Is it mobile app or desktop/browser app, and how is the barcode reader setup?
If its mobile does the device have its own barcode reader built in? or a peripheral device?
Usually a barcode reader just puts the data into the keyboard buffer, so all you actually need to do is provide a field on screen, then when cursor/focus is on the field, and the barcode is scanned the data will go into the field.
Gets a bit more complicated sometimes with devices and barcode scanners being built in, but generally there isn't much that needs doing in my experience...
Callum