All geek questions in one place

Xamarin.Forms needs a WrapLayout

I'm struggling to figure out how to wrap list items in the horizontal direction and fill the available space in my list.

So far, the items in my list view are not migrated.

XAML:

<Grid Grid.Row="4" Grid.RowSpacing="3" Grid.ColumnSpacing="3" BackgroundColor="Silver"> <ListView ItemsSource="{Binding EmployeeIds}" SelectedItem="{Binding SelectedEmployeeId}" BackgroundColor="Black" > <ListView.ItemTemplate> <DataTemplate> <ViewCell> <ViewCell.View> <customcontrols:WrapLayoutOld Orientation="Horizontal"> <Label Text="{Binding Value}" TextColor="Yellow" XAlign="Start" /> </customcontrols:WrapLayoutOld> </ViewCell.View> </ViewCell> </DataTemplate> </ListView.ItemTemplate> </ListView> </Grid>

WrapLayout:

 using System; using System.Linq; using System.Collections.Generic; using Xamarin.Forms; namespace Custom.Controls { /// <summary> /// New WrapLayout /// </summary> /// <author>Jason Smith</author> public class WrapLayout : Layout<View> { Dictionary<View, SizeRequest> layoutCache = new Dictionary<View, SizeRequest>(); /// <summary> /// Backing Storage for the Spacing property /// </summary> public static readonly BindableProperty SpacingProperty = BindableProperty.Create<WrapLayout, double>(w => w.Spacing, 5, propertyChanged: (bindable, oldvalue, newvalue) => ((WrapLayout)bindable).layoutCache.Clear()); /// <summary> /// Spacing added between elements (both directions) /// </summary> /// <value>The spacing.</value> public double Spacing { get { return (double)GetValue(SpacingProperty); } set { SetValue(SpacingProperty, value); } } public WrapLayout() { VerticalOptions = HorizontalOptions = LayoutOptions.FillAndExpand; } protected override void OnChildMeasureInvalidated() { base.OnChildMeasureInvalidated(); layoutCache.Clear(); } protected override SizeRequest OnSizeRequest(double widthConstraint, double heightConstraint) { double lastX; double lastY; var layout = NaiveLayout(widthConstraint, heightConstraint, out lastX, out lastY); return new SizeRequest(new Size(lastX, lastY)); } protected override void LayoutChildren(double x, double y, double width, double height) { double lastX, lastY; var layout = NaiveLayout(width, height, out lastX, out lastY); foreach (var t in layout) { var offset = (int)((width - t.Last().Item2.Right) / 2); foreach (var dingus in t) { var location = new Rectangle(dingus.Item2.X + x + offset, dingus.Item2.Y + y, dingus.Item2.Width, dingus.Item2.Height); LayoutChildIntoBoundingRegion(dingus.Item1, location); } } } private List<List<Tuple<View, Rectangle>>> NaiveLayout(double width, double height, out double lastX, out double lastY) { double startX = 0; double startY = 0; double right = width; double nextY = 0; lastX = 0; lastY = 0; var result = new List<List<Tuple<View, Rectangle>>>(); var currentList = new List<Tuple<View, Rectangle>>(); foreach (var child in Children) { SizeRequest sizeRequest; if (!layoutCache.TryGetValue(child, out sizeRequest)) { layoutCache[child] = sizeRequest = child.GetSizeRequest(double.PositiveInfinity, double.PositiveInfinity); } var paddedWidth = sizeRequest.Request.Width + Spacing; var paddedHeight = sizeRequest.Request.Height + Spacing; if (startX + paddedWidth > right) { startX = 0; startY += nextY; if (currentList.Count > 0) { result.Add(currentList); currentList = new List<Tuple<View, Rectangle>>(); } } currentList.Add(new Tuple<View, Rectangle>(child, new Rectangle(startX, startY, sizeRequest.Request.Width, sizeRequest.Request.Height))); lastX = Math.Max(lastX, startX + paddedWidth); lastY = Math.Max(lastY, startY + paddedHeight); nextY = Math.Max(nextY, paddedHeight); startX += paddedWidth; } result.Add(currentList); return result; } } /// <summary> /// Simple Layout panel which performs wrapping on the boundaries. /// </summary> public class WrapLayoutOld : Layout<View> { /// <summary> /// Backing Storage for the Orientation property /// </summary> public static readonly BindableProperty OrientationProperty = BindableProperty.Create<WrapLayoutOld, StackOrientation>(w => w.Orientation, StackOrientation.Vertical, propertyChanged: (bindable, oldvalue, newvalue) => ((WrapLayoutOld)bindable).OnSizeChanged()); /// <summary> /// Orientation (Horizontal or Vertical) /// </summary> public StackOrientation Orientation { get { return (StackOrientation)GetValue(OrientationProperty); } set { SetValue(OrientationProperty, value); } } /// <summary> /// Backing Storage for the Spacing property /// </summary> public static readonly BindableProperty SpacingProperty = BindableProperty.Create<WrapLayoutOld, double>(w => w.Spacing, 6, propertyChanged: (bindable, oldvalue, newvalue) => ((WrapLayoutOld)bindable).OnSizeChanged()); /// <summary> /// Spacing added between elements (both directions) /// </summary> /// <value>The spacing.