iPhone 的 QR 码阅读器 [关闭]

iPhone的QR码阅读器是一款非常实用的工具，它可以帮助用户快速扫描和解码QR码。QR码（Quick Response Code）是一种二维码，它可以存储大量信息，并且可以快速读取。QR码阅读器可以通过iPhone的摄像头捕捉QR码，并将其解码为文字、链接或其他信息。在本文中，我们将介绍如何使用iPhone的QR码阅读器，并提供一些案例代码来帮助读者更好地理解。

objective-c
// 导入AVFoundation框架
#import 
@interface QRCodeViewController ()
@property (nonatomic, strong) AVCaptureSession *session;
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *previewLayer;
@end
@implementation QRCodeViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 创建AVCaptureSession对象
    self.session = [[AVCaptureSession alloc] init];
    
    // 设置输入设备
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    [self.session addInput:input];
    
    // 设置输出设备
    AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    [self.session addOutput:output];
    
    // 设置元数据类型为QR码
    [output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
    
    // 创建预览图层
    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.session];
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    self.previewLayer.frame = self.view.bounds;
    [self.view.layer insertSublayer:self.previewLayer atIndex:0];
    
    // 启动会话
    [self.session startRunning];
}
#pragma mark - AVCaptureMetadataOutputObjectsDelegate
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    for (AVMetadataObject *metadataObject in metadataObjects) {
        if ([metadataObject isKindOfClass:[AVMetadataMachineReadableCodeObject class]]) {
            // 获取解码后的字符串
            AVMetadataMachineReadableCodeObject *readableObject = (AVMetadataMachineReadableCodeObject *)[self.previewLayer transformedMetadataObjectForMetadataObject:metadataObject];
            NSString *decodedString = readableObject.stringValue;
            
            // 处理解码后的字符串
            [self handleDecodedString:decodedString];
            
            // 停止会话
            [self.session stopRunning];
            
            break;
        }
    }
}
- (void)handleDecodedString:(NSString *)decodedString {
    // 在此处处理解码后的字符串
    NSLog(@"解码后的字符串：%@", decodedString);
}
@end

objective-c
// 导入CoreImage框架
#import 
@interface QRCodeGeneratorViewController ()
@property (nonatomic, strong) UIImageView *imageView;
@end
@implementation QRCodeGeneratorViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 创建CIImage对象
    CIImage *qrCodeImage = [self createQRCodeImageWithString:@"https://www.example.com"];
    
    // 将CIImage对象转换为UIImage对象
    UIImage *qrCodeUIImage = [UIImage imageWithCIImage:qrCodeImage];
    
    // 创建UIImageView对象，并设置图片
    self.imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
    self.imageView.image = qrCodeUIImage;
    self.imageView.center = self.view.center;
    [self.view addSubview:self.imageView];
}
- (CIImage *)createQRCodeImageWithString:(NSString *)string {
    // 创建滤镜
    CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
    
    // 将字符串转换为NSData对象
    NSData *stringData = [string dataUsingEncoding:NSUTF8StringEncoding];
    
    // 设置滤镜的输入值
    [filter setValue:stringData forKey:@"inputMessage"];
    [filter setValue:@"H" forKey:@"inputCorrectionLevel"];
    
    // 获取滤镜的输出图像
    CIImage *outputImage = [filter outputImage];
    
    return outputImage;
}
@end