uitableview 上下滚动
table = [[PullToRefreshTableView alloc] initWithFrame:CGRectMake(0, 45, 320, 480)];
[table setContentSize:CGSizeMake(320, 960)];
//table.contentSize = CGRectMake(0, 0, 320, 960);
table.delegate = self;
table.dataSource = self;
table.backgroundColor = [UIColor clearColor];
[self.view addSubview:table];