.NET Core 3 WPF MVVM框架 Prism系列之导航系统
本文将介绍如何在.net core3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
一.区域导航
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
1.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>
2.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>(); }
3.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:
二.view和viewmodel参与导航过程
1.inavigationaware
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
2.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
3.iconfirmnavigationrequest
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:
三.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:
四.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; }
五.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
六.源码
最后,附上整个demo的源代码:prismdemo源码
上一篇: 工厂方法模式(Factory Method Pattern)
下一篇: C指针 (ノ゚▽゚)ノ
推荐阅读
-
.NET Core 3 WPF MVVM框架 Prism系列之模块化
-
.NET Core 3 WPF MVVM框架 Prism系列之区域管理器
-
.NET Core 3 WPF MVVM框架 Prism系列之事件聚合器
-
.NET Core 3 WPF MVVM框架 Prism系列之对话框服务
-
.NET Core 3 WPF MVVM框架 Prism系列之导航系统
-
.NET Core 3 WPF MVVM框架 Prism系列之区域管理器
-
.NET Core 3 WPF MVVM框架 Prism系列之模块化
-
.NET Core 3 WPF MVVM框架 Prism系列之事件聚合器
-
.NET Core 3 WPF MVVM框架 Prism系列之导航系统
-
.NET Core 3 WPF MVVM框架 Prism系列之对话框服务