使用AVCaptureMetadataOutput和AVFoundation扫描条形码

Question

我正在使用AVFoundation和AVCaptureMetadataOutput来扫描iOS7中的QR条形码，我提供了一个允许用户扫描条形码的视图控制器。它工作正常，即。正在扫描条形码，我可以将条形码字符串输出到控制台。

但是它一遍又一遍地扫描，看屏幕截图。我想要它做的是扫描条形码只是一次然后dismissViewController。

以下是委托方法的代码：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
CGRect highlightViewRect = CGRectZero;

AVMetadataMachineReadableCodeObject *barCodeObject;
NSString *detectionString = nil;
NSArray *barCodeTypes = @[AVMetadataObjectTypeUPCECode, AVMetadataObjectTypeCode39Code, AVMetadataObjectTypeCode39Mod43Code,
        AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode93Code, AVMetadataObjectTypeCode128Code,
        AVMetadataObjectTypePDF417Code, AVMetadataObjectTypeQRCode, AVMetadataObjectTypeAztecCode];

for (AVMetadataObject *metadata in metadataObjects) {
    for (NSString *type in barCodeTypes) {
        if ([metadata.type isEqualToString:type])
        {
            barCodeObject = (AVMetadataMachineReadableCodeObject *)[self.preview transformedMetadataObjectForMetadataObject:(AVMetadataMachineReadableCodeObject *)metadata];
            highlightViewRect = barCodeObject.bounds;
            detectionString = [(AVMetadataMachineReadableCodeObject *)metadata stringValue];
            break;
        }
    }

    if (detectionString != nil)
    {
        NSLog(@"Barcode: %@", detectionString);

        break;
    }
    else
        NSLog(@"None");
}

self.highlightView.frame = highlightViewRect;

}

Answer 1

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
    ....
    self.highlightView.frame = highlightViewRect;
    [_session stopRunning]; //<---I add this and it worked for me.
}

Here is a good link可能有所帮助。

Answer 2

您需要使用以下命令停止captureSesson：    扫描条形码后captureSession.stopRunning()，否则即使videoPreviewLayer停止，它也会继续扫描代码。