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在 mvvm 应用程序中导航后，子 ViewModel 中的命令不起作用

[英]commands in the child ViewModel not working after navigation in mvvm app

 原文  2023-01-23 20:07:01  9   1    wpf/ mvvm/ navigation/ command/ viewmodel

问题描述

我在桌面上工作 wpf MVVM 应用程序包含一个 MainWindow，其中包含为不同的 UserControls 进行导航的内容控件。 MainWindow 中 MainViewModel 的命令运行良好。 但导航 ViewModel 的命令不起作用。 app.cs 的代码：navigationStore 是导航 viewModel 的商店

public partial class App : Application
{

    protected override void OnStartup(StartupEventArgs e)
    {
        NavigationStore navigationStore = new NavigationStore();

        navigationStore.CurrentViewModel = new MainBackGroundVM();

        MainWindow = new MainWindow()
        {
            ///inistiation of the main with passing the CurrentViewModel to the mainVM
            DataContext = new MainVM(navigationStore)
        };
         MainWindow.Show();
        base.OnStartup(e);
    }
}

MainVM NavigateUsersCommand 的代码运行良好并为 usersVM 导航

class MainVM :Utilities.ViewModelBase
{


    private readonly NavigationStore _navigationStore;

    public ViewModelBase CurrentViewModel => _navigationStore.CurrentViewModel;

    public ICommand NavigateUsersCommand { get; }

    public MainVM(NavigationStore navigationStore)
    {
        _navigationStore = navigationStore;

        _navigationStore.CurrentViewModelChanged += _navigationStore_CurrentViewModelChanged;
        
        NavigateUsersCommand = new NavigateUsersCommand(navigationStore);            

 }

    private void _navigationStore_CurrentViewModelChanged()
    {
        OnPropertyChanged(nameof(CurrentViewModel));
    }
}

MainWindow.xml 的代码

<Window x:Class="Yakout.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:fa="http://schemas.fontawesome.io/icons/"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:vm="clr-namespace:Yakout.ViewModels"
    xmlns:v="clr-namespace:Yakout.Views"
    xmlns:local="clr-namespace:Yakout"
    mc:Ignorable="d"
    Title="MainWindow" Height="700" Width="1100" Background="Transparent" AllowsTransparency="True" WindowStartupLocation="CenterScreen" WindowStyle="None" ResizeMode="NoResize" >
<Window.DataContext>
    <vm:NavigationVM></vm:NavigationVM>
</Window.DataContext>
<Border  BorderThickness="2" BorderBrush="BlueViolet" Background="White">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="3*"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="5*"/>
        </Grid.RowDefinitions>
        <Button Style="{StaticResource btnCircle}" Grid.Column="1" Click="Button_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="Close" Grid.Column="1" Style="{StaticResource close}"/>
            </StackPanel >
        </Button>
        <Border Grid.Row="1" Background="BlueViolet" >
            <StackPanel >
                <Button Style="{StaticResource btnMainMenu}" Name="btnPOS" 
                        Command="{Binding NavigatePosCommand}">
                    <StackPanel Style="{StaticResource stack}" Orientation="Horizontal">
                        <fa:ImageAwesome Icon="ShoppingCart" Style="{StaticResource faMainMenu}" Margin="40 0 0 0"/>
                        <TextBlock Text="Point Of Sale" Style="{StaticResource tbMainMenu}" Margin="30 10 0 0"/>
                    </StackPanel>
                </Button>
                <Button Style="{StaticResource btnMainMenu}" Name="btnSetUp" Command="{Binding NavigateUsersCommand}">
                    <StackPanel Style="{StaticResource stack}" Orientation="Horizontal" >
                        <fa:ImageAwesome Icon="Key" Style="{StaticResource faMainMenu}"/>
                        <TextBlock Text="Set Up" Style="{StaticResource tbMainMenu}"/>
                    </StackPanel>
                </Button>

