辅助工具栏项不适合屏幕

Question

我有一个带有Xamarin.Forms的FreshMvvm应用程序，我使用二级ToolbarItems。要在iOS中实现它，我必须做一个定制的渲染器(与安卓系统不同)。我得到了一个关于如何在这里实现它的解决方案：ToolbarItems do not look right in iOS

这个解决方案对我来说非常有效。但到了现在，工具栏菜单越来越长，其中一些元素不适合iPhone的屏幕。我可以滑动菜单并看到所有的元素，但是一旦我释放屏幕，视图就会跳回来，当它被手指控制时，这些元素是不可点击的。如何解决这一问题？菜单能包起来吗?或者别的什么？在Android上，菜单停留在我滚动的位置，我可以点击每个项目。它也能让iOS上滚动的地方停留吗？

这是我渲染者的代码：

using CoreGraphics;
using MobileApp.iOS.Renderers;
using MobileApp.iOS.Services;
using MobileApp.Pages;
using MobileApp.Services;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using UIKit;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(CustomToolbarContentPage), 
typeof(RightToolbarMenuCustomRenderer))]
namespace MobileApp.iOS.Renderers
{
class RightToolbarMenuCustomRenderer : PageRenderer
{
    private List<ToolbarItem> _primaryItems;
    private List<ToolbarItem> _secondaryItems;
    private UITableView _table;
    private UITapGestureRecognizer _tapGestureRecognizer;
    private UIView _transparentView;

    protected override void OnElementChanged(VisualElementChangedEventArgs e)
    {
        if (e.NewElement is IAddToolbarItem item)
        {
            item.ToolbarItemAdded += Item_ToolbarItemAdded;
        }
        base.OnElementChanged(e);
    }

    private void Item_ToolbarItemAdded(object sender, System.EventArgs e)
    {
        if (Element is ContentPage page)
        {
            _primaryItems = page.ToolbarItems.Where(i => i.Order == ToolbarItemOrder.Primary).ToList();
            _secondaryItems = page.ToolbarItems.Where(i => i.Order == ToolbarItemOrder.Secondary).ToList();
            _secondaryItems.ForEach(t => page.ToolbarItems.Remove(t));
        }

        var element = (ContentPage)Element;

        if (_secondaryItems?.Count == 0 && element.ToolbarItems.Any(a => (a.IconImageSource as FileImageSource)?.File == "more.png"))
        {
            element.ToolbarItems.Clear();
        }
        else if (_secondaryItems?.Count >= 1 && !element.ToolbarItems.Any(a => (a.IconImageSource as FileImageSource)?.File == "more.png"))
        {
            element.ToolbarItems.Add(new ToolbarItem()
            {
                Order = ToolbarItemOrder.Primary,
                IconImageSource = "more.png",
                Priority = 1,
                Command = new Command(ToggleDropDownMenuVisibility)
            });
        }
    }

    private void ToggleDropDownMenuVisibility()
    {
        if (!DoesTableExist())
        {
            if ((View?.Subviews != null)
                && (View.Subviews.Length > 0)
                && (View.Bounds != null)
                && (_secondaryItems != null)
                && (_secondaryItems.Count > 0))
            {
                _table = OpenDropDownMenu(Element as IAddToolbarItem);
                Add(_table);
            }
        }
        else
            CloseDropDownMenu();
    }

    private bool DoesTableExist()
    {
        if (View?.Subviews != null)
        {
            foreach (var subview in View.Subviews)
            {
                if (_table != null && subview == _table)
                {
                    return true;
                }
            }
        }
        if (_tapGestureRecognizer != null)
        {
            _transparentView?.RemoveGestureRecognizer(_tapGestureRecognizer);
            _tapGestureRecognizer = null;
        }
        _table = null;
        _tapGestureRecognizer = null;
        return false;
    }

    private UITableView OpenDropDownMenu(IAddToolbarItem secondaryMenuSupport)
    {
        _transparentView = _transparentView = new UIView(new CGRect(0, 0, View.Bounds.Width, View.Bounds.Height))
        {
            BackgroundColor = UIColor.FromRGBA(0, 0, 0, 0)
        };
        _tapGestureRecognizer = new UITapGestureRecognizer(CloseDropDownMenu);
        _transparentView.AddGestureRecognizer(_tapGestureRecognizer);
        Add(_transparentView);

        UITableView table = null;
        if (_secondaryItems != null && _secondaryItems.Count > 0)
        {
            table = new UITableView(GetPositionForDropDownMenu(secondaryMenuSupport.RowHeight, secondaryMenuSupport.TableWidth))
            {
                Source = new TableSource(_secondaryItems, _transparentView),
                ClipsToBounds = false
            };

            table.ScrollEnabled = true;
            table.Layer.ShadowColor = secondaryMenuSupport.ShadowColor.ToCGColor();
            table.Layer.ShadowOpacity = secondaryMenuSupport.ShadowOpacity;
            table.Layer.ShadowRadius = secondaryMenuSupport.ShadowRadius;
            table.Layer.ShadowOffset = new SizeF(secondaryMenuSupport.ShadowOffsetDimension, secondaryMenuSupport.ShadowOffsetDimension);
            table.BackgroundColor = secondaryMenuSupport.MenuBackgroundColor.ToUIColor();
        }
        return table;
    }

    public override void ViewWillDisappear(bool animated)
    {
        CloseDropDownMenu();
        base.ViewWillDisappear(animated);
    }

