公司最近要添加一個二維碼掃描網頁登錄的功能,所以最近研究了一下iOS關于二維碼掃描的功能
因為移動端不涉及二維碼的生成,所以只做關于二維碼的掃描(這里感謝一下SGQRCode的作者)

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攝像頭掃描二維碼

用攝像頭掃描二維碼就需要我們剛才說的AVCaptureSession，具體怎么實現，我們來看demo。

框架

首先導入我們要用到的框架，因為掃描和識別都是在系統AVFoundation下的做的，所以第一步就要把框架主頭文件導入 #import <AVFoundation/AVFoundation.h>

頭文件

/** 回話對象屬性*/
@property (nonatomic, strong) AVCaptureSession *session;

/** 攝像頭預覽圖層*/
@property (nonatomic, strong) AVCaptureVideoPreviewLayer *previewLayer;

實現部分

    // 創建回話對象
    self.session = [[AVCaptureSession alloc] init];
    
    // 設置回話對象圖像采集率
    [self.session setSessionPreset:AVCaptureSessionPresetHigh];
    
    // 獲取攝像頭設備
    AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    
    // 創建回話輸入對象
    NSError *inputError = nil;
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&inputError];
    
    // 添加會話輸入
    [self.session addInput:input];
    
    // 創建輸出對象
    AVCaptureMetadataOutput *output = [[AVCaptureMetadataOutput alloc] init];
    
    // 設置輸出對象代理
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
    
    // 添加會話輸出
    [self.session addOutput:output];
    
    // 設置輸出數據類型,需要將元數據輸出添加到回話后,才能制定元數據,否則會報錯
    // 二維碼和條形碼可以一起設置
    output.metadataObjectTypes = @[AVMetadataObjectTypeQRCode, AVMetadataObjectTypeEAN13Code,  AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code];
    
    // 創建攝像頭預覽圖層
    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.session];
    
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    
    self.previewLayer.frame = self.view.frame;
    
    // 將圖層插入當前圖層
    [self.view.layer insertSublayer:self.previewLayer atIndex:0];
    
    // 啟動會話
    [self.session startRunning];

主體方法實現了以后，我們來看一下AVCaptureMetadataOutputObjectsDelegate方法- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection；，當二維碼掃描成功之后，系統將自動調用這個代理方法。

AVCaptureMetadataOutputObjectsDelegate

- (void)captureOutput:(AVCaptureOutput *)output didOutputMetadataObjects:(NSArray<__kindof AVMetadataObject *> *)metadataObjects fromConnection:(AVCaptureConnection *)connection {
    
    // 1、如果掃描完成，停止會話
    [self.session stopRunning];
    
    // 2、刪除預覽圖層
    [self.previewLayer removeFromSuperlayer];
    
    // 3、設置界面顯示掃描結果
    if (metadataObjects && metadataObjects.count > 0) {
        // 播放音效
        NSString *audioFile = [[NSBundle mainBundle] pathForResource:@"sound" ofType:@"wav"];
        NSURL *fileUrl = [NSURL fileURLWithPath:audioFile];
        
        SystemSoundID soundID = 0;
        AudioServicesCreateSystemSoundID((__bridge CFURLRef)(fileUrl), &soundID);
        AudioServicesAddSystemSoundCompletion(soundID, NULL, NULL, soundCompleteCallback, NULL);
        AudioServicesPlaySystemSound(soundID); // 播放音效
        AVMetadataMachineReadableCodeObject *obj = metadataObjects.firstObject;
        // 取出二維碼掃描到的內容
        NSLog(@"二維碼內容：：：%@",obj.stringValue);
    }
}
// 播放音效成功回調
void soundCompleteCallback (){
   
}

如果想監聽設備攝像頭實時的視頻流就將會話輸出對象添加AVCaptureVideoDataOutputSampleBufferDelegate代理監聽實現- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection;代理方法

AVCaptureVideoDataOutputSampleBufferDelegate

[output setSampleBufferDelegate:self queue:dispatch_get_main_queue()];

實現方法

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    // 這個方法會時時調用，但內存很穩定
    CFDictionaryRef metadataDict = CMCopyDictionaryOfAttachments(NULL,sampleBuffer, kCMAttachmentMode_ShouldPropagate);
    NSDictionary *metadata = [[NSMutableDictionary alloc] initWithDictionary:(__bridge NSDictionary*)metadataDict];
    CFRelease(metadataDict);
    NSDictionary *exifMetadata = [[metadata objectForKey:(NSString *)kCGImagePropertyExifDictionary] mutableCopy];
    float brightnessValue = [[exifMetadata objectForKey:(NSString *)kCGImagePropertyExifBrightnessValue] floatValue];
    
    NSLog(@"%f",brightnessValue);
}