</value> public double Spacing { get { return (double)GetValue(SpacingProperty); } set { SetValue(SpacingProperty, value); } } /// <summary> /// This is called when the spacing or orientation properties are changed - it forces /// the control to go back through a layout pass. /// </summary> private void OnSizeChanged() { this.ForceLayout(); } //http://forums.xamarin.com/discussion/17961/stacklayout-with-horizontal-orientation-how-to-wrap-vertically#latest // protected override void OnPropertyChanged // (string propertyName = null) // { // base.OnPropertyChanged(propertyName); // if ((propertyName == WrapLayout.OrientationProperty.PropertyName) || // (propertyName == WrapLayout.SpacingProperty.PropertyName)) { // this.OnSizeChanged(); // } // } /// <summary> /// This method is called during the measure pass of a layout cycle to get the desired size of an element. /// </summary> /// <param name="widthConstraint">The available width for the element to use.</param> /// <param name="heightConstraint">The available height for the element to use.</param> protected override SizeRequest OnSizeRequest(double widthConstraint, double heightConstraint) { if (WidthRequest > 0) widthConstraint = Math.Min(widthConstraint, WidthRequest); if (HeightRequest > 0) heightConstraint = Math.Min(heightConstraint, HeightRequest); double internalWidth = double.IsPositiveInfinity(widthConstraint) ? double.PositiveInfinity : Math.Max(0, widthConstraint); double internalHeight = double.IsPositiveInfinity(heightConstraint) ? double.PositiveInfinity : Math.Max(0, heightConstraint); return Orientation == StackOrientation.Vertical ? DoVerticalMeasure(internalWidth, internalHeight) : DoHorizontalMeasure(internalWidth, internalHeight); } /// <summary> /// Does the vertical measure. /// </summary> /// <returns>The vertical measure.</returns> /// <param name="widthConstraint">Width constraint.</param> /// <param name="heightConstraint">Height constraint.</param> private SizeRequest DoVerticalMeasure(double widthConstraint, double heightConstraint) { int columnCount = 1; double width = 0; double height = 0; double minWidth = 0; double minHeight = 0; double heightUsed = 0; foreach (var item in Children) { var size = item.GetSizeRequest(widthConstraint, heightConstraint); width = Math.Max(width, size.Request.Width); var newHeight = height + size.Request.Height + Spacing; if (newHeight > heightConstraint) { columnCount++; heightUsed = Math.Max(height, heightUsed); height = size.Request.Height; } else height = newHeight; minHeight = Math.Max(minHeight, size.Minimum.Height); minWidth = Math.Max(minWidth, size.Minimum.Width); } if (columnCount > 1) { height = Math.Max(height, heightUsed); width *= columnCount; // take max width } return new SizeRequest(new Size(width, height), new Size(minWidth, minHeight)); } /// <summary> /// Does the horizontal measure. /// </summary> /// <returns>The horizontal measure.</returns> /// <param name="widthConstraint">Width constraint.</param> /// <param name="heightConstraint">Height constraint.</param> private SizeRequest DoHorizontalMeasure(double widthConstraint, double heightConstraint) { int rowCount = 1; double width = 0; double height = 0; double minWidth = 0; double minHeight = 0; double widthUsed = 0; foreach (var item in Children) { var size = item.GetSizeRequest(widthConstraint, heightConstraint); height = Math.Max(height, size.Request.Height); var newWidth = width + size.Request.Width + Spacing; if (newWidth > widthConstraint) { rowCount++; widthUsed = Math.Max(width, widthUsed); width = size.Request.Width; } else width = newWidth; minHeight = Math.Max(minHeight, size.Minimum.Height); minWidth = Math.Max(minWidth, size.Minimum.Width); } if (rowCount > 1) { width = Math.Max(width, widthUsed); height = (height + Spacing) * rowCount - Spacing; // via MitchMilam } return new SizeRequest(new Size(width, height), new Size(minWidth, minHeight)); } /// <summary> /// Positions and sizes the children of a Layout. /// </summary> /// <param name="x">A value representing the x coordinate of the child region bounding box.</param> /// <param name="y">A value representing the y coordinate of the child region bounding box.</param> /// <param name="width">A value representing the width of the child region bounding box.</param> /// <param name="height">A value representing the height of the child region bounding box.</param> protected override void LayoutChildren(double x, double y, double width, double height) { if (Orientation == StackOrientation.Vertical) { double colWidth = 0; double yPos = y, xPos = x; foreach (var child in Children.Where(c => c.IsVisible)) { var request = child.GetSizeRequest(width, height); double childWidth = request.Request.Width; double childHeight = request.Request.Height; colWidth = Math.Max(colWidth, childWidth); if (yPos + childHeight > height) { yPos = y; xPos += colWidth + Spacing; colWidth = 0; } var region = new Rectangle(xPos, yPos, childWidth, childHeight); LayoutChildIntoBoundingRegion(child, region); yPos += region.Height + Spacing; } } else { double rowHeight = 0; double yPos = y, xPos = x; foreach (var child in Children.Where(c => c.IsVisible)) { var request = child.GetSizeRequest(width, height); double childWidth = request.Request.Width; double childHeight = request.Request.Height; rowHeight = Math.Max(rowHeight, childHeight); if (xPos + childWidth > width) { xPos = x; yPos += rowHeight + Spacing; rowHeight = 0; } var region = new Rectangle(xPos, yPos, childWidth, childHeight); LayoutChildIntoBoundingRegion(child, region); xPos += region.Width + Spacing; } } } } }
+5
source share
3 answers

