Xamarin.forms: NavigationPage.HasBackButton binding doesn't work on iOS

[borbmizzet]

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.

[felipemomm]

@samhouts I've tested it using XF 4.0 and it seems to be working fine (switches between hamburger menu and back button).

CC: @borbmizzet