Windows Phone 8.1 导航到同一页面的新实例答案

【问题标题】：Windows Phone 8.1 navigate to new instance of same pageWindows Phone 8.1 导航到同一页面的新实例
【发布时间】：2014-10-22 18:51:32
【问题描述】：

我有 Windows Phone 8.1 应用程序，我需要从一个页面导航到同一页面的新实例。例如：

主页 -> 画布-？

“画布”在哪里 - xaml 页面， “？” - 实例指南。我知道在 wp8 中是这样的：

NavigationService.Navigate(new Uri("/Canvas.xaml?guid=" + myGuid, UriKind.Relative));

我在 MainPage.cs.Xaml 中编写了这段代码：

private void addNewCanvas_Click(object sender, RoutedEventArgs e)
{
    string cnvsGuid = Guid.NewGuid().ToString();
    System.Diagnostics.Debug.WriteLine(cnvsGuid);

    tabs.Add(new CanvasTab(){label=String.Format("New Canvas {0}",countOfOpenTabs),canvasGuid=cnvsGuid});
    countOfOpenTabs++;
    this.tabsGrid.ItemsSource=null;
    this.tabsGrid.ItemsSource=tabs;
    System.Diagnostics.Debug.WriteLine(tabsGrid.Items.Count());
    this.Frame.Navigate(typeof(Canvas),cnvsGuid);
}

private void tabsGrid_ItemClick(object sender, ItemClickEventArgs e)
{
    this.Frame.Navigate(typeof(Canvas), ((CanvasTab)e.ClickedItem).canvasGuid);
    System.Diagnostics.Debug.WriteLine(((CanvasTab)e.ClickedItem).canvasGuid);
}

private void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
    if (e.PageState != null)
    {
        this.tabs = e.PageState["tabs"] as List<CanvasTab>;
        this.tabsGrid.ItemsSource = null;
        this.tabsGrid.ItemsSource = tabs;
    }
}

private void navigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
    e.PageState["tabs"] = tabs;
}

并将此代码添加到 MainPage 的构造函数中：

this.NavigationCacheMode = NavigationCacheMode.Enabled;
this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += this.navigationHelper_LoadState;
this.navigationHelper.SaveState += this.navigationHelper_SaveState;

并在 Canvas.cs.xaml 中编写代码：

private void navigationHelper_LoadState(object sender, LoadStateEventArgs e)
{
    if (e.PageState != null)
    {
        UIElementCollection canvasItems = e.PageState["canvasItems"] as UIElementCollection;
        foreach (UIElement itm in canvasItems)
        {
            this.mainCanvas.Children.Add(itm);
        }
        this.mainCanvas.UpdateLayout();
    }
}

private void navigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
    e.PageState["canvasItems"] = this.mainCanvas.Children;
}

并在 Canvas 的构造函数中编写这段代码：

this.navigationHelper = new NavigationHelper(this);
this.navigationHelper.LoadState += this.navigationHelper_LoadState;
this.navigationHelper.SaveState += this.navigationHelper_SaveState;
this.NavigationCacheMode = NavigationCacheMode.Required;

而且它总是只为所有 Guid 缓存一个画布。

【问题讨论】：

你试过 this.Frame.Navigate(typeof(Canvas), myGuid) 吗？
WinRT 中的缓存逻辑有点奇怪，如果将缓存设置为 required 则重复使用一种类型的相同页面实例，如果禁用缓存则创建一个新实例但页面是没有缓存，看看这个问题：stackoverflow.com/questions/11539755/…
我重新实现了所有的缓存相关类，以便缓存机制更加灵活，请查看我的库：mytoolkit.codeplex.com/wikipage?title=Paging
非常感谢，我会尽快尝试

标签： c# windows-phone-8 navigation windows-phone-8.1

【解决方案1】：

尝试在您的constructor 中使用NavigationCacheMode.Required。

How to cache a page in Windows Phone 8.1

【讨论】：