WPF: ¿Cómo puedo centrar todos los elementos en un WrapPanel?

Question

Estoy usando un WrapPanel como el ItemsPanel de un ItemsControl . En este momento, los elementos en el control se envuelven así:

|1234567  |
|890      |

Me gustaría que se envuelvan así:

| 1234567 |
|   890   |

Conceptualmente, el proceso de diseño debe alinear cada línea de elementos para que se centre dentro de los límites de WrapPanel .

¿Puede alguien explicar cómo esto es posible, por favor?

Answer 1

El WrapPanel incorporado no le permitirá alinear su contenido, solo a sí mismo. Aquí hay una técnica que le permite configurar HorizontalContentAlignment :

using System;
using System.Windows;
using System.Windows.Controls;

public class AlignableWrapPanel : Panel
{
    public HorizontalAlignment HorizontalContentAlignment
    {
        get { return (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty); }
        set { SetValue(HorizontalContentAlignmentProperty, value); }
    }

    public static readonly DependencyProperty HorizontalContentAlignmentProperty =
        DependencyProperty.Register("HorizontalContentAlignment", typeof(HorizontalAlignment), typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(HorizontalAlignment.Left, FrameworkPropertyMetadataOptions.AffectsArrange));

    protected override Size MeasureOverride(Size constraint)
    {
        Size curLineSize = new Size();
        Size panelSize = new Size();

        UIElementCollection children = base.InternalChildren;

        for (int i = 0; i < children.Count; i++)
        {
            UIElement child = children[i] as UIElement;

            // Flow passes its own constraint to children
            child.Measure(constraint);
            Size sz = child.DesiredSize;

            if (curLineSize.Width + sz.Width > constraint.Width) //need to switch to another line
            {
                panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
                panelSize.Height += curLineSize.Height;
                curLineSize = sz;

                if (sz.Width > constraint.Width) // if the element is wider then the constraint - give it a separate line                    
                {
                    panelSize.Width = Math.Max(sz.Width, panelSize.Width);
                    panelSize.Height += sz.Height;
                    curLineSize = new Size();
                }
            }
            else //continue to accumulate a line
            {
                curLineSize.Width += sz.Width;
                curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
            }
        }

        // the last line size, if any need to be added
        panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
        panelSize.Height += curLineSize.Height;

        return panelSize;
    }

    protected override Size ArrangeOverride(Size arrangeBounds)
    {
        int firstInLine = 0;
        Size curLineSize = new Size();
        double accumulatedHeight = 0;
        UIElementCollection children = this.InternalChildren;

        for (int i = 0; i < children.Count; i++)
        {
            Size sz = children[i].DesiredSize;

            if (curLineSize.Width + sz.Width > arrangeBounds.Width) //need to switch to another line
            {
                ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, i);

                accumulatedHeight += curLineSize.Height;
                curLineSize = sz;

                if (sz.Width > arrangeBounds.Width) //the element is wider then the constraint - give it a separate line                    
                {
                    ArrangeLine(accumulatedHeight, sz, arrangeBounds.Width, i, ++i);
                    accumulatedHeight += sz.Height;
                    curLineSize = new Size();
                }
                firstInLine = i;
            }
            else //continue to accumulate a line
            {
                curLineSize.Width += sz.Width;
                curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
            }
        }

        if (firstInLine < children.Count)
            ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, children.Count);

        return arrangeBounds;
    }

    private void ArrangeLine(double y, Size lineSize, double boundsWidth, int start, int end)
    {
        double x = 0;
        if (this.HorizontalContentAlignment == HorizontalAlignment.Center)
        {
            x = (boundsWidth - lineSize.Width) / 2;
        }
        else if (this.HorizontalContentAlignment == HorizontalAlignment.Right)
        {
            x = (boundsWidth - lineSize.Width);
        }

        UIElementCollection children = InternalChildren;
        for (int i = start; i < end; i++)
        {
            UIElement child = children[i];
            child.Arrange(new Rect(x, y, child.DesiredSize.Width, lineSize.Height));
            x += child.DesiredSize.Width;
        }
    }
}

Answer 2

Lamentablemente, el stock WrapPanel no hará lo que está pidiendo, porque su intención es llenar todo el espacio disponible horizontalmente (o verticalmente) antes de envolver. Probablemente tendrás que diseñar tu propio WrapPanel para manejar este caso. Podría comenzar con esta muestra que muestra cómo crear su propio WrapPanel .

