Xamarin.forms: [Bug] Shell keeps showing menu button in navbar instead of back button in 4.7

[jtorvald]

Description

My code in 4.5 and 4.6 worked fine, but now after upgrading to 4.7 the back button does not show when navigating to a page (iOS). It keeps showing the menu icon (hamburger for the flyout) on every page.

This is probably a terrible bug report because I can't share screenshots/code and can not reproduce it in a new solution with Xamarin Forms 4.7.

Just wanted to file it and I'm hoping that someone can point me in the right direction on how to debug this. Downgrading to 4.6 makes the issue go away.

Steps to Reproduce

I tried to create an example project but there it seems to work

Expected Behavior

Show back on navigating to a page with Shell.Current.GoToAsync or Navigation.PushAsync

Actual Behavior

Shows flyout menu icon

Basic Information

• Version with issue: 4.7
• Last known good version: 4.6

[PureWeen]

@jtorvald are you using BackButtonBehavior on any of your pages?

[jtorvald]

@PureWeen yeah in two login pages but they are not 'hit' in the flow since I'm already logged in and I load a different AppShell on start for logged in users.

[PureWeen]

@jtorvald can you post your XAML file with shell?

How/where do you initialize Shell as the main page?
Can you post the code you are using to navigate ?

Are you setting FlyoutBehavior anywhere?

[PureWeen]

@jtorvald I'm going to mark this one fixed by this PR

https://github.com/xamarin/Xamarin.Forms/pull/11264

Once that's merged if you're still seeing the issue please let me know

[jtorvald]

@PureWeen thanks. Sorry but I didn't have time to supply the requested info yet. It's also not urgent so I will await the new fix and let you know with more details in case it doesn't fix it. Thanks for you time looking into this.

[PureWeen]

@jtorvald

Here are the nugets from this PR if you'd like to test
https://dev.azure.com/xamarin/public/_build/results?buildId=21694&view=artifacts&type=publishedArtifacts

[jtorvald]

@PureWeen I figured it out: I had FlyoutIcon="hamburger.png". I've been developing this app for a while and in the previous xamarin forms versions it was not an issue. Now apparently it is for some reason. Since I'm happy with the default icon I can just remove the attribute, but just wanted to update this issue here with the cause. Not sure if that is expected behavior or not.

[PureWeen]

@jtorvald Aw ok yea I'd say that's a bug

Thank you for checking back in!!

[gresolio]

After upgrading to 4.7.0.1179, shell back button icon disappeared in all views, which previously worked just fine with following options:

Shell.TabBarIsVisible="false"
Shell.FlyoutBehavior="Disabled"

Downgrading to 4.7.0.1142 fixes this rather unpleasant issue.

I read the Release Notes 4.7.0.1179 and found the back button is mentioned here.
Is this expected behaviour? (and we should update our project to work with the new version of Xamarin.Forms). Or is it a bug?

[PureWeen]

@gresolio that will be fixed by the next PR