做iOS的二维码扫描，有两个第三方库可以选择，ZBar和ZXing。今天要介绍的是iOS7.0后AVFoundation框架提供的原生二维码扫描。

首先需要添加AVFoundation.framework框架到你工程中build phase的"Link Binary With Libraries"之下，然后就可以开始了。

一、做好准备工作，搭建UI

UI效果如图 

IBOutlet、IBAction如下：

@property (weak, nonatomic) IBOutlet UIView *viewPreview;
@property (weak, nonatomic) IBOutlet UILabel *lblStatus;
@property (weak, nonatomic) IBOutlet UIButton *startBtn;
- (IBAction)startStopReading:(id)sender;

接下来就都是代码的事情了

二、控制器ViewController.h

首先导入AVFoundation框架

#import <AVFoundation/AVFoundation.h>

然后控制器实现 AVCaptureMetadataOutputObjectsDelegate协议

@interface ViewController ()<AVCaptureMetadataOutputObjectsDelegate>

整体property如下：

@property (strong, nonatomic) UIView *boxView;
@property (nonatomic) BOOL isReading;
@property (strong, nonatomic) CALayer *scanLayer;

-(BOOL)startReading;
-(void)stopReading;

//捕捉会话
@property (nonatomic, strong) AVCaptureSession *captureSession;
//展示layer
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *videoPreviewLayer;

然后在ViewDidLoad方法中初始化

- (void)viewDidLoad {
    [super viewDidLoad];

    _captureSession = nil;
     _isReading = NO;
    
}

接下来实现startReading方法（这可就是重点咯）

- (BOOL)startReading {
  NSError *error;
  //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];
  return YES;
}

实现AVCaptureMetadataOutputObjectsDelegate协议方法

#pragma mark - AVCaptureMetadataOutputObjectsDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
  //判断是否有数据
  if (metadataObjects != nil && [metadataObjects count] > 0) {
    AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:0];
    //判断回传的数据类型
    if ([[metadataObj type] isEqualToString:AVMetadataObjectTypeQRCode]) {
      [_lblStatus performSelectorOnMainThread:@selector(setText:) withObject:[metadataObj stringValue] waitUntilDone:NO];
      [self performSelectorOnMainThread:@selector(stopReading) withObject:nil waitUntilDone:NO];
      _isReading = NO;
    }
  }
}

实现计时器方法moveScanLayer:(NSTimer *)timer

- (void)moveScanLayer:(NSTimer *)timer
{
  CGRect frame = _scanLayer.frame;
  if (_boxView.frame.size.height < _scanLayer.frame.origin.y) {
    frame.origin.y = 0;
    _scanLayer.frame = frame;
  }else{
    frame.origin.y += 5;
    [UIView animateWithDuration:0.1 animations:^{
      _scanLayer.frame = frame;
    }];
  }
}

实现开始和停止方法

- (IBAction)startStopReading:(id)sender {
    if (!_isReading) {
      if ([self startReading]) {
        [_startBtn setTitle:@"Stop" forState:UIControlStateNormal];
        [_lblStatus setText:@"Scanning for QR Code"];
      }
    }
    else{
      [self stopReading];
      [_startBtn setTitle:@"Start!" forState:UIControlStateNormal];
    }
    _isReading = !_isReading;
}
-(void)stopReading{
  [_captureSession stopRunning];
  _captureSession = nil;
  [_scanLayer removeFromSuperlayer];
  [_videoPreviewLayer removeFromSuperlayer];
}

大功告成

示例源码地址： https://github.com/WuKongCoo1/QRCodeReader