Answer 3

Versión con VerticalContentAlignment (para paneles verticales):

public class AlignableWrapPanel : Panel {
    public AlignableWrapPanel() {
        _orientation = Orientation.Horizontal;
    }

    private static bool IsWidthHeightValid(object value) {
        var v = (double)value;
        return (double.IsNaN(v)) || (v >= 0.0d && !double.IsPositiveInfinity(v));
    }

    public static readonly DependencyProperty ItemWidthProperty = DependencyProperty.Register("ItemWidth", typeof(double),
            typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(double.NaN, FrameworkPropertyMetadataOptions.AffectsMeasure),
            IsWidthHeightValid);

    [TypeConverter(typeof(LengthConverter))]
    public double ItemWidth {
        get { return (double)GetValue(ItemWidthProperty); }
        set { SetValue(ItemWidthProperty, value); }
    }

    public static readonly DependencyProperty ItemHeightProperty = DependencyProperty.Register("ItemHeight", typeof(double),
            typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(double.NaN, FrameworkPropertyMetadataOptions.AffectsMeasure),
            IsWidthHeightValid);

    [TypeConverter(typeof(LengthConverter))]
    public double ItemHeight {
        get { return (double)GetValue(ItemHeightProperty); }
        set { SetValue(ItemHeightProperty, value); }
    }

    public static readonly DependencyProperty OrientationProperty = StackPanel.OrientationProperty.AddOwner(typeof(AlignableWrapPanel),
            new FrameworkPropertyMetadata(Orientation.Horizontal, FrameworkPropertyMetadataOptions.AffectsMeasure, OnOrientationChanged));

    public Orientation Orientation {
        get { return _orientation; }
        set { SetValue(OrientationProperty, value); }
    }

    private static void OnOrientationChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
        var p = (AlignableWrapPanel)d;
        p._orientation = (Orientation)e.NewValue;
    }

    private Orientation _orientation;

    private struct UvSize {
        internal UvSize(Orientation orientation, double width, double height) {
            U = V = 0d;
            _orientation = orientation;
            Width = width;
            Height = height;
        }

        internal UvSize(Orientation orientation) {
            U = V = 0d;
            _orientation = orientation;
        }

        internal double U;
        internal double V;
        private readonly Orientation _orientation;

        internal double Width {
            get { return (_orientation == Orientation.Horizontal ? U : V); }
            private set { if (_orientation == Orientation.Horizontal) U = value; else V = value; }
        }

        internal double Height {
            get { return (_orientation == Orientation.Horizontal ? V : U); }
            private set { if (_orientation == Orientation.Horizontal) V = value; else U = value; }
        }
    }

    protected override Size MeasureOverride(Size constraint) {
        var curLineSize = new UvSize(Orientation);
        var panelSize = new UvSize(Orientation);
        var uvConstraint = new UvSize(Orientation, constraint.Width, constraint.Height);
        var itemWidth = ItemWidth;
        var itemHeight = ItemHeight;
        var itemWidthSet = !double.IsNaN(itemWidth);
        var itemHeightSet = !double.IsNaN(itemHeight);

        var childConstraint = new Size(
                (itemWidthSet ? itemWidth : constraint.Width),
                (itemHeightSet ? itemHeight : constraint.Height));

        var children = InternalChildren;

        for (int i = 0, count = children.Count; i < count; i++) {
            var child = children[i];
            if (child == null) continue;

            //Flow passes its own constrint to children 
            child.Measure(childConstraint);

            //this is the size of the child in UV space 
            var sz = new UvSize(
                    Orientation,
                    (itemWidthSet ? itemWidth : child.DesiredSize.Width),
                    (itemHeightSet ? itemHeight : child.DesiredSize.Height));

            if (curLineSize.U + sz.U > uvConstraint.U) {
                //need to switch to another line 
                panelSize.U = Math.Max(curLineSize.U, panelSize.U);
                panelSize.V += curLineSize.V;
                curLineSize = sz;

                if (!(sz.U > uvConstraint.U)) continue;
                //the element is wider then the constrint - give it a separate line
                panelSize.U = Math.Max(sz.U, panelSize.U);
                panelSize.V += sz.V;
                curLineSize = new UvSize(Orientation);
            } else {
                //continue to accumulate a line
                curLineSize.U += sz.U;
                curLineSize.V = Math.Max(sz.V, curLineSize.V);
            }
        }

        //the last line size, if any should be added 
        panelSize.U = Math.Max(curLineSize.U, panelSize.U);
        panelSize.V += curLineSize.V;

