WPF Navigation

在开始学习WPF时，一开始对WPF的Window, Page, UserControl感到很迷惑。不知道何时该使用哪个。下面简单介绍一下这三者的区别。

Window：故名思意，桌面程序的窗体。在WPF桌面应用中，我一般会只用一个主窗体，而后将不一样的操做单元封装在不一样的UserControl中，根据用户的操做展示不一样的UserControl；

Page：Page须要承载在窗体中，经过Navigation进行不一样Page的切换，也是本篇博客中须要讲到的；

UserControl：封装一些能够重复使用的功能。

在这篇博客中将介绍WPF导航应用。WPF Navigation实如今不一样Page之间的切换。

咱们须要在NavigationWindow或者Frame中承载Page，首先看NavigationWindow

新建WelcomePage，而后设置NavigationWindow的Source为WelcomePage

<NavigationWindow x:Class="NavigationBasedApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:NavigationBasedApp"
        mc:Ignorable="d" ShowsNavigationUI="False" Source="WelcomePage.xaml"
        Title="MainWindow" Height="350" Width="525">

</NavigationWindow>

WelcomePage.xaml:

<Page x:Class="NavigationBasedApp.WelcomePage"
      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" 
      xmlns:local="clr-namespace:NavigationBasedApp"
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
      Title="WelcomePage">

    <Grid>
        <TextBlock Text="Hello China!" VerticalAlignment="Center" HorizontalAlignment="Center"/>
    </Grid>
</Page>

运行效果：

再新建一个GreetingPage.xaml，咱们在WelcomePage上添加一个Button，点击Button时跳转到GreetingPage.xaml，在GreetingPage上也有一个Button，点击返回到WelcomePage。

WelcomePage.xaml

<Page x:Class="NavigationBasedApp.WelcomePage"
      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" 
      xmlns:local="clr-namespace:NavigationBasedApp"
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
      Title="WelcomePage">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        
        <TextBlock Text="Welcome to WPF World!" HorizontalAlignment="Center"/>
        
        <Button Grid.Row="1" Width="100" Margin="0,10" Content="Go Forward" Click="GoForwardButton_Click"/>
    </Grid>
</Page>

Code Behind:

        private void GoForwardButton_Click(object sender, RoutedEventArgs e)
        {
            if (this.NavigationService.CanGoForward)
            {
                this.NavigationService.GoForward();
            }
            else
            {
                //GreetingPage greeting = new GreetingPage();

                //this.NavigationService.Navigate(greeting);

                this.NavigationService.Navigate(new Uri("pack://application:,,,/GreetingPage.xaml"));
            }
        }

导航时，能够传递GreetingPage.xaml地址，也能够是GreetingPage对象。能够在 if (this.NavigationService.CanGoForward) 加一个断点，在从GreetingPage返回到WelcomePage后，再次点击Go Forward按钮时，直接使用this.NavigationService.GoForward()这句代码进行了导航，这是由于导航发生后，会在NavigationService中会记录导航记录。

GreetingPage.xaml:

<Page x:Class="NavigationBasedApp.GreetingPage"
      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" 
      xmlns:local="clr-namespace:NavigationBasedApp"
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
      Title="GreetingPage">

    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <TextBlock Text="Hi Yang-Fei!" HorizontalAlignment="Center"/>
        <Button Grid.Row="1" Margin="0,10" Width="100" Content="Go Back" Click="GoBackButton_Click"/>
    </Grid>
</Page>

Code Behind:

        private void GoBackButton_Click(object sender, RoutedEventArgs e)
        {
            this.NavigationService.GoBack();
        }

运行效果：

能够在导航时传递参数。而后再NavigationWindow中获取。例如：

 GreetingPage greeting = new GreetingPage();

 this.NavigationService.Navigate(greeting,"This is a test message.");

在MainWindow中，

        public MainWindow()
        {
            InitializeComponent();

            this.NavigationService.LoadCompleted += NavigationService_LoadCompleted;
        }

        private void NavigationService_LoadCompleted(object sender, NavigationEventArgs e)
        {
            if(e.ExtraData != null)
            {
               // Do something here...
            }
        }

上面提到的Frame也能够做为Page的承载。和NavigationWindow的区别在于NavigationWindow是全局翻页，Frame是局部翻页。

<Window x:Class="FrameNavigationBasedApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:FrameNavigationBasedApp"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <DockPanel>
        <Menu DockPanel.Dock="Top">
            <MenuItem Header="_File"/>
            <MenuItem Header="_View"/>
        </Menu>
        <Frame x:Name="frmMain" NavigationUIVisibility="Hidden" Source="WelcomePage.xaml"/>
    </DockPanel>
</Window>

运行效果：

这篇博客就到这里了，代码点击这里下载。

感谢您的阅读。