Bound ComboBox within a page and frame not working as expected - WinUI 3

youki 996

Hi,

i have a bound ComboBox which i've already posted here.

I'm adding a separator by a TemplateSelector but to disable the separator, I have to iterate the ComboBoxItems in the Tapped event and set the IsEnabled property to false. This has to be happened in the Tapped event because this is the only event where the items are already rendered, I guess.

This is in MainWindow.xaml and is working great.

Now I have the exact same code on another page (SelectFunction.xaml) which is opened by a frame in MainWindow.xaml but the Tapped event is not working as expected like in MainWindow.xaml. The event gets only sporadically fired, mostly only, if you click near the area of the arrow. It's weird. I've tried a few things from posts where people had similar problems:

setting a background on the Frame/ ComboBox
setting the isHitTestVisible property
isSynchronizeWithCurrentItem (this throws an error when opening the ComboBox)

Further, even if i can disable iterate the items i can't get the item as before with ItemContainerGenerator because i get an Access Violation and the item is null even, if I can get the values by casting.

I've tried to change the ComboBox Access by using the name, casting the sender, getting it by a static instance of the page (winrt::App1::implementation::SelectFunction* SelectFunction::s_selectFunction;)

I've added the items from code behind at first because and it's only text that i would need no template. It works great but it's not that practical, so i changed to binding.

From code behind like so but really ugly, if i have 30 items and it's dynamically changing:

winrt::Microsoft::UI::Xaml::Controls::ComboBoxItem cmbi0;
cmbi0.Name(L"cmbiNoAction");
cmbi0.Content(winrt::box_value(L"Keine Aktion"));
cmbFunction().Items().Append(winrt::box_value(cmbi0));

winrt::Microsoft::UI::Xaml::Controls::NavigationViewItemSeparator separator1;

winrt::Microsoft::UI::Xaml::Controls::ComboBoxItem cmbiA;
cmbiA.IsEnabled(false);
cmbiA.Content(winrt::box_value(separator1));
cmbFunction().Items().Append(winrt::box_value(cmbiA));

winrt::Microsoft::UI::Xaml::Controls::ComboBoxItem cmbi1;
cmbi1.Content(winrt::box_value(L"Category1"));
cmbi1.IsEnabled(false);
cmbFunction().Items().Append(winrt::box_value(cmbi1));

It looks like a WinUi 3 bug to me, what are you thinking?

Junjie Zhu - MSFT 15,211 Reputation points Microsoft Vendor

2023-01-25T05:38:27.0133333+00:00

Hi @youki ,

Welcome to Microsoft Q&A!

Could you please show more information about Tapped event in SelectFunction.xaml .

I used your code to populate the ComboBox but didn't reproduce the same issue, maybe I'm missing something?

Thank you.
youki 996 Reputation points

2023-01-25T19:36:53.66+00:00
Hi,

thought this post was deleted because of community rules violation, what it says yesterday but OK. :)

As i've said, it's the same code but it's an unpackaged app in C++.

I've also tried to add the Tapped event by code which changes nothing.

From my memory:

cmbFunction().Tapped({this, &SelectFunction::cmbFunction_Tapped});

What i've found is that 2 more events get the items by ItemContainerGenerator (GotFocus & GettingFocus). I've tried almost all events from the documentation. At the end I'm using GotFocus as a workaround. In the first call I'm deactivating the event with event_token after iterating of the ComboBoxItems because, if the ComboBox closes, the GotFocus gets called a second time. Then it's iterating the items again and throws an Memory Access Violation.

That works.

I think it's not that bad because practically i only need to disable the specific items only 1 time. I mean it also gets disabled in the Tapped event in MainWindow.xaml again and again every time i'm clicking on the ComboBox which is usualy no problem but OK?!

By the way it still throws the following exception the whole time. In an other post an collegue of you said that it's a first chance exception and that i can ignore it, if i can remember correctly.

(I think the new Q&A is still a little bit buggy. If i scroll on through the 4 pages in pager control of my Q&A section in my profile, it shows always the same 30 posts :))

Exception thrown at 0x00007FFC0F7606BC (KernelBase.dll) in App1.exe: 0x40080202: WinRT transform error (parameters: 0x000000008000000B, 0x0000000080070490, 0x0000000000000014, 0x0000001ECEB06C30). Exception thrown at 0x00007FFC0F7606BC (KernelBase.dll) in App1.exe: 0x40080202: WinRT transform error (parameters: 0x000000008000000B, 0x0000000080070490, 0x0000000000000014, 0x0000001ECEB06B10).

I assume you are testing it in C# right.

I think I have to create a new project on the weekend and try to reproduce it. Then it's also ready for the upload on GitHub for the MS Windows.UI.Xaml issue page.

Maybe i have to mention that in the code behind example above you also have to iterate the ComboBox and disable the items, just as a little info in general.
youki 996 Reputation points

2023-01-25T19:45:54.1+00:00
umm,

the code doesn't appear in the code box. Let me try it again.
youki 996 Reputation points

2023-01-27T16:42:17.19+00:00
@Junjie Zhu

OK, GotFocus is not a good workaround this triggers new unsolvable issues.

I think the root of the problem is that I set the selected index of the cmbFunction from the MainWindow.

I'm loading/ calling the SelectFunction.xaml.cpp page

after that i try to set the SelectedIndex

If I do this, the weird behaviour starts that the Tapped event doesn't get fired anymore. If I don't use this function everthing is OK.

Can you reproduce it?

I have this function in SelectFunction.xaml and call it from MainWindow.xaml.cpp. I iterate the comboBox to find the value/ index and then I set SelectedIndex . It's the same value which you can choose in a ListView on MainWindow.xaml. I can't find a solution, may be it's possible by the ViewModel properties?
youki 996 Reputation points

2023-01-27T21:42:50.2+00:00
@Junjie Zhu

I think it must be a bug because I've recognized (very late) that it's similar to a bug that I've already reported and was tested by DarranRowe.

This doesn't seem to be a problem with just AppWindowTitleBar, the problem seems to require WinUI 3 to be active in a window.

C++/WinRT - unpackaged - Customized title bar controls not clickable & SetDragRectangle displays default titlebar

The Tapped event only gets fired, if you click near the arrow button as mentioned and near the border like the bug with the customized title bar. I think it's especially in C++. Man, that makes me sad.

It appears after the first click by the mouse on an item or if you set the selected index.

I found the following post but it doesn't help either:
https://social.msdn.microsoft.com/Forums/vstudio/en-US/4bbd71a3-dc5a-4f70-b4fc-a7e66137e07e/uwpc-pointerreleased-and-tapped-events-of-textbox-are-not-fired-not-fired?forum=wpdevelop

cmbFunction().AddHandler(winrt::Microsoft::UI::Xaml::UIElement::TappedEvent(), winrt::box_value(winrt::Microsoft::UI::Xaml::Input::TappedEventHandler(this, &SelectFunction::cmbFunction_Tapped)), false);
youki 996 Reputation points

2023-01-30T09:18:12.89+00:00

https://github.com/microsoft/microsoft-ui-xaml/issues/8132
Junjie Zhu - MSFT 15,211 Reputation points Microsoft Vendor

2023-01-30T09:24:00.27+00:00

This is my simple test, without adding any other code.

Could you reproduce the same issue in a blank project.