Share width of a Grid-Column in a ViewCell?

问题

I would like to have my columns in my ListViews ViewCell to be all of the same size. It is currently set to auto and the widest name should win and all other columns should be set to the widest labels width. Currently they have all different widths in each row.

ListView ItemTemplate Example:

<ViewCell>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" /> /
            <ColumnDefinition Width="*" />
        </Grid.ColumnDefinitions>

        <Label Grid.Row="0" Text="{Binding Name}"/>
[....]

In WPF we have the property SharedSizeGroup, is there something similar in Xamarin.Forms? Is there a workaround without hacking too much?

回答1:

Unfortunately, no - there is no such property.

This is a rather difficult thing to do since you need to measure all rows before you can figure out which one has the widest text. There is not a cross-platform way to do that. There are ways to do it at the platform level for Android and iOS, but I don't think there is a way for WinPhone.

[edited to reflect a better approach identified in the comments]:

An alternative is to use OneWayToSource bindings and keeping track of the ColumnDefinition entries for each listview row.

XamlPage.Xaml:

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage
    xmlns="http://xamarin.com/schemas/2014/forms"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    x:Class="FormsSandbox.XamlPage">
    <ContentPage.Padding>
        <OnPlatform x:TypeArguments="Thickness" iOS="0,20,0,0" Android="0" WinPhone="0"/>
    </ContentPage.Padding>

    <AbsoluteLayout>
        <ListView x:Name="MyLV" AbsoluteLayout.LayoutBounds="0,0,1,1" AbsoluteLayout.LayoutFlags="All">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid RowSpacing="0" ColumnSpacing="0">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="Auto" />
                                <ColumnDefinition Width="*" />
                            </Grid.ColumnDefinitions>
                            <Label Grid.Column="0" Text="{Binding .}" MinimumWidthRequest="50" HorizontalOptions="StartAndExpand" SizeChanged="LabelSizeChanged" />
                            <Label Grid.Column="1" Text="Second Column"/>
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </AbsoluteLayout>

</ContentPage>

XamlPage.xaml.cs:

using System;
using Xamarin.Forms;
using System.Collections.Generic;

namespace FormsSandbox
{
    public partial class XamlPage : ContentPage
    {
        private double _colSize = 0.0;
        private List<ColumnDefinition> _columns = new List<ColumnDefinition>();

        public XamlPage ()
        {
            InitializeComponent ();

            var data = new List<string> ();

            data.Add ("Lorem ipsum");
            data.Add ("Foo");
            data.Add ("Dolor semet");
            data.Add ("Test");
            data.Add (".");
            data.Add ("Xamarin Forms Is Great");
            data.Add ("Short");
            data.Add ("Longer than Short");
            data.Add ("");
            data.Add ("Hyphenated");
            data.Add ("Non-hyphenated");
            data.Add ("Ironic, eh?");

            MyLV.ItemsSource = data;
        }

        public void LabelSizeChanged (object sender, EventArgs e)
        {
            var label = (Label)sender;
            var grid = (Grid)label.Parent;
            var column = grid.ColumnDefinitions [0];
            if (!_columns.Contains (column)) {
                _columns.Add (column);
            }
            var adjustments = new List<ColumnDefinition> ();
            if (label.Width > _colSize) {
                _colSize = label.Width;
                adjustments.AddRange (_columns);
            } else {
                adjustments.Add (column);
            }
            foreach (var col in adjustments) {
                col.Width = new GridLength (_colSize);
            }
        }
    }
}

来源：https://stackoverflow.com/questions/36584755/share-width-of-a-grid-column-in-a-viewcell

标签

xamarin.forms