EXTJS动态设置GridPanel高度

上代码。自己看。
var girdHeight = Ext.getCmp("gird").getHeight();
var gird3Height = Ext.getCmp("gird3").getHeight();
var gird2Height = girdHeight-gird3Height-10;
//alert(gird2Height);
gird2.setHeight(gird2Height);
//窗口重绘时改变grid2高度
window.onresize=function(){
girdHeight = Ext.getCmp("gird").getHeight();
gird3Height = Ext.getCmp("gird3").getHeight();
gird2Height = girdHeight-gird3Height-10;
gird2.setHeight(gird2Height);
};