将 IsChecked 属性与 xamarin MVVM 中的单选按钮组绑定

Question

我正在寻找一种通过单选按钮控制标签文本的方法。我已经阅读了本网站以及其他网站上的类似问题，但无法找到可行的解决方案。我尝试使用转换器以及将单选按钮放入列表中。当我通过调试器运行代码时，视图模型中的单选按钮代码永远不会到达。任何帮助，将不胜感激。 这是我的视图的代码：

    <?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="sampleRadioButtons.Views.ButtonPage"
                 xmlns:vm="clr-namespace:sampleRadioButtons.ViewModels">
    
    
            <ContentPage.BindingContext>
                <vm:MainPageViewModel/>
            </ContentPage.BindingContext>
                     
            <ContentPage.Content>
                <StackLayout VerticalOptions="Center">
                    <StackLayout Orientation="Horizontal" RadioButtonGroup.GroupName="time">
                        <RadioButton Content="One Year" IsChecked="{Binding YearChecked, Mode=TwoWay}"/>
                        <RadioButton Content="One Month" IsChecked="{Binding MonthChecked, Mode=TwoWay}"/>
                        <RadioButton Content="One Week" IsChecked="{Binding WeekChecked, Mode=TwoWay}"/>
                    </StackLayout>
                    <Label Text="Total is"/>
                    <Label Text="{Binding Total}"/>
                </StackLayout>
            </ContentPage.Content>
        </ContentPage>

这是我对应的视图模型：

            using System;
            using System.ComponentModel;
            using System.Runtime.CompilerServices;
            
            namespace sampleRadioButtons.ViewModels
            {
                public class MainPageViewModel : INotifyPropertyChanged
                {
                    public MainPageViewModel()
                    {
                        total = GetTotal();
                    }
                    public void OnPropertyChange([CallerMemberName] string name = "")
                    {
                        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
                    }
            
                    #region INotifyPropertyChanged
                    public event PropertyChangedEventHandler PropertyChanged;
                    protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
                    {
                        var changed = PropertyChanged;
                        if (changed == null)
                            return;
            
                        changed.Invoke(this, new PropertyChangedEventArgs(propertyName));
                    }
                    #endregion
                    private string total;
                    public string Total
                    {
                        get { return total; }
                        set
                        {
                            total = value;
                            OnPropertyChanged();
                        }
                    }
            
                    private bool yearChecked;
                    public bool YearChecked
                    {
                        get { return yearChecked; }
                        set
                        {
                            yearChecked = value;
                            OnPropertyChange();
                        }
                    }
                    private bool monthChecked;
                    public bool MonthChecked
                    {
                        get { return monthChecked; }
                        set
                        {
                            monthChecked = value;
                            OnPropertyChange();
                        }
                    }
                    private bool weekChecked;
                    public bool WeekChecked
                    {
                        get { return weekChecked; }
                        set
                        {
                            weekChecked = value;
                            OnPropertyChange();
                        }
                    }
                    public string GetTotal()
                    {
                        if(YearChecked == true) { return "$10"; }
                        if(monthChecked == true) { return "$20"; }
                        if(weekChecked == true) { return "30"; }
                        else { return "$50"; }
                    }
                }
            }

Answer 1

在您的构造函数中，您正在设置支持字段而不是属性，将 total 替换为 Total

public MainPageViewModel()
{
Total = GetTotal();
}

您不仅应该在构造函数上调用GetTotal()，而且在三个属性之一发生更改时调用：

                    private bool yearChecked;
                    public bool YearChecked
                    {
                        get { return yearChecked; }
                        set
                        {
                            yearChecked = value;
                            OnPropertyChange();
                            Total = GetTotal();
                        }
                    }
                    private bool monthChecked;
                    public bool MonthChecked
                    {
                        get { return monthChecked; }
                        set
                        {
                            monthChecked = value;
                            OnPropertyChange();
                            Total = GetTotal();
                        }
                    }
                    private bool weekChecked;
                    public bool WeekChecked
                    {
                        get { return weekChecked; }
                        set
                        {
                            weekChecked = value;
                            OnPropertyChange();
                            Total = GetTotal();
                        }
                    }

• 此外，在您的 GetTotal() 中，您应该在 if 条件而不是它们的支持字段中使用属性：MonthChecked 而不是 monthChecked 和 WeekChecked 而不是 weekChecked 。

https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/auto-implemented-properties