I have a problem about Ext.getDOM

[MechecksV]

function LoginItems() {
    return [{
        xtype : 'textfield',
        fieldLabel : "用户名",
        id : 'UserID',
        name : 'UserID',
        allowBlank : false
    }, {
        xtype : 'textfield',
        fieldLabel : "密码",
        inputType : 'password',
        name : 'UserPassword',
        allowBlank : false
    }, {
        xtype : 'textfield',
        fieldLabel : "验证码",
        name: 'validateCode',
        style:"font-size: 15px",
        maxLength: 5,
        width: 80,
        allowBlank:false  
    }]
}

Login = function() {
    var win, form, submitUrl = '/user.mvc/login';  
    return {
        Init : function() {
        //    Ext.state.Manager.setProvider(new Ext.state.CookieProvider());
            var logoPanel = new Ext.Panel({
                baseCls : 'x-plain',
                id : 'login-logo',
                region : 'center'
            });

            var formPanel = new Ext.form.FormPanel({
                baseCls : 'x-plain',
                defaults : {
                    width : 200
                },
                frame : false,
                height : 100,
                id : 'login-form',
                items : LoginItems(),
                labelWidth : 120,
                region : 'south'
            });
            
            
            
            
            win = new Ext.Window({
                buttons : [{
                    scope : Login,
                    text : "登陆",
                    handler : function CheckLogin() {
                        if (form.isValid()) {
                            var formvalue = form.getValues();
                            Ext.Ajax.request({
                                url : submitUrl,
                                method : "POST",
                                waitMsg : "请等待!",
                                params : {
                                    userid : formvalue.UserID,
                                    password : formvalue.UserPassword
                                },
                                success : function(response, options) {
                                    var responseMessage = Ext.util.JSON
                                            .decode(response.responseText);
                                    if (responseMessage.Result) {
                                        win.destroy();
                                        window.location = "/Home.mvc/Index";
                                    } else {
                                        Ext.MessageBox.alert("消息",
                                                responseMessage.Message);
                                    }
                                },
                                failure : function(response, options) {
                                    Ext.MessageBox.hide();
                                    Ext.MessageBox.show({
                                        title :"登陆失败",
                                        msg : response.responseText
                                    });

                                }
                            });
                        } else {
                            form.markInvalid();
                            Ext.MessageBox.alert("消息", "输入错误");
                        }
                    }
                }],
                buttonAlign : 'right',
                closable : false,
                draggable : false,
                height : 250,
                id : 'login-win',
                layout : 'border',
                minHeight : 250,
                minWidth : 530,
                plain : false,
                resizable : false,
                items : [logoPanel, formPanel],
                title : 'Login',
                width : 530
            });

            form = formPanel.getForm();
            win.show();
            
    
        }
        
    };
    
    
}();


Ext.BasicForm.prototype.afterAction = function(action, success) {
    this.activeAction = null;
    var o = action.options;
    if (o.waitMsg) {
        Ext.MessageBox.updateProgress(1);
        Ext.MessageBox.hide();
    }
    if (success) {
        if (o.reset) {
            this.reset();
        }
        Ext.callback(o.success, o.scope, [this, action]);
        this.fireEvent('actioncompleted', this, action);
    } else {
        Ext.callback(o.failure, o.scope, [this, action]);
        this.fireEvent('actionfailed', this, action);
    }
}

function ConvertFormValue(formvalue) {
    var ResultObject = new Object();
    for (var prop in formvalue) {
        ResultObject[prop] = formvalue[prop];
    }
    return ResultObject;
}

/***********************************************/


var bd = Ext.getDom('validateCode'); 
alert(Ext.getDom('validateCode'))     
var bd2 = Ext.get(bd.parentNode);     
bd2.createChild(
 [
  {tag:'span',html:''},
  {tag: 'img',id:'ImgVerifyCode', src: '/Login.mvc/GetImageCode',align:'absbottom'},
  {tag:'span',html:'   <a href=# onclick=GetImgCode()>Retry</a>'}
 ]
);



function GetImgCode()
         {
              var randomnum = Math.random();
              var getimagecode = document.getElementById("ImgVerifyCode");
              getimagecode.src = "/Login.mvc/GetImageCode"+randomnum;
         }

/***********************************************/

Ext.onReady(Login.Init, Login, true);

------------------------------------------------------------------------------------
WHY bd is null?

[MechecksV]

ANYONE can help me?

[Condor]

You can only access the DOM from within Ext.onReady.

Try moving your Ext.getDom code to the Login.init() method.