iOS7，AVFoundation中现在已经内置支持一维和二维码的扫瞄，iOS6及之前的想要扫瞄二维码，还是需要添加第三方库ZXing和ZBar。

ZBar生成二维码：http://blog.csdn.net/cafei111/article/details/8924297

先添加AVFoundation.framework


#import <AVFoundation/AVFoundation.h>

@interface QRcodeViewController :UIViewController<AVCaptureMetadataOutputObjectsDelegate>

@property (strong,nonatomic)AVCaptureDevice *device;
@property (strong,nonatomic)AVCaptureDeviceInput *input;
@property (strong,nonatomic)AVCaptureMetadataOutput *output;
@property (strong,nonatomic)AVCaptureSession *session;
@property (strong,nonatomic)AVCaptureVideoPreviewLayer *preview;

@end


- (void)setupCamera
{
    // Device
    self.device = [AVCaptureDevicedefaultDeviceWithMediaType:AVMediaTypeVideo];
    
    // Input
    self.input = [AVCaptureDeviceInputdeviceInputWithDevice:self.deviceerror:nil];
    
    // Output
    self.output = [[AVCaptureMetadataOutputalloc]init];
    [self.outputsetMetadataObjectsDelegate:selfqueue:dispatch_get_main_queue()];
    
    // Session
    self.session = [[AVCaptureSessionalloc]init];
   [self.sessionsetSessionPreset:AVCaptureSessionPresetHigh];
   if ([self.sessioncanAddInput:self.input])
    {
        [self.sessionaddInput:self.input];
    }
   if ([self.sessioncanAddOutput:self.output])
    {
        [self.sessionaddOutput:self.output];
    }
    
    // 条码类型
    self.output.metadataObjectTypes =@[AVMetadataObjectTypeQRCode];
    
    // Preview
    self.preview = [AVCaptureVideoPreviewLayerlayerWithSession:self.session];
    self.preview.videoGravity =AVLayerVideoGravityResizeAspectFill;
    self.preview.frame =CGRectMake(0,0,self.view.frame.size.width,self.view.frame.size.height);
   [self.view.layeraddSublayer:self.preview];
    
    // Start
    [self.sessionstartRunning];
}

条码类型有如下几种：
1
2
3
4
5
6
7
8
9
10
AVMetadataObjectTypeUPCECode
AVMetadataObjectTypeCode39Code
AVMetadataObjectTypeCode39Mod43Code
AVMetadataObjectTypeEAN13Code
AVMetadataObjectTypeEAN8Code
AVMetadataObjectTypeCode93Code
AVMetadataObjectTypeCode128Code
AVMetadataObjectTypePDF417Code
AVMetadataObjectTypeQRCode
AVMetadataObjectTypeAztecCode

扫瞄到二维码之后，会调用delegate

#pragma mark AVCaptureMetadataOutputObjectsDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
   NSString *stringValue;
    
   if ([metadataObjectscount] >0) {
       AVMetadataMachineReadableCodeObject *metadataObject = [metadataObjectsobjectAtIndex:0];
        stringValue = http://www.mamicode.com/metadataObject.stringValue;
    }
    
    [_sessionstopRunning];
    
    [selfdismissViewControllerAnimated:YEScompletion:^{
       UIAlertView *alert = [[UIAlertViewalloc]initWithTitle:nil
                                                       message:stringValue
                                                      delegate:nil
                                             cancelButtonTitle:@"OK"
                                             otherButtonTitles:nil,nil];
        [alertshow];
    }];
}


这个委托方法里面的字符串stringValue就是二维码的内容