Not able to set Shell top Tabbar width in IOS

To fit the top three tabbar items to the width of the screen, you can use Handlers in MAUI.

Here're the detailed steps on how to implement it:

1. Under folder Platform-->iOS, create the class: MyiOSCustomShellRenderer(please delete the default namespace yourproject.Platforms.iOS) like below:

public class MyiOSCustomShellRenderer : ShellRenderer
{

     protected override IShellSectionRenderer CreateShellSectionRenderer(ShellSection shellSection)
     {
         var shellSectionRenderer = new CustomShellSectionRenderer(this);
         return shellSectionRenderer;

      }
}

public class CustomShellSectionRenderer : ShellSectionRenderer
{
        public CustomShellSectionRenderer(IShellContext context) : base(context){ }
        protected override IShellSectionRootRenderer CreateShellSectionRootRenderer(ShellSection shellSection, IShellContext shellContext)
        {
            var renderer = new CustomShellSectionRootRenderer(shellSection, shellContext);
            return renderer;
        }
}

public class CustomShellSectionRootRenderer : ShellSectionRootRenderer
{
        public CustomShellSectionRootRenderer(ShellSection section, IShellContext context) : base(section, context){ }
        protected override IShellSectionRootHeader CreateShellSectionRootHeader(IShellContext shellContext)
        {
           var renderer = new CustomShellSectionRootHeader(shellContext);
            return renderer;
        }
    }
    public class CustomShellSectionRootHeader : ShellSectionRootHeader
    {
        public CustomShellSectionRootHeader(IShellContext context) : base(context)
    {}
        public override UICollectionViewCell GetCell(UICollectionView collectionView, NSIndexPath indexPath)
        {

            var cell = base.GetCell(collectionView, indexPath) as ShellSectionHeaderCell;

            var layout = new UICollectionViewFlowLayout();
            layout.MinimumInteritemSpacing = UIScreen.MainScreen.Bounds.Size.Width / 5;
            layout.SectionInset = new UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 0);
            layout.ItemSize = new SizeF(120, 50);
            layout.ScrollDirection = UICollectionViewScrollDirection.Horizontal;
            collectionView.CollectionViewLayout = layout;
            return cell;
        }
    }

    public class CustomUICollectionViewFlowLayout : UICollectionViewFlowLayout
    {
        public override UICollectionViewLayoutAttributes[] LayoutAttributesForElementsInRect(CGRect rect)
        {
            return base.LayoutAttributesForElementsInRect(rect);
        }
    }

2. Register the handlers in the MauiProgram.cs:

builder.ConfigureMauiHandlers(h =>
{
#if IOS
       h.AddHandler<Shell, MyiOSCustomShellRenderer>();
#endif
});