127
我最近有問題爲我的wpf應用程序創建添加和編輯對話框。wpf與MVVM中對話框的好壞做法？
我想在我的代碼中做的事情就是這樣的。 （我主要使用與MVVM視圖模型第一種方法）
視圖模型這就要求一個對話窗口：
var result = this.uiDialogService.ShowDialog("Dialogwindow Title", dialogwindowVM);
// Do anything with the dialog result
它是如何工作的？
首先，我創建了一個對話框服務：
public interface IUIWindowDialogService
{
bool? ShowDialog(string title, object datacontext);
}
public class WpfUIWindowDialogService : IUIWindowDialogService
{
public bool? ShowDialog(string title, object datacontext)
{
var win = new WindowDialog();
win.Title = title;
win.DataContext = datacontext;
return win.ShowDialog();
}
}
WindowDialog是一個特殊而簡單的窗口。我需要它來握住我的內容：
<Window x:Class="WindowDialog"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
Title="WindowDialog"
WindowStyle="SingleBorderWindow"
WindowStartupLocation="CenterOwner" SizeToContent="WidthAndHeight">
<ContentPresenter x:Name="DialogPresenter" Content="{Binding .}">
</ContentPresenter>
</Window>
在WPF對話框的問題是隻能用代碼實現的dialogresult = true。這就是爲什麼我爲我的dialogviewmodel創建了一個接口來實現它。
public class RequestCloseDialogEventArgs : EventArgs
{
public bool DialogResult { get; set; }
public RequestCloseDialogEventArgs(bool dialogresult)
{
this.DialogResult = dialogresult;
}
}
public interface IDialogResultVMHelper
{
event EventHandler<RequestCloseDialogEventArgs> RequestCloseDialog;
}
每當我的視圖模型認爲是時候dialogresult = true，則引發此事件。
public partial class DialogWindow : Window
{
// Note: If the window is closed, it has no DialogResult
private bool _isClosed = false;
public DialogWindow()
{
InitializeComponent();
this.DialogPresenter.DataContextChanged += DialogPresenterDataContextChanged;
this.Closed += DialogWindowClosed;
}
void DialogWindowClosed(object sender, EventArgs e)
{
this._isClosed = true;
}
private void DialogPresenterDataContextChanged(object sender,
DependencyPropertyChangedEventArgs e)
{
var d = e.NewValue as IDialogResultVMHelper;
if (d == null)
return;
d.RequestCloseDialog += new EventHandler<RequestCloseDialogEventArgs>
(DialogResultTrueEvent).MakeWeak(
eh => d.RequestCloseDialog -= eh;);
}
private void DialogResultTrueEvent(object sender,
RequestCloseDialogEventArgs eventargs)
{
// Important: Do not set DialogResult for a closed window
// GC clears windows anyways and with MakeWeak it
// closes out with IDialogResultVMHelper
if(_isClosed) return;
this.DialogResult = eventargs.DialogResult;
}
}
至少現在我要創建我的資源文件DataTemplate（app.xaml或東西）：
<DataTemplate DataType="{x:Type DialogViewModel:EditOrNewAuswahlItemVM}" >
<DialogView:EditOrNewAuswahlItem/>
</DataTemplate>
好那好，我現在就可以從我的ViewModels調用對話框：
var result = this.uiDialogService.ShowDialog("Dialogwindow Title", dialogwindowVM);
現在我的問題，你看到這個解決方案的任何問題？
編輯：爲了完整。該視圖模型應該實現IDialogResultVMHelper，然後它可以在OkCommand或這樣的範圍內提高它：
public class MyViewmodel : IDialogResultVMHelper
{
private readonly Lazy<DelegateCommand> _okCommand;
public MyViewmodel()
{
this._okCommand = new Lazy<DelegateCommand>(() =>
new DelegateCommand(() =>
InvokeRequestCloseDialog(
new RequestCloseDialogEventArgs(true)),() =>
YourConditionsGoesHere = true));
}
public ICommand OkCommand
{
get { return this._okCommand.Value; }
}
public event EventHandler<RequestCloseDialogEventArgs> RequestCloseDialog;
private void InvokeRequestCloseDialog(RequestCloseDialogEventArgs e)
{
var handler = RequestCloseDialog;
if (handler != null)
handler(this, e);
}
}
編輯2：我以前從這裏的代碼，使我的事件處理程序註冊弱：
http://diditwith.net/2007/03/23/SolvingTheProblemWithEventsWeakEventHandlers.aspx
（網站沒有不再存在，WebArchive Mirror）
public delegate void UnregisterCallback<TE>(EventHandler<TE> eventHandler)
where TE : EventArgs;
public interface IWeakEventHandler<TE>
where TE : EventArgs
{
EventHandler<TE> Handler { get; }
}
public class WeakEventHandler<T, TE> : IWeakEventHandler<TE>
where T : class
where TE : EventArgs
{
private delegate void OpenEventHandler(T @this, object sender, TE e);
private readonly WeakReference mTargetRef;
private readonly OpenEventHandler mOpenHandler;
private readonly EventHandler<TE> mHandler;
private UnregisterCallback<TE> mUnregister;
public WeakEventHandler(EventHandler<TE> eventHandler,
UnregisterCallback<TE> unregister)
{
mTargetRef = new WeakReference(eventHandler.Target);
mOpenHandler = (OpenEventHandler)Delegate.CreateDelegate(
typeof(OpenEventHandler),null, eventHandler.Method);
mHandler = Invoke;
mUnregister = unregister;
}
public void Invoke(object sender, TE e)
{
T target = (T)mTargetRef.Target;
if (target != null)
mOpenHandler.Invoke(target, sender, e);
else if (mUnregister != null)
{
mUnregister(mHandler);
mUnregister = null;
}
}
public EventHandler<TE> Handler
{
get { return mHandler; }
}
public static implicit operator EventHandler<TE>(WeakEventHandler<T, TE> weh)
{
return weh.mHandler;
}
}
public static class EventHandlerUtils
{
public static EventHandler<TE> MakeWeak<TE>(this EventHandler<TE> eventHandler,
UnregisterCallback<TE> unregister)
where TE : EventArgs
{
if (eventHandler == null)
throw new ArgumentNullException("eventHandler");
if (eventHandler.Method.IsStatic || eventHandler.Target == null)
throw new ArgumentException("Only instance methods are supported.",
"eventHandler");
var wehType = typeof(WeakEventHandler<,>).MakeGenericType(
eventHandler.Method.DeclaringType, typeof(TE));
var wehConstructor = wehType.GetConstructor(new Type[]
{
typeof(EventHandler<TE>), typeof(UnregisterCallback<TE>)
});
IWeakEventHandler<TE> weh = (IWeakEventHandler<TE>)wehConstructor.Invoke(
new object[] { eventHandler, unregister });
return weh.Handler;
}
}
您可能在您的WindowDialog XAML中缺少xmlns：x =「http://schemas.microsoft.com/winfx/2006/xaml」參考。 – 2014-01-02 11:47:40
實際上命名空間是xmlns：x =「[http：//] schemas.microsoft.com/winfx/2006/xaml」沒有括號 – reggaeguitar 2014-04-22 22:04:27
請參閱http://stackoverflow.com/questions/16993433/mvvm-light-wpf - 綁定 - 窗口到視圖模型的多個實例/ 16994523＃16994523 – reggaeguitar 2014-04-24 22:07:41