                <Button Style="{StaticResource btnMainMenu}" Name="btnReports" 
                        Command="{Binding NavigateUsersSelectCommand}">
                    <StackPanel Style="{StaticResource stack}" Orientation="Horizontal">
                        <fa:ImageAwesome Icon="PencilSquare" Style="{StaticResource faMainMenu}"/>
                        <TextBlock Text="Reports" Style="{StaticResource tbMainMenu}"/>
                    </StackPanel>
                </Button>
                <Button Style="{StaticResource btnMainMenu}" Name="btnOptions"
                        Command="{Binding NavigateMainBackGroundCommand}" >
                    <StackPanel Style="{StaticResource stack}" Orientation="Horizontal">
                        <fa:ImageAwesome Icon="HandPaperOutline" Style="{StaticResource faMainMenu}"/>
                        <TextBlock Text="Options" Style="{StaticResource tbMainMenu}"/>
                    </StackPanel>
                </Button>
                <Button Name="btnLogOut" Style="{StaticResource btnMainMenu}" Margin="5 212 5 0" Click="btnLogOut_Click">
                    <StackPanel Style="{StaticResource stack}" Orientation="Horizontal">
                        <fa:ImageAwesome Icon="CircleOutlineNotch" Style="{StaticResource faMainMenu}"/>
                        <TextBlock Text="Log Out" Style="{StaticResource tbMainMenu}"/>
                    </StackPanel>
                </Button>
            </StackPanel>
        </Border>
        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="auto"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>
            <Image Source="/image/R.png"/>
            <StackPanel Orientation="Vertical" Grid.Column="1">
                <TextBlock Text="Yakout POS" Margin="5 10 5 5" FontSize="25" FontWeight="Bold" HorizontalAlignment="Center"/>
                <TextBlock Text="1.0.0.1" FontSize="15" FontWeight="Bold" HorizontalAlignment="Center"/>
                <TextBlock Text="Yakout Company" FontSize="15" Foreground="DodgerBlue" FontWeight="Bold" HorizontalAlignment="Center" TextDecorations="Underline"/>
            </StackPanel>
        </Grid>
        <Border Grid.Column="1" Background="BlueViolet">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*"/>
                    <ColumnDefinition Width="auto"/>
                </Grid.ColumnDefinitions>
                <Canvas>
                    <Label x:Name="lbl" FontSize="15" Foreground="White" Canvas.Top="10" Canvas.Right="20" Content="{Binding MyTimer}"/>
                    <TextBlock Text="Point Of Sale" Canvas.Left="250" FontSize="30" Foreground="White" VerticalAlignment="Center" HorizontalAlignment="Center" Margin="0 25 0 0"/>
                    <Ellipse Width="40" Height="40" Fill="DarkViolet" Canvas.Left="150" Canvas.Top="20" StrokeThickness="10"/>
                    <Ellipse Width="40" Height="40" Fill="DarkViolet" Canvas.Right="230" Canvas.Top="20" StrokeThickness="10"/>
                </Canvas>
            </Grid>
        </Border>
        <Rectangle Stroke="BlueViolet" StrokeThickness="3" Grid.Column="0" Grid.Row="0"/>
        <ContentControl Content="{Binding CurrentViewModel}" Grid.Row="1" Grid.Column="1" >
        </ContentControl>
        <!--CurrentView-->
    </Grid>
</Border>

导航 ViewModel 的代码，它的名称 UsersVM

NavigateUsersSelectCommand 导航到新视图和 NavigateMainBackGroundCommand 导航回 MainBackGroundView 两个命令都不起作用

class UsersVM : Utilities.ViewModelBase
{
    public ICommand NavigateUsersSelectCommand { get; }

    public ICommand NavigateMainBackGroundCommand { get; }

    public UsersVM(NavigationStore navigationStore,SelectedUserStore selectedUserStore)
    {
        _navigationStore = navigationStore;
      
        NavigateMainBackGroundCommand = new NavigateCommand<MainBackGroundVM>(new NavigationService<MainBackGroundVM>(navigationStore, () => new MainBackGroundVM()));

        NavigateUsersSelectCommand = new NavigateCommand<UserSelectVM>(new NavigationService<UserSelectVM>(navigationStore, () => new UserSelectVM(_navigationStore)));

    }


}

用户查看的 xaml 代码

<UserControl x:Class="Yakout.Views.Users"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:fa="http://schemas.fontawesome.io/icons/"
         xmlns:local="clr-namespace:Yakout.Views"
         mc:Ignorable="d" 
         d:DesignHeight="450" d:DesignWidth="800" Style="{StaticResource user}"
         >
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="auto"/>
        <RowDefinition Height="*"/>
    </Grid.RowDefinitions>
    <!--Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.NavigateUsersSelectCommand}">-->

