xamarin/Xamarin.Forms

TemplateBinding issue with iOS

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#2,146 opened on Mar 20, 2018

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a/binding ⛓e/4 :clock4:help wantedp/iOS 🍎t/bug :bug:up-for-grabs

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Description

Description

TemplateBinding for ICommand not working from within a ControlTemplate on Xamarin Forms iOS whereas it works as expected on Xamarin Forms Android.

Steps to Reproduce

  1. Bind the ItemTapped Command Property from an extended ListView contained in a ControlTemplate used on a ContentPage

Expected Behavior

Expected Behavior is that the ICommand in the ViewModel is executed which happens correctly on Android.

Actual Behavior

Actual Behavior on iOS is that somehow the ListView.ItemTapped event appears not to run although the ICommand is executed. The result is that the Command Parameters are never passed. The sample app can be used to illustrate this, a breakpoint in ListViewEx.OnItemTapped is never hit.

Basic Information

  • Version with issue: 2.5.0.28055
  • Last known good version: Unknown
  • IDE: VS2017
  • Platform Target Frameworks:
    • iOS: 11.2
    • Android: 4.0.3
  • Android Support Library Version: 25.4.0.2
  • Nuget Packages: Default Forms App
  • Affected Devices: iOS devices

Reproduction Link

App12.zip

Contributor guide

Research direction
Investigate the iOS specific binding behavior for ICommand in ControlTemplates. Check if there is a difference in how events are propagated on iOS vs Android. Trace the execution path in the reproduction app to identify where the binding fails.
Tech stack
csharp
Domain
mobile dev
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
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.FormsiOS
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70