在后台加载json时出现系统错误

I make an json loader class for load json objects from url . but when I run it its give some system error in logcat . but it do not force close application . I dont know where is my mistake . and another question is that can you show me some class that give it the json url and its get the jsons in background and give the resualt ? tank you . here is my code : I make an json loader class for load json objec