iOS:二维码扫描

二维码(QRCode)的本质其实就是一个字符串,我们的最终目的就是将二维码图片转换成字符串.

首先导入AVFoundation框架

#import <AVFoundation/AVFoundation.h>

实例化有关二维码扫描的四个对象

@interface ViewController ()<AVCaptureMetadataOutputObjectsDelegate>//输入设备 也就是摄像头@property(nonatomic, strong)AVCaptureDeviceInput *input;//输出的元数据@property(nonatomic, strong)AVCaptureMetadataOutput *output;//展示图层@property(nonatomic, strong)AVCaptureVideoPreviewLayer *preLayer;//会话(输入设备、输出的元数据和展示图层都需要与会话相关联)@property(nonatomic, strong)AVCaptureSession *session;@end

将输入设备、输出设备、展示图层与会话关联起来

    AVCaptureDeviceDiscoverySession *discoverySession = [AVCaptureDeviceDiscoverySession discoverySessionWithDeviceTypes:@[AVCaptureDeviceTypeBuiltInWideAngleCamera] mediaType:AVMediaTypeVideo position:AVCaptureDevicePositionBack];    //获取设备 也就是摄像头 这里只获取后置摄像头    NSArray *devices = discoverySession.devices;    self.input = [[AVCaptureDeviceInput alloc]initWithDevice:[devices firstObject] error:nil];    self.output = [[AVCaptureMetadataOutput alloc]init];    self.session = [[AVCaptureSession alloc]init];    //将输入设备与会话关联    if ([self.session canAddInput:self.input]) {        [self.session addInput:self.input];    }    //将输出设备与会话关联    if ([self.session canAddOutput:self.output]) {        [self.session addOutput:self.output];    }    //设置输出设备的代理    [self.output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];//    NSLog(@"%@",[self.output availableMetadataObjectTypes]);    //输出元数据类型为二维码    self.output.metadataObjectTypes = @[AVMetadataObjectTypeQRCode];    //将展示图层与会话关联    self.preLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:self.session];    self.preLayer.frame = self.view.bounds;    [self.view.layer addSublayer:self.preLayer];    [self.session setSessionPreset:AVCaptureSessionPreset1920x1080];    [self.session startRunning];

输出设备代理方法

//解析完毕会调用这个方法- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {    AVMetadataMachineReadableCodeObject *objc = [metadataObjects firstObject];    //输出扫描结果    NSLog(@"%@",objc.stringValue);    [self.preLayer removeFromSuperlayer];    [self.session stopRunning];    //后续对扫描出来的字符串进一步进行操作}

输出的字符串