    private RectangleF GetPositionForDropDownMenu(float rowHeight, float tableWidth)
    {
        if ((View?.Bounds != null)
            && (_secondaryItems != null)
            && (_secondaryItems.Count > 0))
        {
            return new RectangleF(
                (float)View.Bounds.Width - tableWidth,
                0,
                tableWidth,
                _secondaryItems.Count() * rowHeight);
        }
        else
        {
            return new RectangleF(0.0f, 0.0f, 0.0f, 0.0f);
        }
    }

    private void CloseDropDownMenu()
    {
        if (_table != null)
        {
            if (_tapGestureRecognizer != null)
            {
                _transparentView?.RemoveGestureRecognizer(_tapGestureRecognizer);
                _tapGestureRecognizer = null;
            }

            if (View?.Subviews != null)
            {
                foreach (var subview in View.Subviews)
                {
                    if (subview == _table)
                    {
                        _table.RemoveFromSuperview();
                        break;
                    }
                }

                if (_transparentView != null)
                {
                    foreach (var subview in View.Subviews)
                    {
                        if (subview == _transparentView)
                        {
                            _transparentView.RemoveFromSuperview();
                            break;
                        }
                    }
                }
            }
            _table = null;
            _transparentView = null;
        }
    }

    public override void ViewDidLayoutSubviews()
    {
        base.ViewDidLayoutSubviews();

        if (_table != null)
        {
            if (Element is IAddToolbarItem secondaryMenuSupport)
                PositionExistingDropDownMenu(secondaryMenuSupport.RowHeight, secondaryMenuSupport.TableWidth);
        }
    }

    private void PositionExistingDropDownMenu(float rowHeight, float tableWidth)
    {
        if ((View?.Bounds != null)
            && (_secondaryItems != null)
            && (_secondaryItems.Count > 0)
            && (_table != null))
        {
            _table.Frame = GetPositionForDropDownMenu(rowHeight, tableWidth);
        }
    }
}
}

增添：

public class TableSource : UITableViewSource
{
    List<ToolbarItem> _tableItems;
    string[] _tableItemTexts;
    string CellIdentifier = "TableCell";
    UIView _tableSuperView = null;

    public TableSource(List<ToolbarItem> items, UIView tableSuperView)
    {
        _tableItems = items;
        _tableSuperView = tableSuperView;
        _tableItemTexts = items.Select(a => a.Text).ToArray();
    }

    public override nint RowsInSection(UITableView tableview, nint section)
    {
        return _tableItemTexts?.Length ?? 0;
    }

    public override UITableViewCell GetCell(UITableView tableView, NSIndexPath indexPath)
    {
        UITableViewCell cell = tableView.DequeueReusableCell(CellIdentifier);
        string item = _tableItemTexts[indexPath.Row];
        if (cell == null)
        { cell = new UITableViewCell(UITableViewCellStyle.Default, CellIdentifier); }
        cell.TextLabel.Text = item;
        return cell;
    }

    public override nfloat GetHeightForRow(UITableView tableView, NSIndexPath indexPath)
    {
        return 56;
    }

    public override void RowSelected(UITableView tableView, NSIndexPath indexPath)
    {
        var command = _tableItems[indexPath.Row].Command;
        command.Execute(_tableItems[indexPath.Row].CommandParameter);
        tableView.DeselectRow(indexPath, true);
        tableView.RemoveFromSuperview();
        if (_tableSuperView != null)
        {
            _tableSuperView.RemoveFromSuperview();
        }
    }
}

public interface IAddToolbarItem
{
    event EventHandler ToolbarItemAdded;
    Color CellBackgroundColor { get; }
    Color CellTextColor { get; }
    Color MenuBackgroundColor { get; }
    float RowHeight { get; }
    Color ShadowColor { get; }
    float ShadowOpacity { get; }
    float ShadowRadius { get; }
    float ShadowOffsetDimension { get; }
    float TableWidth { get; }
}

在这里，您可以下载复制问题的项目：https://github.com/DavidShochet/Public

Answer 1

好吧，我还是不能用你更新的代码重现问题。如果这是一个解决方案的话，我不知道，我只想在这里澄清我的评论。

在代码中，将_table添加到视图中：

 _table = OpenDropDownMenu(Element as IAddToolbarItem);
 Add(_table);

我希望您尝试的是将_table添加到_transparentView中：

  _table = OpenDropDownMenu(Element as IAddToolbarItem);
  //Add(_table);
  _transparentView.Add(_table);

如果您能提供一个最小的、可复制的示例，这样我就可以在我这一边调试它，这样会更好。

更新：

我发现问题在这里，您设置了表_secondaryItems.Count() * rowHeight)的高度，它比工具栏菜单变长时的视图更长：

private RectangleF GetPositionForDropDownMenu(float rowHeight, float tableWidth)
{
    if ((View?.Bounds != null)
        && (_secondaryItems != null)
        && (_secondaryItems.Count > 0))
    {
        return new RectangleF(
            (float)View.Bounds.Width - tableWidth,
            0,
            tableWidth,

            //here is the cause
            _secondaryItems.Count() * rowHeight);
    }
    else
    {
        return new RectangleF(0.0f, 0.0f, 0.0f, 0.0f);
    }
}

解决方案：将tablview的高度更改为(float)View.Bounds.Height

private RectangleF GetPositionForDropDownMenu(float rowHeight, float tableWidth)
{
    if ((View?.Bounds != null)
        && (_secondaryItems != null)
        && (_secondaryItems.Count > 0))
    {
        return new RectangleF(
            (float)View.Bounds.Width - tableWidth,
            0,
            tableWidth,
            (float)View.Bounds.Height);
    }
    else
    {
        return new RectangleF(0.0f, 0.0f, 0.0f, 0.0f);
    }
}