Xamarin 窗体 Shell 选定选项卡的自定义图标

Question

我正在使用 COOL xamarin shell，但我没有找到更改所选选项卡图标的方法。

<TabBar Route="sections">
    <Tab Title="home">
        <Tab.Icon>
            <FontImageSource FontFamily="{StaticResource AppIcons}" Glyph="{x:Static framework:Icons.HomePage}" />
        </Tab.Icon>
        <ShellContent ContentTemplate="{DataTemplate home:HomePage}" Route="home" />
    </Tab>

目标是仅在选择此选项卡时使用Icons.HomePageFilled而不是用于该选项卡。Icons.HomePage相同的逻辑应该适用于其他选项卡。

我想我迷失在网上找到的解决方案中了。他们谈论自定义渲染器（ShellTabLayoutAppearanceTracker），视觉状态，效果等......但我不知道它是否可行以及理想的解决方案是什么

Answer 1

您需要使用shell 的自定义渲染器来自定义每个平台上的 tabbar 选择图标。

在 iOS 中，重写该CreateTabBarAppearanceTracker方法：

[assembly: ExportRenderer(typeof(AppShell), typeof(MyShellRenderer))]
namespace App30.iOS
{
    public class MyShellRenderer : ShellRenderer
    {
        protected override IShellSectionRenderer CreateShellSectionRenderer(ShellSection shellSection)
        {
            var renderer = base.CreateShellSectionRenderer(shellSection);
            if (renderer != null)
            {

            }
            return renderer;
        }

        protected override IShellTabBarAppearanceTracker CreateTabBarAppearanceTracker()
        {
            return new CustomTabbarAppearance();
        }
    }

    public class CustomTabbarAppearance : IShellTabBarAppearanceTracker
    {
        public void Dispose()
        {

        }

        public void ResetAppearance(UITabBarController controller)
        {

        }

        public void SetAppearance(UITabBarController controller, ShellAppearance appearance)
        {
            UITabBar myTabBar = controller.TabBar;

            if (myTabBar.Items != null)
            {
                UITabBarItem itemOne = myTabBar.Items[0];

                itemOne.Image = UIImage.FromBundle("tab_about.png");
                itemOne.SelectedImage = UIImage.FromBundle("tab_feed.png");


                UITabBarItem itemTwo = myTabBar.Items[1];

                itemTwo.Image = UIImage.FromBundle("tab_feed.png");
                itemTwo.SelectedImage = UIImage.FromBundle("tab_about.png");

                //The same logic if you have itemThree, itemFour....
            }

        }

        public void UpdateLayout(UITabBarController controller)
        {

        }
    }
}

在 Android 中，重写该CreateBottomNavViewAppearanceTracker方法：

[assembly: ExportRenderer(typeof(AppShell), typeof(MyShellRenderer))]
namespace App30.Droid
{
    public class MyShellRenderer : ShellRenderer
    {
        public MyShellRenderer(Context context) : base(context)
        {
        }

        protected override IShellBottomNavViewAppearanceTracker CreateBottomNavViewAppearanceTracker(ShellItem shellItem)
        {
            return new CustomBottomNavAppearance();
        }
    }

    public class CustomBottomNavAppearance : IShellBottomNavViewAppearanceTracker
    {
        public void Dispose()
        {

        }

        public void ResetAppearance(BottomNavigationView bottomView)
        {

        }

        public void SetAppearance(BottomNavigationView bottomView, ShellAppearance appearance)
        {
            IMenu myMenu = bottomView.Menu;

            IMenuItem myItemOne = myMenu.GetItem(0);

            if (myItemOne.IsChecked)
            {
                myItemOne.SetIcon(Resource.Drawable.tab_about);
            }
            else
            {
                myItemOne.SetIcon(Resource.Drawable.tab_feed);
            }

            //The same logic if you have myItemTwo, myItemThree....

        }
    }
}

我在这里上传了一个示例项目，你可以检查一下。