xamarin.forms - TabbedPage 隐藏所有标签

Question

我是 Xamarin 的新手，想创建一个包含多个页面的应用程序，这些页面可通过单击按钮导航到。我已经弄清楚如何通过代码导航到所需的页面，但我正在努力隐藏选项卡以禁用用户导航。

我正在使用 TabbedPage 有我的主页，然后添加 8 个 NavigationPages 作为子页面。

如何隐藏标签页？

Answer 1

要在 Xamarin.Forms 中隐藏选项卡，您需要在 native 项目中包含自定义呈现器。我没有使用 UWP atm，所以只是为 iOS 和 Android 发布渲染器，它们完全隐藏了标签栏。更改我的命名空间并考虑可能将选项卡式页面子类化，这样您就不会在应用程序中隐藏所有选项卡，而只隐藏选定的选项卡。

iOS 渲染器:

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

[assembly: ExportRenderer(typeof(TabbedPage), typeof(HiddenTabbedPageRenderer))]
namespace AppoMobi.iOS
{   
    //***************************************************************************
    public class HiddenTabbedPageRenderer : TabbedRenderer
    //***************************************************************************
    {

        private UITabBarController tabbarController { get; set; }
        private TabbedPage CurrentTabbedPage { get; set; }

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

            if (e.OldElement != null)
            {
                //release any stuff here
            }

            if (e.NewElement != null)
            {
                tabbarController = (UITabBarController) this.ViewController;
                CurrentTabbedPage = (TabbedPage) e.NewElement;
            }
            else
            {
                CurrentTabbedPage = (TabbedPage) e.OldElement;
            }

            //the following commented code is not working
            //as Forms as it just leaves empty white space
            //instead of hidden tabbedbar:     
            //       if (tabbarController != null)
            //         tabbarController.TabBar.Hidden = true;
        }

        //just hide tabbar by setting its height to zero
        // credits:
        // https://stackoverflow.com/a/26255545/7149454
        // "how to change UITabBar height"
        private nfloat newHeight = 0; //change tabbed bar height to this value
        //-------------------------------------------------------------------
        public override void ViewWillLayoutSubviews()
        //-------------------------------------------------------------------
        {
            if (tabbarController != null)
            {
                var tabFrame = tabbarController.TabBar.Frame; //self.TabBar is IBOutlet of your TabBar
                tabFrame.Height = newHeight;
                tabFrame.Offset(0, tabbarController.View.Frame.Height - newHeight);
                tabbarController.TabBar.Frame = tabFrame;
            }
            base.ViewWillLayoutSubviews();
        }
    }
}

安卓渲染器:

using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using System;
using Android.Content;
using Android.Support.Design.Widget;
using Android.Support.V4.View;
using Android.Views;
using AppoMobi.Droid;
using Xamarin.Forms.Platform.Android.AppCompat;

[assembly: ExportRenderer(typeof(TabbedPage), typeof(MyTabbedRenderer))]
namespace AppoMobi.Droid
{
    //****************************************************
    public class MyTabbedRenderer : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
    //****************************************************
    {

        private TabLayout TabsLayout { get; set; }
        private ViewPager PagerLayout { get; set; }
        private NiftyTabbedPage CurrentTabbedPage { get; set; }

        //-------------------------------------------------------------------
        public MyTabbedRenderer(Context context) : base(context)
        //-------------------------------------------------------------------
        {
        }

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

            if (e.OldElement != null)
            {
                //cleanup here
            }

            if (e.NewElement != null)
            {
                CurrentTabbedPage = (NiftyTabbedPage)e.NewElement;
            }
            else
                CurrentTabbedPage = (NiftyTabbedPage)e.OldElement;

            //find the pager and tabs
            for (int i = 0; i < ChildCount; ++i)
            {
                Android.Views.View view = (Android.Views.View)GetChildAt(i);
                if (view is TabLayout)
                    TabsLayout = (TabLayout)view;
                else
                if (view is ViewPager) PagerLayout = (ViewPager)view;
            }

        }


        //-------------------------------------------------------------------------------
        protected override void OnLayout(bool changed, int l, int t, int r, int b)
        //-------------------------------------------------------------------------------    
        {
            TabsLayout.Visibility = ViewStates.Gone;

            base.OnLayout(changed, l, t, r, b);
        }    
    }


}