有没有可达性专家？

Question

我的应用程序一直运行得很好，直到我将Reachability .h和.m文件合并到它中，以检查互联网连接。虽然在大多数情况下，一切仍然运行得很好(所有网页都加载正确，当我故意关闭我的Airport进行测试时，Reachability会优雅地捕捉到它)--我现在确实在奇怪的时候会莫名其妙地崩溃，并出现可怕的"Exc-Bad-Access“错误……我运行了Instruments并找到了僵尸-参见屏幕-抓取：

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查看"RefCt“列，您可以看到它达到了15 -我看到它超过了20！在"Responsible Caller“列(最右边)中，我看到了各种我不认识的方法--而且谁的调用肯定不是我发起的--我假设它们是在运行时由系统内部调用的？

无论哪种方式，我都非常仔细地遵循了苹果的可达性代码和说明，以及来自排名非常高的堆栈溢出线程的提示：How to check for an active Internet connection on iOS or OSX?

但我还是会遇到一些莫名其妙的崩溃。

有人能给点建议吗？

代码如下：

#import "Reachability.h"


-(void) viewWillAppear:(BOOL)animated
{
   // check for internet connection
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkNetworkStatus:) name:kReachabilityChangedNotification object:nil];

internetReachable = [[Reachability reachabilityForInternetConnection] retain];
[internetReachable startNotifier];

// check if a pathway to a random host exists
hostReachable = [[Reachability reachabilityWithHostName: @"www.apple.com"] retain];
[hostReachable startNotifier];

// now patiently wait for the notification
}



-(void) viewDidLoad {

    url = [NSURL URLWithString: @"http://www.google.com"];
    NSURLRequest *req = [NSURLRequest requestWithURL: url];
    [webPageView loadRequest:req];
    [super viewDidLoad];
}



-(void) checkNetworkStatus:(NSNotification *)notice
{
        // called after network status changes

    NetworkStatus internetStatus = [internetReachable currentReachabilityStatus];

    switch (internetStatus) 
    {
        case NotReachable:
        {
            [self displayMessageWithTitle:@"ERROR"
                               andMessage:@"Unable To Connect to Internet"
                              andOKButton:@"OK"];
            [self dismissModalViewControllerAnimated:YES];
            break;

        }
        case ReachableViaWiFi:
        {
            NSLog(@"The internet is working via WIFI.");

            break;

        }
        case ReachableViaWWAN:
        {
            NSLog(@"The internet is working via WWAN.");

            break;

        }
    }

    NetworkStatus hostStatus = [hostReachable currentReachabilityStatus];
    switch (hostStatus)
    {
        case NotReachable:
        {
            // NSLog(@"A gateway to the host server is down.");

            [self displayMessageWithTitle:@"ERROR"
                               andMessage:@"Host Not Reachable"
                              andOKButton:@"OK"];
            [self dismissModalViewControllerAnimated:YES];
            break;

        }

        case ReachableViaWiFi:
        {
            NSLog(@"A gateway to the host server is working via WIFI.");

            break;

        }

        case ReachableViaWWAN:
        {
            NSLog(@"A gateway to the host server is working via WWAN.");

            break;

        }
    }
}



- (void)webViewDidStartLoad:(UIWebView *)webView {
    [activityIndicator startAnimating];
}


- (void)webViewDidFinishLoad:(UIWebView *)webView {
    [activityIndicator stopAnimating];
}


// Since this ViewController is presented Modally, this method removes it 
// via a button click:
-(IBAction) dismissWebTixView:(id)sender {
    [self dismissModalViewControllerAnimated:YES];
}




-(void) viewWillDisappear:(BOOL)animated {
    NSLog(@"In webForTix's 'viewWillDisappear' method....");
    [[NSNotificationCenter defaultCenter] removeObserver:self
name:kReachabilityChangedNotification
                                              object:nil];
}


// Was told it might be good to put "removeObserver" here and not in viewWillDisappear
// well neither worked - the App still crashes....
- (void)dealloc
{
    //NSLog(@"In webForTix's dealloc method....");
//    [[NSNotificationCenter defaultCenter] removeObserver:self
//                                                        name:kReachabilityChangedNotification
//                                                  object:nil];
NSLog(@"In webForTix's dealloc method - removedObserver...");
[super dealloc];

}

Answer 1

您必须小心地平衡对addObserver和removeObserver的调用。

如果在vieWillAppear中为通知添加观察者，则需要在viewWillDisappear中将其删除。

如果您添加了两次观察者，您将被调用两次以获取相同的通知，并且必须调用removeObserver两次才能删除这两个通知。

我没有看到任何明显的内存管理问题。看起来你发布的所有代码都在创建自动释放的对象，这应该没问题。