lanucherImage显示时加载网络任务

显示launchimage直到网络任务完成
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary
*)launchOptions {
    // Override point for customization after application launch.
    dispatch_group_t group =
dispatch_group_create();
    dispatch_group_async(group,
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,
0), ^{
        NSURL *url = [NSURL
URLWithString:@"http://img15.3lian.com/2015/f2/50/d/71.jpg"];
        NSData *content = [NSData
dataWithContentsOfURL:url];
        if (content ==
nil) {
            NSLog(@"download error");
        }
        else {
            NSLog(@"download success");
        }
    });
    dispatch_group_wait(group,
DISPATCH_TIME_FOREVER);
    
    return
YES;
}