我创建了一个自定义TimePicker和Android和iphone的渲染器，目标是允许它可以为空。作为灵感，使用了https://xamgirl.com/clearable-datepicker-in-xamarin-forms/
但是，由于某种原因，事件在设置时间时没有触发，这只发生在android中，更具体地说，在Android 8.1中。
在共享项目上：
public class NullableTimePicker : TimePicker
{
public NullableTimePicker()
{
Time = DateTime.Now.TimeOfDay;
NullableTime = null;
Format = @"HH\:mm";
}
public string _originalFormat = null;
public static readonly BindableProperty PlaceHolderProperty =
BindableProperty.Create(nameof(PlaceHolder), typeof(string), typeof(NullableTimePicker), " : ");
public string PlaceHolder
{
get { return (string)GetValue(PlaceHolderProperty); }
set
{
SetValue(PlaceHolderProperty, value);
}
}
public static readonly BindableProperty NullableTimeProperty =
BindableProperty.Create(nameof(NullableTime), typeof(TimeSpan?), typeof(NullableTimePicker), null, defaultBindingMode: BindingMode.TwoWay);
public TimeSpan? NullableTime
{
get { return (TimeSpan?)GetValue(NullableTimeProperty); }
set { SetValue(NullableTimeProperty, value); UpdateTime(); }
}
private void UpdateTime()
{
if (NullableTime != null)
{
if (_originalFormat != null)
{
Format = _originalFormat;
}
}
else
{
Format = PlaceHolder;
}
}
protected override void OnBindingContextChanged()
{
base.OnBindingContextChanged();
if (BindingContext != null)
{
_originalFormat = Format;
UpdateTime();
}
}
protected override void OnPropertyChanged(string propertyName = null)
{
base.OnPropertyChanged(propertyName);
if (propertyName == TimeProperty.PropertyName ||
(
propertyName == IsFocusedProperty.PropertyName &&
!IsFocused &&
(Time == DateTime.Now.TimeOfDay)))
{
AssignValue();
}
if (propertyName == NullableTimeProperty.PropertyName && NullableTime.HasValue)
{
Time = NullableTime.Value;
if (Time == DateTime.Now.TimeOfDay)
{
//this code was done because when date selected is the actual date the"DateProperty" does not raise
UpdateTime();
}
}
}
public void CleanTime()
{
NullableTime = null;
UpdateTime();
}
public void AssignValue()
{
NullableTime = Time;
UpdateTime();
}
}
在Android项目上：
public class NullableTimePickerRenderer : ViewRenderer<NullableTimePicker, EditText>
{
public NullableTimePickerRenderer(Context context) : base(context)
{
}
TimePickerDialog _dialog;
protected override void OnElementChanged(ElementChangedEventArgs<NullableTimePicker> e)
{
base.OnElementChanged(e);
this.SetNativeControl(new Android.Widget.EditText(Context));
if (Control == null || e.NewElement == null)
return;
this.Control.Click += OnPickerClick;
if (Element.NullableTime.HasValue)
Control.Text = DateTime.Today.Add(Element.Time).ToString(Element.Format);
else
this.Control.Text = Element.PlaceHolder;
this.Control.KeyListener = null;
this.Control.FocusChange += OnPickerFocusChange;
this.Control.Enabled = Element.IsEnabled;
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == Xamarin.Forms.TimePicker.TimeProperty.PropertyName ||
e.PropertyName == Xamarin.Forms.TimePicker.FormatProperty.PropertyName)
SetTime(Element.Time);
}
void OnPickerFocusChange(object sender, Android.Views.View.FocusChangeEventArgs e)
{
if (e.HasFocus)
{
ShowTimePicker();
}
}
protected override void Dispose(bool disposing)
