.NET 5 WPF MVVM框架之Prism导航系统,这系列文章是介绍Prism应用的文章,转载自博客园,在最底部给出了原文链接,因在搭建WPF框架时参考了这些文章,并且使用的是.net 5了,遂将标题做了更改,但总的来说参考的这系列文章还是非常有帮助的。
本文将介绍如何在.NET 5环境下使用MVVM框架Prism基于区域Region的导航系统,在讲解Prism导航系统之前,我们先来看看一个例子,我在之前的demo项目创建一个登录界面:
我们看到这里是不是一开始想象到使用WPF带有的导航系统,通过Frame和Page进行页面跳转,然后通过导航日志的GoBack和GoForward实现后退和前进,其实这是通过使用Prism的导航框架实现的,下面我们来看看如何在Prism的MVVM模式下实现该功能
Prism导航系统
我们在上一篇介绍了Prism的区域管理,而Prism的导航系统也是基于区域的,首先我们来看看如何在区域导航
注册区域
LoginWindow.xaml:
<Window x:Class="PrismMetroSample.Shell.Views.Login.LoginWindow" 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:PrismMetroSample.Shell.Views.Login" xmlns:region="clr-namespace:PrismMetroSample.Infrastructure.Constants;assembly=PrismMetroSample.Infrastructure" mc:Ignorable="d" xmlns:prism="http://prismlibrary.com/" xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" Height="600" Width="400" prism:ViewModelLocator.AutoWireViewModel="True" ResizeMode="NoResize" WindowStartupLocation="CenterScreen" Icon="pack://application:,,,/PrismMetroSample.Infrastructure;Component/Assets/Photos/Home, homepage, menu.png" > <i:Interaction.Triggers> <i:EventTrigger EventName="Loaded"> <i:InvokeCommandAction Command="{Binding LoginLoadingCommand}"/> </i:EventTrigger> </i:Interaction.Triggers> <Grid> <ContentControl prism:RegionManager.RegionName="{x:Static region:RegionNames.LoginContentRegion}" Margin="5"/> </Grid> </Window>
注册导航
App.cs:
protected override void RegisterTypes(IContainerRegistry containerRegistry) { containerRegistry.Register<IMedicineSerivce, MedicineSerivce>(); containerRegistry.Register<IPatientService, PatientService>(); containerRegistry.Register<IUserService, UserService>(); //注册全局命令 containerRegistry.RegisterSingleton<IApplicationCommands, ApplicationCommands>(); containerRegistry.RegisterInstance<IFlyoutService>(Container.Resolve<FlyoutService>()); //注册导航 containerRegistry.RegisterForNavigation<LoginMainContent>(); containerRegistry.RegisterForNavigation<CreateAccount>(); }
区域导航
LoginWindowViewModel.cs:
public class LoginWindowViewModel:BindableBase { private readonly IRegionManager _regionManager; private readonly IUserService _userService; private DelegateCommand _loginLoadingCommand; public DelegateCommand LoginLoadingCommand => _loginLoadingCommand ?? (_loginLoadingCommand = new DelegateCommand(ExecuteLoginLoadingCommand)); void ExecuteLoginLoadingCommand() { //在LoginContentRegion区域导航到LoginMainContent _regionManager.RequestNavigate(RegionNames.LoginContentRegion, "LoginMainContent"); Global.AllUsers = _userService.GetAllUsers(); } public LoginWindowViewModel(IRegionManager regionManager, IUserService userService) { _regionManager = regionManager; _userService = userService; } }
LoginMainContentViewModel.cs:
public class LoginMainContentViewModel : BindableBase { private readonly IRegionManager _regionManager; private DelegateCommand _createAccountCommand; public DelegateCommand CreateAccountCommand => _createAccountCommand ?? (_createAccountCommand = new DelegateCommand(ExecuteCreateAccountCommand)); //导航到CreateAccount void ExecuteCreateAccountCommand() { Navigate("CreateAccount"); } private void Navigate(string navigatePath) { if (navigatePath != null) _regionManager.RequestNavigate(RegionNames.LoginContentRegion, navigatePath); } public LoginMainContentViewModel(IRegionManager regionManager) { _regionManager = regionManager; } }
