ExtJs4.0 TreePanel+CheckBox全选

var mytree = new Ext.tree.TreePanel({
    id: 'ppdTree',
    x: 5,
    y: 5,
    width: 378,
    height: 470,
    useArrows: true,
    autoScroll: true,
    animate: true,
    enableDD: true,
    containerScroll: true,
    store: new Ext.data.TreeStore
                ({
                    proxy:
                    {
                        type: 'ajax',
                        url: 'data/User/UserPopedom.aspx?parameter=ppdTree&userId=' + userId
                    },
                    root:
                    {
                        id: 0,
                        text: "选择权限",
                        leaf: false,
                        expandable: true,
                        expanded: true
                    },
                    sorters: [
                    {
                        property: 'leaf',
                        direction: 'ASC'
                    },
                    {
                        property: 'text',
                        direction: 'ASC'
                    }]
                })
});
mytree.on('checkchange', function (node, checked) {
    node.expand();
    node.checked = checked;
    node.eachChild(function (child) {
        child.set('checked', checked);
        child.fireEvent('checkchange', child, checked);
    });
}, mytree);