        //go from UV space to W/H space
        return new Size(panelSize.Width, panelSize.Height);
    }

    protected override Size ArrangeOverride(Size finalSize) {
        var firstInLine = 0;
        var itemWidth = ItemWidth;
        var itemHeight = ItemHeight;
        double accumulatedV = 0;
        var itemU = (Orientation == Orientation.Horizontal ? itemWidth : itemHeight);
        var curLineSize = new UvSize(Orientation);
        var uvFinalSize = new UvSize(Orientation, finalSize.Width, finalSize.Height);
        var itemWidthSet = !double.IsNaN(itemWidth);
        var itemHeightSet = !double.IsNaN(itemHeight);
        var useItemU = (Orientation == Orientation.Horizontal ? itemWidthSet : itemHeightSet);

        var children = InternalChildren;

        for (int i = 0, count = children.Count; i < count; i++) {
            var child = children[i];
            if (child == null) continue;

            var sz = new UvSize(
                    Orientation,
                    (itemWidthSet ? itemWidth : child.DesiredSize.Width),
                    (itemHeightSet ? itemHeight : child.DesiredSize.Height));

            if (curLineSize.U + sz.U > uvFinalSize.U) {
                //need to switch to another line 
                ArrangeLine(finalSize, accumulatedV, curLineSize, firstInLine, i, useItemU, itemU);

                accumulatedV += curLineSize.V;
                curLineSize = sz;

                if (sz.U > uvFinalSize.U) {
                    //the element is wider then the constraint - give it a separate line 
                    //switch to next line which only contain one element 
                    ArrangeLine(finalSize, accumulatedV, sz, i, ++i, useItemU, itemU);

                    accumulatedV += sz.V;
                    curLineSize = new UvSize(Orientation);
                }

                firstInLine = i;
            } else {
                //continue to accumulate a line
                curLineSize.U += sz.U;
                curLineSize.V = Math.Max(sz.V, curLineSize.V);
            }
        }

        //arrange the last line, if any
        if (firstInLine < children.Count) {
            ArrangeLine(finalSize, accumulatedV, curLineSize, firstInLine, children.Count, useItemU, itemU);
        }

        return finalSize;
    }

    private void ArrangeLine(Size finalSize, double v, UvSize line, int start, int end, bool useItemU, double itemU) {
        double u;
        var isHorizontal = Orientation == Orientation.Horizontal;

        if (_orientation == Orientation.Vertical) {
            switch (VerticalContentAlignment) {
                case VerticalAlignment.Center:
                    u = (finalSize.Height - line.U) / 2;
                    break;
                case VerticalAlignment.Bottom:
                    u = finalSize.Height - line.U;
                    break;
                default:
                    u = 0;
                    break;
            }
        } else {
            switch (HorizontalContentAlignment) {
                case HorizontalAlignment.Center:
                    u = (finalSize.Width - line.U) / 2;
                    break;
                case HorizontalAlignment.Right:
                    u = finalSize.Width - line.U;
                    break;
                default:
                    u = 0;
                    break;
            }
        }

        var children = InternalChildren;
        for (var i = start; i < end; i++) {
            var child = children[i];
            if (child == null) continue;
            var childSize = new UvSize(Orientation, child.DesiredSize.Width, child.DesiredSize.Height);
            var layoutSlotU = (useItemU ? itemU : childSize.U);
            child.Arrange(new Rect(
                    isHorizontal ? u : v,
                    isHorizontal ? v : u,
                    isHorizontal ? layoutSlotU : line.V,
                    isHorizontal ? line.V : layoutSlotU));
            u += layoutSlotU;
        }
    }

    public static readonly DependencyProperty HorizontalContentAlignmentProperty = DependencyProperty.Register(nameof(HorizontalContentAlignment), typeof(HorizontalAlignment),
            typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(HorizontalAlignment.Left, FrameworkPropertyMetadataOptions.AffectsArrange));

    public HorizontalAlignment HorizontalContentAlignment {
        get { return (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty); }
        set { SetValue(HorizontalContentAlignmentProperty, value); }
    }

    public static readonly DependencyProperty VerticalContentAlignmentProperty = DependencyProperty.Register(nameof(VerticalContentAlignment), typeof(VerticalAlignment),
            typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(VerticalAlignment.Top, FrameworkPropertyMetadataOptions.AffectsArrange));

    public VerticalAlignment VerticalContentAlignment {
        get { return (VerticalAlignment)GetValue(VerticalContentAlignmentProperty); }
        set { SetValue(VerticalContentAlignmentProperty, value); }
    }
}

Answer 4

La respuesta simple es que no puede alinear el contenido de un WrapPanel en el centro. Puede alinear el panel en el centro, pero la última línea seguirá estando alineada dentro del panel.