效果如下:
这里我们可以看到我们调用RegionMannager的RequestNavigate方法,其实这样看不能很好的说明是基于区域的做法,如果将换成下面的写法可能更好理解一点:
//在LoginContentRegion区域导航到LoginMainContent _regionManager.RequestNavigate(RegionNames.LoginContentRegion, "LoginMainContent");
换成
//在LoginContentRegion区域导航到LoginMainContent IRegion region = _regionManager.Regions[RegionNames.LoginContentRegion]; region.RequestNavigate("LoginMainContent");
其实RegionMannager的RequestNavigate源码也是大概实现也是大概如此,就是去调Region的RequestNavigate的方法,而Region的导航是实现了一个INavigateAsync接口:
public interface INavigateAsync { void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback); void RequestNavigate(Uri target, Action<NavigationResult> navigationCallback, NavigationParameters navigationParameters); }
我们可以看到有RequestNavigate方法三个形参:
- target:表示将要导航的页面Uri
- navigationCallback:导航后的回调方法
- navigationParameters:导航传递参数(下面会详解)
那么我们将上述加上回调方法:
//在LoginContentRegion区域导航到LoginMainContent IRegion region = _regionManager.Regions[RegionNames.LoginContentRegion]; region.RequestNavigate("LoginMainContent", NavigationCompelted); private void NavigationCompelted(NavigationResult result) { if (result.Result==true) { MessageBox.Show("导航到LoginMainContent页面成功"); } else { MessageBox.Show("导航到LoginMainContent页面失败"); } }
效果如下:
View和ViewModel参与导航过程
我们经常在两个页面之间导航需要处理一些逻辑,例如,LoginMainContent页面导航到CreateAccount页面时候,LoginMainContent退出页面的时刻要保存页面数据,导航到CreateAccount页面的时刻处理逻辑(例如获取从LoginMainContent页面的信息),Prism的导航系统通过一个INavigationAware接口:
public interface INavigationAware : Object { Void OnNavigatedTo(NavigationContext navigationContext); Boolean IsNavigationTarget(NavigationContext navigationContext); Void OnNavigatedFrom(NavigationContext navigationContext); }
- OnNavigatedFrom:导航之前触发,一般用于保存该页面的数据
- OnNavigatedTo:导航后目的页面触发,一般用于初始化或者接受上页面的传递参数
- IsNavigationTarget:True则重用该View实例,Flase则每一次导航到该页面都会实例化一次
我们用代码来演示这三个方法:
LoginMainContentViewModel.cs:
public class LoginMainContentViewModel : BindableBase, INavigationAware { private readonly IRegionManager _regionManager; private DelegateCommand _createAccountCommand; public DelegateCommand CreateAccountCommand => _createAccountCommand ?? (_createAccountCommand = new DelegateCommand(ExecuteCreateAccountCommand)); void ExecuteCreateAccountCommand() { Navigate("CreateAccount"); } private void Navigate(string navigatePath) { if (navigatePath != null) _regionManager.RequestNavigate(RegionNames.LoginContentRegion, navigatePath); } public LoginMainContentViewModel(IRegionManager regionManager) { _regionManager = regionManager; } public bool IsNavigationTarget(NavigationContext navigationContext) { return true; } public void OnNavigatedFrom(NavigationContext navigationContext) { MessageBox.Show("退出了LoginMainContent"); } public void OnNavigatedTo(NavigationContext navigationContext) { MessageBox.Show("从CreateAccount导航到LoginMainContent"); } }
CreateAccountViewModel.cs:
public class CreateAccountViewModel : BindableBase,INavigationAware { private DelegateCommand _loginMainContentCommand; public DelegateCommand LoginMainContentCommand => _loginMainContentCommand ?? (_loginMainContentCommand = new DelegateCommand(ExecuteLoginMainContentCommand)); void ExecuteLoginMainContentCommand() { Navigate("LoginMainContent"); } public CreateAccountViewModel(IRegionManager regionManager) { _regionManager = regionManager; } private void Navigate(string navigatePath) { if (navigatePath != null) _regionManager.RequestNavigate(RegionNames.LoginContentRegion, navigatePath); } public bool IsNavigationTarget(NavigationContext navigationContext) { return true; } public void OnNavigatedFrom(NavigationContext navigationContext) { MessageBox.Show("退出了CreateAccount"); } public void OnNavigatedTo(NavigationContext navigationContext) { MessageBox.Show("从LoginMainContent导航到CreateAccount"); } }
