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(, , _boxView.bounds.size.width, );

    _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] > ) {

        AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:];

        //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 = ;

        _scanLayer.frame = frame;

    }else{

        frame.origin.y += ;

        [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