求助：如何禁用Alertview弹出

我的应用里面有一个Alertview，没有网络连接的时候会弹出来。但是我希望有网络连接的时候它可以自动禁用。代码如下：

-(void)reachabilityChanged:(NSNotification*)note

    {
        Reachability * reach = [note object];

        if([reach isReachable])
        {
            notificationLabel.text = @"Notification Says Reachable";
            NSLog(@"Internet is Up");



        }
        else
        {
            notificationLabel.text = @"Notification Says Unreachable";
            NSLog(@"Internet is Down");
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Please connect to Internet"
                                                            message:nil
                                                           delegate:self
                                                  cancelButtonTitle:nil
                                                  otherButtonTitles:nil];
            UIActivityIndicatorView *progress= [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(125, 50, 30, 30)];
            progress.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
            [alert addSubview:progress];
            [progress startAnimating];
            [alert show];
        }
    }

可以把alertView当做实体变量，然后在ivar调用didDismissWithButtonIndex，然后就可以在viewDidLoad中分配alert，然后：

 -(void)reachabilityChanged:(NSNotification*)note{
        Reachability * reach = [note object];
        if([reach isReachable])
        {
            notificationLabel.text = @"Notification Says Reachable";
            NSLog(@"Internet is Up");
            [self performSelector:@selector(dismissAlert:) withObject:alert afterDelay:0];
        }
        else
        {
            notificationLabel.text = @"Notification Says Unreachable";
            NSLog(@"Internet is Down");

            UIActivityIndicatorView *progress= [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(125, 50, 30, 30)];
            progress.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
            [alert addSubview:progress];
            [progress startAnimating];
            [alert show];
        }
    }

    -(void)dismissAlert:(UIAlertView *)alertView{
              [alertView dismissWithClickedButtonIndex:0 animated:YES];
    }

在头文件里执行UIAlertViewDelegate。