<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2007/09/07/trimming-strings-using-the-flex-stringutil-classs-trim-method/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white" viewSourceURL="srcview/index.html">

    <mx:Style>
        .errorTip {
            borderColor: haloBlue;
        }
    </mx:Style>

    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.controls.TextInput;
            import mx.utils.StringUtil;
            import mx.validators.Validator;

            private function trimStr(evt:FocusEvent):void {
                var ti:TextInput = TextInput(evt.currentTarget);
                ti.text = StringUtil.trim(ti.text);
            }

            private function validateForm():void {
                var errors:Array = Validator.validateAll(validatorArray);
                if (errors.length) {
                    Alert.show("Form is somehow invalid.", "INVALID");
                } else {
                    Alert.show("Form is valid.", "VALID");
                }
            }
        ]]>
    </mx:Script>

    <mx:Array id="validatorArray">
        <mx:StringValidator id="firstNameValidator"
                source="{firstName}"
                property="text"
                required="true" />
        <mx:StringValidator id="lastNameValidator"
                source="{lastName}"
                property="text"
                required="true" />
        <mx:EmailValidator id="emailValidator"
                source="{email}"
                property="text"
                required="true" />
    </mx:Array>

    <mx:Form>
        <mx:FormItem label="First name:" required="true">
            <mx:TextInput id="firstName" focusOut="trimStr(event)" />
        </mx:FormItem>
        <mx:FormItem label="Last name:" required="true">
            <mx:TextInput id="lastName" focusOut="trimStr(event)" />
        </mx:FormItem>
        <mx:FormItem label="Email:" required="true">
            <mx:TextInput id="email" focusOut="trimStr(event)" />
        </mx:FormItem>
        <mx:FormItem>
            <mx:Button label="Submit" click="validateForm()" />
        </mx:FormItem>
    </mx:Form>

</mx:Application>