flutter_barcode_reader/ios/Classes/BarcodeScannerViewController.m

//
// Created by Matthew Smith on 11/7/17.
//

#import "BarcodeScannerViewController.h"
#import <MTBBarcodeScanner/MTBBarcodeScanner.h>


@implementation BarcodeScannerViewController {
}


- (void)viewDidLoad {
    [super viewDidLoad];
    self.previewView = [[UIView alloc] initWithFrame:self.view.bounds];
    self.previewView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:_previewView];
    [self.view addConstraints:[NSLayoutConstraint
            constraintsWithVisualFormat:@"V:[previewView]"
                                options:NSLayoutFormatAlignAllBottom
                                metrics:nil
                                  views:@{@"previewView": _previewView}]];
    [self.view addConstraints:[NSLayoutConstraint
            constraintsWithVisualFormat:@"H:[previewView]"
                                options:NSLayoutFormatAlignAllBottom
                                metrics:nil
                                  views:@{@"previewView": _previewView}]];
    self.scanner = [[MTBBarcodeScanner alloc] initWithPreviewView:_previewView];
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self action:@selector(cancel)];
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    if (self.scanner.isScanning) {
        [self.scanner stopScanning];
    }
    [MTBBarcodeScanner requestCameraPermissionWithSuccess:^(BOOL success) {
        if (success) {
            [self startScan];
        } else {
            [self showNoCameraAccessAlert];
        }
    }];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    if ([self isFlashOn]) {
        [self toggleFlash:NO];
    }
}

- (void)startScan {
    NSError *error;
    [self.scanner startScanningWithResultBlock:^(NSArray<AVMetadataMachineReadableCodeObject *> *codes) {
        [self.scanner stopScanning];
         AVMetadataMachineReadableCodeObject *code = codes.firstObject;
        if (code) {
            [self.delegate barcodeScannerViewController:self didScanBarcodeWithResult:code.stringValue];
            [self dismissViewControllerAnimated:NO completion:nil];
        }
    } error:&error];
}

- (void)cancel {
    [self dismissViewControllerAnimated:true completion:nil];
}

- (void)updateFlashButton {
    if (!self.hasTorch) {
        return;
    }
    if (self.isFlashOn) {
        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Flash Off"
                                                                                  style:UIBarButtonItemStylePlain
                                                                                 target:self action:@selector(toggle)];
    } else {
        self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Flash On"
                                                                                  style:UIBarButtonItemStylePlain
                                                                                 target:self action:@selector(toggle)];
    }
}

- (void)showNoCameraAccessAlert {
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Camera access denied"
                                                                             message:@"Camera access has been disabled for this application. To turn camera access back on, please go to the iOS settings application."
                                                                      preferredStyle:UIAlertControllerStyleAlert];
    [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
        [self dismissViewControllerAnimated:YES completion:nil];
    }]];
    [self presentViewController:alertController animated:YES completion:nil];
}

- (void)toggle {
    [self toggleFlash:!self.isFlashOn];
    [self updateFlashButton];
}

- (BOOL)isFlashOn {
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (device) {
        return device.torchMode == AVCaptureFlashModeOn || AVCaptureTorchModeOn;
    }
    return NO;
}

- (BOOL)hasTorch {
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (device) {
        return device.hasTorch;
    }
    return false;
}

- (void)toggleFlash:(BOOL)on {
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    if (!device) return;

    NSError *err;
    if (device.hasFlash && device.hasTorch) {
        [device lockForConfiguration:&err];
        if (err != nil) return;
        if (on) {
            device.flashMode = AVCaptureFlashModeOn;
            device.torchMode = AVCaptureTorchModeOn;
        } else {
            device.flashMode = AVCaptureFlashModeOff;
            device.torchMode = AVCaptureTorchModeOff;
        }
        [device unlockForConfiguration];
    }
}


@end