ios原生二维码扫描

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];
}

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