我搜索了互联网无济于事...我正在使用MT.D并希望为使用DateElement的人设置生日，但生日可能为空，这意味着尚未收集数据。任何人都知道如何使DateElement接受空值或日期？
答案 0 :(得分：2)
更新 20140106：自iOS7发布以来，Apple希望日期/时间选择器与内容内联，而不是动作表，或者在这种情况下，全屏覆盖。因此，此代码仅用于操作方法和历史目的。
好的，所以我开了自己的课。就个人而言，我认为当前的日期/时间选择器设置看起来并不像具有附加日期选择器的ActionSheet等效弹出一样专业。在MT.D中更有经验的人可能能够弄明白，但我所做的是从DateTimeElement和DateElement复制代码并修改它以使其顶部有三个按钮：左边最近的按钮是取消，右按钮区域有“设置”和“空”按钮。右侧按钮的标题可以设置为类中的任何您喜欢的标题，但可以默认为“设置日期”和“无日期”。
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可空日期时间元素
using MonoTouch.Foundation;
using MonoTouch.UIKit;
using System;
using System.Drawing;
namespace MonoTouch.Dialog
{
public class NullableDateTimeElement : StringElement
{
private class MyViewController : UIViewController
{
private NullableDateTimeElement container;
private bool hasNullValue = false;
private bool hasBeenSet = false;
//private EventHandler nullButtonTouched;
//UIButton isNullButton;
public bool Autorotate
{
get;
set;
}
public MyViewController (NullableDateTimeElement container)
{
this.container = container;
}
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
//isNullButton = UIButton.FromType (UIButtonType.RoundedRect);
//isNullButton.SizeToFit ();
//isNullButton.Frame = new RectangleF(this.View.Frame.Top, this.View.Frame.Left, this.View.Frame.Width - 40f, 40f);
//isNullButton.SetTitle (container.NullButtonCaption, UIControlState.Normal);
this.NavigationItem.RightBarButtonItems = new UIBarButtonItem[]
{
new UIBarButtonItem(container.NullButtonCaption, UIBarButtonItemStyle.Done, NullButtonTapped),
new UIBarButtonItem(container.SetButtonCaption, UIBarButtonItemStyle.Done, SetButtonTapped)
};
this.NavigationItem.LeftBarButtonItem = new UIBarButtonItem(UIBarButtonSystemItem.Cancel, CancelTapped);
this.NavigationItem.HidesBackButton = true;
//this.View.AddSubview (isNullButton);
//this.isNullButton.TouchUpInside += (nullButtonTouched = new EventHandler(nullButtonWasTouched));
}
void CancelTapped(object sender, EventArgs e)
{
hasBeenSet = false;
this.NavigationController.PopViewControllerAnimated (true);
}
void NullButtonTapped(object sender, EventArgs e)
{
hasBeenSet = true;
hasNullValue = true;
this.NavigationController.PopViewControllerAnimated (true);
}
void SetButtonTapped(object sender, EventArgs e)
{
hasBeenSet = true;
hasNullValue = false;
this.NavigationController.PopViewControllerAnimated (true);
}
public override void ViewWillDisappear (bool animated)
{
base.ViewWillDisappear (animated);
if (hasBeenSet)
{
if (!hasNullValue)
this.container.DateValue = this.container.datePicker.Date;
else
this.container.DateValue = null;
}
//this.isNullButton.TouchUpInside -= nullButtonTouched;
//nullButtonTouched = null;
}
/*void nullButtonWasTouched(object sender, EventArgs e)
{
hasNullValue = true;
NavigationController.PopViewControllerAnimated (true);
}*/
public override void DidRotate (UIInterfaceOrientation fromInterfaceOrientation)
{
base.DidRotate (fromInterfaceOrientation);
this.container.datePicker.Frame = NullableDateTimeElement.PickerFrameWithSize (this.container.datePicker.SizeThatFits (SizeF.Empty));
}
public override bool ShouldAutorotateToInterfaceOrientation (UIInterfaceOrientation toInterfaceOrientation)
{
return this.Autorotate;
}
}
public DateTime? DateValue;
public UIDatePicker datePicker;
//public UIButton isNullButton;
public string NullButtonCaption { get; set; }
public string SetButtonCaption { get; set; }
protected internal NSDateFormatter fmt = new NSDateFormatter
{
DateStyle = NSDateFormatterStyle.Short
};
public NullableDateTimeElement (string caption, DateTime? date, string nullButtonCaption, string setButtonCaption) : base (caption)
{
this.DateValue = date;
this.Value = this.FormatDate (date);
