastIndex: {3} {4}",
firstVisibleIndex, lastVisibleIndex, oldFirstVisibleIndex, oldLastVisibleIndex, firstVisibleIndex > oldFirstVisibleIndex ? "Down In" : firstVisibleIndex < oldFirstVisibleIndex ? "UpIn" : "normal");
if ((firstVisibleIndex == oldFirstVisibleIndex && lastVisibleIndex == oldLastVisibleIndex) || oldFirstVisibleIndex == 0 && oldLastVisibleIndex == 0)
return;
//Console.WriteLine("firstVisibleIndex:{0} oldFirstVisibleIndex:{1}", firstVisibleIndex, oldFirstVisibleIndex);
//判断滚动方向
if (firstVisibleIndex > oldFirstVisibleIndex)
{
//垂直 滚动条往下，内容网上
//水平 滚动条往右，内容往左
for (var i = oldLastVisibleIndex; i <= lastVisibleIndex; i++)
{
var _item = this.ItemContainerGenerator.ContainerFromIndex(i) as PowerListBoxItem;
_item.ItemStatus = _panelOrientation == Orientation.Vertical ? PowerListBoxItem.ItemStatusEnum.DownIn : PowerListBoxItem.ItemStatusEnum.RightIn;
//Console.WriteLine("DownIn {0}", i);
}
}
else if (lastVisibleIndex < oldLastVisibleIndex)
{
//垂直 滚动条往上，内容网下
//水平 滚动条往左，内容往右
for (var i = oldFirstVisibleIndex; i >= firstVisibleIndex; i--)
{
var _item = this.ItemContainerGenerator.ContainerFromIndex(i) as PowerListBoxItem;
_item.ItemStatus = _panelOrientation == Orientation.Vertical ? PowerListBoxItem.ItemStatusEnum.UpIn : PowerListBoxItem.ItemStatusEnum.LeftIn;
//Console.WriteLine("UpIn {0}", i);
}
}
}
定义PowerListBox的默认外观
<Style TargetType="{x:Type local:PowerListBox}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:PowerListBox}">
<ScrollViewer x:Name="ScrollViewer" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Foreground="{TemplateBinding Foreground}" Padding="{TemplateBinding Padding}">
<ItemsPresenter/>
</ScrollViewer>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="{x:Type local:PowerListBoxItem}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="Margin" Value="0,8"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:PowerListBoxItem}">
<Border x:Name="LayoutRoot" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="{TemplateBinding HorizontalAlignment}" VerticalAlignment="{TemplateBinding VerticalAlignment}">
<ContentControl x:Name="ContentContainer" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}"
Foreground="{TemplateBinding Foreground}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" RenderTransformOrigin="0.5,0.5">
<ContentControl.RenderTransform>
<TransformGroup>
<TranslateTransform/>
</TransformGroup>
</ContentControl.RenderTransform>
</ContentControl>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
调用 PowerListBox
<local:PowerListBox ItemsSource="{Binding TestModelList}" >
<local:PowerListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="150"/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding Name}" VerticalAlignment="Center" FontSize="20"/>
<Border Width="100" Height="120" Background="#FF4949D3" Grid.Column="1" HorizontalAlignment="Left">
<TextBlock Text="{Binding Id}" VerticalAlignment="Center" HorizontalAlignment="Center" FontSize="40" Foreground="Black"/>
</Border>
</Grid>
</DataTemplate>
</local:PowerListBox.ItemTemplate>
</local:PowerListBox>
效果图
由于gif录制帧数的原因，效果图不是很流畅，但实际运行情况动画效果是非常流畅的