效果如下:
修改IsNavigationTarget为false:
public class LoginMainContentViewModel : BindableBase, INavigationAware { public bool IsNavigationTarget(NavigationContext navigationContext) { return false; } } public class CreateAccountViewModel : BindableBase,INavigationAware { public bool IsNavigationTarget(NavigationContext navigationContext) { return false; } }
效果如下:
我们会发现LoginMainContent和CreateAccount页面的数据不见了,这是因为第二次导航到页面的时候当IsNavigationTarget为false时,View将会重新实例化,导致ViewModel也重新加载,因此所有数据都清空了
IRegionMemberLifetime
同时,Prism还可以通过IRegionMemberLifetime接口的KeepAlive布尔属性控制区域的视图的生命周期,我们在上一篇关于区域管理器说到,当视图添加到区域时候,像ContentControl这种单独显示一个活动视图,可以通过Region的Activate和Deactivate方法激活和失效视图,像ItemsControl这种可以同时显示多个活动视图的,可以通过Region的Add和Remove方法控制增加活动视图和失效视图,而当视图的KeepAlive为false,Region的Activate另外一个视图时,则该视图的实例则会去除出区域,为什么我们不在区域管理器讲解该接口呢?因为当导航的时候,同样的是在触发了Region的Activate和Deactivate,当有IRegionMemberLifetime接口时则会触发Region的Add和Remove方法,这里可以去看下Prism的RegionMemberLifetimeBehavior源码
我们将LoginMainContentViewModel实现IRegionMemberLifetime接口,并且把KeepAlive设置为false,同样的将IsNavigationTarget设置为true
LoginMainContentViewModel.cs:
public class LoginMainContentViewModel : BindableBase, INavigationAware,IRegionMemberLifetime { public bool KeepAlive => false; private readonly IRegionManager _regionManager; private DelegateCommand _createAccountCommand; public DelegateCommand CreateAccountCommand => _createAccountCommand ?? (_createAccountCommand = new DelegateCommand(ExecuteCreateAccountCommand)); void ExecuteCreateAccountCommand() { Navigate("CreateAccount"); } private void Navigate(string navigatePath) { if (navigatePath != null) _regionManager.RequestNavigate(RegionNames.LoginContentRegion, navigatePath); } public LoginMainContentViewModel(IRegionManager regionManager) { _regionManager = regionManager; } public bool IsNavigationTarget(NavigationContext navigationContext) { return true; } public void OnNavigatedFrom(NavigationContext navigationContext) { MessageBox.Show("退出了LoginMainContent"); } public void OnNavigatedTo(NavigationContext navigationContext) { MessageBox.Show("从CreateAccount导航到LoginMainContent"); } }
效果如下:
我们会发现跟没实现IRegionMemberLifetime接口和IsNavigationTarget设置为false情况一样,当KeepAlive为false时,通过断点知道,重新导航回LoginMainContent页面时不会触发IsNavigationTarget方法,因此可以
知道判断顺序是:KeepAlive –>IsNavigationTarget
Prism的导航系统还支持再导航前允许是否需要导航的交互需求,这里我们在CreateAccount注册完用户后寻问是否需要导航回LoginMainContent页面,代码如下:
CreateAccountViewModel.cs:
public class CreateAccountViewModel : BindableBase, INavigationAware,IConfirmNavigationRequest { private DelegateCommand _loginMainContentCommand; public DelegateCommand LoginMainContentCommand => _loginMainContentCommand ?? (_loginMainContentCommand = new DelegateCommand(ExecuteLoginMainContentCommand)); private DelegateCommand<object> _verityCommand; public DelegateCommand<object> VerityCommand => _verityCommand ?? (_verityCommand = new DelegateCommand<object>(ExecuteVerityCommand)); void