ExtJs4.0中点击获取该节点的id或者text,求助

JScript code

var store = Ext.create('Ext.data.TreeStore', {
    root: {
        expanded: true,
        text: "",
        user: "",
        status: "",
        children: [
            { text: "detention", leaf: true },
            { text: "homework", expanded: true,
                children: [
                    { text: "book report", leaf: true,id: "37000" },
                    { text: "alegrbra", leaf: true,id: "37000" }
                ]
            },
            { text: "buy lottery tickets", leaf: true }
        ]
    }
});

var tree = Ext.create('Ext.tree.Panel', {
    store: store,
    viewConfig: {
        plugins: {
            ptype: 'treeviewdragdrop'
        }
    },
    border: 0,
    height: 500,
    rootVisible: false  //默认不显示根节点
});
    tree.on('itemclick', function(node, event) {
    Ext.Msg.alert('信息提示', tree.getRootNode().id);
    });

ExtJs4.0中点击获取该节点的id，这个地方id应该是弹出"37000",可为什么一直是"Ext.data.Store.ImplicitModel-ext-gen1007-ext-record-1" 呢 求助！！！！！！！！！！！！！！！！！1

又是ext……有空得看看 好多分啊……