xamarin/Xamarin.Forms

Crash when calling ChangeCanExecute() from non-UI thread

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#5,679 opened on Mar 25, 2019

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Description

Description

App crashes when running async method which triggers ChangeCanExecute(). I think this should the responsibility of the renderers to trigger any visual updates on the UI thread. The workaround for this problem is to wrap all ChangeCanExecute() in Device.BeginInvokeOnMainThread()

Steps to Reproduce

Run async methods which triggers ChangeCanExecute(). You can i.e. create a button with async Command which changes one of the binding property and this binding property raise ChangeCanExecute() in the setter.

Expected Behavior

App should not crash.

Actual Behavior

App crashes when running async method which triggers ChangeCanExecute(). The problem exists both on Android and iOS.

Basic Information

  • Version with issue: Xamarin Forms 3.6.0.264807
  • Last known good version:
  • IDE: Visual Studio 2017 15.9.4
  • Platform Target Frameworks:
    • iOS: 8.0
    • Android: 8.1

Reproduction Project

Here is a project with a repro:

App1.zip

Contributor guide

Research direction
Investigate the call chain when ChangeCanExecute is invoked from a background thread. Identify where UI updates are triggered and ensure they are marshaled to the main thread.
Tech stack
csharp
Domain
mobile
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#Xamarin.Forms
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75