c# - 从代码中突出显示 ListView 项 - WPF 数据绑定(bind)

Question

我访问过的以前的来源(但没有找到答案):

Highlight Row In WPF

Selected Item Color

Highlighting Items In WPF ListView

Triggers For Styling

Styles For Styling

更密切相关但过于复杂/不完全是我需要的来源。

一般信息:

如标记，此代码位于 c# , 使用 WPF , 带有目标框架 .NET Framework 4.5 .

笔记:
这是我第一次尝试实现 MVVM , 所以 评论 关于我缺少的最佳实践将不胜感激(尽管这是 不是 这个问题的主要主题)。

问题:

带有 ListView 的 WPF和 Button . Button从 ListView 中删除项目.

ListView<String> (View) ---> RemoveStringFromList() (ViewModel)

以上工作。我的问题是 突出显示 .

我希望能够从 ListView 中删除一个字符串，并且在删除后 突出显示不同的项目 .

我最初的想法是通过使用与 SelectedItemProperty 绑定(bind)的属性 ( ListView )的 SelectedItem属性 - 突出显示为 自动 .

但在实践中， SelectedItem属性绑定(bind)有效 - 因为我可以一直按 Button并删除成为 SelectedItem 的项目根据 SelectedItemProperty 中实现的逻辑setter - 但尽管它们是按代码选择的， 它们没有突出显示。

代码:

MainWindow.xaml

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="213.06">
    <Grid>
        <ListView ItemsSource="{Binding ItemsProperty}" SelectedItem="{Binding SelectedItemProperty}" HorizontalAlignment="Left" Height="214" Margin="35,74,0,0" VerticalAlignment="Top" Width="142">
            <ListView.View>
                <GridView>
                    <GridViewColumn/>
                </GridView>
            </ListView.View>
        </ListView>
        <Button Command="{Binding RemoveString}" Content="Remove From List!" HorizontalAlignment="Left" Margin="35,10,0,0" VerticalAlignment="Top" Width="142" Height="46"/>

    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        private readonly MainWindowViewModel _viewModel;

        public MainWindow()
        {
            InitializeComponent();
            _viewModel = new MainWindowViewModel();
            DataContext = _viewModel;
            Show();
        }
    }
}

MainWindowViewModel.cs

using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows.Input;

namespace WpfApplication1
{
    public class MainWindowViewModel : INotifyPropertyChanged
    {
        private ObservableCollection<String> _list;
        private String _selectedItem;

        public MainWindowViewModel()
        {
            _list = new ObservableCollection<String> {"1", "2", "3", "4"};
            RemoveString = new RemoveStringCommand(this);
        }

        public ObservableCollection<String> ItemsProperty
        {
            get { return _list; }
        }

        public String SelectedItemProperty
        {
            get { return _selectedItem; }
            set
            {
                if (value != null)
                {
                    _selectedItem = value;
                }
                else
                {
                    if (_list.Count > 0)
                    {
                        _selectedItem = _list[0];
                    }
                }
            }
        }

        public ICommand RemoveString
        {
            get;
            private set;
        }

        public bool CanRemoveString
        {
            get { return _list.Count > 0; }
        }

        public void RemoveStringFromList()
        {
            if (SelectedItemProperty != null)
            {
                _list.Remove(SelectedItemProperty);
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected void RaisePropertyChanged(String propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }


    }
}

RemoveStringCommand.cs

using System.Windows.Input;
using WpfApplication1;

namespace WpfApplication1
{
    class RemoveStringCommand : ICommand
    {
        private MainWindowViewModel _viewModel;

        public RemoveStringCommand(MainWindowViewModel viewModel)
        {
            _viewModel = viewModel;
        }

        public event System.EventHandler CanExecuteChanged
        {
            add { CommandManager.RequerySuggested += value; }
            remove { CommandManager.RequerySuggested -= value; }
        }

        public bool CanExecute(object parameter)
        {
            return _viewModel.CanRemoveString;
        }

        public void Execute(object parameter)
        {
            _viewModel.RemoveStringFromList();
        }
    }
}

应用图片 - 首次点击前



应用程序图片 - 单击 1 次后(注意 - 无突出显示!)



