C# Xamarin.Forms中的可空时间选择器
我正在使用C# Xamarin.Forms中的可空时间选择器,c#,xamarin,xamarin.forms,nullable,timepicker,C#,Xamarin,Xamarin.forms,Nullable,Timepicker,我正在使用TimePicker在我的应用程序中显示时间。当时间已设置时,它将正确显示,但当时间未设置时,它将显示默认的12:00 AM时间。所以我只想在未设置时间时显示null值。 是否可以在Xamarin表单中将null值设置为TimePicker /// <summary> /// DatePicker der null Werte erlaubt /// </summary> public class CustomDatePicker : DatePicker {
TimePicker
在我的应用程序中显示时间。当时间已设置时,它将正确显示,但当时间未设置时,它将显示默认的12:00 AM时间。所以我只想在未设置时间时显示null
值。
是否可以在Xamarin表单中将null
值设置为TimePicker
/// <summary>
/// DatePicker der null Werte erlaubt
/// </summary>
public class CustomDatePicker : DatePicker
{
/// <summary>
/// PropertyName für die <c>NullableDate</c> Property
/// </summary>
public const string NullableDatePropertyName = "NullableDate";
/// <summary>
/// Die BinableProperty
/// </summary>
public static readonly BindableProperty NullableDateProperty = BindableProperty.Create<CustomDatePicker, DateTime?>(i => i.NullableDate, null, BindingMode.TwoWay, null, NullableDateChanged);
/// <summary>
/// Datumswert welches null Werte akzeptiert
/// </summary>
public DateTime? NullableDate
{
get
{
return (DateTime?)this.GetValue(NullableDateProperty);
}
set
{
this.SetValue(NullableDateProperty, value);
}
}
/// <summary>
/// Der Name der <c>NullText</c> Property
/// </summary>
public const string NullTextPropertyName = "NullText";
/// <summary>
/// Die BindableProperty
/// </summary>
public static readonly BindableProperty NullTextProperty = BindableProperty.Create<CustomDatePicker, string>(i => i.NullText, default(string), BindingMode.TwoWay);
/// <summary>
/// Der Text der angezeigt wird wenn <c>NullableDate</c> keinen Wert hat
/// </summary>
public string NullText
{
get
{
return (string)this.GetValue(NullTextProperty);
}
set
{
this.SetValue(NullTextProperty, value);
}
}
/// <summary>
/// Der Name der <c>DisplayBorder</c> Property
/// </summary>
public const string DisplayBorderPropertyName = "DisplayBorder";
/// <summary>
/// Die BindableProperty
/// </summary>
public static readonly BindableProperty DisplayBorderProperty = BindableProperty.Create<CustomDatePicker, bool>(i => i.DisplayBorder, default(bool), BindingMode.TwoWay);
/// <summary>
/// Gibt an ob eine Umrandung angezeigt werden soll oder nicht
/// </summary>
public bool DisplayBorder
{
get
{
return (bool)this.GetValue(DisplayBorderProperty);
}
set
{
this.SetValue(DisplayBorderProperty, value);
}
}
/// <summary>
/// Erstellt eine neue Instanz von <c>CustomDatePicker</c>
/// </summary>
public CustomDatePicker()
{
this.DateSelected += CustomDatePicker_DateSelected;
this.Format = "dd.MM.yyyy";
}
/// <summary>
/// Wird gefeuert wenn ein neues Datum selektiert wurde
/// </summary>
/// <param name="sender">Der Sender</param>
/// <param name="e">Event Argumente</param>
void CustomDatePicker_DateSelected(object sender, DateChangedEventArgs e)
{
this.NullableDate = new DateTime(
e.NewDate.Year,
e.NewDate.Month,
e.NewDate.Day,
this.NullableDate.HasValue ? this.NullableDate.Value.Hour : 0,
this.NullableDate.HasValue ? this.NullableDate.Value.Minute : 0,
