GCD延时加载
double delayInSeconds = 1;
dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(delay, dispatch_get_main_queue(), ^(void){
//执行的方法
});
主线程更新UI
__weak typeof(self) weakSelf = self;
dispatch_async(dispatch_get_main_queue(), ^{
weakSelf.tableView.tableHeaderView = weakSelf.headView;
[weakSelf.tableView reloadData];
});
