How to scan QR codes and regular barcodes using just your camera app (Android)

Have you ever found yourself in a situation where you want to scan a QR code using your smartphonephone, only to realize that you don't have one of the myriad of dedicated scanning apps available installed on your device? Downloading a relatively small app on the spot is not that big of a hassle, but do you really need yet another app on your phone just for scanning a certain type of barcode that's not all that popular in outside of Asia anyway? The answer is "no, you don't".

In fact, on Android, you can simply use your default camera app, or a substitute of ...