导航服务对象实例错误

本文关键字：错误 实例 对象 服务 导航 | 更新日期: 2023-09-27 18:12:49

我是WPF的新手，并试图寻找和尝试不同的解决方案:我需要导航到另一个页面:从名为MainFrame的页面到Page1。

错误消息:

WPF does not containt a definition for navigation service.

或

Object not set to instance of Object.

我试过了:

    private void CloseApplication_MouseUp(object sender, MouseButtonEventArgs e)
    {
        navService = NavigationService.GetNavigationService(this);
        navService.Navigate(new Uri ("Page1.xaml", UriKind.Relative));
    }

然后我尝试了这个，认为需要在页面加载时实例化一些东西:

    NavigationService navService;
    public MainFrame()
    {
        InitializeComponent();
    }
    void MainFrame_Loaded(object sender, RoutedEventArgs e)
    {
        navService = NavigationService.GetNavigationService(this);
    }
    private void CloseApplication_MouseUp(object sender, MouseButtonEventArgs e)
    {
        navService.Navigate(new Uri ("Page1.xaml", UriKind.Relative));
    }

导航服务对象实例错误

在Page中使用NavigationService实例。阅读MSDN关于导航的文章

private void CloseApplication_MouseUp(object sender, MouseButtonEventArgs e)
    {
        this.NavigationService.Navigate(new Uri ("Page1.xaml", UriKind.Relative));
    }

应该非常简单。导航发生在NavigationWindowPages中的，参见下面的示例:

首先，你的主窗口应该继承自NavigationWindow类: 
public partial class MainWindow : NavigationWindow
{
   public MainWindow()
   {
       InitializeComponent();
   }
}

则xaml必须有NavigationWindow根元素:

<NavigationWindow x:Class="NavigationApp.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window" Height="300" Width="300" Source="MainPage.xaml">
</NavigationWindow>

这个根元素不能包含任何UI元素，因为它们被放置在页面中。根元素包含一个起始页属性MainPage.xaml

<Page x:Class="NavigationApp.MainPage"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
    Title="MainPage">
    <Grid>
        <Frame Source="Page2.xaml"/>
    </Grid>
</Page>

在我的例子中，它包含一个帧到Page2。只有一个按钮的Xaml。

<Page x:Class="NavigationApp.Page2"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
    Title="Page2">
    <Grid>
        <Button Content="Navigate to page 1" HorizontalAlignment="Left" Margin="109,143,0,0" VerticalAlignment="Top" Width="128" Click="Button_Click"/>
    </Grid>
</Page>

通过点击那个按钮，它导航到另一个页面:

 private void Button_Click(object sender, RoutedEventArgs e)
 {
    Uri uri = new Uri("Page1.xaml", UriKind.Relative);
    NavigationService.Navigate(uri);
 }
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