在WPF的MVVM模式中,处理对话框是比较复杂的操作之一。由于视图模型不知道视图的任何信息,因此对话框通信可能会很有趣。我可以公开一个ICommand,当视图调用它时,就会出现一个对话框。
有人知道处理对话框结果的好方法吗?我说的是windows对话框,比如MessageBox。
其中一种方法是在视图模型上设置一个事件,当需要对话框时,视图会订阅该事件。
public event EventHandler<MyDeleteArgs> RequiresDeleteDialog;
这是可以的,但这意味着视图需要代码,这是我想要避免的。
在学习(仍在学习)MVVM时,我真的为这个概念挣扎了一段时间。我的决定,以及我认为其他人已经决定但我不清楚的是:
我最初的想法是ViewModel不应该被允许直接调用对话框,因为它没有业务决定对话框应该如何显示。正因为如此,我开始思考如何像在MVP(即View.ShowSaveFileDialog())一样传递消息。然而,我认为这是错误的方法。
ViewModel直接调用对话框是可以的。然而,当您测试ViewModel时,这意味着对话框要么在测试期间弹出,要么全部失败(从未真正尝试过这个)。
因此,在测试时需要使用对话框的“测试”版本。这意味着,对于您拥有的任何对话,您都需要创建一个Interface,并模拟对话响应,或者创建一个具有默认行为的测试模拟。
您应该已经在使用某种服务定位器或IoC,您可以对其进行配置,以便根据上下文提供正确的版本。
使用这种方法,你的ViewModel仍然是可测试的,根据你如何模拟对话框,你可以控制行为。
希望这能有所帮助。
编辑:是的,我同意这不是一个正确的MVVM方法,我现在使用类似于由blindmeis建议的东西。
其中一种方法是
在你的主视图模型中(打开模态的地方):
void OpenModal()
{
ModalWindowViewModel mwvm = new ModalWindowViewModel();
Window mw = new Window();
mw.content = mwvm;
mw.ShowDialog()
if(mw.DialogResult == true)
{
// Your Code, you can access property in mwvm if you need.
}
}
在你的模态窗口View/ViewModel中:
XAML:
<Button Name="okButton" Command="{Binding OkCommand}" CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}">OK</Button>
<Button Margin="2" VerticalAlignment="Center" Name="cancelButton" IsCancel="True">Cancel</Button>
ViewModel:
public ICommand OkCommand
{
get
{
if (_okCommand == null)
{
_okCommand = new ActionCommand<Window>(DoOk, CanDoOk);
}
return _okCommand ;
}
}
void DoOk(Window win)
{
<!--Your Code-->
win.DialogResult = true;
win.Close();
}
bool CanDoOk(Window win) { return true; }
或者类似于这里发布的WPF MVVM:如何关闭一个窗口
Sorry, but I have to chime in. I have been through several of the suggested solutions, before finding the Prism.Wpf.Interactivity namespace in the Prism project. You can use interaction requests and popup window action to either roll a custom window or for simpler needs there are built in Notification and Confirmation popups. These create true windows and are managed as such. you can pass a context object with any dependencies you need in the dialog. We use this solution at my work since I found it. We have numerous senior devs here and noone has come up with anything better. Our previous solution was the dialog service into an overlay and using a presenter class to make it happen, but you had to have factories for all of the dialog viewmodels, etc.
这不是小事,但也不是超级复杂。而且它是内置在Prism中,因此是最好(或更好)的实践。
我的2分钱!
使用可冻结命令
<Grid>
<Grid.DataContext>
<WpfApplication1:ViewModel />
</Grid.DataContext>
<Button Content="Text">
<Button.Command>
<WpfApplication1:MessageBoxCommand YesCommand="{Binding MyViewModelCommand}" />
</Button.Command>
</Button>
</Grid>
public class MessageBoxCommand : Freezable, ICommand
{
public static readonly DependencyProperty YesCommandProperty = DependencyProperty.Register(
"YesCommand",
typeof (ICommand),
typeof (MessageBoxCommand),
new FrameworkPropertyMetadata(null)
);
public static readonly DependencyProperty OKCommandProperty = DependencyProperty.Register(
"OKCommand",
typeof (ICommand),
typeof (MessageBoxCommand),
new FrameworkPropertyMetadata(null)
);
public static readonly DependencyProperty CancelCommandProperty = DependencyProperty.Register(
"CancelCommand",
typeof (ICommand),
typeof (MessageBoxCommand),
new FrameworkPropertyMetadata(null)
);
public static readonly DependencyProperty NoCommandProperty = DependencyProperty.Register(
"NoCommand",
typeof (ICommand),
typeof (MessageBoxCommand),
new FrameworkPropertyMetadata(null)
);
public static readonly DependencyProperty MessageProperty = DependencyProperty.Register(
"Message",
typeof (string),
typeof (MessageBoxCommand),
new FrameworkPropertyMetadata("")
);
public static readonly DependencyProperty MessageBoxButtonsProperty = DependencyProperty.Register(
"MessageBoxButtons",
typeof(MessageBoxButton),
typeof(MessageBoxCommand),
new FrameworkPropertyMetadata(MessageBoxButton.OKCancel)
);
public ICommand YesCommand
{
get { return (ICommand) GetValue(YesCommandProperty); }
set { SetValue(YesCommandProperty, value); }
}
public ICommand OKCommand
{
get { return (ICommand) GetValue(OKCommandProperty); }
set { SetValue(OKCommandProperty, value); }
}
public ICommand CancelCommand
{
get { return (ICommand) GetValue(CancelCommandProperty); }
set { SetValue(CancelCommandProperty, value); }
}
public ICommand NoCommand
{
get { return (ICommand) GetValue(NoCommandProperty); }
set { SetValue(NoCommandProperty, value); }
}
public MessageBoxButton MessageBoxButtons
{
get { return (MessageBoxButton)GetValue(MessageBoxButtonsProperty); }
set { SetValue(MessageBoxButtonsProperty, value); }
}
public string Message
{
get { return (string) GetValue(MessageProperty); }
set { SetValue(MessageProperty, value); }
}
public void Execute(object parameter)
{
var messageBoxResult = MessageBox.Show(Message);
switch (messageBoxResult)
{
case MessageBoxResult.OK:
OKCommand.Execute(null);
break;
case MessageBoxResult.Yes:
YesCommand.Execute(null);
break;
case MessageBoxResult.No:
NoCommand.Execute(null);
break;
case MessageBoxResult.Cancel:
if (CancelCommand != null) CancelCommand.Execute(null); //Cancel usually means do nothing ,so can be null
break;
}
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
protected override Freezable CreateInstanceCore()
{
throw new NotImplementedException();
}
}