this.NullableDate.HasValue ? this.NullableDate.Value.Second : 0);
}
/// <summary>
/// Gefeuert wenn sich <c>NullableDate</c> ändert
/// </summary>
/// <param name="obj">Der Sender</param>
/// <param name="oldValue">Der alte Wert</param>
/// <param name="newValue">Der neue Wert</param>
private static void NullableDateChanged(BindableObject obj, DateTime? oldValue, DateTime? newValue)
{
var customDatePicker = obj as CustomDatePicker;
if (customDatePicker != null)
{
if (newValue.HasValue)
{
customDatePicker.Date = newValue.Value;
}
}
}
}
//
///空Werte erlaubt的日期选择器
///
公共类CustomDatePicker:DatePicker
{
///
///PropertyName für die NullableDate属性
///
public const字符串NullableDatePropertyName=“NullableDate”;
///
///模具二进制属性
///
public static readonly BindableProperty NullableDateProperty=BindableProperty.Create(i=>i.NullableDate,null,BindingMode.TwoWay,null,NullableDateChanged);
///
///Datumswert welches空值为akzeptiert
///
公共日期时间?NullableDate
{
得到
{
return(DateTime?)this.GetValue(NullableDateProperty);
}
设置
{
this.SetValue(NullableDateProperty,value);
}
}
///
///Der Name Der NullText属性
///
公用常量字符串NullTextPropertyName=“NullText”;
///
///模具可装订性
///
公共静态只读BindableProperty NullTextProperty=BindableProperty.Create(i=>i.NullText,默认值(字符串),BindingMode.TwoWay);
///
///文本中的所有内容均为空日期
///
公共字符串空文本
{
得到
{
返回(字符串)this.GetValue(NullTextProperty);
}
设置
{
this.SetValue(NullTextProperty,value);
}
}
///
///Der Name Der DisplayBorder属性
///
public const string DisplayBorderPropertyName=“DisplayBorder”;
///
///模具可装订性
///
公共静态只读BindableProperty DisplayBorderProperty=BindableProperty.Create(i=>i.DisplayBorder,默认值(bool),BindingMode.TwoWay);
///
///我的工作是独立完成的
///
公共边界
{
得到
{
返回(bool)this.GetValue(DisplayBorderProperty);
}
设置
{
此.SetValue(DisplayBorderProperty,value);
}
}
///
///客户数据采集器的新实例
///
公共CustomDatePicker()
{
this.DateSelected+=CustomDatePicker\u DateSelected;
this.Format=“dd.MM.yyyy”;
}
///
///我们将在新的基准面上进行测量
///
///发信人
///事件辩论
void CustomDatePicker\u DateSelected(对象发送方,DateChangedEventArgs e)
{
this.NullableDate=新的日期时间(
e、 新年,
e、 新日期,月份,
e、 NewDate,Day,
this.NullableDate.HasValue?this.NullableDate.Value.Hour:0,
this.NullableDate.HasValue?this.NullableDate.Value.Minute:0,
this.NullableDate.HasValue?this.NullableDate.Value.Second:0);
}
///
///格弗厄特·韦恩(Gefeuert wenn sich NullableDateändert)
///
///发信人
///阿尔特沃特酒店
///德尔纽维特酒店
私有静态无效NullableDateChanged(BindableObject obj、DateTime?oldValue、DateTime?newValue)
{
var customDatePicker=obj作为customDatePicker;
if(customDatePicker!=null)
{
if(newValue.HasValue)
{
customDatePicker.Date=newValue.Value;
}
}
}
}
您可以使用计时器
和标签创建一个自定义视图
。如果未选择时间,则将显示“hh:mm”,否则时间将显示在标签上。要显示时间选择器对话框,有一个tappesturerecognizer
,当点击标签时,它会将焦点设置为时间选择器
public class NullableTimePicker : ContentView
{
private const string NullTimeLabel = "hh : mm";
private readonly TimePicker _timePicker;
private readonly Label _label;
public static readonly BindableProperty TimeProperty = BindableProperty.Create<NullableTimePicker, TimeSpan?>(t => t.Time, null, BindingMode.TwoWay, propertyChanged: OnTimeChanged);
public NullableTimePicker()
{
_label = new Label
{
Text = NullTimeLabel,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.Fill,
