Updating Your Barcode Scanning Integration (v1.9.5+)

Who is this guide for? This guide is for developers using BlinkReceipt SDK 1.9.5 or newer, we already migrated to Google MLKit Barcode. If you are implementing barcode scanning for the first time or upgrading from an older version, please read this carefully.

Due to a migration to Google’s MLKit for barcode scanning in SDK v1.9.5, there is a fundamental behavioral change in how RecognizerView handles a scanning session. This guide explains the change and how to adapt your implementation.

TL;DR: The Quick Summary

The barcode scanner now automatically pauses after the very first result it produces, which is often an empty result right after the camera starts.

Your Action: You must now check for empty results and explicitly call recognizerView.resumeScanning(true) when you are ready to scan again.

---

Understanding the Change

To build a robust implementation, it’s important to understand what is happening behind the scenes.

• Cause: We now use Google’s MLKit, which begins analyzing frames from the camera immediately upon initialization.

• Effect: As soon as RecognizerView starts, it analyzes the camera view. Because the user hasn’t yet aimed at a barcode, it quickly produces a result: “no barcodes found.”

• The Problem: The SDK is designed to pause the scanning session after every result to allow your app to process it. This means the initial “empty” result immediately PAUSES the scanner. By the time the user aims their camera at a barcode, the RecognizerView is in a PAUSED state and won’t detect anything further.

---

How to Update Your Implementation

You must update your code to handle this “pause on result” behavior. The correct approach depends on your app’s use case.

Scenario A: Scan a Single Barcode

Use this if you want the user to scan one barcode, get the result, and then stop.

In this scenario, you should ignore the initial empty result and only act when a valid barcode is found. You do not need to resume scanning automatically.

val recognizerView = findViewById<RecognizerView>(R.id.recognizerView)

recognizerView.metadataCallbacks(
    MetadataCallbacks().apply {
        recognizerCallback { results: RecognizerResults ->
            // This callback provides the actual scan data.
            // First, check if the result is valid and not the initial empty one.
            if (results.barcodes().isNotEmpty()) {
                // SUCCESS: A barcode was found!
                // The scanner is now PAUSED automatically.

                // Get your barcode data and Process the result (e.g., close this screen, show data)
                // You DO NOT need to call resumeScanning() here if you're done.
                // showResultAndFinish(barcodeText) 
            }
            // If the result is empty, do nothing and let the scanner continue.
            // The resumeScanning() call in scanResultListener will handle restarting it.
        }

        failedDetectionCallback {
            // Optional: Handle cases where a barcode-like object was detected but failed to be parsed.
            // You can provide user feedback here, like "Hold the camera steady."
        }
    }
)

// This listener is a generic callback that fires whenever a result is processed.
// It's the perfect place to manage the scanning lifecycle.
recognizerView.scanResultListener {
    // Each time your app receives a result (even an empty one), the scanning session pauses.
    // To ensure the user can scan, we must resume scanning if no valid barcode has been found yet.
    // We pass `true` to reset the internal state for the next scan.
    recognizerView.resumeScanning(true)
})

Scenario B: Continuous Scanning

Use this for applications like inventory management, where a user might scan multiple barcodes one after another without closing the scanner.

The logic is similar to the single-scan scenario, but you will call recognizerView.resumeScanning(true) after you have successfully processed a barcode.

val recognizerView = findViewById<RecognizerView>(R.id.recognizerView)

recognizerView.metadataCallbacks(
    MetadataCallbacks().apply {
        recognizerCallback { results: RecognizerResults ->
            // Check if a valid barcode was found.
            if (results.barcodeResults().isNotEmpty()) {
                // SUCCESS: A barcode was found!
                // The scanner is now PAUSED automatically.

                // 1. Add the result to your list or process it.
                // 2. Provide feedback to the user (e.g., a "beep" sound or vibration).
                // 3. The scanner is now PAUSED. The scanResultListener below will resume it.
            }
        }
    }
)

recognizerView.scanResultListener {
    // For continuous scanning, we *always* want to resume after any result.
    // This allows the user to immediately point the camera at the next barcode.
    // Consider adding a small delay here if you want to prevent accidental double-scans.
    recognizerView.resumeScanning(true)
})

---

Best Practices

• Provide User Feedback: Don’t leave the user guessing. When a barcode is successfully scanned, provide immediate feedback like a sound, vibration, or a brief animation on the screen.
• Handle Empty States: In your recognizerCallback, always check results.barcodes().isNotEmpty() before trying to access the data to avoid crashes.
• Manual Rescan Button (Optional): For some UIs, it’s helpful to add a button that allows the user to manually trigger a new scan. This gives them more control.

val resumeBtn = findViewById<Button>(R.id.resumeBtn)

resumeBtn.setOnClickListener {
    // The 'true' parameter resets the recognizer state, which is recommended.
    recognizerView.resumeScanning(true)
}