我有一个简单的WPF应用程序，它有一个数据网格。我想要的是单击按钮后选择并设置焦点数据网格行。选择该行后，我需要使用键盘向上/向下箭头键更改所选(焦点(行。最无能为力的是，我想在 MVVM 设计模式中做到这一点。我的申请如下。
Item.cs模型如下：
public class Item
{
public string ItemCode { get; set; }
public string ItemName { get; set; }
public double ItemPrice { get; set; }
public Item(string itemCode, string itemName, double itemPrice)
{
this.ItemCode = itemCode;
this.ItemName = itemName;
this.ItemPrice = itemPrice;
}
}
ItemViewModel.cs如下：
public class ItemsViewModel : INotifyPropertyChanged
{
private List<Item> _items;
public List<Item> ItemsCollection
{
get { return this._items; }
set
{
_items = value;
OnPropertyChanged(nameof(ItemsCollection));
}
}
public ItemsViewModel()
{
this.ItemsCollection = new List<Item>();
//Add default items
this.ItemsCollection.Add(new Item("I001", "Text Book", 10));
this.ItemsCollection.Add(new Item("I002", "Pencil", 20));
this.ItemsCollection.Add(new Item("I003", "Bag", 15));
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
MainWindowViewModel.cs如下：
public class MainWindowViewModel : INotifyPropertyChanged
{
public ICommand SelectRow { get; private set; }
public MainWindowViewModel()
{
this.SelectRow = new RelayCommand(this.SelectGridRow, o => true);
}
private void SelectGridRow(object param)
{
//TODO: Code should goes here
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
我编写了以下RelayCommand.cs来处理命令绑定。
public class RelayCommand : ICommand
{
#region Fields
/// <summary>
/// Encapsulated the execute action
/// </summary>
private Action<object> execute;
/// <summary>
/// Encapsulated the representation for the validation of the execute method
/// </summary>
private Predicate<object> canExecute;
#endregion // Fields
#region Constructors
/// <summary>
/// Initializes a new instance of the RelayCommand class
/// Creates a new command that can always execute.
/// </summary>
/// <param name="execute">The execution logic.</param>
public RelayCommand(Action<object> execute)
: this(execute, DefaultCanExecute)
{
}
/// <summary>
/// Initializes a new instance of the RelayCommand class
/// Creates a new command.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <param name="canExecute">The execution status logic.</param>
public RelayCommand(Action<object> execute, Predicate<object> canExecute)
{
if (execute == null)
{
throw new ArgumentNullException("execute");
}
if (canExecute == null)
{
throw new ArgumentNullException("canExecute");
}
this.execute = execute;
this.canExecute = canExecute;
}
#endregion // Constructors
#region ICommand Members
/// <summary>
/// An event to raise when the CanExecute value is changed
/// </summary>
/// <remarks>
/// Any subscription to this event will automatically subscribe to both
/// the local OnCanExecuteChanged method AND
/// the CommandManager RequerySuggested event
/// </remarks>
public event EventHandler CanExecuteChanged
{
add
{
CommandManager.RequerySuggested += value;
this.CanExecuteChangedInternal += value;
}
remove
{
CommandManager.RequerySuggested -= value;
this.CanExecuteChangedInternal -= value;
}
}
/// <summary>
/// An event to allow the CanExecuteChanged event to be raised manually
/// </summary>
private event EventHandler CanExecuteChangedInternal;
/// <summary>
/// Defines if command can be executed
/// </summary>
/// <param name="parameter">the parameter that represents the validation method</param>
/// <returns>true if the command can be executed</returns>
public bool CanExecute(object parameter)
{
return this.canExecute != null && this.canExecute(parameter);
}
/// <summary>
/// Execute the encapsulated command
/// </summary>
/// <param name="parameter">the parameter that represents the execution method</param>
public void Execute(object parameter)
{
this.execute(parameter);
}
#endregion // ICommand Members
/// <summary>
/// Raises the can execute changed.
/// </summary>
public void OnCanExecuteChanged()
{
EventHandler handler = this.CanExecuteChangedInternal;
if (handler != null)
{
//DispatcherHelper.BeginInvokeOnUIThread(() => handler.Invoke(this, EventArgs.Empty));
handler.Invoke(this, EventArgs.Empty);
}
}
/// <summary>
/// Destroys this instance.
