ContinuationManager恢复冻结WP8.1

Question

I am using PickSingleFileAndContinue() method to pick the picture and resuming to my app. In overrided OnActivated() I call RestoreAsync() and after that calling ContinueFileOpenPicker() from ContinuationManager class:

var settingsPage = SimpleIoc.Default.GetInstance<SettingsViewModel>();
if (settingsPage != null && args is FileOpenPickerContinuationEventArgs)
 {
  settingsPage.ContinueFileOpenPicker(args as FileOpenPickerContinuationEventArgs);
 }

To debug app I am using information from this page: https://msdn.microsoft.com/en-us/library/dn631755.aspx

After picking image from provider, application successfully calling ContinueFileOpenPicker with right arguments with StorageFile object, when I am continue to step over by step, at the and of last method at the constructor of the ViewModel I cannot continue to debug, because the app and sometimes VS2013 freezing. I can hold back and Swipe-down app, but whatever need to waiting for app. After that, app is crashing. Please, I cannot catch exception... Help. :(

Answer 1

Your SettingsViewModel should inherit IFileOpenPickerContinuable ,

public class SettingsViewModel : Screen, IFileOpenPickerContinuable

Frames are in some cases associated with the View not the ViewModel. Thus you should add a custom method for this to work:

Add in ContinuationManager.cs

internal void Continue(IContinuationActivatedEventArgs args, IFileOpenPickerContinuable filepickerPage)
{
    if (args == null)
        throw new ArgumentNullException("args");

    if (this.args != null && !handled)
        throw new InvalidOperationException("Can't set args more than once");

    this.args = args;
    this.handled = false;
    this.id = Guid.NewGuid();

    if (wabPage == null)
        return;

    switch (args.Kind)
    {
        case ActivationKind.PickFileContinuation:
            if (filepickerPage != null)
            {
                filepickerPage.ContinueFileOpenPicker(args as FileOpenPickerContinuationEventArgs);
            }
            break;

        case ActivationKind.PickSaveFileContinuation:
            break;

        case ActivationKind.PickFolderContinuation:
            break;

        case ActivationKind.WebAuthenticationBrokerContinuation:
            break;
    }
}

Ensure that the SettingsViewModel that is returned from

var settingsPage = SimpleIoc.Default.GetInstance<SettingsViewModel>();

is the same instance that called PickSingleFileAndContinue , otherwise it will not work, it will keep on suspending and waiting for something to return control.

Then in App.xaml.cs you can add:

 protected override void OnActivated(IActivatedEventArgs e)
 {
      base.OnActivated(e);
      // Add all of the Frame code

      var continuationEventArgs = e as IContinuationActivatedEventArgs;
      continuationManager = new ContinuationManager();
      SettingsViewModel settingsPage = SimpleIoc.Default.GetInstance<SettingsViewModel>();

      if (continuationEventArgs != null)
      {
          continuationManager.Continue(continuationEventArgs, settingsPage);
      }
  }

But should I repeat code from OnLaunched?

No, only the OnActivate code should be called, the rest should stay as is (but you could do whatever you want)