FlexLayout was introduced in Xamarin.Forms 3.0, so if you can upgrade it, you should definitely use it:

FlexLayout is similar to Xamarin.Forms StackLayout in that it can arrange its children horizontally and vertically on the stack. However, FlexLayout can also wrap its children if there are too many of them to fit in a single row or column, and it also has many options for orientation, alignment, and adaptation to different screen sizes.

White papers

+2
source

I have this list of images, and they correctly terminate using the same class that you are using, this could be due to LayoutOptions:

 WrapLayout container = new WrapLayout { VerticalOptions = LayoutOptions.FillAndExpand, HorizontalOptions = LayoutOptions.StartAndExpand, Orientation = StackOrientation.Horizontal, Padding = 10, Spacing = 10 }; Image thumbnail = new Image { HeightRequest = 80, WidthRequest = 80, HorizontalOptions = LayoutOptions.Start, VerticalOptions = LayoutOptions.Start, //BackgroundColor = Color.Black Source = item.ImageText, Aspect = Aspect.AspectFit };
0
source

I think this package will help you: https://www.nuget.org/packages/Xamarin.Forms.WrapLayout/

enter link description here

because xamarin.form does not have an element like StackLayout for data transfer. This example will help you: WrapLayout example

Xamarin.Forms.WrapLayout

-1
source

Source: https://habr.com/ru/post/1241435/

More articles:


All Articles