TapGestureRecognizer NumberOfTapsRequired=2 Handled Differently on Windows and Android

[david-maw]

Description

If a Label control specifies two TapGestureRecognizer items, on for a single tap, one for a double tap the behavior in Windows and Android differs. If you double tap on the Label in Android it fires the double tap event, but in Windows it fires the tap event twice and then the double tap event.

Steps to Reproduce

1. Load the git repository and open up the project
2. Build and run on Android
3. Double Tap/Click on the "Tap Me" Text
4. In the output window you should see "[0:] >>> OnDoubleTap Called"
5. Build and run on Windows
6. Double Tap/Click on the "Tap Me" Text
7. In the output window you should see

>>> OnTap Called
>>> OnTap Called
>>> OnDoubleTap Called

Link to public reproduction project repository

https://github.com/david-maw/Bug-MAUI-Taps.git

Version with bug

Unknown/Other

Last version that worked well

Unknown/Other

Affected platforms

Windows

Affected platform versions

Windows 10

Did you find any workaround?

Using Buttons=Secondary instead of NumberOfTapsRequired=2 on Windows worked in my case. It changed the UI slightly but did the job. So you end up with attributes like this:
NumberOfTapsRequired="{OnPlatform Default=2, WinUI=1}" Buttons="Secondary"

Which creates a 'double tap' event that works (if slightly differently) on both Windows and Android

Relevant log output

No response

[XamlTest]

Verified this on Visual Studio Enterprise 17.8.0 Preview 1.0. Repro on iOS 16.4 and Windows 11(8.0.100-preview.6.23330.14), not repro on Android 13.0-API33 with below Project:
Taps.zip

[jfversluis]

Almost duplicate but not entirely, at least related to #6407

[MartyIX]

WinUI 3 behavior seems to be described by this document https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.uielement.tapped?view=winrt-22621#remarks which mentions

If a user interaction also fires DoubleTapped, Tapped will fire first to represent the first tap, but the second tap won't fire an additional Tapped. If you want different logic for Tapped versus DoubleTapped, your Tapped handler may need to use app-specific variables and a timer in order to avoid running on interactions that are eventually interpreted as a DoubleTap action.

So on Windows one would expect:

1. >>> OnTap Called
2. >>> OnDoubleTap Called

I think.

[david-maw]

Right @MartyIX it's a question every UI platform must answer - do you report a tap immediately or delay reporting it until after you are sure there will not be another one. Either answer is understandable, but a cross-platform solution should ideally pick one or the other and stick with it even when that's not the mechanism the underlying platform surfaces. For me I prefer the approach that says a double tap (or triple, or whatever) should not report a single tap first, because that's harder to code for, but IMHO it doesn't matter which is chosen, just that it is consistent across platforms.

[david-maw]

Right @MartyIX it's a question every UI platform has to answer for itself - do you report a tap immediately or wait and see if there'll be another one before reporting it. Either answer is understandable, but a cross-platform solution should ideally pick one or the other and stick with it even when that's not the mechanism the underlying implemetation surfaces. For me I prefer the approach that says a double tap (or triple, or whatever) should not report a single tap first because it's harder to code for, but IMHO it doesn't matter which is chosen, just that it is consistent across platforms.

[MartyIX]

@david-maw I tend to agree. My concern is that changing to one behavior or the other would be a breaking change at this point. Anyway, my expectation was that on Windows I would also get only a double tap and not a single tap¹ so I was a bit surprised.

I actually opened #20870 which tries to improve the behavior on Windows a bit. It can't be merged but maybe it will spark some discussion at least.

Footnotes

1. But the page mentions tap+double tap as an intentional behavior. So I guess the rationale behind it is something like "double tap" interval can be long and as such one would get tap events "late" and an app would feel not responsive. I can only speculate about reasons though. Not sure how Android/iOS define double taps. ↩

[david-maw]

@MartyIX It might be a breaking change for apps that run only on one platform but anyone writing cross platform apps involving Windows and Android, for example, must already deal with the fact that more than one event is sometimes generated for a multiple tap notification (presumably triple tap would be accompanied by single and double tap notifications, and so on).

I suppose anyone who's interested in responsiveness is looking for "button down" type notifications anyway, tap notifications being just too slow to arrive since they wait for button up.

I'm curious how IOS, Mac and Tizen handle multi tap, perhaps that could inform how it ought to be handled.

[jcsnider]

Just appending some additional info:

iOS in MAUI 8.0.40 works as described in this comment above where the first tap triggers the tapped event and then the second tap triggers the double tapped event. #16235 (comment)

Android never fires the single tap event and only fires the double tapped event.