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

// 1.創建過濾器
  CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
 
  // 2.恢復默認
  [filter setDefaults];
 
  // 3.給過濾器添加數據(正則表達式/賬號和密碼)
  NSString *dataString = @"http://www.520it.com";
  NSData *data = [dataString dataUsingEncoding:NSUTF8StringEncoding];
  [filter setValue:data forKeyPath:@"inputMessage"];
 
  // 4.獲取輸出的二維碼
  CIImage *outputImage = [filter outputImage];
 
  //因為生成的二維碼模糊，所以通過createNonInterpolatedUIImageFormCIImage:outputImage來獲得高清的二維碼圖片
 
  // 5.顯示二維碼
  self.imageView.image = [self createNonInterpolatedUIImageFormCIImage:outputImage withSize:200];

/**
 * 根據CIImage生成指定大小的UIImage
 *
 * @param image CIImage
 * @param size 圖片寬度
 */
- (UIImage *)createNonInterpolatedUIImageFormCIImage:(CIImage *)image withSize:(CGFloat) size
{
  CGRect extent = CGRectIntegral(image.extent);
  CGFloat scale = MIN(size/CGRectGetWidth(extent), size/CGRectGetHeight(extent));
 
  // 1.創建bitmap;
  size_t width = CGRectGetWidth(extent) * scale;
  size_t height = CGRectGetHeight(extent) * scale;
  CGColorSpaceRef cs = CGColorSpaceCreateDeviceGray();
  CGContextRef bitmapRef = CGBitmapContextCreate(nil, width, height, 8, 0, cs, (CGBitmapInfo)kCGImageAlphaNone);
  CIContext *context = [CIContext contextWithOptions:nil];
  CGImageRef bitmapImage = [context createCGImage:image fromRect:extent];
  CGContextSetInterpolationQuality(bitmapRef, kCGInterpolationNone);
  CGContextScaleCTM(bitmapRef, scale, scale);
  CGContextDrawImage(bitmapRef, extent, bitmapImage);
 
  // 2.保存bitmap到圖片
  CGImageRef scaledImage = CGBitmapContextCreateImage(bitmapRef);
  CGContextRelease(bitmapRef);
  CGImageRelease(bitmapImage);
  return [UIImage imageWithCGImage:scaledImage];
}

// 1.創建捕捉會話
  AVCaptureSession *session = [[AVCaptureSession alloc] init];
  self.session = session;
 
  // 2.添加輸入設備(數據從攝像頭輸入)
  AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
  AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
  [session addInput:input];
 
  // 3.添加輸出數據(示例對象-->類對象-->元類對象-->根元類對象)
  AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
  [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
  [session addOutput:output];
 
  // 3.1.設置輸入元數據的類型(類型是二維碼數據)
  [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
 
  // 4.添加掃描圖層
  AVCaptureVideoPreviewLayer *layer = [AVCaptureVideoPreviewLayer layerWithSession:session];
  layer.frame = self.view.bounds;
  [self.view.layer addSublayer:layer];
  self.layer = layer;
 
  // 5.開始掃描
  [session startRunning];

// 當掃描到數據時就會執行該方法
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
  if (metadataObjects.count > 0) {
    //獲得掃描數據，最后一個時最新掃描的數據
    AVMetadataMachineReadableCodeObject *object = [metadataObjects lastObject];
    NSLog(@"%@", object.stringValue);
 
    // 停止掃描
    [self.session stopRunning];
 
    // 將預覽圖層移除
    [self.layer removeFromSuperlayer];
  } else {
    NSLog(@"沒有掃描到數據");
  }
}