简单按钮命令不会触发-谁能看到错误？

问题描述

我看不到我在哪里做错。通常，我已经正确实现了所有内容，以便在Xamarin.Forms AppShell项目中使用button命令，但是不会触发按钮。也许有人可以看到问题？

虽然按钮的页面/视图是孩子，但我不知道它是否相关。我从这样的父视图中使用TabBar导航到它：

AppShell.xaml：

xmlns:local="clr-namespace:LVNGtoGo.Views"

<TabBar>
<ShellContent Title="Home" Icon="home_icon.png" Route="AboutPage" ContentTemplate="{DataTemplate local:AboutPage}" />
<ShellContent Title="B O M" Icon="new_icon.png" Route="NewBomPage" ContentTemplate="{DataTemplate local:NewBomPage}"  />
</TabBar>

具有INotifyPropertyChanged的Baseviewmodel：

public class Baseviewmodel : INotifyPropertyChanged
    {
      
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
        {
            var changed = PropertyChanged;
            if (changed == null)
                return;

            changed.Invoke(this,new PropertyChangedEventArgs(propertyName));
        }
            }

从Baseviewmodel和构造方法继承的viewmodel：

public class NewBomviewmodel : Baseviewmodel
    {
        private string text;
        public ICommand RallyCarCommand { get; }
        

        public NewBomviewmodel()
        {
            RallyCarCommand = new Command(ChooseRallyCar);
        }

        private void ChooseRallyCar()
        {
            text = "Rally Car was chosen!!!";
        }

        public string Text 
        {
            get => text;
            set => SetProperty(ref text,value);
        }
}

具有绑定上下文的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="LVNGtoGo.Views.NewBomPage"
             xmlns:vm="clr-namespace:LVNGtoGo.viewmodels"
             Shell.PresentationMode="ModalAnimated"
             Title="Create new  B O M">

    <ContentPage.BindingContext >
        <vm:NewBomviewmodel />
    </ContentPage.BindingContext>

    <StackLayout Spacing="3" Padding="15" >

        <Label Text="{Binding Text}" VerticalOptions="Center" Margin="20" />
       
        <Button Text="Click me" Command="{Binding RallyCarCommand}" />

    </StackLayout>
</ContentPage>

解决方法

您要设置内部私有字段，而不是公共财产

text = "Rally Car was chosen!!!";

应该是

Text = "Rally Car was chosen!!!";