{
if (Control != null)
{
this.Control.Click -= OnPickerClick;
this.Control.FocusChange -= OnPickerFocusChange;
if (_dialog != null)
{
_dialog.Hide();
_dialog.Dispose();
_dialog = null;
}
}
base.Dispose(disposing);
}
void OnPickerClick(object sender, EventArgs e)
{
ShowTimePicker();
}
void SetTime(TimeSpan time)
{
Control.Text = DateTime.Today.Add(time).ToString(Element.Format);
Element.Time = time;
}
private void ShowTimePicker()
{
CreateTimePickerDialog(this.Element.Time.Hours, this.Element.Time.Minutes);
_dialog.Show();
}
void CreateTimePickerDialog(int hours, int minutes)
{
NullableTimePicker view = Element;
_dialog = new TimePickerDialog(Context, (o, e) =>
{
view.Time = new TimeSpan(hours: e.HourOfDay, minutes: e.Minute, seconds: 0);
view.AssignValue();
((IElementController)view).SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
Control.ClearFocus();
_dialog = null;
}, hours, minutes, true);
_dialog.SetButton("ok", (sender, e) =>
{
SetTime(Element.Time);
this.Element.Format = this.Element._originalFormat;
this.Element.AssignValue();
});
_dialog.SetButton2("clear", (sender, e) =>
{
this.Element.CleanTime();
Control.Text = this.Element.Format;
});
}
}
在iOS项目上：
public class NullableTimePickerRenderer : TimePickerRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<TimePicker> e)
{
base.OnElementChanged(e);
var timePicker = (UIDatePicker)Control.InputView;
timePicker.Locale = new NSLocale("no_nb");
if (e.NewElement != null && this.Control != null)
{
this.UpdateDoneButton();
this.AddClearButton();
this.Control.BorderStyle = UITextBorderStyle.Line;
Control.Layer.BorderColor = UIColor.LightGray.CGColor;
Control.Layer.BorderWidth = 1;
if (Device.Idiom == TargetIdiom.Tablet)
{
this.Control.Font = UIFont.SystemFontOfSize(25);
}
}
}
private void UpdateDoneButton()
{
var toolbar = (UIToolbar)Control.InputAccessoryView;
var doneBtn = toolbar.Items[1];
doneBtn.Clicked += (sender, args) =>
{
NullableTimePicker baseTimePicker = this.Element as NullableTimePicker;
if (!baseTimePicker.NullableTime.HasValue)
{
baseTimePicker.AssignValue();
}
};
}
private void AddClearButton()
{
var originalToolbar = this.Control.InputAccessoryView as UIToolbar;
if (originalToolbar != null && originalToolbar.Items.Length <= 2)
{
var clearButton = new UIBarButtonItem("clear", UIBarButtonItemStyle.Plain, ((sender, ev) =>
{
NullableTimePicker baseTimePicker = this.Element as NullableTimePicker;
this.Element.Unfocus();
this.Element.Time = DateTime.Now.TimeOfDay;
baseTimePicker.CleanTime();
}));
var newItems = new List<UIBarButtonItem>();
foreach (var item in originalToolbar.Items)
{
newItems.Add(item);
}
newItems.Insert(0, clearButton);
originalToolbar.Items = newItems.ToArray();
originalToolbar.SetNeedsDisplay();
}
}
}
此代码适用于iOS和Android 8.1或更高版本，但在较低版本中，这不会触发事件设置时间，始终设置默认时间。
我也提供了代码的git repo，也许，让我很容易理解我的问题。 https://github.com/aismaniotto/Nullable24hTimePicker
谢谢你的帮助。在进一步挖掘代码和调试之后，我意识到问题出现在OkButton实现上。在Android 8上，显然，在OkButton实现之前调用了TimePickerDialog的回调，那里被忽略了。在旧版本中，之前调用了OKButton实现，并且由于某种原因，取消了对回调的调用。
这样，删除OkButton实现，问题就解决了......记住在工作版本上，无论如何都被忽略了。最终，我将提交到存储库，进行注册。
非常感谢。