UWP开发笔记——嵌套式页面的实现

绪论

UWP开发中，Page是最常用的Control之一，通常情况下，在开发的application中，每一个页面就是一个Page。有时候，为了开发整合度更高，UI表现更为一致的UI，开发者需要把UI控件和功能整合到一个页面的子页面中，子页面拥有自己的UI表现和生命周期，这就需要在Page中嵌套Page来达到需要实现的效果。

一种实现方法

其实，实现嵌套页面是一件很简单的事情，我们知道，page都是通过Frame显示和控制Navigation的，基于这点，就可以在主页面（即最外层的页面）中添加一个Frame，通过控制这个Frame来实现子Page的显示和导航。

在xmal中添加Frame

<Frame x:Name="contentFrame" Grid.Row="1"/>

在code中实现子Page的navigation

contentFrame.Navigate(typeof(Page1));

为子Frame添加默认的Page

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    if (e.NavigationMode == NavigationMode.New)
    {
        contentFrame.Navigate(typeof(Page1));
    }
    base.OnNavigatedTo(e);
}

为back键添加Event

public MainPage()
{
    this.InitializeComponent();
    SystemNavigationManager.GetForCurrentView().BackRequested += PageBackRequested;
}

private void PageBackRequested(object sender, BackRequestedEventArgs e)
{
    if (contentFrame == null)
        return;
    if (contentFrame.CanGoBack)
    {
        e.Handled = true;
        contentFrame.GoBack();
    }
}

一个例子

在这个例子中，外层的MainPage有一个汉堡键配合SplitView菜单实现内层Page的切换，back键用来实现contentFrame的Navigation。其中，Page1和Page2是嵌套在MainPage里面的两个Page。

MainPage.xaml

<Page
    x:Class="NestedFrameExample.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:NestedFrameExample"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid Height="48" VerticalAlignment="Top" Background="White">
            <Button x:Name="hamburgerButton" Background="Transparent" Grid.Column="0" VerticalAlignment="Center" HorizontalAlignment="Left" Click="SplitViewToggle_Click">
                <TextBlock Text="&#xE700;" FontFamily="{ThemeResource SymbolThemeFontFamily}"/>
            </Button>
        </Grid>
        <!-- 这个Frame用于显示子Page页面。 -->
        <Frame x:Name="contentFrame" Grid.Row="1"/>

        <SplitView x:Name="splitView" Grid.Row="1" IsPaneOpen="False" OpenPaneLength="300" CompactPaneLength="48" DisplayMode="Overlay" HorizontalContentAlignment="Stretch">
            <SplitView.Pane>
                <ListView ItemsSource="{x:Bind Path=NavLinks}" IsItemClickEnabled="True" ItemClick="NavLinkClick" SelectionMode="None"/>
            </SplitView.Pane>
        </SplitView>
    </Grid>
</Page>

MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

// The Blank Page item template is documented at http://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x409

namespace NestedFrameExample
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class MainPage : Page
    {

        public List<NavLink> NavLinks = new List<NavLink>()
        {
            new NavLink() { Label = "Page1", LinkType = typeof(Page1) },
            new NavLink() { Label = "Page2", LinkType = typeof(Page2) }
        };

        public MainPage()
        {
            this.InitializeComponent();
            SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = AppViewBackButtonVisibility.Visible;
            SystemNavigationManager.GetForCurrentView().BackRequested += PageBackRequested;
        }

        private void NavLinkClick(object sender, ItemClickEventArgs e)
        {
            NavLink link = e.ClickedItem as NavLink;
            if (link != null && link.LinkType != null)
                contentFrame.Navigate(link.LinkType);
            splitView.IsPaneOpen = false;
        }

        private void SplitViewToggle_Click(object sender, RoutedEventArgs e)
        {
            splitView.IsPaneOpen = !splitView.IsPaneOpen;
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            //this.InitialBackButton();
            if (e.NavigationMode == NavigationMode.New)
            {
                contentFrame.Navigate(typeof(Page1));
            }
            base.OnNavigatedTo(e);
        }

        private void PageBackRequested(object sender, BackRequestedEventArgs e)
        {
            if (contentFrame == null)
                return;
            if (contentFrame.CanGoBack)
            {
                e.Handled = true;
                contentFrame.GoBack();
            }
        }
    }

    public class NavLink
    {
        public String Label { get; set; }
        public Type LinkType { get; set; }
        public override String ToString()
        {
            return Label;
        }
    }
}

总结

嵌套式的页面使每个Page的结构更加清晰，更能专注于自己的功能实现，也使代码更加清晰，容易维护，避免代码冗余，推荐使用，希望本文能给大家带来帮助！！