点按当前选项卡以刷新页面时的Xamarin.Forms TabbedPage事件 [英] Xamarin.Forms TabbedPage event when current tab is tapped to refresh the page

问题描述

我正在使用Xamarin.Forms来构建iOS/Android应用，并且具有TabbedPage.

I'm using Xamarin.Forms to build an iOS/Android app, and have a TabbedPage.

如果用户已经在选项卡2上，并且单击了Tab2，并且我希望刷新Tab2或运行自己的功能，以便我自己刷新它.

If a user is already on Tab 2, and Tab2 is clicked, and I want either the tab2 to refresh, or for a function of my own to run so I can refresh it myself.

是否可以在Xamarin.Forms中执行此操作，还是可以使用自定义渲染器执行此操作?

Is there a way to do this within Xamarin.Forms or a way to do it with custom renderers?

推荐答案

以下是我最终解决此问题的方法.我的TabbedPage由每个选项卡的NavigationPage组成，因此，如果您不使用导航页面，您的代码将不得不稍作更改，但只需稍作更改.您可以将刷新"逻辑放在iOS的OnTabbarControllerItemSelected和Android的OnTabbarControllerItemSelected中.请查看下面的代码.

Here is how I ended up solving the issue. My TabbedPage consisted of a NavigationPage for each tab, so if you are not using navigation pages your code will have to change a little bit but only slightly. You can put your "refresh" logic inside of OnTabbarControllerItemSelected for iOS and OnTabbarControllerItemSelected for Android. Check out the code below.

Android Renderer(由Mike Ma提供)

Android Renderer (courtesy of Mike Ma)

using Android.Support.Design.Widget;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Xamarin.Forms.Platform.Android.AppCompat;
[assembly: ExportRenderer(typeof(MainTabbedPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
    {
        private MainTabbedPage _page;
        protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
        {
            base.OnElementChanged(e);
            if (e.NewElement != null)
            {
                _page = (MainTabbedPage)e.NewElement;
            }
            else
            {
                _page = (MainTabbedPage)e.OldElement;
            }

        }
        async void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
        {
            await _page.CurrentPage.Navigation.PopToRootAsync();
        }
    }
}

iOs渲染器:

using UIKit;
using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(MainTabbedPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedRenderer
    {
        private MainTabbedPage _page;
        protected override void OnElementChanged(VisualElementChangedEventArgs e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
            {
                _page = (MainTabbedPage)e.NewElement;
            }
            else
            {
                _page = (MainTabbedPage)e.OldElement;
            }

            try
            {
                var tabbarController = (UITabBarController)this.ViewController;
                if (null != tabbarController)
                {
                    tabbarController.ViewControllerSelected += OnTabbarControllerItemSelected;
                }
            }
            catch (Exception exception)
            {
                Console.WriteLine(exception);
            }
        }

        private async void OnTabbarControllerItemSelected(object sender, UITabBarSelectionEventArgs eventArgs)
        {
            if (_page?.CurrentPage?.Navigation != null && _page.CurrentPage.Navigation.NavigationStack.Count > 0)
            {
                await _page.CurrentPage.Navigation.PopToRootAsync();
            }

        }
    }
}

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