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[Bug] CollectionView is broken on Android, when items have different sizes and ItemSizingStrategy="MeasureAllItems" #13781

Open Elashi opened 3 years ago

Elashi commented 3 years ago

Description

In CollectionView (vertically oriented) when I have items of different sizes , the CollectionView wrongly adds a white/blank space above smaller items. When I scroll back and forth , the white space goes away.

Steps to Reproduce

  1. Create a vertical CollectionView with items of different sizes. Make sure you have more items than what the screen fits to make sure scrolling is required.
  2. Scroll down to items that are smaller than what is currently displayed
  3. A white space will appear before each small item
  4. Scroll down a little bit more to hide the erroneous item (until it is completely hidden)
  5. Then scroll back up to show the erroneous item . The space will go away.

Expected Behavior

Each item should have the correct height without empty space above.

Actual Behavior

Smaller hidden items are displayed with space above it when we scroll down to them.

Basic Information

Environment

Show/Hide Visual Studio info ``` Microsoft Visual Studio Community 2019 Version 16.8.4 VisualStudio.16.Release/16.8.4+30907.101 Microsoft .NET Framework Version 4.8.04084 Installed Version: Community Visual C++ 2019 00435-60000-00000-AA648 Microsoft Visual C++ 2019 ASP.NET and Web Tools 2019 16.8.557.25636 ASP.NET and Web Tools 2019 ASP.NET Core Razor Language Services 16.1.0.2052803+84e121f1403378489b842e1797df2f3f5a49ac3c Provides languages services for ASP.NET Core Razor. ASP.NET Web Frameworks and Tools 2019 16.8.557.25636 For additional information, visit https://www.asp.net/ Azure App Service Tools v3.0.0 16.8.557.25636 Azure App Service Tools v3.0.0 Azure Functions and Web Jobs Tools 16.8.557.25636 Azure Functions and Web Jobs Tools C# Tools 3.8.0-5.20604.10+9ed4b774d20940880de8df1ca8b07508aa01c8cd C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used. Common Azure Tools 1.10 Provides common services for use by Azure Mobile Services and Microsoft Azure Tools. Extensibility Message Bus 1.2.6 (master@34d6af2) Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration. GitHub.VisualStudio 2.11.106.19330 A Visual Studio Extension that brings the GitHub Flow into Visual Studio. IntelliCode Extension 1.0 IntelliCode Visual Studio Extension Detailed Info Microsoft Azure Tools 2.9 Microsoft Azure Tools for Microsoft Visual Studio 2019 - v2.9.30924.1 Microsoft Continuous Delivery Tools for Visual Studio 0.4 Simplifying the configuration of Azure DevOps pipelines from within the Visual Studio IDE. Microsoft JVM Debugger 1.0 Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines Microsoft Library Manager 2.1.113+g422d40002e.RR Install client-side libraries easily to any web project Microsoft MI-Based Debugger 1.0 Provides support for connecting Visual Studio to MI compatible debuggers Microsoft Visual C++ Wizards 1.0 Microsoft Visual C++ Wizards Microsoft Visual Studio Tools for Containers 1.1 Develop, run, validate your ASP.NET Core applications in the target environment. F5 your application directly into a container with debugging, or CTRL + F5 to edit & refresh your app without having to rebuild the container. Microsoft Visual Studio VC Package 1.0 Microsoft Visual Studio VC Package Mono Debugging for Visual Studio 16.8.43 (00471f8) Support for debugging Mono processes with Visual Studio. NuGet Package Manager 5.8.1 NuGet Package Manager in Visual Studio. For more information about NuGet, visit https://docs.nuget.org/ ProjectServicesPackage Extension 1.0 ProjectServicesPackage Visual Studio Extension Detailed Info SQL Server Data Tools 16.0.62012.31170 Microsoft SQL Server Data Tools Test Adapter for Boost.Test 1.0 Enables Visual Studio's testing tools with unit tests written for Boost.Test. The use terms and Third Party Notices are available in the extension installation directory. Test Adapter for Google Test 1.0 Enables Visual Studio's testing tools with unit tests written for Google Test. The use terms and Third Party Notices are available in the extension installation directory. TypeScript Tools 16.0.21016.2001 TypeScript Tools for Microsoft Visual Studio Visual Basic Tools 3.8.0-5.20604.10+9ed4b774d20940880de8df1ca8b07508aa01c8cd Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used. Visual F# Tools 16.8.0-beta.20507.4+da6be68280c89131cdba2045525b80890401defd Microsoft Visual F# Tools Visual Studio Code Debug Adapter Host Package 1.0 Interop layer for hosting Visual Studio Code debug adapters in Visual Studio Visual Studio Container Tools Extensions 1.0 View, manage, and diagnose containers within Visual Studio. Visual Studio Tools for CMake 1.0 Visual Studio Tools for CMake Visual Studio Tools for Containers 1.0 Visual Studio Tools for Containers VisualStudio.DeviceLog 1.0 Information about my package VisualStudio.Mac 1.0 Mac Extension for Visual Studio Xamarin 16.8.000.261 (d16-8@bb99248) Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android. Xamarin Designer 16.8.0.507 (remotes/origin/d16-8@e87b24884) Visual Studio extension to enable Xamarin Designer tools in Visual Studio. Xamarin Templates 16.8.112 (86385a3) Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms. Xamarin.Android SDK 11.1.0.26 (d16-8/a36ce73) Xamarin.Android Reference Assemblies and MSBuild support. Mono: 5e9cb6d Java.Interop: xamarin/java.interop/d16-8@79d9533 ProGuard: Guardsquare/proguard/proguard6.2.2@ebe9000 SQLite: xamarin/sqlite/3.32.1@1a3276b Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-8@2fb1cbc Xamarin.iOS and Xamarin.Mac SDK 14.8.0.3 (c51fabee8) Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support. ```

Screenshots

When scrolling down to smaller items, notice the blank area above the last two items: Screenshot_1613505058

After scrolling down a little bit more until the erroneous item is hidden up then scroll back up to re show the previous erroneous item, you will notice that the blank space has gone away (I think because it is refreshed). But this only happens for the first erroneous item because I did not scroll down enough to hide the second erroneous item to cause a refresh to it so it kept the white space above it: Screenshot_1613505068

This is how it works in XF 4.8: Screenshot_1613506924

Worth mentioning

This application is setup to work as a Right To Left application. As you may have noticed from the screenshots.

Elashi commented 3 years ago

By the way, the problem exists in iOS too..

I get bad (and depressing) feedback from my clients for both platforms (iOS and Android) ! This causes a lot of flickering and unstable scrolling also.

Elashi commented 3 years ago

Any news :'-(