this.NullButtonCaption = nullButtonCaption;
this.SetButtonCaption = setButtonCaption;
}
public NullableDateTimeElement(string caption, DateTime? date, string nullButtonCaption) : this(caption, date, nullButtonCaption, "Set Date")
{}
public NullableDateTimeElement(string caption, DateTime? date) : this(caption, date, "No Date", "Set Date")
{}
public override UITableViewCell GetCell (UITableView tv)
{
this.Value = this.FormatDate (this.DateValue);
UITableViewCell cell = base.GetCell (tv);
cell.Accessory = UITableViewCellAccessory.DisclosureIndicator;
return cell;
}
protected override void Dispose (bool disposing)
{
base.Dispose (disposing);
if (disposing)
{
if (this.fmt != null)
{
this.fmt.Dispose ();
this.fmt = null;
}
/* if (this.isNullButton != null)
{
this.isNullButton.Dispose ();
this.isNullButton = null;
}*/
if (this.datePicker != null)
{
this.datePicker.Dispose ();
this.datePicker = null;
}
}
}
public virtual string FormatDate (DateTime? dt)
{
if (dt.HasValue)
return this.fmt.ToString (dt.Value) + " " + dt.Value.ToLocalTime ().ToShortTimeString ();
else
return NullButtonCaption;
}
public virtual UIDatePicker CreatePicker ()
{
return new UIDatePicker (RectangleF.Empty)
{
AutoresizingMask = UIViewAutoresizing.FlexibleWidth,
Mode = UIDatePickerMode.DateAndTime,
Date = this.DateValue ?? DateTime.Now
};
}
private static RectangleF PickerFrameWithSize (SizeF size)
{
RectangleF applicationFrame = UIScreen.MainScreen.ApplicationFrame;
float y = 0f;
float x = 0f;
switch (UIApplication.SharedApplication.StatusBarOrientation)
{
case UIInterfaceOrientation.Portrait:
case UIInterfaceOrientation.PortraitUpsideDown:
{
x = (applicationFrame.Width - size.Width) / 2f;
y = (applicationFrame.Height - size.Height) / 2f - 25f;
break;
}
case UIInterfaceOrientation.LandscapeRight:
case UIInterfaceOrientation.LandscapeLeft:
{
x = (applicationFrame.Height - size.Width) / 2f;
y = (applicationFrame.Width - size.Height) / 2f - 17f;
break;
}
}
return new RectangleF (x, y, size.Width, size.Height);
}
public override void Selected (DialogViewController dvc, UITableView tableView, NSIndexPath path)
{
NullableDateTimeElement.MyViewController myViewController = new NullableDateTimeElement.MyViewController (this)
{
Autorotate = dvc.Autorotate
};
this.datePicker = this.CreatePicker ();
this.datePicker.Frame = NullableDateTimeElement.PickerFrameWithSize (this.datePicker.SizeThatFits (SizeF.Empty));
myViewController.View.BackgroundColor = UIColor.Black;
myViewController.View.AddSubview (this.datePicker);
dvc.ActivateController (myViewController);
}
}
}
无法使用日期元素
using System;
using MonoTouch.Foundation;
using MonoTouch.UIKit;
namespace MonoTouch.Dialog
{
public class NullableDateElement : NullableDateTimeElement
{
public NullableDateElement (string caption, DateTime? date, string nullButtonCaption, string setButtonCaption) : base (caption, date, nullButtonCaption, setButtonCaption)
{
initDateOnlyPicker ();
}
public NullableDateElement (string caption, DateTime? date, string nullButtonCaption) : base(caption, date, nullButtonCaption)
{
initDateOnlyPicker ();
}
public NullableDateElement (string caption, DateTime? date) : base(caption, date)
{
initDateOnlyPicker ();
}
void initDateOnlyPicker()
{
this.fmt.DateStyle = NSDateFormatterStyle.Medium;
}
public override string FormatDate (DateTime? dt)
{
if (dt.HasValue)
return this.fmt.ToString (dt);
else
return base.NullButtonCaption;
}
public override UIDatePicker CreatePicker ()
{
UIDatePicker uIDatePicker = base.CreatePicker ();
uIDatePicker.Mode = UIDatePickerMode.Date;
return uIDatePicker;
}
}
}
@Miguel，请考虑将此添加到MonoTouch.Dialog，因为对于空日期/日期时间存在非常合法的业务需求，并且此解决方案似乎可以解决问题。我的代码必须稍微清理一下，但这样可行。