iOS:以编程方式调用的 segue 不起作用

Question

我正在使用通过方法调用但未被触发的 SWRevealViewController segue。不会向日志报告任何错误，也不会导致应用程序挂起或崩溃。我已经检查了 Storyboard上的 segue 链接，它具有正确的类和标识符。

- (void)viewDidLoad {

    [super viewDidLoad];

    NSURL *url = [NSURL URLWithString:loadUrl];
    NSLog(loadUrl);
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    NSOperationQueue *queue = [[NSOperationQueue alloc]init];
    [NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
    {
        if([data length] > 0 && error == nil)
            [mWebView loadRequest:request];         
        else if (error != nil) 
            NSLog(@"Error: %", error);}
    ];    
}

- (void)     captureOutput:(AVCaptureOutput *)captureOutput   
  didOutputMetadataObjects:(NSArray *)metadataObjects
            fromConnection:(AVCaptureConnection *)connection
{
     [metadataObjects
     enumerateObjectsUsingBlock:^(AVMetadataObject *obj,
                              NSUInteger idx,
                              BOOL *stop)
     {
         if ([obj isKindOfClass:
              [AVMetadataMachineReadableCodeObject class]])
         {
         // 3
             AVMetadataMachineReadableCodeObject *code =
             (AVMetadataMachineReadableCodeObject*)
             [_previewLayer transformedMetadataObjectForMetadataObject:obj];
         // 4
             Barcode * barcode = [Barcode processMetadataObject:code];

             for(NSString * str in self.allowedBarcodeTypes){
                 if([barcode.getBarcodeType isEqualToString:str]){
                     [self validBarcodeFound:barcode];
                     return;
                 }
             }
         }
     }];
}


- (void) validBarcodeFound:(Barcode *)barcode{ 

    [self stopRunning];
    [self.foundBarcodes addObject:barcode];   

    NSString *input = [barcode getBarcodeData];
    [NSString stringWithFormat:@"%lu",(unsigned long) [self.foundBarcodes count]-1];

    if ([input length] >= 13)
    {
        input = [input substringToIndex:12];
    }

    loadUrl = [[@"http://www.mywebsite.com/" stringByAppendingString:input] stringByAppendingString:@"?utm_source=iphone"];
    [super viewDidLoad];
    [self performSegueWithIdentifier:@"toWebControl" sender:self];
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {

    [super viewDidLoad];
}

Answer 1

始终在主队列中执行转场。您的回调在单独的 NSOperationQueue 中执行，您需要将 performSegueWithIdentifier 包装在 dispatch_async(dispatch_get_main_queue,... 中。

此外，正如@rory-mckinnel 在评论中提到的那样，删除不必要的 [super viewDidLoad] 调用可能会导致意外结果。