1) Add a QRCodeFunctions as a entity (data) to the mashup
How to Generate QR Code
2) Add to the mashup: Textbox, Button, Valuedisplay Widgets
3) Text from textbox connect to the content parametr in GenerateQRCode
4) Result from Returned data (All data) conect to the Valuedisplay
5) Click function from Button connect to the GenerateQRCode
6) Save and test
Ewerton, I´m at the beginning of creating apps. As I wrote my first replay to your question, reading QR code looks much easier. I use output from GenerateQRCode as input to ReadQRCode.
However when I tried to read picture to app/mashup from external source (windows folder at first step), I´m still unsuccessful. I´m looking for some method how to use bar/QR code for object searching in manufacturing.