我想创建一个数据绑定的水平布局ItemsControl,其中每个项目都有一个Button.当我向集合添加新项时,ItemsControl应该相对于它所在的Window增长,直到它达到它的MaxWidth属性.然后所有按钮应均匀缩小以适合MaxWidth.类似于Chrome浏览器标签的内容.
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到目前为止,我已经达到了这个目的：
<ItemsControl Name="ButtonsControl" MaxWidth="400">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type dataclasses:TextNote}">
<Button Content="{Binding Title}" MinWidth="80"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
添加项目时,StackPanel和Window的扩展很好,但是当达到MaxWidth时,项目才会开始消失.
最佳答案 我不认为使用标准WPF控件的任何组合产生该行为是可能的,但是这个自定义StackPanel控件应该完成这项工作：
public class SqueezeStackPanel : Panel
{
private const double Tolerance = 0.001;
public static readonly DependencyProperty OrientationProperty = DependencyProperty.Register
("Orientation", typeof (Orientation), typeof (SqueezeStackPanel),
new FrameworkPropertyMetadata(Orientation.Horizontal, FrameworkPropertyMetadataOptions.AffectsMeasure,
OnOrientationChanged));
private readonly Dictionary<UIElement, Size> _childToConstraint = new Dictionary<UIElement, Size>();
private bool _isMeasureDirty;
private bool _isHorizontal = true;
private List<UIElement> _orderedSequence;
private Child[] _children;
static SqueezeStackPanel()
{
DefaultStyleKeyProperty.OverrideMetadata
(typeof (SqueezeStackPanel),
new FrameworkPropertyMetadata(typeof (SqueezeStackPanel)));
}
protected override bool HasLogicalOrientation
{
get { return true; }
}
protected override Orientation LogicalOrientation
{
get { return Orientation; }
}
public Orientation Orientation
{
get { return (Orientation) GetValue(OrientationProperty); }
set { SetValue(OrientationProperty, value); }
}
protected override Size ArrangeOverride(Size finalSize)
{
var size = new Size(_isHorizontal ? 0 : finalSize.Width, !_isHorizontal ? 0 : finalSize.Height);
var childrenCount = Children.Count;
var rc = new Rect();
for (var index = 0; index < childrenCount; index++)
{
var child = _orderedSequence[index];
var childVal = _children[index].Val;
if (_isHorizontal)
{
rc.Width = double.IsInfinity(childVal) ? child.DesiredSize.Width : childVal;
rc.Height = Math.Max(finalSize.Height, child.DesiredSize.Height);
size.Width += rc.Width;
size.Height = Math.Max(size.Height, rc.Height);
child.Arrange(rc);
rc.X += rc.Width;
}
else
{
rc.Width = Math.Max(finalSize.Width, child.DesiredSize.Width);
rc.Height = double.IsInfinity(childVal) ? child.DesiredSize.Height : childVal;
size.Width = Math.Max(size.Width, rc.Width);
size.Height += rc.Height;
child.Arrange(rc);
rc.Y += rc.Height;
}
}
return new Size(Math.Max(finalSize.Width, size.Width), Math.Max(finalSize.Height, size.Height));
}
protected override Size MeasureOverride(Size availableSize)
{
for (var i = 0; i < 3; i++)
{
_isMeasureDirty = false;
var childrenDesiredSize = new Size();
var childrenCount = Children.Count;
if (childrenCount == 0)
return childrenDesiredSize;
var childConstraint = GetChildrenConstraint(availableSize);
_children = new Child[childrenCount];
_orderedSequence = Children.Cast<UIElement>().ToList();
for (var index = 0; index < childrenCount; index++)
{
if (_isMeasureDirty)
break;
var child = _orderedSequence[index];
const double minLength = 0.0;
const double maxLength = double.PositiveInfinity;
MeasureChild(child, childConstraint);
if (_isHorizontal)
{
childrenDesiredSize.Width += child.DesiredSize.Width;
_children[index] = new Child(minLength, maxLength, child.DesiredSize.Width);
childrenDesiredSize.Height = Math.Max(childrenDesiredSize.Height, child.DesiredSize.Height);
}
else
{
childrenDesiredSize.Height += child.DesiredSize.Height;
_children[index] = new Child(minLength, maxLength, child.DesiredSize.Height);
childrenDesiredSize.Width = Math.Max(childrenDesiredSize.Width, child.DesiredSize.Width);
}
}
if (_isMeasureDirty)
continue;
var current = _children.Sum(s => s.Val);
var target = GetSizePart(availableSize);
var finalSize = new Size
(Math.Min(availableSize.Width, _isHorizontal ? current : childrenDesiredSize.Width),
Math.Min(availableSize.Height, _isHorizontal ? childrenDesiredSize.Height : current));
if (double.IsInfinity(target))
return finalSize;
RecalcChilds(current, target);
current = 0.0;
for (var index = 0; index < childrenCount; index++)
{
var child = _children[index];
