how to block the navigation with alert?

Question

Hi!

in a special page, in particular situation, it is usefull ask to the user if he agrees to exit from this page.

how to block the navigation with alert?

i think that the right place is OnNavigatingFrom...

Dario

Answer 1

The documentation states:

        // Summary:
        //     Invoked immediately after the Page is unloaded and is no longer the current
        //     source of a parent Frame.
        //
        // Parameters:
        //   e:
        //     Event data that can be examined by overriding code. The event data is representative
        //     of the navigation that has unloaded the current Page.
        protected virtual void OnNavigatedFrom(NavigationEventArgs e);

-

Hence that position looks a little too late in the processing. What I'd do:

- e.g. in the Grid App template, break with the debugger in the LayoutAwarePage.OnNavigateFrom(...) override
- find out where you are called from (itemView_ItemClick / GoBack button / other): examine the Call Stack for place of invocation
- place your user interaction there, just before invoking Frame.Navigate(...)

Answer 2

@forinfo: I think there is a misunderstanding, chida is referring to OnNavigatingFrom.

@chida: you are right about OnNavigatingFrom. You can simply override this method. and you are looking for something like:

protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
    var dialog = new MessageDialog("Do you really want to navigate away from this page?", "Please Confirm");
    dialog.Commands.Add(new UICommand("OK", null, 0));
    dialog.Commands.Add(new UICommand("Cancel", null, 1));

    dialog.CancelCommandIndex = 1;
    dialog.DefaultCommandIndex = 0;

    var result = dialog.ShowAsync();

    if (result.Id == 1)
    {
        e.Cancel = true;
    }
    else
    {
        base.OnNavigatingFrom(e);
    }
}

---

Can Bilgin
Blog CompuSight

Answer 3

thank you very much

Answer 4

Of course .. misread

Answer 5

don't work, there is a problem with e.cancel = false :( and first e.Cancel = true

protected async override void OnNavigatingFrom(NavigatingCancelEventArgs e)
        {
            base.OnNavigatingFrom(e);
            e.Cancel = true;

            var dialog = new MessageDialog("Do you really want to navigate away from this page?", "Please Confirm");
            dialog.Commands.Add(new UICommand("OK", null, 0));
            dialog.Commands.Add(new UICommand("Cancel", null, 1));

            dialog.CancelCommandIndex = 1;
            dialog.DefaultCommandIndex = 0;

            var result = await dialog.ShowAsync();
            
            if ( Convert.ToInt16(result.Id) == 1)
            {
                e.Cancel = true;
            }
            else
            {
                base.OnNavigatingFrom(e);
                e.Cancel = false;
            }

        }

Answer 6

a solution

bool _navigabile = false;

protected async override void OnNavigatingFrom(NavigatingCancelEventArgs e)
        {
            base.OnNavigatingFrom(e);
            if (!_navigabile)
            {
                e.Cancel = true;

                var dialog = new MessageDialog("Do you really want to navigate away from this page?", "Please Confirm");
                dialog.Commands.Add(new UICommand("OK", null, 0));
                dialog.Commands.Add(new UICommand("Cancel", null, 1));

                dialog.CancelCommandIndex = 1;
                dialog.DefaultCommandIndex = 0;

                var result = await dialog.ShowAsync();

                if (Convert.ToInt16(result.Id) != 1)
                {
                    _navigabile = true;
                    this.Frame.Navigate(e.SourcePageType);
                }
            }

        }