//1.初始化捕捉设备（AVCaptureDevice），类型为AVMediaTypeVideo

AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

//2.用captureDevice创建输入流

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];

if (!input) {

NSLog(@"%@", [error localizedDescription]);

return NO;

}

//3.创建媒体数据输出流

AVCaptureMetadataOutput *captureMetadataOutput = [[AVCaptureMetadataOutput alloc] init];

//4.实例化捕捉会话

_captureSession = [[AVCaptureSession alloc] init];

//4.1.将输入流添加到会话

[_captureSession addInput:input];

//4.2.将媒体输出流添加到会话中

[_captureSession addOutput:captureMetadataOutput];

//5.创建串行队列，并加媒体输出流添加到队列当中

dispatch_queue_t dispatchQueue;

dispatchQueue = dispatch_queue_create("myQueue", NULL);

//5.1.设置代理

[captureMetadataOutput setMetadataObjectsDelegate:self queue:dispatchQueue];

//5.2.设置输出媒体数据类型为QRCode

[captureMetadataOutput setMetadataObjectTypes:[NSArray arrayWithObject:AVMetadataObjectTypeQRCode]];

//6.实例化预览图层

_videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];

//7.设置预览图层填充方式

[_videoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

//8.设置图层的frame

[_videoPreviewLayer setFrame:_viewPreview.layer.bounds];

//9.将图层添加到预览view的图层上

[_viewPreview.layer addSublayer:_videoPreviewLayer];

//10.设置扫描范围

captureMetadataOutput.rectOfInterest = CGRectMake(0.2f, 0.2f, 0.8f, 0.8f);

//10.1.扫描框

_boxView = [[UIView alloc] initWithFrame:CGRectMake(_viewPreview.bounds.size.width * 0.2f, _viewPreview.bounds.size.height * 0.2f, _viewPreview.bounds.size.width - _viewPreview.bounds.size.width * 0.4f, _viewPreview.bounds.size.height - _viewPreview.bounds.size.height * 0.4f)];

_boxView.layer.borderColor = [UIColor greenColor].CGColor;

_boxView.layer.borderWidth = 1.0f;

[_viewPreview addSubview:_boxView];

//10.2.扫描线

_scanLayer = [[CALayer alloc] init];

_scanLayer.frame = CGRectMake(0, 0, _boxView.bounds.size.width, 1);

_scanLayer.backgroundColor = [UIColor brownColor].CGColor;

[_boxView.layer addSublayer:_scanLayer];

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.2f target:self selector:@selector(moveScanLayer:) userInfo:nil repeats:YES];

[timer fire];

//10.开始扫描

[_captureSession startRunning];