    <StackPanel Orientation="Horizontal">
        <Button x:Name="select" Style="{StaticResource btnUsers}"
                Command="{Binding NavigateUsersSelectCommand}">
            <StackPanel>
                <fa:ImageAwesome Icon="HandPointerOutline"  Style="{StaticResource fa}"/>
                <TextBlock Text="Select" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="new" Style="{StaticResource btnUsers}" Click="new_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="NewspaperOutline"  Style="{StaticResource fa}"/>
                <TextBlock Text="New" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="save" Style="{StaticResource btnUsers}" Click="save_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="Save"  Style="{StaticResource fa}"/>
                <TextBlock Text="Save" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="first" Style="{StaticResource btnUsers}" Click="first_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="FastBackward"  Style="{StaticResource fa}"/>
                <TextBlock Text="First" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="back" Style="{StaticResource btnUsers}" Click="back_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="Backward"  Style="{StaticResource fa}"/>
                <TextBlock Text="Back" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="next" Style="{StaticResource btnUsers}" Click="next_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="Forward"  Style="{StaticResource fa}"/>
                <TextBlock Text="Next" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>
        <Button x:Name="last" Style="{StaticResource btnUsers}" Click="last_Click">
            <StackPanel>
                <fa:ImageAwesome Icon="FastForward"  Style="{StaticResource fa}"/>
                <TextBlock Text="Last" Style="{StaticResource btnText}"/>
            </StackPanel>
        </Button>

    </StackPanel>
    <Grid Grid.Row="1">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="1*"/>
            <ColumnDefinition Width="3*"/>
            <ColumnDefinition Width="1*"/>
        </Grid.ColumnDefinitions>
        <StackPanel>
            <Label Content="User Name" Style="{StaticResource  labelUsers}"/>
            <Label Content="Password" Style="{StaticResource  labelUsers}"/>
            <Label Content="Full Name" Style="{StaticResource  labelUsers}"/>
            <Label Content="Job Des" Style="{StaticResource  labelUsers}"/>
            <Label Content="Email" Style="{StaticResource  labelUsers}"/>
            <Label Content="Phone" Style="{StaticResource  labelUsers}"/>

        </StackPanel>
        <StackPanel Grid.Column="1">
            <TextBox Name="tx1" Style="{StaticResource box}" Text="{Binding Path=UserName,Mode=OneWay}"/>
            <TextBox Name="tx2" Style="{StaticResource box}" Text="{Binding Path=Password,Mode=OneWay}"/>
            <TextBox Name="tx3" Style="{StaticResource box}" Text="{Binding Path=FullName,Mode=OneWay }"/>
            <TextBox Name="tx4" Style="{StaticResource box}" Text="{Binding Path=JobDes,Mode=OneWay}"/>
            <TextBox Name="tx5" Style="{StaticResource box}" Text="{Binding Path=Email,Mode=OneWay }"/>
            <TextBox Name="tx6" Style="{StaticResource box}" Text="{Binding Path=Phone,Mode=OneWay }"/>
        </StackPanel>
        <Canvas Grid.Column="2">
            <Button  x:Name="btnBack" Style="{StaticResource btnPages}"
                     Canvas.Right="5" Canvas.Bottom="5"
                     Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.NavigateMainBackGroundCommand}">
                <StackPanel>
                    <fa:ImageAwesome Icon="Backward" Style="{StaticResource faPagesBack}"/>
                    <TextBlock Text="Back" Style="{StaticResource tbPagesBack}"/>
                </StackPanel>
            </Button>
        </Canvas>
    </Grid>
</Grid>

mainBackGroundView 的 xaml 代码

<UserControl x:Class="Yakout.Views.MainBackGround"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:Yakout.Views"
         mc:Ignorable="d" 
         d:DesignHeight="450" d:DesignWidth="800">
<Grid>
    <Image Source="/image/kkk.jpg" Stretch="Fill"/>
</Grid>

应用程序的数据模板

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:vm="clr-namespace:Yakout.ViewModels"
                xmlns:view="clr-namespace:Yakout.Views">



<DataTemplate DataType="{x:Type vm:OptionsVM}">
    <view:Options/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:MainBackGroundVM}">
    <view:MainBackGround/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:SetUpVM}">
    <view:SetUP/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:PosVM}">
    <view:Pos/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:ReportsVM}">
    <view:Reports/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:UsersVM}">
    <view:Users/>
</DataTemplate>

<DataTemplate DataType="{x:Type vm:UserSelectVM}">
    <view:UserSelect/>
</DataTemplate>

app.xml 的代码

<Application x:Class="Yakout.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:local="clr-namespace:Yakout"
         >

