在WPF MVVM中，此按钮单击如何工作? [英] How does this button click work in WPF MVVM?
问题描述
我开始研究WFM MVVM模式.
I'm starting to study about WFM MVVM pattern.
但是我不明白为什么 Button 单击没有绑定任何事件或动作就可以起作用.
But I can't understand why this Button click works without binding any event or action.
查看
<Window x:Class="WPF2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vm="clr-namespace:WPF2.ViewModel"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<vm:MainWindowViewModel x:Key="MainViewModel" />
</Window.Resources>
<Grid x:Name="LayoutRoot"
DataContext="{Binding Source={StaticResource MainViewModel}}">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,7,0,0" Name="txtID" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=ListViewProducts,Path=SelectedItem.ProductId}" />
<TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,35,0,0" Name="txtName" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=ListViewProducts,Path=SelectedItem.Name}" />
<TextBox Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="80,61,0,0" Name="txtPrice" VerticalAlignment="Top" Width="178" Text="{Binding ElementName=ListViewProducts,Path=SelectedItem.Price}" />
<Label Content="ID" Grid.Row="1" HorizontalAlignment="Left" Margin="12,12,0,274" Name="label1" />
<Label Content="Price" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,59,0,0" Name="label2" VerticalAlignment="Top" />
<Label Content="Name" Grid.Row="1" Height="28" HorizontalAlignment="Left" Margin="12,35,0,0" Name="label3" VerticalAlignment="Top" />
<Button Grid.Row="1" HorizontalAlignment="Left" VerticalAlignment="Top" Width="141" Height="23" Margin="310,40,0,0" Content="Update" />
<ListView Name="ListViewProducts" Grid.Row="1" Margin="4,109,12,23" ItemsSource="{Binding Path=Products}" >
<ListView.View>
<GridView x:Name="grdTest">
<GridViewColumn Header="Product ID" DisplayMemberBinding="{Binding ProductId}" Width="100"/>
<GridViewColumn Header="Name" DisplayMemberBinding="{Binding Name}" Width="250" />
<GridViewColumn Header="Price" DisplayMemberBinding="{Binding Price}" Width="127" />
</GridView>
</ListView.View>
</ListView>
</Grid>
</Window>
ViewModel
class MainWindowViewModel : INotifyPropertyChanged
{
public const string ProductsPropertyName = "Products";
private ObservableCollection<Product> _products;
public ObservableCollection<Product> Products
{
get
{
return _products;
}
set
{
if (_products == value)
{
return;
}
_products = value;
RaisePropertyChanged(ProductsPropertyName);
}
}
public MainWindowViewModel()
{
_products = new ObservableCollection<Product>
{
new Product {ProductId=1, Name="Pro1", Price=11},
new Product {ProductId=2, Name="Pro2", Price=12},
new Product {ProductId=3, Name="Pro3", Price=13},
new Product {ProductId=4, Name="Pro4", Price=14},
new Product {ProductId=5, Name="Pro5", Price=15}
};
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
我从我阅读的教程中找到了这段代码.当我单击列表视图中的一行时，将设置文本框值.当我编辑这些值并单击一个按钮时，列表视图上的值将更新.
I found this code from a tutorial i've read. When i click on a row from listview, the textbox values are set. And when I edit those values and click a button, the values on listview are updated.
按钮上没有事件或命令.那么如何单击按钮以更新列表视图中的值?
There is no event nor command bound on the button. So how do button click update the values from listview??
推荐答案
我知道这很旧，但是我正在研究这种情况并找到了答案.首先，在MVVM理论中，隐藏代码"不应该包含代码，所有代码都应位于ViewModel类中.因此，为了实现按钮单击，您需要在ViewModel中包含以下代码(除了INotifyPropertyChanged实现之外):
I know this is old but I was looking into this scenario and found my answer. First, in MVVM theory the "code-behind" shouldn't have code all the code should be in the ViewModel class. So in order to implement button click, you have this code in the ViewModel (besides the INotifyPropertyChanged implementation):
public ICommand ButtonCommand { get; set; }
public MainWindowViewModel()
{
ButtonCommand = new RelayCommand(o => MainButtonClick("MainButton"));
}
private void MainButtonClick(object sender)
{
MessageBox.Show(sender.ToString());
}
使用课程:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
namespace <your namespace>.ViewModels
{
public class RelayCommand : ICommand
{
private readonly Action<object> _execute;
private readonly Predicate<object> _canExecute;
public RelayCommand(Action<object> execute, Predicate<object> canExecute = null)
{
if (execute == null) throw new ArgumentNullException("execute");
_execute = execute;
_canExecute = canExecute;
}
public bool CanExecute(object parameter)
{
return _canExecute == null || _canExecute(parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameter)
{
_execute(parameter ?? "<N/A>");
}
}
}
在XAML中:
<Window.DataContext>
<viewModels:MainWindowViewModel />
</Window.DataContext> <Button Content="Button" Command="{Binding ButtonCommand}" />
这篇关于在WPF MVVM中，此按钮单击如何工作?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
