xamarin 表单中的 datepicker 和 timepicker 多次触发 Focus 和 Unfocus 事件答案

【问题标题】：Focus and Unfocus events are triggering multiple times for datepicker and timepicker in xamarin formsxamarin 表单中的 datepicker 和 timepicker 多次触发 Focus 和 Unfocus 事件
【发布时间】：2021-09-27 20:19:13
【问题描述】：

我在我的应用程序中使用了日期选择器和时间选择器。

我为日期选择器和时间选择器实现了焦点和非焦点事件。使用 focus 和 unfocus 事件验证最大日期的时间。

那些焦点和非焦点事件会触发多次。当我们点击日期选择器或时间选择器时需要触发一次。

XAML：

<controls:DatePickerCustom x:Name="DatePicker" FontSize="14" HeightRequest="35" Date="{Binding CustomDate,Mode=TwoWay}" MaximumDate="{Binding MaximumDate}" FontFamily="Segoe UI" Format="D"  HorizontalOptions="FillAndExpand" Unfocused="DatePickerUnfocused" TranslationX="-4">
                                    <DatePicker.Triggers>
                                        <DataTrigger TargetType="DatePicker" Binding="{Binding IsCustomSelected}" Value="true">
                                            <Setter Property="TextColor" Value="{DynamicResource HeadingTextColor}" />
                                            <Setter Property="TextColor" Value="{DynamicResource HeadingTextColor}" />
                                        </DataTrigger>
                                    </DatePicker.Triggers>
                                </controls:DatePickerCustom>


<controls:TimePickerCustom x:Name="TimePicker" FontSize="14" HeightRequest="35" Time="{Binding CustomTime,Mode=TwoWay}" FontFamily="Segoe UI" Focused="TimePickerFocused" Unfocused="TimePickerUnfocused" >
                                    <TimePicker.Triggers>
                                        <DataTrigger TargetType="TimePicker" Binding="{Binding IsCustomSelected}" Value="true">
                                            <Setter Property="TextColor" Value="{DynamicResource HeadingTextColor}" />
                                        </DataTrigger>
                                    </TimePicker.Triggers>
                                </controls:TimePickerCustom>

CS：

protected void TimePickerUnfocused(object sender, FocusEventArgs e)
        {
            TimePicker picker = sender as TimePicker;
            if (DatePicker.Date.ToString("dd/MM/yyyy") == DatePicker.MaximumDate.ToString("dd/MM/yyyy"))
            {
                //var t1 = Convert.ToDateTime(DateTime.Now).ToString("HH:mm");
                //var t2 = Convert.ToDateTime(picker.Time.ToString()).ToString("HH:mm");

                var result = DateTime.Compare(Convert.ToDateTime(Convert.ToDateTime(DateTime.Now).ToString("HH:mm")), Convert.ToDateTime(Convert.ToDateTime(picker.Time.ToString()).ToString("HH:mm")));

                if (result > 0)
                {
                    if (endValue.ToString() != "00:00:00")
                    {
                        TimePicker.Time = endValue;
                    }
                    else
                    {
                        endValue = picker.Time;
                        TimePicker.Time = endValue;
                    }
                }
                else
                {
                    DisplayAlert("Alert!", "Please select the valid time", "OK");
                    TimePicker.Time = TimeSpan.Parse(DateTime.Now.AddHours(-1).ToString("HH:mm"));
                }
            }

        }

        protected void DatePickerUnfocused(object sender, FocusEventArgs e)
        {
            if (DatePicker.Date.ToString("dd/MM/yyyy HH:mm") == DatePicker.MaximumDate.ToString("dd/MM/yyyy HH:mm"))
            {
                if(endValue.ToString() != "00:00:00")
                {
                    TimePicker.Time = endValue;
                }
                else if (startValue.ToString() != "00:00:00")
                {
                    TimePicker.Time = startValue;
                }
                else
                {
                    startValue= TimeSpan.Parse(DateTime.Now.AddHours(-1).ToString("HH:mm"));
                    TimePicker.Time = startValue;
                }
            }
        }

        protected void TimePickerFocused(object sender, FocusEventArgs e)
        {
            if (DatePicker.Date.ToString("dd/MM/yyyy HH:mm") == DatePicker.MaximumDate.ToString("dd/MM/yyyy HH:mm") && startValue != null)
            {
                TimePicker.Time = startValue;
            }
        }

并且日期选择器的MinimumDate和MaximumDate属性在Android 10版本的真机上不起作用。相同的属性在模拟器中起作用。

【问题讨论】：

我无法重现您的问题，它只会在我身边触发一次焦点和取消焦点。也许您可以尝试使用 PropertyChanged 方法来监听选择时间事件。

标签： xamarin.forms datepicker focus timepicker

【解决方案1】：

可能的解决方法：

根据特定选择器是否获得焦点设置一个布尔值。忽略任何重复的焦点消息。

日期选择器示例：

private bool _datePickerFocused = false;

protected void DatePickerFocused(...)
{
    // Skip if already focused.
    if (_datePickerFocused)
        return;

    _datePickerFocused = true;
    ...
}

protected void DatePickerUnfocused(...)
{
    // Skip if not focused.
    if (!_datePickerFocused)
        return;

    _datePickerFocused = false;
    ...
}

【讨论】：