iOS : ZBarCode reader not working on custom UISegmentedControl click

Question

我关注了这个 tutorial在我的 iOS 应用程序中实现 zbarcode 阅读器。由于我使用的是自定义 UISegmentedControl，因此相机应在该段单击时立即启动并开始扫描 QR 码。相机正在启动，但缺少红线，因此无法扫描 QR 码。

我在提到的日志中收到此警告

Warning: Attempt to present <ZBarReaderViewController: 0x7befb50> on <UINavigationController: 0x7b6f950> while a presentation is in progress!

我在 ScanViewController 段的 viewWill 加载中编写了按钮逻辑。
使用 Xcode 4.6 并在 iPad 2 中进行测试。
这是我的代码

- (void) imagePickerController: (UIImagePickerController*) reader didFinishPickingMediaWithInfo: (NSDictionary*) info
{
    // ADD: get the decode results
    id<NSFastEnumeration> results =    
    [info objectForKey: ZBarReaderControllerResults];
    ZBarSymbol *symbol = nil;
    for(symbol in results)
        // EXAMPLE: just grab the first barcode
        break;

    // EXAMPLE: do something useful with the barcode data
    resultText.text = symbol.data;

    // EXAMPLE: do something useful with the barcode image
    resultImage.image =
    [info objectForKey: UIImagePickerControllerOriginalImage];

    // ADD: dismiss the controller (NB dismiss from the *reader*!)
    [reader dismissModalViewControllerAnimated: YES];
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    NSLog(@"Starting Camera to scan QR Code...");
    // ADD: present a barcode reader that scans from the camera feed
    ZBarReaderViewController *reader = [ZBarReaderViewController new];
    reader.readerDelegate = self;
    reader.supportedOrientationsMask = ZBarOrientationMaskAll;

    ZBarImageScanner *scanner = reader.scanner;
    // TODO: (optional) additional reader configuration here

    // EXAMPLE: disable rarely used I2/5 to improve performance
    [scanner setSymbology: ZBAR_I25
                   config: ZBAR_CFG_ENABLE
                       to: 0];

    // present and release the controller
    [self presentModalViewController: reader
                            animated: YES];

    NSString *checkURL = self.resultText.text;
    NSLog(@"Checking URL scanned from QR Code before passing to List :: %@", checkURL);

Answer 1

将您的代码移至

- (void) viewDidAppear:(BOOL) animate { }

而不是 viewWillAppear。

问题是您试图在 View 出现之前呈现ModalViewController。