应用程序图像 - 单击 2 次后(仍然没有突出显示...)

Answer 1

首先删除一个错误

public MainWindow()
{
    InitializeComponent();
    _viewModel = new MainWindowViewModel();
    DataContext = _viewModel;
    // Show(); remove this, it's not needed
}

我用两个可重用的辅助类做了一个例子。

1) 第一个公共(public)类实现 INotifyPropertyChanged .在每个 ViewModel 类中重复 INPC 实现可能会有所帮助。

public class NotifyPropertyChanged : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = null)
        => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

[CallerMemberName]这里允许不包括属性名称到每个 OnPropertyChanged()称呼。编译器会自动完成。

2) 便于命令使用的类。 (抢到 here)

public class RelayCommand : ICommand
{
    private readonly Action<object> _execute;
    private readonly Func<object, bool> _canExecute;

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public RelayCommand(Action<object> execute, Func<object, bool> canExecute = null)
    {
        _execute = execute;
        _canExecute = canExecute;
    }

    public bool CanExecute(object parameter) => _canExecute == null || _canExecute(parameter);
    public void Execute(object parameter) => _execute(parameter);
}

3)在以下示例中，我根据您的要求更改了属性名称。不要命名属性，例如 SomethingProperty为避免与依赖属性冲突，此命名模式仅对 DP 有用。

标记:

<Grid>
    <ListView ItemsSource="{Binding ItemsList}" SelectedIndex="{Binding SelectedItemIndex}" HorizontalAlignment="Left" Height="214" Margin="35,74,0,0" VerticalAlignment="Top" Width="142">
        <ListView.View>
            <GridView>
                <GridViewColumn/>
            </GridView>
        </ListView.View>
    </ListView>
    <Button Command="{Binding RemoveItem}" Content="Remove From List!" HorizontalAlignment="Left" Margin="35,10,0,0" VerticalAlignment="Top" Width="142" Height="46"/>
</Grid>

4) View 模型:

public class MainWindowViewModel : NotifyPropertyChanged
{
    private ObservableCollection<string> _itemsList;
    private int _selectedItemIndex;
    private ICommand _removeItem;

    public MainWindowViewModel()
    {
        // never interact with fields outside of the property 'set' clause
        // use property name instead of back-end field
        ItemsList = new ObservableCollection<string> { "1", "2", "3", "4" };
    }

    public ObservableCollection<string> ItemsList
    {
        get => _itemsList;
        set
        {
            _itemsList = value;
            OnPropertyChanged(); // Notify UI that property was changed

            //other ways doing the same call
            // OnPropertyChanged("ItemsList");
            // OnPropertyChanged(nameof(ItemsList));
        }
    }

    public int SelectedItemIndex
    {
        get => _selectedItemIndex;
        set
        {
            _selectedItemIndex = value;
            OnPropertyChanged();
        }
    }

    // command will be initialized in "lazy" mode, at a first call.
    public ICommand RemoveItem => _removeItem ?? (_removeItem = new RelayCommand(parameter =>
    {
        ItemsList.RemoveAt(SelectedItemIndex);
    }, 
    // SelectedItemIndex -1 means nothing is selected
    parameter => SelectedItemIndex >=0 && ItemsList.Count > 0));
}

作为奖励，您可以通过编程方式更改 SelectedIndex的 ListView只需将任何值设置为 SelectedItemIndex .

编辑:

抱歉，我忘记在删除后保留选择。修改命令:

public ICommand RemoveItem => _removeItem ?? (_removeItem = new RelayCommand(parameter =>
{
    int index = SelectedItemIndex;
    ItemsList.RemoveAt(index);
    if (ItemsList.Count > 0)
        SelectedItemIndex = (index == ItemsList.Count) ? index - 1 : index;
}, parameter => SelectedItemIndex >= 0 && ItemsList.Count > 0));