Fix issue 6878 | [Bug] ShellItem.Items.Clear() crashes when the ShellItem has bottom tabs

[felipebaltazar]

Description of Change

I followed another PR (#8079) feedback and create a null check to avoid NullException for ShellBottomNavViewAppearanceTracker.SetBackgroundColor

Issues Resolved

• fixes [Bug] ShellItem.Items.Clear() crashes when the ShellItem has bottom tabs #6878

API Changes

Changed:

• void ShellBottomNavViewAppearanceTracker.SetBackgroundColor
  • added this validation:

	var child = menuView.GetChildAt(index);

	if (child == null)
		return;

Platforms Affected

• Core/XAML (all platforms)

Behavioral/Visual Changes

None

Before/After Screenshots

Not applicable

Testing Procedure

1. Create a ShellItem in that contains tabs and set background-color
2. In code, call Items.Clear() on your ShellItem.
3. No exceptions at this point

• Or just run 6878 issue at Control Galery:

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[felipebaltazar]

@PureWeen @rmarinho
Hello, any position about this PR?

[felipebaltazar]

I`ve made the changes proposed by @PureWeen and updated this branch

[PureWeen]

@felipebaltazar can you rebase this to 4.4?

Then I'll give the UI tests one more run through and merge.

Thank you!!

[felipebaltazar]

@felipebaltazar can you rebase this to 4.4?

Then I'll give the UI tests one more run through and merge.

Thank you!!

@PureWeen I've rebased this branch to 4.4.0, but now we have 41 additional commits, seems like changes made on master.. so can I only revert theses commits?

[PureWeen]

@felipebaltazar you'll need to rebase and force push. If you're having issues I can give it a go

git rebase --onto 4.4.0 master issue-6878

Then fix merge conflicts

Then do a force push to your branch

[minahenin]

Hi, This is still broken in IOS

even when the Tab has multiple ShellItems when I try to Remove the first item "Items.RemoveAt(0);" it still crashes.

[francis2]

Hi guys,

I am using Xamarin.Forms.4.5.0.282-pre4

I don't get crashes, but I am unable to remove the first item.

These calls do nothing. The first Item always remains in the Items collection.
Items.RemoveAt(0)
Items.Remove(Tab.CurrentItem)
Items.Clear()

In my use case, the top menus are created based on the user data. I must create a default placeholder in xaml, but i need to delete it (or make it invisible, but that is not available yet).

<TabBar>
    <Tab
        x:Name="mainTab"
        Title="SomeText"
        Route="someroute">
        <ShellContent
            Title="Empty"
            Route="blank">
            <ShellContent.ContentTemplate>
                <DataTemplate>
                    <MyPage>
                        <x:Arguments>
                            <x:String></x:String>
                        </x:Arguments>
                    </MyPage>
                </DataTemplate>
            </ShellContent.ContentTemplate>
        </ShellContent>            
    </Tab>
</TabBar>

EDIT
This may help: the Items collection is empty, but there is a VisibleItems collection that still contains the empty tab. I couldn't find a way to access it to clear it manually.

[PureWeen]

@francis2 do you have a repro you can attach?

[francis2]

Sure, here you go.

PickerTestApp.zip

[PureWeen]

Thank you @francis2

#9615

[francis2]

Hi guys,

Tab.Items.Clear() crashes on 4.5.0.356.

System.ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

Attached is a repro solution. Crash occurs in AppShell.xaml.cs line 28 on Tab.Items.Clear()

Thanks

PickerTestApp.zip

[PureWeen]

@francis2

Created this issue for tracking
#9801

I'll test and let you know over there what I find