[英]Force a break in a items control with wrap panel template
我一直想解决一个有趣的问题。 基本上,我有一个WrapPanel
控件,它使用WrapPanel
作为ItemsPanel
来模拟由多个绑定字符串构建的段落。 但是,有时候我需要强制中断,例如当我开始一个新段落时,但是在TextBlock
DateTemplate
中插入一个中断实际上并没有在父包装面板中插入一个中断。 这是代码:
<ItemsControl ItemsSource="{Binding Fragments}" >
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock
TextWrapping="Wrap"
Text="{Binding}"/> <!--If this text has a break it won't
propagate that break to the wrap panel,
but instead just in this text block which
causes the formatting to look wrong-->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
这是片段的简单定义,将显示我在说什么:
Fragments = new ObservableCollection<string>();
Fragments.Add("This is");
Fragments.Add("the first line, ");
Fragments.Add("it is very long and will drift to the ");
Fragments.Add("second line naturally since it is controlled by a wrap panel");
Fragments.Add("\n\r This I want to force to the line below where the line above ends");
Fragments.Add("rapid \n\r new \n\r lines");
我希望这些段落可以继续串联在一起,但是请您在遇到手动中断时遵守它们。 像这样:
This is the first line, it is very long and will drift to the second line naturally since it is controlled by a wrap panel. This I want to force to the line below where the line above ends. rapid new lines
我会抛弃ItemsControl并使用文本块的Inlines集合代替。 不幸的是,您不能直接绑定字符串集合,因为TextBlock.Inlines
不是依赖项属性,但是使用附加的依赖项属性来解决它并不难:
我还添加了对CollectionChanged事件的传播的支持,因此向ViewModel.Fragments
添加一个字符串将更新文本块。 删除也将起作用,尽管限制是将删除与字符串匹配的第一个Fragment。
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
<Window.DataContext>
<local:ViewModel />
</Window.DataContext>
<Grid>
<TextBlock local:FlowSupport.Fragments="{Binding Fragments}" TextWrapping="WrapWithOverflow" Margin="10" Background="Beige" />
</Grid>
</Window>
视图模型:
public class ViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
private ObservableCollection<string> _fragments;
public ObservableCollection<string> Fragments { get { return _fragments; } set { _fragments = value; OnPropertyChanged("Fragments"); } }
public ViewModel()
{
Fragments = new ObservableCollection<string>();
Fragments.Add("This is ");
Fragments.Add("the first line, ");
Fragments.Add("it is very long and will drift to the ");
Fragments.Add("second line naturally since it is controlled by a wrap panel");
Fragments.Add("\nThis I want to force to the line below where the line above ends\n");
Fragments.Add("rapid \nnew \nlines");
}
}
FlowSupport:
using System;
using System.Linq;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Collections.Specialized;
namespace WpfApplication1
{
public static class FlowSupport
{
private static Dictionary<TextBlock, NotifyCollectionChangedEventHandler> _collChangedHandlers = new Dictionary<TextBlock,NotifyCollectionChangedEventHandler>();
public static ObservableCollection<string> GetFragments(TextBlock tb) { return (ObservableCollection<string>)tb.GetValue(FragmentsProperty); }
public static void SetFragments(TextBlock tb, ObservableCollection<string> value) { tb.SetValue(FragmentsProperty, value); }
public static readonly DependencyProperty FragmentsProperty = DependencyProperty.RegisterAttached("Fragments", typeof(ObservableCollection<string>), typeof(FlowSupport), new PropertyMetadata(new ObservableCollection<string>(), OnFragmentsChanged));
private static void OnFragmentsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var tb = d as TextBlock;
if (tb != null)
{
CreateCollectionChangedHandler(tb); // create handler, once per textblock
tb.Inlines.Clear();
var oldInlines = e.OldValue as ObservableCollection<string>;
if (oldInlines != null)
{
oldInlines.CollectionChanged -= _collChangedHandlers[tb];
}
var inlines = e.NewValue as ObservableCollection<string>;
if (inlines != null)
{
inlines.CollectionChanged += _collChangedHandlers[tb];
foreach (string s in inlines)
tb.Inlines.Add(s);
}
}
}
private static void CreateCollectionChangedHandler(TextBlock tb)
{
if (!_collChangedHandlers.ContainsKey(tb))
{
_collChangedHandlers.Add(tb, (s1, e1) =>
{
if (e1.NewItems != null)
{
foreach (string text in e1.NewItems)
tb.Inlines.Add(text);
}
if (e1.OldItems != null)
{
foreach (string text in e1.OldItems)
{
Inline inline = tb.Inlines.FirstOrDefault(i => ((Run)i).Text == text);
if (inline != null)
tb.Inlines.Remove(inline);
}
}
});
}
}
}
}
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