Alterar sugerencias:

Usa Grid con filas y columnas. Si no está agregando elementos a la colección dinámicamente, esto podría funcionar bien.

Crea tu propia versión de WrapPanel que funcione de la forma que lo necesites. Este documento de MSDN describe cómo funcionan los paneles e incluye una sección en Creando paneles personalizados. También tiene un enlace a un panel personalizado de muestra.

Answer 5

Aquí está la versión de Silverlight

Gracias especiales a @DTig ,

using System.Windows.Controls;
using System.Windows;
using Telerik.Windows;
using System;
using System.Linq;

public class AlignableWrapPanel : Panel
{
    public HorizontalAlignment HorizontalContentAlignment
    {
        get { return (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty); }
        set { SetValue(HorizontalContentAlignmentProperty, value); }
    }

    public static readonly DependencyProperty HorizontalContentAlignmentProperty =
        DependencyProperty.Register("HorizontalContentAlignment", typeof(HorizontalAlignment), typeof(AlignableWrapPanel), new FrameworkPropertyMetadata(HorizontalAlignment.Left, FrameworkPropertyMetadataOptions.AffectsArrange));

    protected override Size MeasureOverride(Size constraint)
    {
        Size curLineSize = new Size();
        Size panelSize = new Size();

        UIElementCollection children = base.Children;

        for (int i = 0; i < children.Count; i++)
        {
            UIElement child = children[i] as UIElement;

            // Flow passes its own constraint to children
            child.Measure(constraint);
            Size sz = child.DesiredSize;

            if (curLineSize.Width + sz.Width > constraint.Width) //need to switch to another line
            {
                panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
                panelSize.Height += curLineSize.Height;
                curLineSize = sz;

                if (sz.Width > constraint.Width) // if the element is wider then the constraint - give it a separate line                    
                {
                    panelSize.Width = Math.Max(sz.Width, panelSize.Width);
                    panelSize.Height += sz.Height;
                    curLineSize = new Size();
                }
            }
            else //continue to accumulate a line
            {
                curLineSize.Width += sz.Width;
                curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
            }
        }

        // the last line size, if any need to be added
        panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
        panelSize.Height += curLineSize.Height;

        return panelSize;
    }

    protected override Size ArrangeOverride(Size arrangeBounds)
    {
        int firstInLine = 0;
        Size curLineSize = new Size();
        double accumulatedHeight = 0;
        UIElementCollection children = this.Children;

        for (int i = 0; i < children.Count; i++)
        {
            Size sz = children[i].DesiredSize;

            if (curLineSize.Width + sz.Width > arrangeBounds.Width) //need to switch to another line
            {
                ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, i);

                accumulatedHeight += curLineSize.Height;
                curLineSize = sz;

                if (sz.Width > arrangeBounds.Width) //the element is wider then the constraint - give it a separate line                    
                {
                    ArrangeLine(accumulatedHeight, sz, arrangeBounds.Width, i, ++i);
                    accumulatedHeight += sz.Height;
                    curLineSize = new Size();
                }
                firstInLine = i;
            }
            else //continue to accumulate a line
            {
                curLineSize.Width += sz.Width;
                curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
            }
        }

        if (firstInLine < children.Count)
            ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, children.Count);

        return arrangeBounds;
    }

    private void ArrangeLine(double y, Size lineSize, double boundsWidth, int start, int end)
    {
        double x = 0;
        if (this.HorizontalContentAlignment == HorizontalAlignment.Center)
        {
            x = (boundsWidth - lineSize.Width) / 2;
        }
        else if (this.HorizontalContentAlignment == HorizontalAlignment.Right)
        {
            x = (boundsWidth - lineSize.Width);
        }

        UIElementCollection children = Children;
        for (int i = start; i < end; i++)
        {
            UIElement child = children[i];
            var rect = new System.Windows.Rect(x, y, child.DesiredSize.Width, lineSize.Height);
            child.Arrange(rect);
            x += child.DesiredSize.Width;
        }
    }
}

