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.addListener(LabelCaptureBasicOverlayListener(
  brushForLabel: (overlay, label) {
    return null;
  },
  brushForField: (overlay, field, label) {
    if (field.name == '<your-barcode-field-name>') {
      return Brush(
        fillColor: Colors.blue.withOpacity(0.2),
        strokeColor: Colors.blue,
        strokeWidth: 0,
      );
    }

    if (field.name == '<your-expiry-date-field-name>') {
      return Brush(
        fillColor: Colors.red.withOpacity(0.2),
        strokeColor: Colors.red,
        strokeWidth: 0,
      );
    }

    return null;
  },
));

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.

final advancedOverlay = LabelCaptureAdvancedOverlay.newInstance(
  labelCapture,
  dataCaptureView,
);

advancedOverlay.addListener(LabelCaptureAdvancedOverlayListener(
  viewForCapturedLabel: (overlay, capturedLabel) {
    return null; // We only care about specific fields
  },
  anchorForCapturedLabel: (overlay, capturedLabel) {
    return Anchor.center;
  },
  offsetForCapturedLabel: (overlay, capturedLabel, view) {
    return PointWithUnit.withPixel(0, 0);
  },
  viewForCapturedLabelField: (overlay, labelField) {
    if (labelField.name.toLowerCase().contains("expiry") &&
        labelField.type == LabelFieldType.text) {

      final daysUntilExpiry = daysUntilExpiryFunction(labelField.text); // Your method
      const dayLimit = 3;

      if (daysUntilExpiry < dayLimit) {
        return Container(
          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
          color: Colors.red,
          child: Row(
            mainAxisSize: MainAxisSize.min,
            children: const [
              Icon(Icons.warning, color: Colors.white),
              SizedBox(width: 8),
              Text("Item expires soon!", style: TextStyle(color: Colors.white)),
            ],
          ),
        );
      }
    }

    return null;
  },
  anchorForCapturedLabelField: (overlay, labelField) {
    return Anchor.bottomCenter;
  },
  offsetForCapturedLabelField: (overlay, labelField, view) {
    return PointWithUnit.withUnit(0, 22, 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.

final validationFlowOverlay = LabelCaptureValidationFlowOverlay.newInstance(
  context,
  labelCapture,
  dataCaptureView,
);

// Set the listener
validationFlowOverlay.addListener(MyValidationFlowListener());

Adjust the Hint Messages

final validationSettings = LabelCaptureValidationFlowSettings.newInstance();

validationSettings.missingFieldsHintText = "Please add this field";
validationSettings.standbyHintText = "No label detected, camera paused";
validationSettings.validationHintText = "fields captured"; // X/Y (X fields out of total Y) is shown in front
validationSettings.validationErrorText = "Input not valid";
validationSettings.requiredFieldErrorText = "This field is required";
validationSettings.manualInputButtonText = "Add info manually";

// Apply the settings
validationFlowOverlay.applySettings(validationSettings);

Define a Listener

To handle validation events, implement the LabelCaptureValidationFlowOverlayListener interface.

class MyValidationFlowListener extends LabelCaptureValidationFlowOverlayListener {
  @override
  void onValidationFlowLabelCaptured(List<LabelField> fields) {
    String? barcodeData;
    String? expiryDate;

    for (final field in fields) {
      if (field.name == "<your-barcode-field-name>") {
        barcodeData = field.barcode?.data;
      } else if (field.name == "<your-expiry-date-field-name>") {
        expiryDate = field.text;
      }
    }

    // Handle the captured values
  }
}