<Application.Resources>

        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="Styles/StylesMainWindow.xaml" />
                <ResourceDictionary Source="Styles/StylesMain.xaml" />
                <ResourceDictionary Source="Styles/StylesUcOptions.xaml" />
                <ResourceDictionary Source="/Utilities/DataTemplate.xaml"/>
                <ResourceDictionary Source="/Styles/StylesUsers.xaml"/>
                <ResourceDictionary Source="/Styles/StylesUserSelect.xaml"/>
        </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>


</Application.Resources>

导航服务

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Yakout.Stores;

namespace Yakout.Utilities
{
    class NavigationService<TViewModel> 
        where TViewModel:ViewModelBase
    {
        private readonly NavigationStore _navigationStore;

        private readonly Func<TViewModel> _CreateViewModel;

        public NavigationService(NavigationStore navigationStore,Func<TViewModel>CreateViewModel)
        {
            _navigationStore = navigationStore;
            _CreateViewModel = CreateViewModel;
        }
        public void Navigate()
        {
            _navigationStore.CurrentViewModel = _CreateViewModel();
        }
    }
}

参数导航服务

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Yakout.Stores;

namespace Yakout.Utilities
{
    class ParameterNavigationService<TParameter, TViewModel>
        where TViewModel:ViewModelBase
    {
        private readonly NavigationStore _navigationStore;
        private readonly Func<TParameter,TViewModel> _createVM;

        public ParameterNavigationService(NavigationStore navigationStore, Func<TParameter, TViewModel> createVM)
        {
            _navigationStore = navigationStore;
            _createVM= createVM;

        }

        public void Navigate(TParameter parameter)
        {
            _navigationStore.CurrentViewModel = _createVM(parameter);
        }
    }
}

NavigateMainBackGroundCommand

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Navigation;
using Yakout.Stores;
using Yakout.Utilities;
using Yakout.ViewModels;

namespace Yakout.Commands
{
    class NavigateMainBackGroundCommand : Utilities.CommandBase
    {
        /// <summary>
        /// حاليا مفيش احتياج لاوامر دي 
        /// </summary>

        private readonly NavigationService<MainBackGroundVM> _navigationService;

        private readonly MainBackGroundVM _mainBackGroundVM;

        public NavigateMainBackGroundCommand(MainBackGroundVM mainBackGroundVM,  NavigationService<MainBackGroundVM>  navigationService)
        {
            _navigationService = navigationService;
            _mainBackGroundVM = mainBackGroundVM;
        }

        public override void Execute(object parameter)
        {
            _navigationService.Navigate();
        }
    }
}

导航用户命令

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using Yakout.Stores;
using Yakout.ViewModels;

namespace Yakout.Commands
{
    class NavigateUsersCommand : Utilities.CommandBase
    {
        private readonly NavigationStore _navigationStore;

        private readonly SelectedUserStore _selectedUserStore;

        public NavigateUsersCommand(NavigationStore navigationStore, SelectedUserStore selectedUserStore)
        {
            _navigationStore = navigationStore;
            _selectedUserStore = selectedUserStore;
        }

        public override void Execute(object parameter)
        {
            _navigationStore.CurrentViewModel = new UsersVM(_navigationStore,_selectedUserStore);
        }
    }
}

这是我在 GitHub github.com/amryakout1990/Yakout.git 上的代码，我想解决我的问题

1 个解决方案

解决方案1
 0  2023-01-24 11:26:51

查看您认为的这些命令之一：

    <Button x:Name="select" Style="{StaticResource btnUsers}"
            Command="{Binding NavigateUsersSelectCommand}">

在视图模型中：

  NavigateUsersSelectCommand = new NavigateCommand<UserSelectVM>(new NavigationService<UserSelectVM>(navigationStore, () => new UserSelectVM(_navigationStore)));

这需要一个 UserSelectVM 类型的命令参数。

你没有通过它，因为你在 xaml 中没有定义命令参数。

它甚至绑定吗？ 我还以为你的 xaml 错误 window in vs2022 或 output window 会出错。

我想这是您想要的选定用户，因此您可以创建命令参数 selecteditem 或者您可以绑定 selecteditem 并在您那里的匿名方法中引用它。

但这就是该命令不起作用的原因。

我没有查看其他命令，因为要查看的代码非常多。 我建议你先解决那个问题，看看你是否重复出现类似的问题。

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