WPF下制作的简单瀑布流效果

最近又在搞点小东西,美化界面的时候发现瀑布流效果比较不错.顺便就搬到了WPF,下面是界面

 

我对WEB前端不熟,JS和CSS怎么实现的,我没去研究过,这里就说下WPF的实现思路,相当简单.

1.最重要的就是每个子项的顺序填充,我是把界面看做N列,然后在每列里依次加载子项.最后结果就是,界面放一个Uniform,设置Columns,再添加几个ItemsControl.

2.添加Item的时候,判断每个ItemsControl的实际高度,把子项添加到最小的那个ItemsControl,这样避免了某一列拉得很长.

3.再做一层封装,就变成了一个支持Binding的WaterfallControl.

 

这里上几段控件的源码,供参考:

1.WaterfallControl.cs

[TemplatePart(Name = "grdRoot", Type = typeof(UniformGrid))]
    public class WaterfallControl : ItemsControl
    {
        private UniformGrid grdRoot;

        private List<ItemsControl> itemsContorls;

        public int Columns
        {
            get { return (int)GetValue(ColumnsProperty); }
            set { SetValue(ColumnsProperty, value); }
        }

        // Using a DependencyProperty as the backing store for Columns.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty ColumnsProperty =
            DependencyProperty.Register("Columns", typeof(int), typeof(WaterfallControl), new PropertyMetadata(3, OnColumnsChanged));

        private static void OnColumnsChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            int columns = (int)e.NewValue;
            if (columns < 1)
            {
                throw new ArgumentOutOfRangeException("Columns");
            }
            var control = sender as WaterfallControl;
            control.Columns = columns;
            control.InitPanel();
        }

        public WaterfallControl()
        {
            this.Loaded += WaterfallControl_Loaded;
            this.itemsContorls = new List<ItemsControl>();
        }

        void WaterfallControl_Loaded(object sender, RoutedEventArgs e)
        {
            this.InitPanel();
        }

        private void InitPanel()
        {
            if (!this.IsLoaded)
            {
                return;
            }

            grdRoot.Children.Clear();
            itemsContorls.Clear();
            for (var i = 0; i < this.Columns; i++)
            {
                var ic = new ItemsControl();
                ic.ItemTemplate = this.ItemTemplate;
                ic.VerticalAlignment = System.Windows.VerticalAlignment.Top;
                grdRoot.Children.Add(ic);
                itemsContorls.Add(ic);
            }

            if (this.ItemsSource != null)
            {
                var enumerator = this.ItemsSource.GetEnumerator();
                while (enumerator.MoveNext())
                {
                    this.AddChild(enumerator.Current);
                }
            }
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            grdRoot = (UniformGrid)this.GetTemplateChild("grdRoot");
        }

        protected override void AddChild(object value)
        {
            var ic = itemsContorls.OrderBy(t => t.ActualHeight).FirstOrDefault();
            ic.Items.Add(value);
            ic.UpdateLayout();
        }

        protected override void OnItemsChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            if (e.Action == NotifyCollectionChangedAction.Add || e.Action == NotifyCollectionChangedAction.Remove)
            {
                var enumerator = e.NewItems.GetEnumerator();
                while (enumerator.MoveNext())
                {
                    if (e.Action == NotifyCollectionChangedAction.Add)
                    {
                        this.AddChild(enumerator.Current);
                    }
                    else
                    {
                        foreach (var ic in this.itemsContorls)
                        {
                            ic.Items.Remove(enumerator.Current);
                        }
                    }
                }
            }
        }
    }

2.WaterfallControl的样式

<Style TargetType="controls:WaterfallControl">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="controls:WaterfallControl">
                    <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}" VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
                        <UniformGrid Name="grdRoot" Columns="{TemplateBinding Columns}">

                        </UniformGrid>
                    </ScrollViewer>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

3.调用

WaterfallControl继承自ItemsControl,所以和ItemsControl的使用没有区别,只需要额外指定一个Columns即可.

 

可能遇到的问题:

1.遇到图片不能直接计算高度,可能导致某列很长.可以用扩展属性给图片指定一个初始占位高度.

2.遇到界面大小变化,列数是不是应该动态变化,这个要实现也简单,监视下Window.SizeChanged,然后改变Columns就行了.

3.我直接把ScrollViewer放到WaterfallControl的模板里了,建议抽出来,监视下滚动事件,实现滚动到底加载数据.

4.不知道是否有更简单明了的方法.