xamarin - 为 TabbedPage 重用 CustomRender

Question

我的 Xamarin Forms 项目有一个选项卡式页面。选项卡过去常常滑动，但我已经实现了 CustomRender 来阻止这种情况。

这非常有效，除非我需要将页面重新添加到选项卡栏。我似乎无法重复使用自定义渲染？

现在我正在将页面重新添加到 CustomRendered TabbedPage，如下所示:

var masterTabPage = this.Parent.Parent as NoSlideTabbedPage;

Xamarin.Forms.NavigationPage Page1 = new Xamarin.Forms.NavigationPage(new Page1("example string"));
Page1.Title = "Page Example";
Page1.Icon = "pageexample.png";

masterTabPage.Children.RemoveAt(1);
masterTabPage.Children.Insert(1, Page1);

masterTabPage.CurrentPage = masterTabPage.Children[1];

我的布局页面看起来像

[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class Layout : NoSlideTabbedPage
{
    public Layout()
    {
        InitializeComponent();

        On<Android>().SetBarItemColor(Color.FromHex("#cccccc"));
        On<Android>().SetBarSelectedItemColor(Color.FromHex("#123456"));

        // SET NAV BAR TO BOTTOM
        On<Android>().SetToolbarPlacement(ToolbarPlacement.Bottom);

        // CREATE TABS
        NavigationPage Page0 = new NavigationPage(new Page0());
        Page0.Title = "Page0";
        Page0.Icon = "Page0.png";

        NavigationPage Page1 = new NavigationPage(new Page1());
        Page1.Title = "Page1";
        Page1.Icon = "Page1.png";

        NavigationPage Page2 = new NavigationPage(new Page2());
        Page2.Title = "Page2";
        Page2.Icon = "Page2.png";

        NavigationPage Page3 = new NavigationPage(new Page3());
        Page3.Title = "Page3";
        Page3.Icon = "Page3.png";

        // ADD TABS
        Children.Add(Page0);
        Children.Add(Page1);
        Children.Add(Page2);
        Children.Add(Page3);
    }
}

自定义渲染器代码:

public class NoSlideTabbedPageRenderer : TabbedPageRenderer
{
    private bool _isShiftModeSet;

    public NoSlideTabbedPageRenderer(Context context)
        : base(context)
    {

    }

    protected override void OnLayout(bool changed, int l, int t, int r, int b)
    {
        base.OnLayout(changed, l, t, r, b);
        try
        {
            if (!_isShiftModeSet)
            {
                var children = GetAllChildViews(ViewGroup);

                if (children.SingleOrDefault(x => x is BottomNavigationView) is BottomNavigationView bottomNav)
                {
                    bottomNav.SetShiftMode(false, false);
                    _isShiftModeSet = true;
                }
            }
        }
        catch (Exception e)
        {
            Console.WriteLine($"Error setting ShiftMode: {e}");
        }
    }

    private List<View> GetAllChildViews(View view)
    {
        if (!(view is ViewGroup group))
        {
            return new List<View> { view };
        }

        var result = new List<View>();

        for (int i = 0; i < group.ChildCount; i++)
        {
            var child = group.GetChildAt(i);

            var childList = new List<View> { child };
            childList.AddRange(GetAllChildViews(child));

            result.AddRange(childList);
        }

        return result.Distinct().ToList();
    }
}

布局页面可以正常工作，因为我正在使用上面的 CustomRender。这样就可以让标签栏正常了。但是，当我删除并重新添加页面(显示在第一个代码块中)时，CustomRender 将停止使用。如何在重新添加此 Page1 的同时继续使用此自定义渲染？

Answer 1

您可以监听元素更改的属性并再次调用shiftmode。

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

        if(e.NewElement !=null)
        {
             var children = GetAllChildViews(ViewGroup);

            if (children.SingleOrDefault(x => x is BottomNavigationView) is BottomNavigationView bottomNav)
            {
                bottomNav.SetShiftMode(false, false);
                _isShiftModeSet = true;
            }
        }
    }