ExecuteLoginMainContentCommand() { Navigate("LoginMainContent"); } public CreateAccountViewModel(IRegionManager regionManager) { _regionManager = regionManager; } private void Navigate(string navigatePath) { if (navigatePath != null) _regionManager.RequestNavigate(RegionNames.LoginContentRegion, navigatePath); } public bool IsNavigationTarget(NavigationContext navigationContext) { return true; } public void OnNavigatedFrom(NavigationContext navigationContext) { MessageBox.Show("退出了CreateAccount"); } public void OnNavigatedTo(NavigationContext navigationContext) { MessageBox.Show("从LoginMainContent导航到CreateAccount"); } //注册账号 void ExecuteVerityCommand(object parameter) { if (!VerityRegister(parameter)) { return; } MessageBox.Show("注册成功!"); LoginMainContentCommand.Execute(); } //导航前询问 public void ConfirmNavigationRequest(NavigationContext navigationContext, Action<bool> continuationCallback) { var result = false; if (MessageBox.Show("是否需要导航到LoginMainContent页面?", "Naviagte?",MessageBoxButton.YesNo) ==MessageBoxResult.Yes) { result = true; } continuationCallback(result); } }
效果如下:
导航期间传递参数
Prism提供NavigationParameters类以帮助指定和检索导航参数,在导航期间,可以通过访问以下方法来传递导航参数:
- INavigationAware接口的IsNavigationTarget,OnNavigatedFrom和OnNavigatedTo方法中IsNavigationTarget,OnNavigatedFrom和OnNavigatedTo中形参NavigationContext对象的NavigationParameters属性
- IConfirmNavigationRequest接口的ConfirmNavigationRequest形参NavigationContext对象的NavigationParameters属性
- 区域导航的INavigateAsync接口的RequestNavigate方法赋值给其形参navigationParameters
- 导航日志IRegionNavigationJournal接口CurrentEntry属性的NavigationParameters类型的Parameters属性(下面会介绍导航日志)
这里我们CreateAccount页面注册完用户后询问是否需要用当前注册用户来作为登录LoginId,来演示传递导航参数,代码如下:
CreateAccountViewModel.cs(修改代码部分):
private string _registeredLoginId; public string RegisteredLoginId { get { return _registeredLoginId; } set { SetProperty(ref _registeredLoginId, value); } } public bool IsUseRequest { get; set; } void ExecuteVerityCommand(object parameter) { if (!VerityRegister(parameter)) { return; } this.IsUseRequest = true; MessageBox.Show("注册成功!"); LoginMainContentCommand.Execute(); } public void ConfirmNavigationRequest(NavigationContext navigationContext, Action<bool> continuationCallback) { if (!string.IsNullOrEmpty(RegisteredLoginId) && this.IsUseRequest) { if (MessageBox.Show("是否需要用当前注册的用户登录?", "Naviagte?", MessageBoxButton.YesNo) == MessageBoxResult.Yes) { navigationContext.Parameters.Add("loginId", RegisteredLoginId); } } continuationCallback(true); }
LoginMainContentViewModel.cs(修改代码部分):
public void OnNavigatedTo(NavigationContext navigationContext) { MessageBox.Show("从CreateAccount导航到LoginMainContent"); var loginId= navigationContext.Parameters["loginId"] as string; if (loginId!=null) { this.CurrentUser = new User() { LoginId=loginId}; } }
效果如下:
导航日志
Prism导航系统同样的和WPF导航系统一样,都支持导航日志,Prism是通过IRegionNavigationJournal接口来提供区域导航日志功能,
public interface IRegionNavigationJournal { bool CanGoBack { get; } bool CanGoForward { get; } IRegionNavigationJournalEntry CurrentEntry {get;} INavigateAsync NavigationTarget { get; set; } void GoBack(); void GoForward(); void RecordNavigation(IRegionNavigationJournalEntry entry, bool persistInHistory); void Clear(); }
我们将在登录界面接入导航日志功能,代码如下:
LoginMainContent.xaml(前进箭头代码部分):
