copy private key and send it to your facebook messages
Copy paste on computer from facebook private keys.
Are you kidding me? I have no control over the data sent through facebook or messenger. Sending private keys through services you don't control is not a great idea.
I'm looking for a secure and open source qr-code reader for android, one that don't collect data, hopefully one that can send the information through a USB cable, don't really know how yet. Maybe I need to order a webcam...
You could avoid doing it through a third party service by saving your private keys in a txt fale and then, transfer it to your computer with your USB.
If you want a app that does read your QR code and sends to your PC, there is this app called Barcode to PC for Android and IOS that does the trick[1].
[1]
https://barcodetopc.com/OP, if you have an air-gapped pc that's always offline, I don't see too much of a point in using paper wallets (though it does give a bit extra security).
Just as a note, if you're trying to store it in a txt file as tryninja suggests, ensure you use a piece of software on your phone that can handle .txt files (my suggestion would be Python).
Also, if their is a loose/faulty connection or you have particular security software then the barcode app directly scanning to a computer may not work. You can always look into downloading a copy of electrum in order to resolve this.
Electrum download: electrum.org/#download -
https://play.google.com/store/apps/details?id=org.electrum.electrumPython/text editor download:
https://play.google.com/store/apps/details?id=org.qpython.qpy3
DEFINITELY DO NOT DO WHAT WAS SUGGESTED SECOND TO THE OP AND IMPORT YOUR PRIVATE KEYS TO MESSENGER - it may seem a nifty idea but putting them there is a bad idea (unless you have a password with AT LEAST 20 characters in it but even then it's risky).