**小弟初学EXT有些小问题要请教**

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>用户登录</title>
    <link href="CSS/global.css" rel="stylesheet" type="text/css" />
    <link href="CSS/index.css" rel="stylesheet" type="text/css" />
    <link href="Script/Ext/resources/css/ext-all.css" rel="stylesheet" type="text/css" />
    <script src="Script/Ext/adapter/ext/ext-base.js" type="text/javascript"></script>
    <script src="Script/Ext/ext-all.js" type="text/javascript"></script>
    <script src="Script/Ext/ext-lang-zh_CN.js" type="text/javascript"></script>
    <script src="Script/PageJs/index.js" type="text/javascript"></script>
</head>
<body>
    <div id="div_main">
        <div id="div_title">
        </div>
        <div id="div_login_usename">
            <div id="div_lblusername">
                用户名:</div>
            <div id="div_username">
            </div>
        </div>
        <div id="div_login_password">
            <div id="div_lblpassword">
                用户名:</div>
            <div id="div_password">
            </div>
        </div>
        <div id="div_submit">
        </div>
    </div>
</body>
</html>
/// <reference path="../Ext/vswd-ext_2.0.2.js" />
Ext.onReady(function () {
    //启用提示
    Ext.QuickTips.init();    var txtUserName = new Ext.form.TextField({
        width: 140,
        id: 'txtUserName',
        allowBlank: false,
        blankText: '用户名不可以为空',
        renderTo: "div_username"
    });    var txtPassword = new Ext.form.TextField({
        inputType: 'password',
        width: 140,
        id: 'txtPassword',
        allowBlank: false,
        blankText: '密码不可以为空',
        renderTo: "div_password"
    });    var buttonName = new Ext.Button({
        id: "btnName",
        buttonAlign: 'center',
        text: "登录",
        tooltip: "登录",
        tooltipType: "title",
        type: "button",
        handleMouseEvents: true,
        handler: function () 
            Ext.Msg.alert('提示消息框', Ext.get('txtUserName').getValue() + '' + Ext.get('txtPassword').getValue()); 
            
        },
        renderTo: "div_submit"
    });});以上是小弟的代码.我想在点击按钮时如果以上两个文本框的非空验证不通过.慢不执行点击事件.除了手写代码外
if( Ext.get('txtUserName').getValue()!="" &&  Ext.get('txtPassword').getValue()!=""){Ext.Msg.alert('提示消息框', Ext.get('txtUserName').getValue() + '' + Ext.get('txtPassword').getValue()); }还有什么方法.或是我这种写法还有更好的方法吗