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Advanced Configurations

Customization of the Overlays​

To customize the appearance of an overlay you can implement a LabelCaptureBasicOverlayListener and/or LabelCaptureAdvancedOverlayListener interface, depending on the overlay(s) you are using.

The method brushForLabel() is called every time a label is captured, and brushForField() is called for each of its fields to determine the brush for the label or field.

overlay.listener = object : LabelCaptureBasicOverlayListener {
    /*
     * Customize the appearance of the overlay for the individual fields.
     */
    override fun brushForField(
        overlay: LabelCaptureBasicOverlay,
        field: LabelField,
        label: CapturedLabel
    ): Brush? = when (field.name) {
        "<your-barcode-field-name>" -> Brush(Color.CYAN.withAlpha(128), Color.CYAN, 1f)
        "<your-expiry-date-field-name>" -> Brush(Color.GREEN.withAlpha(128), Color.GREEN, 1f)
        else -> Brush(Color.TRANSPARENT, Color.TRANSPARENT, 0f)
    }

    /*
     * Customize the appearance of the overlay for the full label.
     * In this example, we disable label overlays by returning null always.
     */
    override fun brushForLabel(
        overlay: LabelCaptureBasicOverlay,
        label: CapturedLabel
    ): Brush? = null

    override fun onLabelTapped(
        overlay: LabelCaptureBasicOverlay,
        label: CapturedLabel
    ) { 
        /*
         * Handle the user tap gesture on the label.
         */
    }
}

tip

You can also use LabelCaptureBasicOverlay.setLabelBrush() and LabelCaptureBasicOverlay.setCapturedFieldBrush() to configure the overlay if you don't need to customize the appearance based on the name or content of the fields.

Advanced Overlay​

For more advanced use cases, such as adding custom views or implementing Augmented Reality (AR) features, you can use the LabelCaptureAdvancedOverlay. The example below creates an advanced overlay, configuring it to display a styled warning message below expiry date fields when they’re close to expiring, while ignoring other fields.

// Create an advanced overlay that allows for custom views to be added over detected label fields
// This is the key component for implementing Augmented Reality features
val advancedOverlay = LabelCaptureAdvancedOverlay.newInstance(dataCaptureManager.getLabelCapture(), view)

// Configure the advanced overlay with a listener that handles AR content creation and positioning
advancedOverlay.listener = object : LabelCaptureAdvancedOverlayListener {
    
    // This method is called when a label is detected - we return null since we're only adding AR elements to specific fields, not the entire label
    override fun viewForCapturedLabel(
        overlay: LabelCaptureAdvancedOverlay,
        capturedLabel: CapturedLabel
    ): View? = null

    // This defines where on the detected label the AR view would be anchored 
    override fun anchorForCapturedLabel(
        overlay: LabelCaptureAdvancedOverlay,
        capturedLabel: CapturedLabel
    ): Anchor = Anchor.CENTER

    // This defines the offset from the anchor point for the label's AR view
    override fun offsetForCapturedLabel(
        overlay: LabelCaptureAdvancedOverlay,
        capturedLabel: CapturedLabel,
        view: View
    ): PointWithUnit = PointWithUnit(0f, 0f, MeasureUnit.PIXEL)

    // This method is called when a field is detected in a label
    override fun viewForCapturedLabelField(
        overlay: LabelCaptureAdvancedOverlay,
        labelField: LabelField
    ): View? {
        // We only want to create AR elements for expiry date fields that are text-based
        if (labelField.name.contains("expiry", ignoreCase = true) && labelField.type == LabelFieldType.TEXT) {
        
            //
            // data extraction from expiry date field and days until expiry date calculation
            //
            
            // Check if scanned expiry date is to close to actual date
            if (daysUntilExpiry < dayLimit) {
            
                // Create and configure the AR element - a TextView with appropriate styling
                // This view will appear as an overlay on the camera feed
                return TextView(context).apply {
                
                    text = "Item expires soon!"
                    setTextColor(Color.WHITE)
                    setBackgroundColor(Color.RED)
                    setPadding(16, 8, 16, 8)
                    
                    // Add an icon to the left of the text for visual guidance
                    // This enhances the AR experience by providing clear visual cues
                    val drawable = ContextCompat.getDrawable(context, R.drawable.ic_warning)
                    drawable?.setBounds(0, 0, drawable.intrinsicWidth, drawable.intrinsicHeight)
                    setCompoundDrawables(drawable, null, null, null)
                    compoundDrawablePadding = 16 // Add some padding between icon and text
                }
            }
        }
        // Return null for any fields that aren't expiry dates, which means no AR overlay
        return null
    }
    
    // This defines where on the detected field the AR view should be anchored
    // BOTTOM_CENTER places it right below the expiry date text for better visibility
    override fun anchorForCapturedLabelField(
        overlay: LabelCaptureAdvancedOverlay,
        labelField: LabelField
    ): Anchor = Anchor.BOTTOM_CENTER

    // This defines the offset from the anchor point
    override fun offsetForCapturedLabelField(
        overlay: LabelCaptureAdvancedOverlay,
        labelField: LabelField,
        view: View
    ): PointWithUnit = PointWithUnit(0f, 22f, MeasureUnit.DIP)
}

Validation Flow​

Implementing a validation flow in your Smart Label Capture application differs from the Get Started steps outlined earlier as follows:

Visualize the Scan Process​

Validation flow uses a different overlay, the LabelCaptureValidationFlowOverlay. This overlay provides a user interface that guides users through the label capture process, including validation steps.

// Create the overlay
validationFlowOverlay = LabelCaptureValidationFlowOverlay.newInstance(
    requireContext(),
    dataCaptureManager.getLabelCapture(),
    view
)

// Set the listener to receive validation events
validationFlowOverlay?.listener = this

Adjust the Hint Messages​

// Configure the validation flow with custom settings
val validationSettings = LabelCaptureValidationFlowSettings.newInstance()
validationSettings.apply {
    missingFieldsHintText = "Please add this field"
    standbyHintText = "No label detected, camera paused"
    validationHintText = "fields captured" // X/Y (X fields out of total Y) is  shown in front of this string
    validationErrorText = "Input not valid"
    requiredFieldErrorText = "This field is required"
    manualInputButtonText = "Add info manually"
}

// Apply the settings to the overlay
validationFlowOverlay?.applySettings(validationSettings)

Define a Listener​

To handle validation events, implement the LabelCaptureValidationFlowOverlayListener interface.

// This is called by the validation flow overlay when a label has been fully captured and validated
override fun onValidationFlowLabelCaptured(fields: List<LabelField>) {
    
    val barcodeData = fields.find { it.name == "<your-barcode-field-name>" }?.barcode?.data
        
    val expiryDate = fields.find { it.name == "<your-expiry-date-field-name>" }?.text
}