HorizontalTextAlignment = TextAlignment.Start,
VerticalTextAlignment = TextAlignment.Center,
TextColor = Color.Black,
FontSize = Device.GetNamedSize(NamedSize.Medium, typeof(Label))
};
_timePicker = new TimePicker
{
IsVisible = false,
HorizontalOptions = LayoutOptions.FillAndExpand,
VerticalOptions = LayoutOptions.Fill
};
Content = new StackLayout
{
Children =
{
_label,
_timePicker
},
Padding = 0,
Spacing = 0,
Margin = 0
};
Padding = 0;
Margin = 0;
var tapGestureRecognizer = new TapGestureRecognizer();
tapGestureRecognizer.Tapped += TapGestureRecognizer_Tapped;
GestureRecognizers.Add(tapGestureRecognizer);
_timePicker.PropertyChanged += timePicker_PropertyChanged;
PropertyChanged += NullableTimePicker_PropertyChanged;
}
private void NullableTimePicker_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (_label != null && e.PropertyName == IsEnabledProperty.PropertyName)
{
_label.TextColor = IsEnabled ? Color.Black : Color.Gray;
}
}
private void timePicker_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == TimePicker.TimeProperty.PropertyName && _timePicker != null)
{
Time = _timePicker.Time;
}
}
private void TapGestureRecognizer_Tapped(object sender, EventArgs e)
{
if (IsEnabled == false)
{
return;
}
if (_timePicker.IsFocused)
{
_timePicker.Unfocus();
}
_timePicker.Focus();
}
private static void OnTimeChanged(BindableObject bindable, TimeSpan? oldvalue, TimeSpan? newvalue)
{
var nullableTimePicker = bindable as NullableTimePicker;
if (nullableTimePicker != null && oldvalue != newvalue)
{
nullableTimePicker.Time = newvalue;
}
}
public TimeSpan? Time
{
get
{
return GetValue(TimeProperty) as TimeSpan?;
}
set
{
SetValue(TimeProperty, value);
if (value.HasValue && _timePicker.Time != value)
{
_timePicker.Time = value.Value;
}
SetLabelText(value);
}
}
private void SetLabelText(TimeSpan? value)
{
_label.Text = value.HasValue ? ConvertTimeSpanToString(value.Value) : NullTimeLabel;
}
}
公共类NullableTimePicker:ContentView
{
私有常量字符串NullTimeLabel=“hh:mm”;
私有只读时间选择器_TimePicker;
专用只读标签_标签;
public static readonly BindableProperty TimeProperty=BindableProperty.Create(t=>t.Time,null,BindingMode.TwoWay,propertyChanged:OnTimeChanged);
公共NullableTimePicker()
{
_标签=新标签
{
Text=空时间标签,
HorizontalOptions=LayoutOptions.FillAndExpand,
垂直选项=布局选项。填充,
HorizontalTextAlignment=TextAlignment.Start,
VerticalTextAlignment=TextAlignment.Center,
TextColor=Color.Black,
FontSize=Device.GetNamedSize(NamedSize.Medium,typeof(Label))
};
_计时器选择器=新计时器选择器
{
IsVisible=false,
HorizontalOptions=LayoutOptions.FillAndExpand,
垂直选项=布局选项。填充
};
内容=新的堆栈布局
{
孩子们=
{
_标签,
_计时器选择器
},
填充=0,
间距=0,
保证金=0
};
填充=0;
保证金=0;
var tapGestureRecognizer=新的tapGestureRecognizer();
tapGestureRecognizer.Tapped+=tapGestureRecognizer_Tapped;
添加(点击手势识别器);
_timePicker.PropertyChanged+=timePicker\u PropertyChanged;
PropertyChanged+=NullableTimePicker\u PropertyChanged;
}
私有void NullableTimePicker\u PropertyChanged(对象发送方,PropertyChangedEventArgs e)
{
if(_label!=null&&e.PropertyName==IsEnabledProperty.PropertyName)
{
_label.TextColor=IsEnabled?颜色。黑色:颜色。灰色;
}
}
私有无效时间选择器\u属性已更改(对象se