關於iPhone上的HTTP異常處理的問題

Question

我嘗試添加一種處理異常的方法，但該程序只是崩潰而不是彈出AlertView。

1）我建立連接：

-(void)connect:(NSString *)strURL
{
    NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:strURL]
                                                            cachePolicy:NSURLRequestUseProtocolCachePolicy    
                                                            timeoutInterval:60.0];

    NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    if (theConnection) 
    {
        // receivedData is declared as a method instance elsewhere
        receivedData = [[NSMutableData data] retain];
    } 
    else 
    { 
        // inform the user that the download could not be made
    }

}

2）我添加方法來接收數據並將其轉換為字符串：

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // append the new data to the receivedData
    // receivedData is declared as a method instance elsewhere
    [receivedData appendData:data];
    ReturnStr = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
}

3）我添加了異常處理方法：

-(void) connection:(NSURLConnection *)connection didFailWithError: (NSError *)error {

    UIAlertView *errorAlert = [[UIAlertView alloc]
                               initWithTitle: [error localizedDescription]
                               message: [error localizedFailureReason]
                               delegate:self
                               cancelButtonTitle:@"OK"
                               otherButtonTitles:nil];
    [errorAlert show];
}   

在將strURL更改為錯誤的URL后，該程序崩潰了。 有什么想法為什么AlertView沒有彈出？

Answer 1

檢查一下此文件中存在的錯誤處理 。 如果將URL設置為無效URL，則在我的示例中，它確實會返回一個不錯的對話框錯誤消息。 我只是嘗試確定一下。

鏈接文件中的相關代碼為：

-(void) connection:(NSURLConnection *)connection
  didFailWithError: (NSError *)error {
  UIAlertView *errorAlert = [[UIAlertView alloc]
                 initWithTitle: [error localizedDescription]
                 message: [error localizedFailureReason]
                 delegate:nil
                 cancelButtonTitle:@"OK"
                 otherButtonTitles:nil];
  [errorAlert show];
  [errorAlert release];
  [activityIndicator stopAnimating];
  NSLog (@"Connection Failed with Error");
}