Answer 6

Necesitaba un WrapPanel que pueda expandir su contenido, por lo que basado en https://stackoverflow.com/a/7747002/121122 y algunos problemas que se me ocurrieron con esto:

public class AlignableWrapPanel : Panel
{
    public HorizontalAlignment HorizontalContentAlignment
    {
        get => (HorizontalAlignment)GetValue(HorizontalContentAlignmentProperty);
        set => SetValue(HorizontalContentAlignmentProperty, value);
    }

    public static readonly DependencyProperty HorizontalContentAlignmentProperty = DependencyProperty.Register(
        nameof(HorizontalContentAlignment),
        typeof(HorizontalAlignment),
        typeof(AlignableWrapPanel),
        new FrameworkPropertyMetadata(HorizontalAlignment.Left, FrameworkPropertyMetadataOptions.AffectsArrange));

    protected override Size MeasureOverride(Size constraint)
    {
        var curLineSize = new Size();
        var panelSize = new Size();

        var children = InternalChildren;

        for (var i = 0; i < children.Count; i++)
        {
            var child = children[i];

            // flow passes its own constraint to children
            child.Measure(constraint);
            var sz = child.DesiredSize;

            if (curLineSize.Width + sz.Width > constraint.Width) // need to switch to another line
            {
                panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
                panelSize.Height += curLineSize.Height;
                curLineSize = sz;

                if (sz.Width > constraint.Width) // if the element is wider then the constraint - give it a separate line                    
                {
                    panelSize.Width = Math.Max(sz.Width, panelSize.Width);
                    panelSize.Height += sz.Height;
                    curLineSize = new Size();
                }
            }
            else // continue to add to the line
            {
                curLineSize.Width += sz.Width;
                curLineSize.Height = Math.Max(sz.Height, curLineSize.Height);
            }
        }

        // the last line size, if any need to be added
        panelSize.Width = Math.Max(curLineSize.Width, panelSize.Width);
        panelSize.Height += curLineSize.Height;

        return panelSize;
    }

    protected override Size ArrangeOverride(Size arrangeBounds)
    {
        var firstInLine = 0;
        var curLineSize = new Size();
        var accumulatedHeight = 0D;
        var children = InternalChildren;

        for (var i = 0; i < children.Count; i++)
        {
            var desiredSize = children[i].DesiredSize;

            if (curLineSize.Width + desiredSize.Width > arrangeBounds.Width) // need to switch to another line
            {
                ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, i);

                accumulatedHeight += curLineSize.Height;
                curLineSize = desiredSize;

                if(
                    desiredSize.Width > arrangeBounds.Width || 
                    children[i] is FrameworkElement element && element.HorizontalAlignment == HorizontalAlignment.Stretch)
                {
                    // the element is wider then the constraint or it stretches - give it a separate line
                    ArrangeLine(accumulatedHeight, desiredSize, arrangeBounds.Width, i, ++i);
                    accumulatedHeight += desiredSize.Height;
                    curLineSize = new Size();
                }
                firstInLine = i;
            }
            else // continue to add to the line
            {
                curLineSize.Width += desiredSize.Width;
                curLineSize.Height = Math.Max(desiredSize.Height, curLineSize.Height);
            }
        }

        if (firstInLine < children.Count)
        {
            ArrangeLine(accumulatedHeight, curLineSize, arrangeBounds.Width, firstInLine, children.Count);
        }

        return arrangeBounds;
    }

    private void ArrangeLine(double y, Size lineSize, double boundsWidth, int start, int end)
    {
        var children = InternalChildren;

        var x = 0D;
        if (HorizontalContentAlignment == HorizontalAlignment.Center)
        {
            x = (boundsWidth - lineSize.Width) / 2;
        }
        else if (HorizontalContentAlignment == HorizontalAlignment.Right)
        {
            x = boundsWidth - lineSize.Width;
        }

        var stretchChildren = new List<UIElement>();
        for (var i = start; i < end; i++)
        {
            var child = children[i];
            if (child is FrameworkElement element && element.HorizontalAlignment == HorizontalAlignment.Stretch)
            {
                stretchChildren.Add(child);
            }
        }

        var spaceAvailableForStretchChildren = boundsWidth - lineSize.Width;
        var spaceAvailablePerStretchChild = 0D;
        if (stretchChildren.Any())
        {
            x = 0; // all available space will be filled so start at 0
            spaceAvailablePerStretchChild = spaceAvailableForStretchChildren / stretchChildren.Count;
            spaceAvailablePerStretchChild = spaceAvailablePerStretchChild >= 0 ? spaceAvailablePerStretchChild : 0;
        }

        for (var i = start; i < end; i++)
        {
            var child = children[i];
            double itemWidth;
            if(stretchChildren.Contains(child))
            {
                itemWidth = child.DesiredSize.Width + spaceAvailablePerStretchChild;
            }
            else
            {
                itemWidth = child.DesiredSize.Width;
            }

            child.Arrange(new Rect(x, y, itemWidth, lineSize.Height));
            x += itemWidth;
        }
    }
}