xamarin/Xamarin.Forms

NavigationPage.HasBackButton binding doesn't work on iOS

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#3,389 opened on Jul 24, 2018

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e/3 :clock3:help wantedinactivep/iOS 🍎t/bug :bug:up-for-grabs

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Description

Description

NavigationPage.HasBackButton binding doesn't work on iOS (works on android)

Steps to Reproduce

  1. Bind NavigationPage.HasBackButton in xaml to a bool (initialize to false) in the view model
  2. Wait a bit after the page loads, and change the bool to true

Expected Behavior

Back button should appear when the bool is set to true

Actual Behavior

The PropertyChanged notification of the bool does not cause the back button to appear.

Basic Information

  • Version with issue: 3.1.0.637273
  • Last known good version: Unknown
  • IDE: Vs 15.7.5
  • Platform Target Frameworks: .NetStandard 2.0
    • iOS: 11.4
  • Nuget Packages:
  • Affected Devices: iPhone

Reproduction Link

HasBackButtonFailure.zip

Download the zip, deploy the ios project, click one of the list items, click the EnableBackButton Button. IT doesnt work. Deploy it on android, and it works properly.

Contributor guide

Research direction
Investigate the iOS platform specific handler for NavigationPage.HasBackButton binding. Check if the property change is being propagated to the native navigation bar. Compare with Android implementation to find the gap.
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.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Xamarin.FormsiOS development
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60