ios - setNetworkActivityIndi​​catorVisible 微调器不显示

Question

正如标题所说，这里有一些代码：

- (void)refreshMap {
    NSLog(@"refreshing");
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
    lat = [[NSNumber numberWithDouble:myUserLocation.coordinate.latitude] stringValue];
    lon = [[NSNumber numberWithDouble:myUserLocation.coordinate.longitude] stringValue];

    NSString *url = [[NSString alloc] initWithFormat:@"http://mywebsite.com/geo_search.json?lat=%@&lon=%@", lat, lon];
    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url]
                                              cachePolicy:NSURLRequestUseProtocolCachePolicy
                                          timeoutInterval:60.0];
    [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    [url release];
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
}

网络活动指示器（在状态栏中）根本不出现（不在模拟器中，也不在真实设备上）。我该如何解决这个问题？

Answer 1

除非您的代码将控制权返回给运行循环，否则 UI 不会更新。因此，如果您以相同的方法启用和禁用网络指示器，它将永远不会真正显示。解决方法是调用

[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];

在您的 url 连接委托方法（conectionDidFinishLoading:和connection:didFailWithError:）中。