1:基本的知识

    Base class for any ​​Component​​ that is to be sized as a box, using width and height.

    BoxComponent provides automatic box model adjustments for sizing and positioning and will work correctly within the Component rendering model.

    A BoxComponent may be created as a custom Component which encapsulates any HTML element, either a pre-existing element, or one that is created to your specifications at render time. Usually, to participate in layouts, a Component will need to be a BoxComponent in order to have its width and height managed.

   To use a pre-existing element as a BoxComponent, configure it so that you preset the el property to the element to reference:

   

var pageHeader = new Ext.BoxComponent({
el: 'my-header-div'
});


  This may then be

​added​​ to a

​Container​​ as a child item.

 To create a BoxComponent based around a HTML element to be created at render time, use the ​​autoEl​​​ config option which takes the form of a ​​DomHelper​​ specification:


var myImage = new Ext.BoxComponent({
autoEl: {
tag: 'img',
src: '/images/my-image.jpg'
}
});


2:用法

   它继承子Ext.Component类,并实现了定位和控制自身大小的功能,可以使用pageX,pageY,x,y为Ext.BoxComponent指定具体的坐标从而固定元素的位置,也可以使用width和height指定长度和宽度,或者使用autoHeight和autoWidth让Ext.BoxComponent根据自身的内容调整长度和高度

  举例说明:


Ext.onReady(function() {
var box = new Ext.BoxComponent( { //设置BoxComponent属性的配置
region: 'b1',
el: 'b1',
style: 'background-image: url(images/a.jpg); position: absolute;',
pageX: 630,
pageY: 260,
width: 228,
height: 182
});
box.render();
});


然后在页面的body标签中定义一个层:

<div id="b1"></div>