xamarin NumberCompareValidationBehavior

最新推荐文章于 2025-12-04 11:18:26 发布

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本文介绍了如何在Xamarin应用中使用NumberCompareValidationBehavior进行数值比较验证，详细阐述了该行为的实现和应用场景。

public class NumberCompareValidationBehavior : Behavior<Entry>
    {
        public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string),
            typeof(NumberCompareValidationBehavior), null, BindingMode.TwoWay, null, propertyChanged: null);
        public static readonly BindableProperty CompareTypeProperty = BindableProperty.Create("CompareType", typeof(string),
            typeof(NumberCompareValidationBehavior), string.Empty);

        public string Text
        {
            get
            {
                return (string)GetValue(TextProperty);
            }
            set
            {
                SetValue(TextProperty, value);
            }
        }

        public string CompareType
        {
            get
            {
                return (string)GetValue(CompareTypeProperty);
            }
            set
            {
                SetValue(CompareTypeProperty, value);
            }
        }

        protected override void OnAttachedTo(Entry bindable)
        {
            bindable.TextChanged += HandleTextChanged;
            base.OnAttachedTo(bindable);
        }

        void HandleTextChanged(object sender, TextChangedEventArgs e)
        {
            if (!string.IsNullOrEmpty(e.NewTextValue))
            {
                bool IsValid = false;
                //IsValid = e.NewTextValue == Text;
                int compareValue;
                bool compareIsValid = int.TryParse(Text, out compareValue);
                int inputValue;
                compareIsValid = int.TryParse(e.NewTextValue, out inputValue);

                switch (CompareType.ToLower())
                {
                    case "greater":
                        IsValid = compareIsValid && (inputValue > compareValue);
                        break;
                    case "greaterandequal":
                        IsValid = compareIsValid && (inputValue >= compareValue);
                        break;
                    case "lessthanandequal":
                        IsValid = compareIsValid && (inputValue <= compareValue);
                        break;
                    case "lessthan":
                        IsValid = compareIsValid && (inputValue < compareValue);
                        break;
                    default:
                        IsValid = true;
                        break;
                }

            ((Entry)sender).TextColor = IsValid ? Color.Default : Color.Red;
                ((Entry)sender).Text = IsValid ? e.NewTextValue : e.OldTextValue;
            }
        }

        protected override void OnDetachingFrom(Entry bindable)
        {
            bindable.TextChanged -= HandleTextChanged;
            base.OnDetachingFrom(bindable);
        }
    }

使用：

 <Entry.Behaviors>
                                <behaviors:EventToCommandBehavior Command="{Binding TextChangedCommand}" EventName="TextChanged" />
                                <customBehavior:NumberValidationBehavior/>
                                <customBehavior:NumberCompareValidationBehavior  Text="{Binding Path= Text, Source={x:Reference controlName}}" 
                                                                                 CompareType="lessthanandequal"/>
                            </Entry.Behaviors>