[[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
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如果未允许开启摄像头，直接设置摄像头，会发生闪退：
-
#1467 NSInvalidArgumentException*** -[AVCaptureMetadataOutput setMetadataObjectTypes:] Unsupported type found - use -availableMetadataObjectTypes