问题
I'm playing with the COOL xamarin shell, but I didn't found a way to change icon of the selected tab.
<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>
The goal is to use Icons.HomePageFilled instead of Icons.HomePage for this tab only when it's selected. Same logic should apply to other tabs.
I think I got lost in the solutions found on the web. They talk about Custom renderers(ShellTabLayoutAppearanceTracker), Visual states, effects etc ... But I do not know if it is feasible and what is the ideal solution
回答1:
You need to use custom renderer of shell to customize the tabbar selected icon on each platform.
In iOS, override the CreateTabBarAppearanceTracker method:
[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)
{
}
}
}
In Android, override the CreateBottomNavViewAppearanceTracker method:
[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....
}
}
}
I uploaded a sample project here and you can check it.
来源：https://stackoverflow.com/questions/58635349/xamarin-forms-shell-custom-icon-for-selected-tab