我也在使用 MVVM Light。我有一个名为 PageConductor 的类,它基于 Microsoft 的 John Papa(Silverlight MVP)使用的类。这是我使用的 PageConductor 服务
public class PageConductor : IPageConductor
{
protected Frame RootFrame { get; set; }
public PageConductor()
{
Messenger.Default.Register<Messages.FrameMessage>(this, OnReceiveFrameMessage);
}
public void DisplayError(string origin, Exception e, string details)
{
string description = string.Format("Error occured in {0}. {1} {2}", origin, details, e.Message);
var error = new Model.Error() { Description = description, Title = "Error Occurred" };
Messenger.Default.Send(new Messages.ErrorMessage() { Error = error });
}
public void DisplayError(string origin, Exception e)
{
DisplayError(origin, e, string.Empty);
}
private void OnReceiveFrameMessage(Messages.FrameMessage msg)
{
RootFrame = msg.RootFrame;
}
private void Go(string path, string sender)
{
RootFrame.Navigate(new Uri(path, UriKind.Relative));
}
public void GoBack()
{
RootFrame.GoBack();
}
}
在我的 MainPage.xaml.cs 构造函数中,我有这个,它在我的 PageConductor 服务中创建 ContentFrame 的实例:
Messenger.Default.Send(new Messages.FrameMessage() { RootFrame = ContentFrame });
然后,我使用依赖项注入将 PageConductor 服务的实例实例化到我的 MainPage ViewModel 中。这是我的 MainViewModel 类:
protected Services.IPageConductor PageConductor { get; set; }
public RelayCommand<string> NavigateCommand { get; set; }
public MainViewModel(Services.IPageConductor pageConductor)
{
PageConductor = pageConductor;
RegisterCommands();
}
private void RegisterCommands()
{
NavigateCommand = new RelayCommand<string>(
(source) => OnNavigate(source));
}
private void OnNavigate(string sender)
{
PageConductor.GoToView(sender, "main");
}
请注意,我的 PageConductorService 实例作为 MainViewModel 构造函数方法中的参数。我通过 ViewModelLocator 传递此信息:
private readonly TSMVVM.Services.ServiceProviderBase _sp;
public ViewModelLocator()
{
_sp = Services.ServiceProviderBase.Instance;
CreateMain(_sp);
}
#region MainPageViewModel
public static MainViewModel MainStatic
{
get
{
Services.ServiceProviderBase SP = Services.ServiceProviderBase.Instance;
if (_main == null)
{
CreateMain(SP);
}
return _main;
}
}
[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance",
"CA1822:MarkMembersAsStatic",
Justification = "This non-static member is needed for data binding purposes.")]
public MainViewModel Main
{
get
{
return MainStatic;
}
}
public static void ClearMain()
{
_main.Cleanup();
_main = null;
}
public static void CreateMain(Services.ServiceProviderBase SP)
{
if (_main == null)
{
_main = new MainViewModel(SP.PageConductor);
}
}
#endregion
为了进一步参考,我的 Messages.FrameMessage 类很简单:
internal class FrameMessage
{
public Frame RootFrame { get; set; }
}
我对前进/后退按钮没有任何问题。