Question

Extjs4 中怎么获取根节点并展开第一层

Answer 1

展开节点的代码放到你的store的load事件中，ajax是异步加载的，执行展开代码先于ajax返回数据
var store = Ext.create('Ext.data.TreeStore', {
//autoLoad : true,
proxy: {
type: 'ajax',
url: 'extjs/compassApi_loadTableListTree.action',
reader: {
type: 'json',
root: 'children'
}
},
sorters: [{
property: 'leaf',
direction: 'ASC'
}],
root: {
expanded: true
},
listeners:{load: function () {
var rootnode = tree.getRootNode();

console.log(tree.getRootNode());

if (rootnode.childNodes.length > 0) {
console.log(1);
rootnode.childNodes[0].expand();
}
}}
});