search

xamarin / Xamarin.Forms

Xamarin.Forms is no longer supported. Migrate your apps to .NET MAUI.
https://aka.ms/xamarin-upgrade
Other
5.62k stars 1.87k forks source link

CarouselView issue when adding new pages while scrolling[Bug] #14260

Open dzebas opened 3 years ago

dzebas commented 3 years ago

Description

CarouselView initializes pages which are not in view yet while adding new items to ItemSoucce during ThresholdReached or CurrentItemChanged events/commands. It works correctly if you add pages via button, e.g. when CarouselView is not scrolling. Because of this WebView height inside CarouselView is not correct.

Steps to Reproduce

Scenario with the issue:

  1. Get demo project https://github.com/dzebas/CarouselDemo
  2. Set a breakpoint in Android's CustomWebViewRenderer.cs line 41
  3. Run Android project
  4. When MainPage is loaded carousel_CurrentItemChanged will be triggered in MainPage.xaml.cs and LoadMore in MainPageViewModel.cs is called
  5. Breakpoint will be triggered, note the value of view.ContentHeight (always correct for 1st and 2nd pages)
  6. Scroll to second page
  7. Breakpoint will be triggered again, this time for second page as it's being displayed (height will be correct again)
  8. Once you scroll to the middle carousel_CurrentItemChanged will be triggered as well and 3rd page will be loaded This is where problem happens - breakpoint will be triggered for 3rd page even if it's not being presented yet. You will notice than in the renderer view.Width is 0, so height will be incorrect.
  9. If you keep scrolling same happens with the rest of pages

Scenario without the issue:

  1. Comment code in carousel_CurrentItemChanged
  2. Run Android project
  3. First page will be created
  4. Click 'Add' in toolbar, it will create second page
  5. Scroll to second page, breakpoint will be triggered as second page is about to be presented (height is correct)
  6. Click 'Add' again to create third page
  7. Scroll to third page and so on - all pages will be created with correct heights

Expected Behavior

Scenario 1 should work exactly the same as scenario 2, e.g. when new items are added to ItemsSource if page is off screen it should not be rendered/calculated.

Actual Behavior

Pages are initialized/calculated while off screen if adding new items during scrolling.

Basic Information

Environment

Show/Hide Visual Studio info ``` Microsoft Visual Studio Community 2019 Version 16.9.4 VisualStudio.16.Release/16.9.4+31205.134 Microsoft .NET Framework Version 4.8.04084 Installed Version: Community Visual C++ 2019 00435-60000-00000-AA544 Microsoft Visual C++ 2019 ASP.NET and Web Tools 2019 16.9.693.2781 ASP.NET and Web Tools 2019 ASP.NET Core Razor Language Services 16.1.0.2112521+5741df381174d72f08e3632bb99f52e8635b6a1a Provides languages services for ASP.NET Core Razor. ASP.NET Web Frameworks and Tools 2019 16.9.693.2781 For additional information, visit https://www.asp.net/ Azure App Service Tools v3.0.0 16.9.693.2781 Azure App Service Tools v3.0.0 Azure Functions and Web Jobs Tools 16.9.693.2781 Azure Functions and Web Jobs Tools C# Tools 3.9.0-6.21160.10+59eedc33d35754759994155ea2f4e1012a9951e3 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. ConvertToDevExtremeCommand Extension 1.0 ConvertToDevExtremeCommand Visual Studio Extension Detailed Info CreateLayoutWizard 1.0 Create layout wizard. DevExpress Reporting Extension 1.2 A Visual Studio extension that invokes the Report Designer editor for report definition REPX files. DevExpress Reporting Tools Extension 1.0 Extends Visual Studio with tools required for the Report Designer editor. DevExpress.DeploymentTool 1.0 A useful tool for deploying DevExpress assemblies. DevExpress.Win.LayoutAssistant Extension 1.0 DevExpress.Win.LayoutAssistant Visual Studio Extension Detailed Info Extensibility Message Bus 1.2.6 (master@34d6af2) Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration. IntelliCode Extension 1.0 IntelliCode Visual Studio Extension Detailed Info Microsoft Azure Tools 2.9 Microsoft Azure Tools for Microsoft Visual Studio 2019 - v2.9.40331.1 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 16.9.7 (df23ba6) Support for debugging Mono processes with Visual Studio. NuGet Package Manager 5.9.0 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 Remoting SDK for .NET 1.0 Visual Studio Integration package SQL Server Data Tools 16.0.62103.10080 Microsoft SQL Server Data Tools TypeScript Tools 16.0.30201.2001 TypeScript Tools for Microsoft Visual Studio Visual Basic Tools 3.9.0-6.21160.10+59eedc33d35754759994155ea2f4e1012a9951e3 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 16.9.0-beta.21102.9+7ce7132f1459095e635194d09d6f73265352029a 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 Containers 1.0 Visual Studio Tools for Containers VisualStudio.DeviceLog 1.0 Information about my package VisualStudio.Foo 1.0 Information about my package VisualStudio.Mac 1.0 Mac Extension for Visual Studio Xamarin 16.9.000.273 (d16-9@1bba9e0) Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android. Xamarin Designer 16.9.0.318 (remotes/origin/7b35adcdd1b204bbdcb279e0f029d151a20a4bf3@7b35adcdd) Visual Studio extension to enable Xamarin Designer tools in Visual Studio. Xamarin Templates 16.9.72 (426ebf6) Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms. Xamarin.Android SDK 11.2.2.1 (d16-9/877f572) Xamarin.Android Reference Assemblies and MSBuild support. Mono: 5e9cb6d Java.Interop: xamarin/java.interop/d16-9@54f8c24 ProGuard: Guardsquare/proguard/v7.0.1@912d149 SQLite: xamarin/sqlite/3.34.1@daff8f4 Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-9@d210f11 Xamarin.iOS and Xamarin.Mac SDK 14.14.2.5 (3836759d4) Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support. ```

Reproduction Link

https://github.com/dzebas/CarouselDemo

mubaarakhassan commented 3 years ago

Experiencing the same issues. Seems like the in the OnElementChanged of the CustomWebViewRenderer gets called only twice after that it just goes straight into NavigationDelegate.

The weird thing is if you set a breakpoint inside carousel_CurrentItemChanged at the end of the function and press add it seems to be working smoothly.