<TextBlock Width="30" Height="30" HorizontalAlignment="Right" Text="" FontWeight="Bold" FontFamily="pack://application:,,,/PrismMetroSample.Infrastructure;Component/Assets/Fonts/#iconfont" FontSize="30" Margin="10" Visibility="{Binding IsCanExcute,Converter={StaticResource boolToVisibilityConverter}}"> <i:Interaction.Triggers> <i:EventTrigger EventName="MouseLeftButtonDown"> <i:InvokeCommandAction Command="{Binding GoForwardCommand}"/> </i:EventTrigger> </i:Interaction.Triggers> <TextBlock.Style> <Style TargetType="TextBlock"> <Style.Triggers> <Trigger Property="IsMouseOver" Value="True"> <Setter Property="Background" Value="#F9F9F9"/> </Trigger> </Style.Triggers> </Style> </TextBlock.Style> </TextBlock>
BoolToVisibilityConverter.cs:
public class BoolToVisibilityConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { if (value==null) { return DependencyProperty.UnsetValue; } var isCanExcute = (bool)value; if (isCanExcute) { return Visibility.Visible; } else { return Visibility.Hidden; } } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotImplementedException(); } }
LoginMainContentViewModel.cs(修改代码部分):
IRegionNavigationJournal _journal; private DelegateCommand<PasswordBox> _loginCommand; public DelegateCommand<PasswordBox> LoginCommand => _loginCommand ?? (_loginCommand = new DelegateCommand<PasswordBox>(ExecuteLoginCommand, CanExecuteGoForwardCommand)); private DelegateCommand _goForwardCommand; public DelegateCommand GoForwardCommand => _goForwardCommand ?? (_goForwardCommand = new DelegateCommand(ExecuteGoForwardCommand)); private void ExecuteGoForwardCommand() { _journal.GoForward(); } private bool CanExecuteGoForwardCommand(PasswordBox passwordBox) { this.IsCanExcute=_journal != null && _journal.CanGoForward; return true; } public void OnNavigatedTo(NavigationContext navigationContext) { //MessageBox.Show("从CreateAccount导航到LoginMainContent"); _journal = navigationContext.NavigationService.Journal; var loginId= navigationContext.Parameters["loginId"] as string; if (loginId!=null) { this.CurrentUser = new User() { LoginId=loginId}; } LoginCommand.RaiseCanExecuteChanged(); }
CreateAccountViewModel.cs(修改代码部分):
IRegionNavigationJournal _journal; private DelegateCommand _goBackCommand; public DelegateCommand GoBackCommand => _goBackCommand ?? (_goBackCommand = new DelegateCommand(ExecuteGoBackCommand)); void ExecuteGoBackCommand() { _journal.GoBack(); } public void OnNavigatedTo(NavigationContext navigationContext) { //MessageBox.Show("从LoginMainContent导航到CreateAccount"); _journal = navigationContext.NavigationService.Journal; }
效果如下:
选择退出导航日志
如果不打算将页面在导航过程中不加入导航日志,例如LoginMainContent页面,可以通过实现IJournalAware并从PersistInHistory()返回false
public class LoginMainContentViewModel : IJournalAware { public bool PersistInHistory() => false; }
小结
prism的导航系统可以跟wpf导航并行使用,这是prism官方文档也支持的,因为prism的导航系统是基于区域的,不依赖于wpf,不过更推荐于单独使用prism的导航系统,因为在MVVM模式下更灵活,支持依赖注入,通过区域管理器能够更好的管理视图View,更能适应复杂应用程序需求,wpf导航系统不支持依赖注入模式,也依赖于Frame元素,而且在导航过程中也是容易强依赖View部分,下一篇将会讲解Prism的对话框服务。
Prism系列相关文章
- .NET 5 WPF MVVM框架之Prism数据绑定
- .NET 5 WPF MVVM框架之Prism命令
- .NET 5 WPF MVVM框架Prism模块化
- .NET 5 WPF MVVM框架Prism事件聚合器
- .NET 5 WPF MVVM框架Prism区域管理器
- .NET 5 WPF MVVM框架Prism导航系统
- .NET 5 WPF MVVM框架Prism对话框服务
源码
最后,附上整个demo的源代码:PrismDemo源码
作者: RyzenAdorer
出处:https://www.cnblogs.com/ryzen/p/12703914.html
版权:本文采用「署名-非商业性使用-相同方式共享 4.0 国际」知识共享许可协议进行许可。
本文转载自博客园,原文链接:https://www.cnblogs.com/ryzen/p/12703914.html,本文观点不代表江湖人士立场,转载请联系原作者。