<script src="~/Scripts/Extjs4.2/ext-all.js"></script>
<link href="~/Scripts/Extjs4.2/resources/ext-theme-neptune/ext-theme-neptune-all.css" rel="stylesheet" />
<script src="~/Scripts/Extjs4.2/ext-theme-neptune.js"></script>
<script src="~/Scripts/jquery-3.3.1.min.js"></script>
<script>
    Ext.onReady(function () {
        //声明用户名文本框
        var userfield = new Ext.form.TextField({
            width: 200,
            //判断是否允许空白
            allowBlank: false,
            maxLength: 20,
            name: ‘username‘,
            fieldLabel: ‘用户名称‘,
            //提示用户信息
            blankText: ‘请输入用户名‘,
            maxLengthText: ‘用户名不能超过20个字符‘
        });

        //声明密码文本框
        var pwdfield = new Ext.form.TextField({
            width: 200,
            height:20,
            allowBlank: false,
            maxLength: 20,
            inputType: ‘password‘,
            name: ‘password‘,
            fieldLabel: ‘密码‘,
            maxLengthText:‘密码不能超过20个字符‘
        });

        //声音panel来放置两个文本框
        Ext.create(‘Ext.form.Panel‘, {
            title: ‘Login‘,
            width: 300,
            bodyPadding: 10,
            renderTo: Ext.getBody(),
            items: [userfield,pwdfield]
        });

    })
</script>

注意：不可以直接把文本框放置在windows窗体中，需要声明panel后放置入其中，否则会出现错误。

EXTJS4.2——3.1 添加文本框