好的，所以我正在尝试让这个应用程序显示网络错误警报代码。我添加了 SystemConfiguration.framework 框架和 Apple 的“Reachability”示例代码。

这是 viewcontroller.h 文件:

#import <UIKit/UIKit.h>

@class Reachability;

@interface Test_Internet_ConnectionViewController : UIViewController {

    Reachability* internetReachable;
    Reachability* hostReachable;
}

@property BOOL internetActive;
@property BOOL hostActive;

- (void) checkNetworkStatus:(NSNotification *)notice;

@end

这是 viewcontroller.m 文件:

#import "Test_Internet_ConnectionViewController.h"
#import "Reachability.h";

@implementation Test_Internet_ConnectionViewController

@synthesize internetActive;
@synthesize hostActive;

/*
// The designated initializer. Override to perform setup that is required before the view is loaded.
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}
*/

/*
// Implement loadView to create a view hierarchy programmatically, without using a nib.
- (void)loadView {
}
*/


// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];

        // 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
    }

/*
// Override to allow orientations other than the default portrait orientation.
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
*/

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

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

    NetworkStatus internetStatus = [internetReachable currentReachabilityStatus];
    switch (internetStatus)

    {
        case NotReachable:
        {
            NSLog(@"The internet is down.");
            self.internetActive = NO;

            UIAlertView *errorView = [[UIAlertView alloc] initWithTitle:@"Internet Unavailable" message:@"This page cannot load, please check your internet connection and try again." delegate:nil cancelButtonTitle:@"Dismiss" otherButtonTitles:nil];
            [errorView show];
            [errorView release];

            break;

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

            break;

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

            break;

        }
    }

    NetworkStatus hostStatus = [hostReachable currentReachabilityStatus];
    switch (hostStatus)

    {
        case NotReachable:
        {
            NSLog(@"A gateway to the host server is down.");
            self.hostActive = NO;

            break;

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

            break;

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

            break;

        }
    }
}

- (void)dealloc {
    [super dealloc];

        [[NSNotificationCenter defaultCenter] removeObserver:self];

    }

@end

如果打开应用程序时没有互联网，错误会按预期工作，但如果应用程序在最初通过互联网连接打开后失去连接，错误会显示 3 次，而我显然只希望它显示一次。

我认为它可能在 Reachability 类中发送了 3 次通知，可能是在 3 个不同的地方。我不知道它为什么这样做，但我认为解决方案可能是从 Reachability 类中删除我不想要的两个调用，但我不知道该怎么做。

有人能帮帮我吗？ 提前致谢。

编辑:

8个警告和4个错误如下:

'TestViewController' may not respond to '+checkConnectivity'

Initialization makes integer from pointer without a cast

Local declaration of 'connectivity' hides instance variable

'MyReachability' undeclared

'reachability' undeclared

'TestViewController' may not respond to '-siteAvailable'

'TestViewController' may not respond to '-addConnectivityView'

Redefinition of '-[TestViewController reachabilityChanged:]'

'MyReachability' undeclared

TestViewController may not respond to '-siteAvailable'

TestViewController may not respond to '-addConnectivityView'

TestViewController may not respond to '-removeConnectivityView'

最佳答案

是的，它出于某种原因多次发送通知。为了克服这个问题，我在应用程序委托(delegate)中维护了一个网络状态变量，它是 kReachabilityChangedNotification 的观察者。该 View 是自定义 kViewReachabilityChangedNotification 的观察者，它在值实际更改时由应用程序委托(delegate)发送。不仅如此，在收到来自可达性的通知后，我调用了一个可达性函数来获取当前网络状态，并相应地更改了我的应用程序委托(delegate)变量。然后我可以向 View 发送通知以更新自身。

这个变通办法很丑陋，但有效。我花了很多时间来理解为什么以这种方式发送通知，最后放弃寻找这种解决方案。

编辑: 这是您的示例 - 我仍然没有放置所有工作示例的好地方，因此请尝试从代码示例中找出解决方案: 子类可达性:

@interface MyReachability : 可达性 { } +(BOOL) 连接到网络； @结束

@implementation MyReachability

+ (BOOL) connectedToNetwork {
    // Create zero addy
    struct sockaddr_in zeroAddress;
    bzero(&zeroAddress, sizeof(zeroAddress));
    zeroAddress.sin_len = sizeof(zeroAddress);
    zeroAddress.sin_family = AF_INET;

    // Recover reachability flags
    SCNetworkReachabilityRef defaultRouteReachability = SCNetworkReachabilityCreateWithAddress(NULL, (struct sockaddr *)&zeroAddress);
    SCNetworkReachabilityFlags flags;

    BOOL didRetrieveFlags = SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags);
    CFRelease(defaultRouteReachability);

    if (!didRetrieveFlags)
    {
        return NO;
    }

    BOOL isReachable = flags & kSCNetworkFlagsReachable;
    BOOL needsConnection = flags & kSCNetworkFlagsConnectionRequired;
    if (needsConnection && (flags & kSCNetworkReachabilityFlagsIsWWAN)) {
        needsConnection = NO;
    }
    return (isReachable && !needsConnection) ? YES : NO;
}

@结束 在 YourApplicationDelegate.h 中:

@interface YourApplicationDelegate :NSObject
{
     BOOL connectivity;
}
- (void) reachabilityChanged:(NSNotification *) note;
- (BOOL) checkConnectivity;
@end

在 YourApplicationDelegate.m 中添加函数 initReachability 调用它以初始化来自 Reachability 类的通知。

- (void) initReachability
{
    MyReachability * reachability = [ MyReachability sharedReachability ];

    //[ reachability setHostName: [self hostName] ];
    [ reachability setNetworkStatusNotificationsEnabled: YES ];

    [self siteAvailable];

    NSNotificationCenter * notificationCenter = [ NSNotificationCenter defaultCenter ];
    [ notificationCenter addObserver: self
                            selector: @selector( reachabilityChanged: )
                                name: @"kNetworkReachabilityChangedNotification"
                              object: nil ];

    connectivity = [MyReachability testConnection:NO];
    if (!connectivity) {
        if (![MyReachability testConnection:NO]) {
            [self addConnectivityView];
        }
    }
}


- (BOOL) checkConnectivity
{
    return connectivity;
}

- (void) reachabilityChanged:(NSNotification *) note
{
    BOOL    newConnectivity = [MyReachability testConnection:NO];
    if (connectivity != newConnectivity) {
        connectivity = newConnectivity;
        [self siteAvailable];
        if (![MyReachability testConnection:NO]) {
            [self addConnectivityView];
        } else {
            [self removeConnectivityView];
            connectivity = YES;
            [[NSNotificationCenter defaultCenter] postNotificationName:@"kAppNetworkReachabilityChangedNotification" object:nil];
        }
    }
}

请注意，@"kAppNetworkReachabilityChangedNotification"是一个自定义通知，您的 View 应该订阅它。

在你的 View Controller 的 viewDidLoad 函数中:

-(void) viewDidLoad
{
       // your customization
    NSNotificationCenter * notificationCenter = [ NSNotificationCenter defaultCenter ];
    [ notificationCenter addObserver: self
                            selector: @selector( reachabilityChanged: )
                                name: @"kAppNetworkReachabilityChangedNotification"
                              object: nil ];

}


- (void) reachabilityChanged: (NSNotification *) note
{
    BOOL connectivity = [YourAppDelegate checkConnectivity];

    if (connectivity) {
           // update your view accordingly
    } 

}

关于iphone - 试图让网络错误警报正确显示在 iPhone 应用程序上？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4821710/