iOS 多个异步下载 全部下载完后同步加载

//异步下载 同步加载

dispatch_group_t  group = dispatch_group_create();

dispatch_queue_t queue = dispatch_queue_create("hxy.test", DISPATCH_QUEUE_CONCURRENT);

dispatch_group_async(group, queue, ^{

NSLog(@"queue1");

});

dispatch_group_async(group, queue, ^{

NSLog(@"queue2");

});

dispatch_group_async(group, queue, ^{

NSLog(@"queue3");

});

dispatch_group_notify(group, queue, ^{

NSLog(@"全部下载完成了");

});