Xamarin 从 Image Tap 显示 iOS UIDatePicker

Question

所以我正在使用 Xamarin 并尝试创建一个图像渲染器，当点击它时将显示 iOS 的 UIDatePicker。我的渲染器非常适合 Android，但我无法让日期选择器在 iOS 上显示。我的代码在渲染器下面，我对其进行了调试，我一直通过 mTextField.BecomeFirstResponder();我“认为”会让日期选择器显示出来。

谁能指出我正确的方向？我只需要那个选择器显示在屏幕上。一旦我可以让它显示出来，我就可以随心所欲地处理它。

private void _DatePickerHasBeenTapped( object sender, EventArgs e )
    {
        if( mDatePickerDialog != null )
        {
            mDatePickerDialog.TouchCancel -= _DatePickerDialogOnCancelEvent;
            mDatePickerDialog.ValueChanged -= _DatePickerDialogOnValueChanged;
        }

        var date = mDatePicker.PickerDate == DateTime.MinValue
            ? DateTime.Today
            : mDatePicker.PickerDate;


        mTextField = new UITextField();

        mDatePickerDialog = new UIDatePicker { Mode = UIDatePickerMode.Date, TimeZone = new NSTimeZone( "UTC" ) };

        mDatePickerDialog.ValueChanged += _DatePickerDialogOnValueChanged;
        mDatePickerDialog.SetDate( date.ToNSDate(), false );

        var width = UIScreen.MainScreen.Bounds.Width;
        var toolbar = new UIToolbar( new RectangleF( 0, 0, (float)width, 44 ) ) { BarStyle = UIBarStyle.Default, Translucent = true };
        var spacer = new UIBarButtonItem( UIBarButtonSystemItem.FlexibleSpace );
        var doneButton = new UIBarButtonItem( UIBarButtonSystemItem.Done, ( o, a ) => mDatePickerDialog.ResignFirstResponder() );

        toolbar.SetItems( new[] { spacer, doneButton }, false );

        mTextField.InputView = mDatePickerDialog;
        mTextField.InputAccessoryView = toolbar;

        if( mTextField.CanBecomeFirstResponder )
        {
            mTextField.BecomeFirstResponder();
        }
    }

Answer 1

如果UITextField 实际正在显示，您的方法将起作用。现在您可以破解它，方法是将 UITextField 添加到 VC 视图层次结构中，但使用负 cgrect 将其从屏幕上移开，然后在 UIBarButtonItem 处理程序中将其删除：

var mTextField = new UITextView(new CGRect(-1000, -1000, 10, 10));
yourViewController.Add(mTextField);

注意：我见过屏幕外控件的响应器失败，当我需要它们成为虚假响应器时避免它们，但我知道其他人这样做...用户要小心...：-/

或者：

您可以通过编程方式或从包含选择器和 关闭 按钮的情节提要设计一个 UIViewController，并在用户点击您的图像时显示它。点击关闭按钮，关闭控制器并将您的选择器日期发送到某个地方......

或者：

对于这样的事情，我通常使用弹出式视图控制器。

示例：

var parentVC = this; // This would the "main" Form's ViewController, obtain it within your renderer

PopoverDelegate popoverDelegate = null;
var datePicker = new UIDatePicker(new CGRect(0, 0, parentVC.View.Frame.Width, 300));
popoverDelegate = new PopoverDelegate(datePicker, (date) =>
{
    // Post the date change back to Forms via an event, etc... 
    Console.WriteLine($"Date Choosen: {date}");
    datePicker.Dispose();
    popoverDelegate.Dispose();
});
using (var popOverStyleVC = new UIViewController
{
    ModalPresentationStyle = UIModalPresentationStyle.Popover
})
{
    var pc = popOverStyleVC.PopoverPresentationController;
    {
        pc.Delegate = popoverDelegate;
        pc.SourceView = parentVC.View;
        pc.SourceRect = imageButton.Frame; // a CGRect where you want the popup arrow to point
    }
    popOverStyleVC.PreferredContentSize = datePicker.Frame.Size;
    popOverStyleVC.View.Add(datePicker);
    parentVC.PresentViewController(popOverStyleVC, true, null);
}

结果：

上面缺少的部分是UIPopoverPresentationControllerDelegate，因为您有通过UIModalPresentationStyle GetAdaptivePresentationStyle返回UIModalPresentationStyle.None，其他弹出框未正确显示，这也是我在哪里赶上解雇并提供带有日期的回调。

UIPopoverPresentationControllerDelegate：

public class PopoverDelegate : UIPopoverPresentationControllerDelegate
{
    public delegate void DatePicked(NSDate date);
    UIDatePicker datePicker;
    DatePicked datePicked;

    public PopoverDelegate(UIDatePicker datePicker, DatePicked datePicked)
    {
        this.datePicked = datePicked;
        this.datePicker = datePicker;
    }

    public override UIModalPresentationStyle GetAdaptivePresentationStyle(UIPresentationController forPresentationController)
    {
        return UIModalPresentationStyle.None;
    }

    public override void DidDismissPopover(UIPopoverPresentationController popoverPresentationController)
    {
        datePicked(datePicker.Date);
    }
}