[英]Changing View Wpf MVVM
我是WPF和MVVM的初學者,但想通過構建一些小項目來學習它。
我有一個基於Rachel Lim示例的使用Model-View-ViewModel模式的WPF應用程序。 在我的應用程序中,我有2個視圖-EmployeesList和EmployeeDetails。 員工列表存儲在GidView中。
我的主要問題是
基本導航在帶有DataTmplate和ItmCntrol的xaml中:
<Window.Resources>
<DataTemplate DataType="{x:Type local:HomeViewModel}">
<local:HomeView />
</DataTemplate>
<DataTemplate DataType="{x:Type local:EmployeesListViewModel}">
<local:EmployeesListView />
</DataTemplate>
</Window.Resources>
<ItemsControl ItemsSource="{Binding PageViewModels}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Content="{Binding Name}"
Command="{Binding DataContext.ChangePageCommand, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
CommandParameter="{Binding }"
Margin="2,5"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
我也有ApplicationViewModel在哪里視圖列表
public class ApplicationViewModel : ObservableObject
{
#region Fields
private ICommand _changePageCommand;
private IPageViewModel _currentPageViewModel;
private List<IPageViewModel> _pageViewModels;
#endregion
public ApplicationViewModel()
{
// Add available pages
PageViewModels.Add(new HomeViewModel());
PageViewModels.Add(new EmployeesListViewModel());
PageViewModels.Add(new EmployeeDetailsViewModel());
// Set starting page
CurrentPageViewModel = PageViewModels[0];
}
#region Properties / Commands
public ICommand ChangePageCommand
{
get
{
if (_changePageCommand == null)
{
_changePageCommand = new RelayCommand(
p => ChangeViewModel((IPageViewModel)p),
p => p is IPageViewModel);
}
return _changePageCommand;
}
}
public List<IPageViewModel> PageViewModels
{
get
{
if (_pageViewModels == null)
_pageViewModels = new List<IPageViewModel>();
return _pageViewModels;
}
}
public IPageViewModel CurrentPageViewModel
{
get
{
return _currentPageViewModel;
}
set
{
if (_currentPageViewModel != value)
{
_currentPageViewModel = value;
OnPropertyChanged("CurrentPageViewModel");
}
}
}
#endregion
#region Methods
private void ChangeViewModel(IPageViewModel viewModel)
{
if (!PageViewModels.Contains(viewModel))
PageViewModels.Add(viewModel);
CurrentPageViewModel = PageViewModels
.FirstOrDefault(vm => vm == viewModel);
}
#endregion
}
雙擊行時如何更改視圖
首先,您需要為MouseDoubleClick事件添加EventTrigger:
<DataGrid Name="gridEmployees" ItemsSource="{Binding Employees}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDoubleClick">
<local:CustomCommandAction Command="{Binding DoubleClickCommand}" CommandParameter="{Binding ElementName=gridEmployees, Path=SelectedItems[0]}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</DataGrid>
CustomCommandAction是一個類,它繼承自TriggerAction,並用作視圖模型中事件和命令之間的鏈接。 這是代碼:
public sealed class CustomCommandAction : TriggerAction<DependencyObject>
{
public static readonly DependencyProperty CommandParameterProperty =
DependencyProperty.Register("CommandParameter", typeof(object), typeof(CustomCommandAction), null);
public static readonly DependencyProperty CommandProperty = DependencyProperty.Register(
"Command", typeof(ICommand), typeof(CustomCommandAction), null);
public ICommand Command
{
get
{
return (ICommand)this.GetValue(CommandProperty);
}
set
{
this.SetValue(CommandProperty, value);
}
}
public object CommandParameter
{
get
{
return this.GetValue(CommandParameterProperty);
}
set
{
this.SetValue(CommandParameterProperty, value);
}
}
protected override void Invoke(object parameter)
{
if (this.AssociatedObject != null)
{
ICommand command = this.Command;
if (command != null)
{
if (this.CommandParameter != null)
{
if (command.CanExecute(this.CommandParameter))
{
command.Execute(this.CommandParameter);
}
}
else
{
if (command.CanExecute(parameter))
{
command.Execute(parameter);
}
}
}
}
}
}
之后,最簡單的解決方案是在您的命令Execute方法中使用ChangeViewModel方法,例如:
...
_doubleClickCommand = new RelayCommand(OnDoubleClick);
...
private RelayCommand _doubleClickCommand = null;
private ApplicationViewModel _applicationViewModel;
private void OnDoubleClick(object obj)
{
EmployeeDetailsViewModel selectedModel = obj as EmployeeDetailsViewModel;
_applicationViewModel.ChangeViewModel(selectedModel);
}
public ICommand DoubleClickCommand
{
get
{
return _doubleClickCommand;
}
}
如何從第一列(employee_id)獲取值並將其傳遞到EmployeeDetails視圖
對於您的DataGrid,您可以使用EmployeeDetailsViewModel的集合作為ItemsSource。 如果這樣做,所選項目將作為EmployeeDetailsViewModel的實例傳遞到命令Execute方法,您將能夠從那里獲取ID。
您似乎缺少顯示所選視圖所需的元素。 如果查看鏈接的示例,請注意ItemsControl包含在Border中 ,而Border又在DockPanel內部。
在DockPanel下方有一個ContentControl ,它是顯示所選視圖所需的關鍵元素。
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