QR Scanner Speed

Good day,
I am building a QR reader that scan race numbers for laps for cycling.
The basics are working 100%, writing all the logs to a txt.
The biggest issue I have is the delay between the scans , as it first write to the txt.

I am a complete Noob, so any help wil be appreciate, how to speed up the process, or maby the functionality to be able to scan multiple qr codes at once.
Herewith a screenshot of my blocks.

Thanks in advance


You are using recursion (using a AfterScan to call the Scanner continuously) .

Yes, that is to be expected. How often is this delay?

How can you speed this up? Perhaps you can’t. You might change your barcode scanner app on your device for another that might cycle faster; you could try a different device that has a faster cpu to process the data. If you are also printing results to a Label, stop that and only show the File results after your scanning session. One of the slowest processes in AI (even though writing to the screen is fast), it is not as fast as when using a java based compiler like Android Studio.

What is required of your device is to ‘take a picture’; convert that to numbers; post the results. A similar question might be is how fast can your device’s camera take a picture with successive camera presses. Notice, there is a delay. Your delay is probably related to the ability of the camera to provide a new image as a guess.

Functionality to be able to scan multiple qr codes at once? Not possible probably.

Consider, App Inventor 2 projects execute code asynchronously (one instruction after another); each time you issue a command, it takes a few ms to execute. These delays are additive.

You may not be able to use the scanner in your Android to be a High Speed Scanner. The link points to possible alternatives for you bicycle racing scanning activity.


Hi, thanks for the thourough answer, really helped a lot.
So, the question is, is it worth the effort to use qr codes then at all? Isn’t ir better to use nfc tags rather? I know it is being used at running events. For cyclist, the nfc tag might be too far to read?

This article explains NFC range https://www.quora.com/What-is-the-maximum-distance-for-NFC-communication

essentially, 20cm is possible, 6 cm is more likely. NFC is SUPPOSED to be used at close distance for security reasons.

Can you use a QR code at all for your project? I imagine you will have to place a large placard on each cyclist with the QR . Try this simple experiment. Place a QR code on your PC screen. Use your present code to scan it? How close do you have to be achieve a scan? How far away can you be and still achieve a scan using your Android? Will your Android be that close to a cyclist?

Good luck.