我正在将Windows Store应用转换为Windows Phone 8。对于WinRT，当调用frame.navigate时，您可以将任何对象作为参数传递。(frame.navigate(type sourcePageType, object parameter))
在Windows Phone上，导航似乎有所不同，您需要通过调用uri来导航，例如：frame.navigate(new uri("mypage.xaml", UriKind.Relative))
Windows文档指出，您可以通过将字符串添加到uri中来将其作为参数传递。
是否有一种接受的方式可以在页面之间传递复杂对象，而我只是没有找到？
我最终扩展了NavigationService类，如下所示：
public static class NavigationExtensions
{
private static object _navigationData = null;
public static void Navigate(this NavigationService service, string page, object data)
{
_navigationData = data;
service.Navigate(new Uri(page, UriKind.Relative));
}
public static object GetLastNavigationData(this NavigationService service)
{
object data = _navigationData;
_navigationData = null;
return data;
}
}
在源页面中，您需要调用 NavigationService.Navigate("mypage.xaml", myParameter); 方法。然后，在目标页面的 OnNavigatedTo 方法中调用 var myParameter = NavigationService.GetLastNavigationData(); 方法以获取参数数据。
我希望能够提供一份VB.net版本的优秀答案翻译，Zik已经提供了很好的答案。一旦我弄清楚了如何将他的代码转换为VB，我立即使导航与WinRT / Windows 8方式类似。
我创建了一个带有以下代码的模块：
Module NavigationExtensionsModule
Sub New()
End Sub
Private _navigationData As Object = Nothing
<System.Runtime.CompilerServices.Extension> _
Public Sub Navigate(service As NavigationService, page As String, data As Object)
_navigationData = data
service.Navigate(New Uri(page, UriKind.Relative))
End Sub
<System.Runtime.CompilerServices.Extension> _
Public Function GetLastNavigationData(service As NavigationService) As Object
Dim data As Object = _navigationData
_navigationData = Nothing
Return data
End Function
End Module
然后像这样转到另一个页面：
NavigationService.Navigate("pagename.xaml", ObjectToPassToThePage)
最后，在OnNavigatedTo子程序中获取另一页中的对象：
ThisPageData = NavigationService.GetLastNavigationData()
Me.DataContext = ThisPageData
Messenger.Default.Send(new PageMessage{message="Hello World"});
Messenger.Default.Register<PageMessage>(this, (action) => ReceiveMessage(action));
private object ReceiveMessage(PageMessage action)
{
string receivedMessage=action.message;
return null;
}
MSDN概述了3种在页面之间传递非字符串参数的方法。包括：自定义导航扩展、静态属性和JSON+隔离存储。代码摘自Microsoft：
/// <summary>
/// Custom Navigation Extensions.
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnMethod1_Click(object sender, RoutedEventArgs e)
{
NavigationService.Navigate("/Result.xaml?name=1", listString);
}
/// <summary>
/// Static properties
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnMethod2_Click(object sender, RoutedEventArgs e)
{
App.ObjectNavigationData = listString;
NavigationService.Navigate(new Uri("/Result.xaml?name=2", UriKind.Relative));
}
/// <summary>
/// Json + IsolatedStorage
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnMethod3_Click(object sender, RoutedEventArgs e)
{
string filePath = "objectData";
using (IsolatedStorageFile isolatedStorage = IsolatedStorageFile.GetUserStoreForApplication())
{
if (isolatedStorage.FileExists(filePath))
{
isolatedStorage.DeleteFile(filePath);
}
using (IsolatedStorageFileStream fileStream = isolatedStorage.OpenFile(filePath, FileMode.Create, FileAccess.Write))
{
string writeDate = string.Empty;
// Json serialization.
using (MemoryStream ms = new MemoryStream())
{
var ser = new DataContractJsonSerializer(typeof(List<string>));
ser.WriteObject(ms, listString);
ms.Seek(0, SeekOrigin.Begin);
var reader = new StreamReader(ms);
writeDate = reader.ReadToEnd();
}
// Save to IsolatedStorage.
using (StreamWriter writer = new StreamWriter(fileStream))
{
writer.WriteLine(writeDate);
}
}
}
NavigationService.Navigate(new Uri("/Result.xaml?name=3", UriKind.Relative));
}
Yes there is a way to use a complex object in different pages in wp8 or wp7. You can use complex objects between pages by IsolatedStorageSettings.
IsolatedStorageSettings AppSettings = IsolatedStorageSettings.ApplicationSettings;
// to save an object in isolatedstoragesettings
if (!AppSettings.Contains("ObjectKey"))
AppSettings.Add("ObjectKey", Your object value);
else
AppSettings["ObjectKey"] = Your object value;
// to retrieve value of an object from isolatedstoragesettings
if(AppSettings.Contains("ObjectKey"))
{
var objectValue = (Cast object to type)AppSettings["ObjectKey"];
//Remove
AppSettings.Remove("ObjectKey");
}
我建议在两个视图模型之间使用服务代理。
首先，定义一个视图模型定位器。在app.xaml的资源字典中创建此类的实例。将每个页面的DataContext设置为视图模型定位器的属性之一。请参见John Papa's blog以获取示例。
其次，创建一个服务代理，其中包含像GetAllItems()和GetItem(string id)这样的方法。在视图模型定位器中创建此服务代理的实例。将此引用传递到两个视图模型中。
第三，通过将DataContext强制转换为视图模型类型来从第二个视图访问视图模型。将导航参数传递给视图模型，以便它可以调用GetItem并填充其属性。
无法发送非字符串的导航参数。我通常使用DataContractJsonSerializer来序列化需要传输的数据（但要注意Uri长度限制）。 还要记得使用Uri.EscapeDataString(parameter)来转义查询字符串参数中的字符。