我有一个使用FreshMvvm的Xamarin.Forms应用，我使用了二级ToolbarItems。为了在iOS中做到这一点，我不得不做一个自定义的渲染器（与Android中不同）。在这里给了我一个如何实现它的解决方案。在iOS中，ToolbarItems看起来并不正确。
这个解决方案对我来说是完美的。但是到了现在，工具栏菜单变长了，其中的一些元素不适合iPhone的屏幕。我可以滑动菜单，看到所有的元素，但只要我一松开屏幕，视图就会重新跳起来，虽然用手指握住它，但元素却无法点击。请问如何解决这个问题？能不能把菜单做成包起来，或者是其他的？在安卓系统上，菜单停留在我滚动的地方，我可以点击每个项目。在安卓系统上，菜单停留在我滚动的地方，我可以点击每一个项目。在iOS系统上，它也可以停留在滚动的地方吗？
这是我的渲染器的代码。
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);
}
}
}
}
ADDITION:
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; }
}
这里你可以下载重现这个问题的项目。https:/github.comDavidShochetPublic）。
好吧，我还是不能用你更新的代码重现这个问题。我不知道这是否是一个解决方案，我只是想澄清一下我的评论。
在你的代码中，你添加了 _table 到视图中。
_table = OpenDropDownMenu(Element as IAddToolbarItem);
Add(_table);
我想让你尝试一下，在 "视图 "中添加... _table 到 _transparentView :
_table = OpenDropDownMenu(Element as IAddToolbarItem);
//Add(_table);
_transparentView.Add(_table);
如果你能给我们提供一个最小的、可复制的例子，这样我就可以在我这边调试了。
更新一下。
我发现问题出在这里，你把桌子的高度设置为 _secondaryItems.Count() * rowHeight) 当工具栏菜单变长时，它就会变长。
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);
}
}
解决办法: 将tablview的高度改为 (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);
}
}