用AVCaptureMetadataOutput和AVFoundation扫描条形码

Question

我正在使用AVFoundation和AVCaptureMetadataOutput在iOS7中扫描二维码，我提供了一个允许用户扫描条形码的视图控制器。它工作得很好，即。正在扫描条形码，我可以将条形码字符串输出到控制台。

但它会一遍又一遍地扫描，见屏幕截图。我想让它做的是只扫描条形码一次，然后dismissViewController。

下面是我的委托方法代码：

- (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可能会有帮助。

Answer 2

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