Xamarin.IOS MonoTouch.Dialog ExpandableDatePickerElement无法正常工作

Question

我写了一个expandableDatePickerElement作为MonoTouch.Dialog.Element

（更改了代码：here）

这是我的代码：

using System;
using MonoTouch.Dialog;
using MonoTouch.UIKit;
using System.Drawing;

namespace ImageToDo
{
    public class ExpandableDatePickerElement : Element, IElementSizing
    {
        Section _parentSection;
        UITableViewCell _stringElementCell;
        DateTime _minDate;
        DateTime _maxDate;
        public UIDatePicker Picker{ get; set; }
        UIViewElement _viewElement;

        public ExpandableDatePickerElement (Section parentSection, DateTime minDate, DateTime maxDate)
            :base("date")
        {
            this._maxDate = maxDate;
            this._minDate = minDate;
            _parentSection = parentSection;
            InitializePicker ();
        }

        private void InitializePicker()
        {
            Picker = new UIDatePicker (new RectangleF (0, 0, 320, 200));
            Picker.Mode = UIDatePickerMode.DateAndTime;
            Picker.MinimumDate = _minDate;
            Picker.MaximumDate = _maxDate;

            _viewElement = new UIViewElement (String.Empty, Picker, true);
        }

        public override void Selected (DialogViewController dvc, MonoTouch.UIKit.UITableView tableView, MonoTouch.Foundation.NSIndexPath path)
        {
            base.Selected (dvc, tableView, path);

            _stringElementCell.DetailTextLabel.Text = DateTimeHelper.NSDateToDateTime (Picker.Date).ToString ();

            if (_parentSection.Elements.Contains (_viewElement))
                Collapse ();
            else
                _parentSection.Add (_viewElement);
        }

        public override UITableViewCell GetCell (UITableView tv)
        {
            const string cellKey = "ExpandableDatePickerElement";
            var cell = tv.DequeueReusableCell (cellKey);

            if (cell == null)
            {
                cell = new UITableViewCell (UITableViewCellStyle.Value1, cellKey);
                cell.TextLabel.Font = UIFont.SystemFontOfSize (17f);
                cell.TextLabel.TextColor = UIColor.Black;
                cell.TextLabel.AdjustsFontSizeToFitWidth = true;
                cell.TextLabel.MinimumScaleFactor = .5f;
                cell.Accessory = UITableViewCellAccessory.None;
                cell.SelectionStyle = UITableViewCellSelectionStyle.None;
                cell.TextLabel.Text="Date";

                cell.DetailTextLabel.Font = UIFont.SystemFontOfSize (16f);
                cell.DetailTextLabel.TextColor = UIColor.LightGray;
                cell.DetailTextLabel.AdjustsFontSizeToFitWidth = true;
                cell.DetailTextLabel.MinimumScaleFactor = .5f;
                cell.DetailTextLabel.Text=DateTime.Now.ToString();
            }

            _stringElementCell = cell;

            return _stringElementCell;
        }

        public void Collapse()
        {
            _parentSection.Remove (_viewElement);
        }

        #region IElementSizing implementation
        public float GetHeight (MonoTouch.UIKit.UITableView tableView, MonoTouch.Foundation.NSIndexPath indexPath)
        {
            return 44;
        }
        #endregion
    }
}

此代码工作正常。每当我在Dialog上有这个元素时，如果用户点击元素，它就会以正确的方式扩展。

但是，如果我将它添加到现有的根元素（已经显示），它将无法正常工作。看起来表格不会扩展单元格。

此方案的示例代码：

RootElement root = new RootElement ("Root");

                Section defaultSection = new Section ("Default");
                CheckboxElement checkElem = new CheckboxElement ("Check");
                defaultSection.Add (checkElem);
                Section section = new Section ("expandable");
                var expandableElement = new ExpandableDatePickerElement(section, DateTime.Now, DateTime.Now.AddYears(2));

                checkElem.Tapped += delegate()
                {
                    if(section.Elements.Contains(expandableElement))
                        section.Remove(expandableElement);
                    else
                        section.Add (expandableElement);
                };

                root.Add (defaultSection);
                root.Add (section);

                DialogViewController dv = new DialogViewController (root);

                NavigationController.PushViewController (dv, true);

这是展开元素的图片（滚动日期选择器仅适用于选取器的上侧）：

有谁知道这个问题发生了什么，或者我对这段代码做错了什么？

Answer 1

我发现从未调用过expandableElement上的GetHeight。

添加以下行为我解决了问题：

root.UnevenRows = true;