Question

我有这样的NSURL：

NSURL *url = [NSURL URLWithString:@"http://jamessuske.com/isthedomeopen/isthedomeopenGetData.php"];

但如果没有互联网连接或手机信号，我的应用程序崩溃了。在使用前是否先测试连接？

我是否必须尝试抓住？我一直在阅读NSURLConnection，但我不清楚它是如何工作的。有什么想法吗？

我得到的错误是Thread 6:signal SIGABRT我不知道这意味着什么，我已经尝试了下面的所有示例，但都没有效果。

我补充说：

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    // release the connection, and the data object
    // receivedData is declared as a method instance elsewhere

    [connection release];

    // inform the user
    UIAlertView *didFailWithErrorMessage = [[UIAlertView alloc] initWithTitle: @"NSURLConnection " message: @"didFailWithError"  delegate: self cancelButtonTitle: @"Ok" otherButtonTitles: nil];
    [didFailWithErrorMessage show];
    [didFailWithErrorMessage release];

}

我将我的Mac从互联网上拔下并在模拟器上运行我的应用程序，显示Thread 6:signal SIGABRT

我在下面使用了这段代码

Reachability *networkReachability = [Reachability reachabilityForInternetConnection];
    NetworkStatus networkStatus = [networkReachability currentReachabilityStatus];
    if (networkStatus == NotReachable) {
        dispatch_async(dispatch_get_main_queue(), ^{
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Announcement" message: @"No Connection" delegate: nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release];
        });
    } else {
        dispatch_async(dispatch_get_main_queue(), ^{
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle: @"Announcement" message: @"Connection" delegate: nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release];
        });

当我连接到输入时工作，但是当我关闭我的互联网时，我收到此错误并且没有出现其他警报

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'data parameter is nil'

Answer 1

您可以使用Apple提供的示例代码来测试可达性：

http://developer.apple.com/library/ios/#samplecode/Reachability/Introduction/Intro.html

使用所需的主机名初始化可达性，然后您可以：

启动/停止通知程序，您将收到通知，指示此主机的可访问性何时更改
或只是获取当前的可访问性状态

Reachability *reachability = [Reachability reachabilityForInternetConnection];
NetworkStatus internetStatus = [reachability currentReachabilityStatus];
if (internetStatus == NotReachable) {
    // You have internet
} else {
    // You do not have internet
}

Answer 2

我喜欢做的一件事是检查与其他NSURL的连接并更改BOOL以进行连接。我做了这样的方法..

- (void)checkConnection
{
NSURL *checkURL = [NSURL URLWithString:@"http://www.apple.com"];
NSData *data = [NSData dataWithContentsOfURL:checkURL];

if (data)
{
    _connected = YES;
}
else
{
    _connected = NO;
}
}

现在我有一个BOOL _connected让我知道我是否已连接。然后在你需要确保你连接的任何方法中首先做这样的事情..

- (void)viewWillAppear:(BOOL)animated
{
[self checkConnection];
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;

if (_connected == YES)
{
    [self fetchTweets];
    [self reFresh];
    [self.tableView reloadData];
}else
{
    UIAlertView *message = [[UIAlertView alloc] initWithTitle:@"No Internet"
                                                      message:@"You must have an internet connection."
                                                     delegate:self
                                            cancelButtonTitle:@"OK"
                                            otherButtonTitles:nil];
    [message show];
    [self.refreshControl endRefreshing];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    return;
}
}

这就是我为我编写的一些应用程序所做的。它很快，你不需要大量的代码或进口。或者您可以查看NSURLConnection和NSURLRequest。它们结合使用的方法可以让您显示警告，如果没有数据则显示警告。这正是Rob所说的。只是一个想法！

Answer 3

Tony Million's Apple的Reachability代码是一个很好的基于块的解决方案来解决这个问题： https://github.com/tonymillion/Reachability

// allocate a reachability object
Reachability* reach = [Reachability reachabilityWithHostname:@"www.google.com"];

// set the blocks 
reach.reachableBlock = ^(Reachability*reach)
{
    NSLog(@"REACHABLE!");
};

reach.unreachableBlock = ^(Reachability*reach)
{
    NSLog(@"UNREACHABLE!");
};

// start the notifier which will cause the reachability object to retain itself!
[reach startNotifier];

使用前NSURL测试连接

3 个答案: