iOS - 利用原生框架實現掃一掃功能

利用系統自帶框架實現掃一掃功能

實現功能前的專案配置

因為該專案要使用到相機和相簿。所以我們要在info.plist中設定詢問使用者是否允許訪問的許可權。因為需要呼叫攝像頭，所以要在真機上執行(在模擬器執行會崩潰)。

功能分析

從功能需求分析來看，掃一掃該功能可以分為以下幾個功能點:

• 在啟動裝置時設定loading view
• 使用CGContextRef繪製掃一掃介面UI
• 使用NSTimer實現掃描線動畫
• 使用AVFoundation框架實現掃描功能
• 實現掃描二維碼圖片(系統只支援二維碼，不支援條形碼)，呼叫系統閃光燈
• 在掃描完成後將值傳給上一個介面(Block反向傳值)

具體實現

• 在啟動裝置時設定loading view
  1.建立繼承 UIActivityIndicatorView 的LoadView，在.m檔案中寫初始化程式碼:

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        // 菊花背景的大小
        self.frame = CGRectMake((ScreenWidth - 100)/2, (ScreenHeight - 100)/2, 100, 100);
        // 菊花的背景色
        self.backgroundColor = [UIColor blackColor];
        self.layer.cornerRadius = 10;
        // 菊花的顏色和格式（白色、白色大、灰色）
        self.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
        // 在菊花下面新增文字
        UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(10, 60, 80, 40)];
        label.text = @"loading...";
        label.font = [UIFont systemFontOfSize:14];
        label.textAlignment = NSTextAlignmentCenter;
        label.textColor = [UIColor whiteColor];
        [self addSubview:label];
    }
    return  self;
}複製程式碼

2.將LoadView新增到bgView中:

- (void)setupBgView {
    _bgView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, ScreenWidth, ScreenHeight)];
    _bgView.backgroundColor = [UIColor blackColor];

    LoadView *loadView = [[LoadView alloc]init];
    [_bgView addSubview:loadView];
    // 動畫開始
    [loadView startAnimating];
}複製程式碼

• 使用CGContextRef繪製掃一掃介面UI
  1.建立繼承與UIView的ScanView，在.m檔案中寫下面的繪製程式碼:

- (void)drawRect:(CGRect)rect {
    CGFloat rectWidth = 50;
    CGFloat rectHeight = 200;
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGFloat black[4] = {0.0, 0.0, 0.0, _alphaValue};
    CGContextSetFillColor(context, black);
    //top
    CGRect rect1 = CGRectMake(0, 0, self.frame.size.width, rectHeight);
    CGContextFillRect(context, rect1);
    //left
    rect1 = CGRectMake(0, rectHeight, rectWidth, rectHeight);
    CGContextFillRect(context, rect1);
    //bottom
    rect1 = CGRectMake(0, rectHeight * 2, self.frame.size.width, self.frame.size.height - rectHeight * 2);
    CGContextFillRect(context, rect1);
    //right
    rect1 = CGRectMake(self.frame.size.width - rectWidth, rectHeight, rectWidth, rectHeight);
    CGContextFillRect(context, rect1);
    CGContextStrokePath(context);

    //中間畫矩形(正方形)
    CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
    CGContextSetLineWidth(context, 1);
    CGContextAddRect(context, CGRectMake(rectWidth, rectHeight, self.frame.size.width - rectWidth * 2, rectHeight));
    CGContextStrokePath(context);

    CGFloat lineWidth = 10;

    CGContextSetStrokeColorWithColor(context, [UIColor greenColor].CGColor);
    CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);

    // Draw them with a 2.0 stroke width so they are a bit more visible.
    CGContextSetLineWidth(context, 2.0);
    //左上角水平線
    CGContextMoveToPoint(context, rectWidth, rectHeight);
    CGContextAddLineToPoint(context, rectWidth + lineWidth, rectHeight);

    //左上角垂直線
    CGContextMoveToPoint(context, rectWidth, rectHeight);
    CGContextAddLineToPoint(context, rectWidth, rectHeight + lineWidth);

    //左下角水平線
    CGContextMoveToPoint(context, rectWidth, rectHeight * 2);
    CGContextAddLineToPoint(context, rectWidth + lineWidth, rectHeight * 2);

    //左下角垂直線
    CGContextMoveToPoint(context, rectWidth, rectHeight * 2 - lineWidth);
    CGContextAddLineToPoint(context, rectWidth, rectHeight * 2);

    //右上角水平線
    CGContextMoveToPoint(context, self.frame.size.width - rectWidth - lineWidth, rectHeight);
    CGContextAddLineToPoint(context, self.frame.size.width - rectWidth, rectHeight);

    //右上角垂直線
    CGContextMoveToPoint(context, self.frame.size.width - rectWidth, rectHeight);
    CGContextAddLineToPoint(context, self.frame.size.width - rectWidth, rectHeight + lineWidth);

    //右下角水平線
    CGContextMoveToPoint(context, self.frame.size.width - rectWidth - lineWidth, rectHeight * 2);
    CGContextAddLineToPoint(context, self.frame.size.width - rectWidth, rectHeight * 2);
    //右下角垂直線
    CGContextMoveToPoint(context, self.frame.size.width - rectWidth, rectHeight * 2 - lineWidth);
    CGContextAddLineToPoint(context, self.frame.size.width - rectWidth, rectHeight * 2);
    CGContextStrokePath(context);
}複製程式碼

2.將scanView新增到self.view中:

- (void)setupScanView {
    _scan = [[ScanView alloc]initWithFrame:self.view.bounds];
    _scan.backgroundColor = [UIColor clearColor];

    _slideLineView = [[UIView alloc]initWithFrame:CGRectMake(_viewWidth, 201, ScreenWidth - _viewWidth * 2, 1)];
    _slideLineView.backgroundColor = [UIColor greenColor];
    [_scan addSubview:_slideLineView];
    [self.view addSubview:_scan];
    [self setupSubView];
}複製程式碼

3.設定self.view中的閃光燈按鈕和訪問相簿按鈕:

- (void)setupSubView {
    _titleLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 500, ScreenWidth, 50.0)];
    _titleLabel.text = @"請將二維碼放入框內";
    _titleLabel.textAlignment = NSTextAlignmentCenter;
    _titleLabel.textColor = [UIColor whiteColor];
    [_scan addSubview:_titleLabel];

    _lightButton = [[UIButton alloc]initWithFrame:CGRectMake(100, 580, 50, 50)];
    [_lightButton setTitle:@"light" forState:UIControlStateNormal];
    [_lightButton addTarget:self action:@selector(lightButtonDidTouch) forControlEvents:UIControlEventTouchUpInside];
    [_scan addSubview:_lightButton];

    _imageButton = [[UIButton alloc]initWithFrame:CGRectMake(200, 580, 50, 50)];
    [_imageButton setTitle:@"相簿" forState:UIControlStateNormal];
    [_imageButton addTarget:self action:@selector(imageButtonDidTouch) forControlEvents:UIControlEventTouchUpInside];
    [_scan addSubview:_imageButton];
}複製程式碼

4.閃光燈按鈕的點選事件:

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (![device hasTorch]) {
        NSLog(@"no torch");
    }else {
        [device lockForConfiguration:nil];
        if (!self.isOpen) {
            [device setTorchMode: AVCaptureTorchModeOn];
            self.isOpen = YES;
        }
        else {
            [device setTorchMode: AVCaptureTorchModeOff];
            self.isOpen = NO;
        }
        [device unlockForConfiguration];
    }複製程式碼

5.訪問相簿按鈕的點選事件:

- (void)imageButtonDidTouch {
    [_timer invalidate];
    _timer = nil;

    UIImagePickerController *picker = [[UIImagePickerController alloc]init];
    //設定圖片源(相簿)
    picker.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    //設定代理
    picker.delegate = self;
    //設定可以編輯
    picker.allowsEditing = YES;
    //開啟拾取器介面
    [self presentViewController:picker animated:YES completion:nil];
}

#pragma mark UIImagePickerControllerDelegate methods
//完成選擇圖片
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo {
    // 銷燬控制器
    [picker dismissViewControllerAnimated:YES completion:nil];
    // 根據URL找到CIImage
    CIImage *ciImage = [[CIImage alloc]initWithCGImage:image.CGImage];
    if (ciImage){
        // 建立CIDetector
        CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{ CIDetectorAccuracy: CIDetectorAccuracyHigh }];
        NSArray *features = [detector featuresInImage:ciImage];
        if ([features count] > 0) {
            for (CIFeature *feature in features) {
                if (![feature isKindOfClass:[CIQRCodeFeature class]]) {
                    continue;
                }
                CIQRCodeFeature *qrFeature = (CIQRCodeFeature *)feature;
                NSString *code = qrFeature.messageString;
                if (self.resultBlock) {
                    self.resultBlock(code);
                    [self scanSuccess];
                }
                //輸出掃描字串
                [self.navigationController popViewControllerAnimated:YES];
            }
        }else {
            [self setupTimer];
        }
    }
}
//取消選擇圖片
-(void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {
    [picker dismissViewControllerAnimated:YES completion:nil];
}複製程式碼

• 使用NSTimer實現掃描線動畫
  實現掃描線程式碼如下:

- (void)setupTimer {
    _timer = [NSTimer scheduledTimerWithTimeInterval:1.8 target:self selector:@selector(animationView) userInfo:nil repeats:YES];
    [_timer fire];
}

- (void)animationView {
    [UIView animateWithDuration:1.5 animations:^{
        _slideLineView.transform = CGAffineTransformMakeTranslation(0, 200);
    } completion:^(BOOL finished) {
        _slideLineView.transform = CGAffineTransformIdentity;
    }];
}複製程式碼

• 使用AVFoundation實現掃描功能
  1.匯入，遵守AVCaptureMetadataOutputObjectsDelegate。
  初始化程式碼如下:

- (void)setupAVFoundation {
    //獲取攝像裝置
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    //建立輸入流
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    //建立輸出流
    AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc]init];
    //設定代理 在主執行緒裡重新整理
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    //初始化連結物件
    _session = [[AVCaptureSession alloc]init];
    //高質量採集率
    [_session setSessionPreset:AVCaptureSessionPresetHigh];
    [_session addInput:input];
    [_session addOutput:output];
    //設定掃碼支援的編碼格式(如下設定條形碼和二維碼相容)
    output.metadataObjectTypes=@[AVMetadataObjectTypeQRCode,AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code];

    _previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:_session];
    _previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    _previewLayer.frame = self.view.layer.bounds;
    [self.view.layer insertSublayer:_previewLayer atIndex:0];
    //開始捕獲
    [_session startRunning];
    //移除loading view
    [_bgView removeFromSuperview];
}複製程式碼

2.實現AVCaptureMetadataOutputObjectsDelegate

#pragma mark 輸出的代理
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    if (metadataObjects.count > 0) {
        [_timer invalidate];
        _timer = nil;
        [_session stopRunning];
        AVMetadataMachineReadableCodeObject *metadataObject = [metadataObjects objectAtIndex: 0];
        if (self.resultBlock) {
            self.resultBlock(metadataObject.stringValue);
            [self scanSuccess];
        }
        //輸出掃描字串
        [self.navigationController popViewControllerAnimated:YES];
    }
}
//掃描成功的提示音
- (void)scanSuccess {
    AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);
    AudioServicesPlaySystemSound(1109);
}複製程式碼

結束語

至此，即可實現利用原生框架掃描二維碼的功能，使用原生有一個缺陷就是無法掃描圖片中的條形碼。如要實現這個功能可以使用 ZXingObjC 框架。
完整專案地址，第十個

參考連結

• iOS 二維碼掃描
• iOS解碼二維碼圖片
• iOS 原生二維碼掃描（可限制掃描區域）
• iOS7使用原生API進行二維碼和條形碼的掃描
• ios8原生庫實現掃描相簿內二維碼圖片
• iOS呼叫閃光燈的程式碼
• iOS開發中在載入頁面新增菊花動畫（非第三方
• 蘋果開發 筆記（48） UIImage CIImage CGImageRef
• iOS 原生掃 QR 碼的那些事
• CGContextRef使用簡要教程