Validating negative numbers using the NumberValidator in Flex

The following example shows how you can prevent or allow negative numbers when using the NumberValidator class by setting the Boolean allowNegative property.

Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/31/validating-negative-numbers-using-the-numbervalidator-in-flex/ -->
<mx:Application name="NumberValidator_allowNegative_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.events.ValidationResultEvent;

            private function numberValidator_invalid(evt:ValidationResultEvent):void {
                Alert.show(evt.message);
            }

            private function numberValidator_valid(evt:ValidationResultEvent):void {
                Alert.show(evt.type);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="allowNegative:">
                <mx:CheckBox id="checkBox"
                        selected="true" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:NumberValidator id="numberValidator"
            allowNegative="{checkBox.selected}"
            source="{textInput}"
            property="text"
            trigger="{button}"
            triggerEvent="click"
            invalid="numberValidator_invalid(event);"
            valid="numberValidator_valid(event);" />

    <mx:HBox defaultButton="{button}">
        <mx:TextInput id="textInput"
                restrict="0-9\.\-"
                maxChars="10" />
        <mx:Button id="button"
                label="validate" />
    </mx:HBox>

</mx:Application>

View source is enabled in the following example.

You can also set the allowNegative property using ActionScript, as seen in the following example:

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/08/31/validating-negative-numbers-using-the-numbervalidator-in-flex/ -->
<mx:Application name="NumberValidator_allowNegative_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.events.ValidationResultEvent;

            private function checkBox_change(evt:Event):void {
                numberValidator.allowNegative = checkBox.selected;
            }

            private function numberValidator_invalid(evt:ValidationResultEvent):void {
                Alert.show(evt.message);
            }

            private function numberValidator_valid(evt:ValidationResultEvent):void {
                Alert.show(evt.type);
            }
        ]]>
    </mx:Script>

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="allowNegative:">
                <mx:CheckBox id="checkBox"
                        selected="true"
                        change="checkBox_change(event);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:NumberValidator id="numberValidator"
            allowNegative="true"
            source="{textInput}"
            property="text"
            trigger="{button}"
            triggerEvent="click"
            invalid="numberValidator_invalid(event);"
            valid="numberValidator_valid(event);" />

    <mx:HBox defaultButton="{button}">
        <mx:TextInput id="textInput"
                restrict="0-9\.\-"
                maxChars="10" />
        <mx:Button id="button"
                label="validate" />
    </mx:HBox>

</mx:Application>