Ios 修复我的网络活动指示器

我的网络活动指示器有一个问题，有时它会在不应该显示的时候继续显示

我为它编写了自己的管理器，并将其替换为一个使用

NSAssert

语句的管理器，如下所示

- (void)setNetworkActivityIndicatorVisible:(BOOL)setVisible {
    static NSInteger NumberOfCallsToSetVisible = 0;
    if (setVisible)
        NumberOfCallsToSetVisible++;
    else
        NumberOfCallsToSetVisible--;

    // The assertion helps to find programmer errors in activity indicator management.
    // Since a negative NumberOfCallsToSetVisible is not a fatal error,
    // it should probably be removed from production code.
    NSAssert(NumberOfCallsToSetVisible >= 0, @"Network Activity Indicator was asked to hide more often than shown");

    // Display the indicator as long as our static counter is > 0.
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:(NumberOfCallsToSetVisible > 0)];
}

- (void)sendRequest:(NSURLRequest *)request
{
    NSError *error = nil;
    NSURLResponse *response = nil;

    [[NetworkManager sharedInstance] setNetworkActivityIndicatorVisible:YES];
    NSData *data = [NSURLConnection sendSynchronousRequest:request
                                         returningResponse:&response
                                                     error:&error];
    [[NetworkManager sharedInstance] setNetworkActivityIndicatorVisible:NO];

    // other stuff...

    [self processData:data];
}

我发现它是这样的，它立即指出我使用这个函数时出了问题

我的所有网络活动都是通过单个

NSOperationQueue

独家运行的，该队列由singleton类管理。每个操作都是NSOperation的子类（实际上是TemplateOperation的子类，TemplateOperation是NSOperation的子类）

不管怎样，所有的下载和上传都很好，我就是这样做的

- (void)setNetworkActivityIndicatorVisible:(BOOL)setVisible {
    static NSInteger NumberOfCallsToSetVisible = 0;
    if (setVisible)
        NumberOfCallsToSetVisible++;
    else
        NumberOfCallsToSetVisible--;

    // The assertion helps to find programmer errors in activity indicator management.
    // Since a negative NumberOfCallsToSetVisible is not a fatal error,
    // it should probably be removed from production code.
    NSAssert(NumberOfCallsToSetVisible >= 0, @"Network Activity Indicator was asked to hide more often than shown");

    // Display the indicator as long as our static counter is > 0.
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:(NumberOfCallsToSetVisible > 0)];
}

- (void)sendRequest:(NSURLRequest *)request
{
    NSError *error = nil;
    NSURLResponse *response = nil;

    [[NetworkManager sharedInstance] setNetworkActivityIndicatorVisible:YES];
    NSData *data = [NSURLConnection sendSynchronousRequest:request
                                         returningResponse:&response
                                                     error:&error];
    [[NetworkManager sharedInstance] setNetworkActivityIndicatorVisible:NO];

    // other stuff...

    [self processData:data];
}

重要的行在我同步发送

NSURLConnection

之前和之后

在发送请求之前，我立即将网络活动指示器设置为可见（使用我的manager类），然后立即将其设置为不可见

但NSAssert指出，在某些地方，这种情况并没有正常发生

---

是否从多个线程运行此函数可能会导致问题？如何解决这个问题？

整数递增或递减不是线程安全的（据我所知），因此如果两个线程“同时”调用您的方法，计数可能无法正确更新

一种解决方案是添加一些同步指令（例如

@synchronized

） 按照你的方法。或者使用原子递增/递减函数：

#include <libkern/OSAtomic.h>

- (void)setNetworkActivityIndicatorVisible:(BOOL)setVisible {
    static volatile int32_t NumberOfCallsToSetVisible = 0;
    int32_t newValue = OSAtomicAdd32((setVisible ? +1 : -1), &NumberOfCallsToSetVisible);

    NSAssert(newValue >= 0, @"Network Activity Indicator was asked to hide more often than shown");
    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:(newValue > 0)];
}

#包括
-（void）SetNetworkActivityIndicator可视：（BOOL）setVisible{
静态易失性int32_t NumberOfCallsToSetVisible=0；
int32_t newValue=OSAtomicAdd32（（setVisible？+1:-1），&NumberOfCallsToSetVisible）；
NSAssert（newValue>=0，@“要求网络活动指示器隐藏的频率高于显示的频率”）；
[[UIApplication sharedApplication]SetNetworkActivityIndicator可视：（newValue>0）]；
}

这应该会有帮助，非常感谢！两个很棒的答案：D@Fogmeister当前位置请看一下我答案中的缺陷：-）