Xamarin.Forms：是否可以在不调用 ViewModel 的情况下将行动态添加到网格？

封装您需要的功能以使视图和视图模型不耦合的一种方法是创建用户控件。

我创建了一个名为 TotalsGridControl 的新用户控件。这是 XAML

<?xml version="1.0" encoding="UTF-8"?>
<Grid xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="ScratchPad.UserControls.TotalsGridControl"
             x:Name="TotalsGrid">

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

</Grid>

这是背后的代码。

public partial class TotalsGridControl : Grid
{
    public TotalsGridControl()
    {
        InitializeComponent();
    }

    public static readonly BindableProperty TotalsProperty =
        BindableProperty.Create(nameof(Totals), typeof(List<TotalItem>), typeof(TotalsGridControl), null,
            BindingMode.OneWay, null, OnTotalsChanged);

    private static void OnTotalsChanged(BindableObject bindable, object oldvalue, object newvalue)
    {
        var control = (TotalsGridControl)bindable;
        if (control != null)
        {
            if (newvalue is List<TotalItem> totals)
            {
                var rowNumber = -1;
                double grandTotal = 0;

                foreach (var totalItem in totals)
                {
                    grandTotal += totalItem.Value;

                    var descLabel = new Label {Text = totalItem.Description};
                    var valueLabel = new Label { Text = totalItem.Value.ToString("c") };

                    rowNumber++;
                    control.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto});
                    control.Children.Add(descLabel, 0, rowNumber);
                    control.Children.Add(valueLabel, 1, rowNumber);
                }

                var grandTotalDescLabel = new Label { Text = "Total" };
                var grandTotalValueLabel = new Label { Text = grandTotal.ToString("c") };

                rowNumber++;
                control.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
                control.Children.Add(grandTotalDescLabel, 0, rowNumber);
                control.Children.Add(grandTotalValueLabel, 1, rowNumber);
            }
        }
    }

    public List<TotalItem> Totals
    {
        get => (List<TotalItem>)GetValue(TotalsProperty);
        set => SetValue(TotalsProperty, value);
    }
}

我使用了一个可绑定属性来允许将 TotalItem 列表绑定到用户控件。

这是视图模型中的数据

public List<TotalItem> Totals { get; set; }

Totals = new List<TotalItem>
{
    new TotalItem {Description = "SubTotal", Value = 99.91},
    new TotalItem {Description = "GST", Value = 5.0},
    new TotalItem {Description = "PST", Value = 4.9}
};

这是页面中的 XAML

<userControls:TotalsGridControl Totals="{Binding Totals}"/>

和输出