if (IsGreater(current + child.Val, target, Tolerance) &&
IsGreater(target, current, Tolerance))
{
var rest = IsGreater(target, current, Tolerance) ? target - current : 0.0;
if (IsGreater(rest, child.Min, Tolerance))
child.Val = rest;
}
current += child.Val;
}
RemeasureChildren(finalSize);
finalSize = new Size
(Math.Min(availableSize.Width, _isHorizontal ? target : childrenDesiredSize.Width),
Math.Min(availableSize.Height, _isHorizontal ? childrenDesiredSize.Height : target));
if (_isMeasureDirty)
continue;
return finalSize;
}
return new Size();
}
public static double GetHeight(Thickness thickness)
{
return thickness.Top + thickness.Bottom;
}
public static double GetWidth(Thickness thickness)
{
return thickness.Left + thickness.Right;
}
protected override void OnVisualChildrenChanged(DependencyObject visualAdded, DependencyObject visualRemoved)
{
base.OnVisualChildrenChanged(visualAdded, visualRemoved);
var removedUiElement = visualRemoved as UIElement;
if (removedUiElement != null)
_childToConstraint.Remove(removedUiElement);
}
private Size GetChildrenConstraint(Size availableSize)
{
return new Size
(_isHorizontal ? double.PositiveInfinity : availableSize.Width,
!_isHorizontal ? double.PositiveInfinity : availableSize.Height);
}
private double GetSizePart(Size size)
{
return _isHorizontal ? size.Width : size.Height;
}
private static bool IsGreater(double a, double b, double tolerance)
{
return a - b > tolerance;
}
private void MeasureChild(UIElement child, Size childConstraint)
{
Size lastConstraint;
if ((child.IsMeasureValid && _childToConstraint.TryGetValue(child, out lastConstraint) &&
lastConstraint.Equals(childConstraint))) return;
child.Measure(childConstraint);
_childToConstraint[child] = childConstraint;
}
private static void OnOrientationChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var panel = (SqueezeStackPanel) d;
panel._isHorizontal = panel.Orientation == Orientation.Horizontal;
}
private void RecalcChilds(double current, double target)
{
var shouldShrink = IsGreater(current, target, Tolerance);
if (shouldShrink)
ShrinkChildren(_children, target);
}
private void RemeasureChildren(Size availableSize)
{
var childrenCount = Children.Count;
if (childrenCount == 0)
return;
var childConstraint = GetChildrenConstraint(availableSize);
for (var index = 0; index < childrenCount; index++)
{
var child = _orderedSequence[index];
if (Math.Abs(GetSizePart(child.DesiredSize) - _children[index].Val) > Tolerance)
MeasureChild(child, new Size(_isHorizontal ? _children[index].Val : childConstraint.Width,
!_isHorizontal ? _children[index].Val : childConstraint.Height));
}
}
private static void ShrinkChildren(IEnumerable<Child> children, double target)
{
var sortedChilds = children.OrderBy(v => v.Val).ToList();
var minValidTarget = sortedChilds.Sum(s => s.Min);
if (minValidTarget > target)
{
foreach (var child in sortedChilds)
child.Val = child.Min;
return;
}
do
{
var tmpTarget = target;
for (var iChild = 0; iChild < sortedChilds.Count; iChild++)
{
var child = sortedChilds[iChild];
if (child.Val*(sortedChilds.Count - iChild) >= tmpTarget)
{
var avg = tmpTarget/(sortedChilds.Count - iChild);
var success = true;
for (var jChild = iChild; jChild < sortedChilds.Count; jChild++)
{
var tChild = sortedChilds[jChild];
tChild.Val = Math.Max(tChild.Min, avg);
// Min constraint skip success expand on this iteration
if (Math.Abs(avg - tChild.Val) <= Tolerance) continue;
target -= tChild.Val;
success = false;
sortedChilds.RemoveAt(jChild);
jChild--;
}
if (success)
return;
break;
}
tmpTarget -= child.Val;
}
} while (sortedChilds.Count > 0);
}
private class Child
{
public readonly double Min;
public double Val;
public Child(double min, double max, double val)
{
Min = min;
Val = val;
Val = Math.Max(min, val);
Val = Math.Min(max, Val);
}
}
}
尝试将它用作ItemsPanelTemplate：
<ItemsControl Name="ButtonsControl" MaxWidth="400">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<local:SqueezeStackPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type dataclasses:TextNote}">
<Button Content="{Binding Title}" MinWidth="80"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
我无法根据您提供的代码确定,但我认为通过删除ItemsControl上的MaxWidth,您将获得更好的布局结果.
