为什么不直接传递一个类型呢？这样就没有魔线了
例如
public void NavigateOverview()
{
base._eventAggregator.Publish(new NavigateEvent(typeof(OverviewViewModel)));
}
然后：
public void Handle(NavigateEvent navigate)
{
InnerViewModel target;
// EDIT: Remove the case (only works with integral types so you can't use typeof etc)
// but you could do this with standard conditional logic
this.CurrentInnerViewModel = target;
}
编辑2：
好的，既然您询问了如何构建到 CMs IoC 中，这里是一个将 IoC 与 Castle Windsor 一起使用的示例，以及一个将附加参数传递给导航的解决方案（借用自EventAggregator）
引导程序只需要一些零碎的东西来配置容器：
public class AppBootstrapper : Bootstrapper<ShellViewModel>
{
// The Castle Windsor container
private IWindsorContainer _container;
protected override void Configure()
{
base.Configure();
// Create the container, install from the current assembly (installer code shown in next section below)
_container = new WindsorContainer();
_container.Install(FromAssembly.This());
}
// Matches up with Windsors ResolveAll nicely
protected override IEnumerable<object> GetAllInstances(Type service)
{
return (IEnumerable<object>)_container.ResolveAll(service);
}
// Matches up with Windsors Resolve
protected override object GetInstance(Type service, string key)
{
return string.IsNullOrEmpty(key) ? _container.Resolve(service) : _container.Resolve(key, service);
}
// Windsor doesn't do property injection by default, but it's easy enough to get working:
protected override void BuildUp(object instance)
{
// Get all writable public properties on the instance we will inject into
instance.GetType().GetProperties().Where(property => property.CanWrite && property.PropertyType.IsPublic)
// Make sure we have a matching service type to inject by looking at what's registered in the container
.Where(property => _container.Kernel.HasComponent(property.PropertyType))
// ...and for each one inject the instance
.ForEach(property => property.SetValue(instance, _container.Resolve(property.PropertyType), null));
}
}
CM 的 Windsor 安装程序可能很简单：
public class CaliburnMicroInstaller : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
// Register the window manager
container.Register(Component.For<IWindowManager>().ImplementedBy<WindowManager>());
// Register the event aggregator
container.Register(Component.For<IEventAggregator>().ImplementedBy<EventAggregator>());
}
}
我还有一个导航服务界面来帮助应用程序导航：
public interface INavigationService
{
void Navigate(Type viewModelType, object modelParams);
}
这是由NavigationService（在几秒钟内向您展示）实现的
这也需要一个 Windsor 安装程序：
public class NavigationInstaller : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
container.Register(Component.For<INavigationService>().ImplementedBy<NavigationService>());
}
}
NavigationService工作原理很像，暴露导航参数的EventAggregator类型应该为它可以接收的每个参数类实现一个通用接口......
界面看起来像这样（大量借鉴 EventAggregator）：
// This is just to help with some reflection stuff
public interface IViewModelParams { }
public interface IViewModelParams<T> : IViewModelParams
{
// It contains a single method which will pass arguments to the viewmodel after the nav service has instantiated it from the container
void ProcessParameters(T modelParams);
}
例子：
public class ExampleViewModel : Screen,
// We can navigate to this using DefaultNavigationArgs...
IViewModelParams<DefaultNavigationArgs>,
// or SomeNavigationArgs, both of which are nested classes...
IViewModelParams<SomeOtherNavigationArgs>
{
public class DefaultNavigationArgs
{
public string Value { get; private set; }
public DefaultNavigationArgs(string value)
{
Value = value;
}
}
public class OtherNavigationArgs
{
public int Value { get; private set; }
public DefaultNavigationArgs(int value)
{
Value = value;
}
}
public void ProcessParameters(DefaultNavigationArgs modelParams)
{
// Do something with args
DisplayName = modelParams.Value;
}
public void ProcessParameters(OtherNavigationArgs modelParams)
{
// Do something with args. this time they are int!
DisplayName = modelParams.Value.ToString();
}
}
这会导致一些强类型导航（例如，重构友好！）
NavigationService.Navigate(typeof(ExampleViewModel), new ExampleViewModel.DefaultNavigationArgs("hello"));
或者
NavigationService.Navigate(typeof(ExampleViewModel), new ExampleViewModel.OtherNavigationArgs(15));
这也意味着 ViewModel 仍然可以控制它自己的导航参数
好的，回到温莎一会儿；显然我们需要从我们的视图命名空间安装任何视图——Windsors fluent API 使这非常容易：
public class ViewInstaller : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
// The 'true' here on the InSameNamespaceAs causes windsor to look in all sub namespaces too
container.Register(Classes.FromThisAssembly().InSameNamespaceAs<ShellViewModel>(true));
}
}
好的，现在NavigationService实现：
public class NavigationService : INavigationService
{
// Depends on the aggregator - this is how the shell or any interested VMs will receive
// notifications that the user wants to navigate to someplace else
private IEventAggregator _aggregator;
public NavigationService(IEventAggregator aggregator)
{
_aggregator = aggregator;
}
// And the navigate method goes:
public void Navigate(Type viewModelType, object modelParams)
{
// Resolve the viewmodel type from the container
var viewModel = IoC.GetInstance(viewModelType, null);
// Inject any props by passing through IoC buildup
IoC.BuildUp(viewModel);
// Check if the viewmodel implements IViewModelParams and call accordingly
var interfaces = viewModel.GetType().GetInterfaces()
.Where(x => typeof(IViewModelParams).IsAssignableFrom(x) && x.IsGenericType);
// Loop through interfaces and find one that matches the generic signature based on modelParams...
foreach (var @interface in interfaces)
{
var type = @interface.GetGenericArguments()[0];
var method = @interface.GetMethod("ProcessParameters");
if (type.IsAssignableFrom(modelParams.GetType()))
{
// If we found one, invoke the method to run ProcessParameters(modelParams)
method.Invoke(viewModel, new object[] { modelParams });
}
}
// Publish an aggregator event to let the shell/other VMs know to change their active view
_aggregator.Publish(new NavigationEventMessage(viewModel));
}
}
现在，shell 可以处理聚合器消息并激活新注入和额外配置的 VM
public class ShellViewModel : Conductor<IScreen>, IHandle<NavigationEventMessage>
{
private IEventAggregator _aggregator;
private INavigationService _navigationService;
public ShellViewModel(IEventAggregator aggregator, INavigationService _navigationService)
{
_aggregator = aggregator;
_aggregator.Subscribe(this);
_navigationService.Navigate(typeof (OneSubViewModel), null);
}
public void Handle(NavigationEventMessage message)
{
ActivateItem(message.ViewModel);
}
}
实际上，我将导航限制为 IScreen 实现，所以我的 NavigationEventMessage 实际上看起来像这样：
public class NavigationEventMessage
{
public IScreen ViewModel { get; private set; }
public NavigationEventMessage(IScreen viewModel)
{
ViewModel = viewModel;
}
}
这是因为我总是想要我的子视图模型的生命周期