如何在GraphObject中获取内部属性？

Question

ma android app从FB获得此回复：

GraphObject graphObject=

   GraphObject{graphObjectClass=GraphObject, state={"data":{"is_silhouette":false,"url":"https:\/\/fbcdn-profile-a.akamaihd.net\/hprofile-ak-xpa1\/v\/t1.0-1\/s200x200\/10491996_10154355617635153_5470840249552886594_n.jpg?oh=4dd714d8106d30cd7e548ad3380c7f24&oe=54924987&__gda__=1417856790_ad378b84581edeba05e0d429332eb889"}}}

如何获得＆＃34; url＆＃34;的价值？仅？

我尝试过失败：

GraphObject graphObject = response.getGraphObject();
    Object a = graphObject.getProperty("data").getProperty("url");