如何在Xamarin.Forms中检测到标签按钮的单击？

Question

这是我的代码.我想知道当用户点击已经选中的标签时我怎么能检测到我想要在play.png和pause.png之间切换aPage的图标加上我也想在APage上调用一个方法.

public partial class MainPage : TabbedPage
{
    public MainPage()
    {
        InitializeComponent();

        var aPage = new NavigationPage(new APage())
        {
            Title = "Play",
            Icon = "play.png"
        };
        var bPage = new NavigationPage(new BPage())
        { 
            Title = "Settings",
            Icon = "b.png"
        };

        Children.Add(aPage);
        Children.Add(bPage);
    }
}

请注意,如果可能,我想找到一个不涉及iOS和Android自定义渲染器的解决方案.我想知道我可以重新定义TabbedPage并将逻辑放在该类中吗？

Answer 1

我知道您要避免使用自定义渲染器,但这只能通过使用自定义渲染器来实现.

码

Xamarin.Android自定义渲染器

using Android.Content;
using Android.Support.Design.Widget;

using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Xamarin.Forms.Platform.Android.AppCompat;

[assembly: ExportRenderer(typeof(MainPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
    {
        MainPage _page;

        public MainPageRenderer(Context context) : base(context) { }

        protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
                _page = e.NewElement as MainPage;
            else
                _page = e.OldElement as MainPage;
        }

        void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
        {
            System.Diagnostics.Debug.WriteLine("Tab Reselected");
            //Handle Tab Reselected
        }
    }
}

Xamarin.iOS自定义渲染器

using System;
using System.Diagnostics;

using UIKit;

using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(MainPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedRenderer
    {
        MainPage _page;

        protected override void OnElementChanged(VisualElementChangedEventArgs e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
                _page = e.NewElement as MainPage;
            else
                _page = e.OldElement as MainPage;

            try
            {
                if (ViewController is UITabBarController tabBarController)
                    tabBarController.ViewControllerSelected += OnTabbarControllerItemSelected;
            }
            catch (Exception exception)
            {
                Debug.WriteLine(exception);
            }
        }

        void OnTabbarControllerItemSelected(object sender, UITabBarSelectionEventArgs eventArgs)
        {
            if (_page?.CurrentPage?.Navigation != null && _page.CurrentPage.Navigation.NavigationStack.Count > 0)
            {
                Debug.WriteLine("Tab Tapped");
                //Handle Tab Tapped
            }
        }
    }
}

代码信用:@Kyle /sf/answers/3003644241/