/// </summary>
public void Destroy()
{
this.canExecute = _ => false;
this.execute = _ => { return; };
}
/// <summary>
/// Defines if command can be executed (default behaviour)
/// </summary>
/// <param name="parameter">The parameter.</param>
/// <returns>Always true</returns>
private static bool DefaultCanExecute(object parameter)
{
return true;
}
}
我有一个ItemView.xaml用户控件，如下所示：
<UserControl x:Class="DataGrid_FocusRow.ItemView"
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:DataGrid_FocusRow"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<StackPanel Orientation="Vertical">
<DataGrid x:Name="grdItems" ItemsSource="{Binding ItemsCollection}" AutoGenerateColumns="False" ColumnWidth="*">
<DataGrid.Columns>
<DataGridTextColumn Header="Item Code" Binding="{Binding ItemCode}" />
<DataGridTextColumn Header="Item Name" Binding="{Binding ItemName}" />
<DataGridTextColumn Header="Item Price" Binding="{Binding ItemPrice}" />
</DataGrid.Columns>
</DataGrid>
</StackPanel>
</Grid>
我MainWindow.xaml如下：
<Window x:Class="DataGrid_FocusRow.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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:DataGrid_FocusRow"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<StackPanel>
<local:ItemView/>
<Button Command="{Binding SelectRow}">Select Row</Button>
</StackPanel>
有人可以帮我解决这个问题吗？
更新：我已经尝试过设置"选定索引"和"选定项"。它选择数据网格中的行。但它不会将焦点设置为特定行。因此，我无法通过键盘中的向上/向下键更改选择。
我找到了一种方法。 我在以下类中处理了行选择SelectingItemAttachedProperty.cs
public class SelectingItemAttachedProperty
{
public static readonly DependencyProperty SelectingItemProperty = DependencyProperty.RegisterAttached("SelectingItem", typeof(Item), typeof(SelectingItemAttachedProperty), new PropertyMetadata(default(Item), OnSelectingItemChanged));
public static Item GetSelectingItem(DependencyObject target)
{
return (Item)target.GetValue(SelectingItemProperty);
}
public static void SetSelectingItem(DependencyObject target, Item value)
{
target.SetValue(SelectingItemProperty, value);
}
static void OnSelectingItemChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
var grid = sender as DataGrid;
if (grid == null || grid.SelectedItem == null)
return;
grid.Dispatcher.InvokeAsync(() =>
{
grid.UpdateLayout();
grid.ScrollIntoView(grid.SelectedItem, null);
var row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromIndex(grid.SelectedIndex);
row.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
});
}
}
在ItemView.xaml用户控件中，我添加按钮并设置我们在上面实现的SelectingItemAttachedProperty，如下所示。
<UserControl x:Class="DataGrid_FocusRow.ItemView"
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:DataGrid_FocusRow"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid>
<StackPanel Orientation="Vertical">
<DataGrid x:Name="grdItems" ItemsSource="{Binding ItemsCollection}" AutoGenerateColumns="False" ColumnWidth="*"
SelectedItem="{Binding SelectingItem}" local:SelectingItemAttachedProperty.SelectingItem="{Binding SelectingItem}">
<DataGrid.Columns>
<DataGridTextColumn Header="Item Code" Binding="{Binding ItemCode}" />
<DataGridTextColumn Header="Item Name" Binding="{Binding ItemName}" />
<DataGridTextColumn Header="Item Price" Binding="{Binding ItemPrice}" />
</DataGrid.Columns>
</DataGrid>
<Button Command="{Binding SelectRow}">Select Row</Button>
</StackPanel>
</Grid>
</UserControl>
然后我在视图模型中SelectGridRow()方法中设置所选项目，如下所示
public class ItemsViewModel : INotifyPropertyChanged
{
private Item _selectingItem;
private List<Item> _items;
public Item SelectingItem
{
get { return this._selectingItem; }
set
{
this._selectingItem = value;
OnPropertyChanged(nameof(this.SelectingItem));
}
}
public List<Item> ItemsCollection
{
get { return this._items; }
set
{
_items = value;
OnPropertyChanged(nameof(ItemsCollection));
}
}
public ICommand SelectRow { get; private set; }
public ItemsViewModel()
{
this.ItemsCollection = new List<Item>();
//Add default items
this.ItemsCollection.Add(new Item("I001", "Text Book", 10));
this.ItemsCollection.Add(new Item("I002", "Pencil", 20));
this.ItemsCollection.Add(new Item("I003", "Bag", 15));
this.SelectRow = new RelayCommand(this.SelectGridRow, o => true);
}
private void SelectGridRow(object param)
{
this.SelectingItem = this.ItemsCollection[0];
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}