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AVCaptureMetadataOutput setMetadataObjectTypes unsupported type found

I know someone asked this question. But I wish I could find an answer.

dispatchQueue = dispatch_queue_create("myQueue", NULL);
[captureMetadaOutput setMetadataObjectsDelegate:self queue:dispatchQueue];
//  [captureMetadaOutput setMetadataObjectTypes:[NSArray arrayWithObject:AVMetadataObjectTypeQRCode]];
//  设置条码类型
captureMetadaOutput.metadataObjectTypes = @[AVMetadataObjectTypeQRCode];

I got crash information from Crashlytics:

[AVCaptureMetadataOutput setMetadataObjectTypes:] - unsupported type found. Use -availableMetadataObjectTypes.

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3 answers


We must first add the output to the session and then install metadataObjectTypes

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This is because you are closing the resolution of the camera. You can open your camera's authorization and then open the canner to scan the QRCode. Strike gives typical examples:



AVAuthorizationStatus status = [AVCaptureDevice authorizationStatusForMediaType:AVMediaTypeVideo]; 
if(status == AVAuthorizationStatusAuthorized) {  
    // authorized  
    [self setupCamera];  
} else {  
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Tips" message:@"Authorization is required to use the camera, please check your permission settings: Settings> Privacy> Camera" delegate:nil cancelButtonTitle:nil otherButtonTitles:@"Ok", nil];
        [alert show];  
}
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you need to do like this:

        if ([_captureSession canAddOutput:self.metadataOutput]) {
        [_captureSession addOutput:self.metadataOutput];
        // 这里注意,必须先将metadataOutput 加入到session,然后才能设置metadataObjectTypes,注意顺序,不然会crash
        self.metadataOutput.metadataObjectTypes = @[AVMetadataObjectTypeQRCode];
        [self.metadataOutput setMetadataObjectsDelegate:self queue:_videoDataOutputQueue];
    }
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