在使用Catel和Modern UI时创建多个虚拟机

本文关键字：创建 虚拟机 UI Modern Catel | 更新日期: 2023-09-27 17:50:52

我爱Catel框架。现代UI看起来很不错。但是当我试图让他们一起工作时，我遇到了问题。

我在mui项目中添加了两个用户控件Home和Second。问题是，当从Home过渡到Second时，执行HomeViewModel已经创建了3次。

由TransitioningContentControl

中的下一个代码引起的行为
    private void StartTransition(object oldContent, object newContent)
    {
        // both presenters must be available, otherwise a transition is useless.
        if (CurrentContentPresentationSite != null && PreviousContentPresentationSite != null) {
            CurrentContentPresentationSite.Content = newContent;
            PreviousContentPresentationSite.Content = oldContent;
            // and start a new transition
            if (!IsTransitioning || RestartTransitionOnContentChange) {
                IsTransitioning = true;
                VisualStateManager.GoToState(this, NormalState, false);
                VisualStateManager.GoToState(this, Transition, true);
            }
        }
    }

如果我注释一些行:

private void StartTransition(object oldContent, object newContent)
    {
        // both presenters must be available, otherwise a transition is useless.
        if (CurrentContentPresentationSite != null && PreviousContentPresentationSite != null) {
            CurrentContentPresentationSite.Content = newContent;
            //PreviousContentPresentationSite.Content = oldContent;
            // and start a new transition
            if (!IsTransitioning || RestartTransitionOnContentChange) {
                IsTransitioning = true;
                //VisualStateManager.GoToState(this, NormalState, false);
                //VisualStateManager.GoToState(this, Transition, true);
            }
        }
    }

在这种情况下，相同的过渡导致创建HomeViewModel 1次，但我不想在从Home控件执行导航时创建HomeViewModel。我怎样才能做到这一点呢?

项目品味

在使用Catel和Modern UI时创建多个虚拟机

有两个选项可以解决这个问题:

1)使用现有功能(closeviewmodelonunload)。

那么你需要在TransitioningContentControl中使用这段代码。StartTransition 

var userControl = oldContent as Catel.Windows.Controls.UserControl;
if (userControl != null)
{
    userControl.CloseViewModelOnUnloaded = false;
}
PreviousContentPresentationSite.Content = oldContent;

将此添加到OnTransitionCompleted:

var userControl = PreviousContentPresentationSite.Content as Catel.Windows.Controls.UserControl;
if (userControl != null)
{
    userControl.CloseViewModelOnUnloaded = true;
    var vm = userControl.ViewModel;
    if (vm != null)
    {
        vm.CloseViewModel(true);
    }
}
AbortTransition();

2)使用新功能(PreventViewModelCreation)将不会在转换期间保持VM存活

那么你需要在TransitioningContentControl中使用这段代码。StartTransition 

var vmContainer = oldContent as IViewModelContainer;
if (vmContainer != null)
{
    vmContainer.PreventViewModelCreation = true;
}
PreviousContentPresentationSite.Content = oldContent;

将此添加到OnTransitionCompleted方法中:

var vmContainer = PreviousContentPresentationSite.Content as IViewModelContainer;
if (vmContainer != null)
{
    vmContainer.PreventViewModelCreation = false;
}
AbortTransition();
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