1 首先使APP獲得相機(jī)使用權(quán)限

在plist文件中用source code的方式打開，添加如下代碼：

<key>NSCameraUsageDescription</key>
    <string>cameraDesciption</string>

如果沒有使應(yīng)用獲取相機(jī)使用權(quán)限，則使用過程中會(huì)崩潰。

2 判斷權(quán)限

也就是針對(duì)是否獲得相機(jī)使用權(quán)限做檢驗(yàn)：

[AVCaptureDevice requestAccessForMediaType:AVMediaTypeVideo completionHandler:^(BOOL granted) {
        dispatch_async(dispatch_get_main_queue(), ^{
            
            if (granted) {
              //配置掃描view
                [self loadScanView];
            } else {
                NSString *title = @"請(qǐng)?jiān)趇Phone的”設(shè)置-隱私-相機(jī)“選項(xiàng)中，允許App訪問你的相機(jī)";
                UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:title message:@"" delegate:nil cancelButtonTitle:@"好" otherButtonTitles:nil];
                [alertView show];
            }
            
        });
    }];

3 配置掃描view

- (void)loadScanView {
    //1.初始化捕捉設(shè)備（AVCaptureDevice），類型為AVMediaTypeVideo
    AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    //2.用captureDevice創(chuàng)建輸入流
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:nil];
    //3.創(chuàng)建媒體數(shù)據(jù)輸出流
    AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
    //4.實(shí)例化捕捉會(huì)話
    _captureSession = [[AVCaptureSession alloc] init];
    //4.1.將輸入流添加到會(huì)話
    [_captureSession addInput:input];
    //4.2.將媒體輸出流添加到會(huì)話中
    [_captureSession addOutput:output];
    //5.設(shè)置代理 在主線程里刷新
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    //5.2.設(shè)置輸出媒體數(shù)據(jù)類型為QRCode
    [output setMetadataObjectTypes:[NSArray arrayWithObject:AVMetadataObjectTypeQRCode]];
    //6.實(shí)例化預(yù)覽圖層
    _videoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_captureSession];
    //7.設(shè)置預(yù)覽圖層填充方式
    [_videoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    //8.設(shè)置圖層的frame
    [_videoPreviewLayer setFrame:_viewPreview.layer.bounds];
    //9.將圖層添加到預(yù)覽view的圖層上
    [_viewPreview.layer addSublayer:_videoPreviewLayer];
    //10.設(shè)置掃描范圍
    output.rectOfInterest = CGRectMake(0.2f, 0.2f, 0.8f, 0.8f);
    //10.1.掃描框
    _boxView = [[UIView alloc] initWithFrame:CGRectMake(_viewPreview.bounds.size.width * 0.2, _viewPreview.bounds.size.height*0.2, _viewPreview.bounds.size.width - _viewPreview.bounds.size.width * 0.4f, _viewPreview.bounds.size.width - _viewPreview.bounds.size.width * 0.4f)];
    _boxView.layer.borderColor = [UIColor redColor].CGColor;
    _boxView.layer.borderWidth = 1.0;
    
    [_viewPreview addSubview:_boxView];
    
    _scanLayer = [[CALayer alloc] init];
    _scanLayer.frame = CGRectMake(0, 0, _boxView.bounds.size.width, 1);
    _scanLayer.backgroundColor = [UIColor blackColor].CGColor;
    [_boxView.layer addSublayer:_scanLayer];
    
    [self startRunning];
}

這里我們用到rectOfInterest 這個(gè)cgrect跟平時(shí)用的不一樣，在這里用的是比例來表示，也就是利用這個(gè)可以設(shè)置掃描的方框的范圍

4 開始掃描

#pragma mark 開始
- (void)startRunning {
   if (self.captureSession) {
       self.isReading = YES;
       [self.captureSession startRunning];
       _timer=[NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(moveUpAndDownLine) userInfo:nil repeats: YES];
   }
}

5 掃描線移動(dòng)

- (void)moveUpAndDownLine {
    CGRect frame = self.scanLayer.frame;
    if (_boxView.frame.size.height < self.scanLayer.frame.origin.y) {
        frame.origin.y = 0;
        self.scanLayer.frame = frame;
    } else {
        frame.origin.y += 5;
        [UIView animateWithDuration:0.2 animations:^{
            self.scanLayer.frame = frame;
        }];
    }
}

6 AVCaptureMetadataOutputObjectsDelegate

這個(gè)是里面用到的最重要的方法，在這個(gè)代理方法里我們可以獲得掃描二維碼解析出來的數(shù)據(jù)，然后在里面進(jìn)行操作

#pragma mark - AVCaptureMetadataOutputObjectsDelegate
- (void)captureOutput:(AVCaptureOutput *)output didOutputMetadataObjects:(NSArray<__kindof AVMetadataObject *> *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    //判斷是否有數(shù)據(jù)
    if (!_isReading) {
        return;
    }
    if (metadataObjects.count > 0) {
        _isReading = NO;
        AVMetadataMachineReadableCodeObject *metadataObject = metadataObjects[0];
        NSString *result = metadataObject.stringValue;
        if (self.resultBlock) {
            self.resultBlock(result?:@"");
        }
        [self.navigationController popViewControllerAnimated:NO];
    }
}

7 退出時(shí)記得關(guān)閉

#pragma mark 結(jié)束
- (void)stopRunning {
    if ([_timer isValid]) {
        [_timer invalidate];
        _timer = nil ;
    }
    [self.captureSession stopRunning];
    [_scanLayer removeFromSuperlayer];
    [_videoPreviewLayer removeFromSuperlayer];
}

代碼地址：https://github.com/irembeu/ScanSignDemo.git