NSTimer？ - 檢查連接iOS

Question

我正在使用以下方法來檢查我的應用是否有連接。這很簡單，對我的需求很好。

+ (void)checkInternet:(connection)block 
{ 
    NSURL *url = [NSURL URLWithString:@"http://www.google.com/"]; 
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
    request.HTTPMethod = @"HEAD"; 
    request.cachePolicy = NSURLRequestReloadIgnoringLocalAndRemoteCacheData; 
    request.timeoutInterval = 10.0; 

    [NSURLConnection sendAsynchronousRequest:request 
             queue:[NSOperationQueue mainQueue] 
          completionHandler: 
    ^(NSURLResponse *response, NSData *data, NSError *connectionError) 
    { 
     block([(NSHTTPURLResponse *)response statusCode] == 200); 
    }]; 
} 

但是，我想要做的是如果狀態不返回200，我想再次檢查，至少幾次。以1秒的間隔完成此操作的最佳方法是什麼？

下面是我如何調用上述方法。

[self checkInternet:^(BOOL internet) 
    { 
     if (internet) 
     { 
      // "Internet" aka Google 
     } 
     else 
     { 
      // No "Internet" aka no Google 
     } 
    }]; 

Answer 1

我使用Reachability檢測一般網絡連接問題（請參閱答案的結束）。我使用以下方法執行重試。

- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay; 

您可以調整您的系統，如下所示，以獲得具有可選次數的重試的新類方法。

注意：未測試以下內容。這只是給你一個總的想法。

// Variable to track number of retries left. If you had a shared instance 
// a property would be easier. 
static NSUInteger maxConnectionTries = 0; 

// New method which lets you pass a retry count. 
+ (void)checkInternet:(connection)block withMaxTries:(NSUInteger)maxTries 
{ 
    maxConnectionTries=maxTries; 
    [self checkInternet:block]; 
} 

// Your original code extended to retry by calling itself when code 200 
// is seen on a delay of 1s. Defaults to old code when retry limit exceeded 
// or non 200 code received. 
+ (void)checkInternet:(connection)block 
{ 
    NSURL *url = [NSURL URLWithString:@"http://www.google.com/"]; 
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
    request.HTTPMethod = @"HEAD"; 
    request.cachePolicy = NSURLRequestReloadIgnoringLocalAndRemoteCacheData; 
    request.timeoutInterval = 10.0; 

    [NSURLConnection sendAsynchronousRequest:request 
             queue:[NSOperationQueue mainQueue] 
          completionHandler: 
    ^(NSURLResponse *response, NSData *data, NSError *connectionError) 
    { 
     if ([(NSHTTPURLResponse *)response statusCode] != 200 && 
      maxConnectionRetries > 0){ 
      maxConnectionRetries--; 
      [self performSelector:@selector(checkInternet:) withObject:block afterDelay:1.0]; 
     } 
     else{ 
      maxConnectionRetries = 0; 
      block([(NSHTTPURLResponse *)response statusCode] == 200); 
     } 
    }]; 
} 

對於互聯網連接的普遍檢測，最好使用可達性。見here。

我從AppDelegate代碼啓動可達性處理程序，然後在發生連接性更改時發佈本地通知。這允許應用程序始終在viewWillAppear和viewWillDisappear之內接收連接更改通知和瞬態視圖控制器，以便在本地通知註冊並取消註冊（如果他們對連接更改感興趣）。

Answer 2

FYI這裏是我想出了：

+ (void)checkInternet:(connection)block withMaxTries:(NSUInteger)maxTries 
{ 
    NSURL *url = [NSURL URLWithString:@"http://www.google.com/"]; 
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
    request.HTTPMethod = @"HEAD"; 
    request.cachePolicy = NSURLRequestReloadIgnoringLocalAndRemoteCacheData; 
    request.timeoutInterval = 10.0; 

    [NSURLConnection sendAsynchronousRequest:request 
             queue:[NSOperationQueue mainQueue] 
          completionHandler: 
    ^(NSURLResponse *response, NSData *data, NSError *connectionError) 
    { 
     if ([(NSHTTPURLResponse *)response statusCode] != 200 && 
      maxTries > 0){ 

      dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{ 

       [self checkInternet:block withMaxTries:maxTries - 1]; 
      }); 
     } 
     else{ 
      block([(NSHTTPURLResponse *)response statusCode] == 200); 
     } 
    }]; 
}