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In this guide you will learn step-by-step how to add Barcode Selection to your application.

The general steps are:

  • Create a new data capture context instance, initialized with your license key.
  • Create a barcode selection settings and choose the right configuration.
  • Create a new barcode selection mode instance and initialize it with the settings created above.
  • Register a barcode selection listener to receive scan events. Process the successful scans according to your application’s needs, e.g. by looking up information in a database. After a successful scan, decide whether more codes will be scanned, or the scanning process should be stopped.
  • Obtain a camera instance and set it as the frame source on the data capture context.
  • Display the camera preview by creating a data capture view.
  • If displaying a preview, optionally create a new overlay and add it to data capture view for a better visual feedback.

Create the Data Capture Context​

The first step to add capture capabilities to your application is to create a new data capture context. The context expects a valid Scandit Data Capture SDK license key during construction.

DataCaptureContext context = DataCaptureContext.ForLicenseKey("-- ENTER YOUR SCANDIT LICENSE KEY HERE --");

Configure the Barcode Selection Behavior​

Symbologies

Barcode selection is orchestrated by the BarcodeSelection data capture mode. It is configured through BarcodeSelectionSettings and allows to register one or more listeners that will get informed whenever new codes have been selected.

For this tutorial, we will setup barcode scanning for a small list of different barcode types, called symbologies. The list of symbologies to enable is highly application specific. We recommend that you only enable the list of symbologies your application requires.

BarcodeSelectionSettings settings = BarcodeSelectionSettings.Create();
HashSet<Symbology> symbologies = new HashSet<Symbology>()
{
Symbology.Qr,
Symbology.Ean8,
Symbology.Upce,
Symbology.Ean13Upca
};
settings.EnableSymbologies(symbologies);

Selection Types

The behavior of Barcode Selection can be changed by using a different selection type. This defines the method used by BarcodeSelection to select codes. Currently there are two types.

If you want the user to select barcodes with a tap, then use BarcodeSelectionTapSelection. This selection type can automatically freeze the camera preview to make the selection easier. You can configure the freezing behavior via BarcodeSelectionTapSelection.FreezeBehavior. With BarcodeSelectionTapSelection.TapBehavior you can decide if a second tap on a barcode means that the barcode is unselected or if it is selected another time (increasing the counter).

note

Using BarcodeSelectionTapSelection requires the MatrixScan add-on.

If you want the selection to happen automatically based on where the user points the camera, then use BarcodeSelectionAimerSelection. It is possible to choose between two different selection strategies. Use BarcodeSelectionAutoSelectionStrategy if you want the barcodes to be selected automatically when aiming at them as soon as the intention is understood by our internal algorithms. Use BarcodeSelectionManualSelectionStrategy if you want the barcodes to be selected when aiming at them and tapping anywhere on the screen.

Single Barcode Auto Detection

If you want to automatically select a barcode when it is the only one on screen, turn on BarcodeSelectionSettings.SingleBarcodeAutoDetection.

Creating the mode

Next, create a BarcodeSelection instance with the settings initialized in the previous step:

barcodeSelection = BarcodeSelection.Create(context, settings);

Register the Barcode Selection Listener​

To get informed whenever a new code has been recognized, add a IBarcodeSelectionListener through BarcodeSelection.AddListener() and implement the listener methods to suit your application’s needs.

First implement the IBarcodeSelectionListener interface. For example:

public class MyBarcodeSelectionListener : NSObject, IBarcodeSelectionListener
{
public void OnObservationStarted(BarcodeSelection barcodeSelection)
{
// Called when Barcode Selection is started.
// We don't use this callback in this guide.
}

public void OnObservationStopped(BarcodeSelection barcodeSelection)
{
// Called when Barcode Selection is stopped.
// We don't use this callback in this guide.
}

public void OnSessionUpdated(
BarcodeSelection barcodeSelection,
BarcodeSelectionSession session,
IFrameData frameData)
{
// Called every new frame.
// We don't use this callback in this guide.

// Dispose the frame when you have finished processing it. If the frame is not properly disposed,
// different issues could arise, e.g. a frozen, non-responsive, or "severely stuttering" video feed.
frameData.Dispose();
}

public void OnSelectionUpdated(
BarcodeSelection barcodeSelection,
BarcodeSelectionSession session,
IFrameData frameData)
{
IList<Barcode> newlySelectedBarcodes = session.NewlySelectedBarcodes;
IList<Barcode> selectedBarcodes = session.SelectedBarcodes;
IList<Barcode> newlyUnselectedBarcodes = session.NewlyUnselectedBarcodes;
// Do something with the retrieved barcodes.

// Dispose the frame when you have finished processing it. If the frame is not properly disposed,
// different issues could arise, e.g. a frozen, non-responsive, or "severely stuttering" video feed.
frameData.Dispose();
}
}

Then add the listener:

barcodeSelection.AddListener(new MyBarcodeSelectionListener());

Alternatively to register IBarcodeSelectionListener interface it is possible to subscribe to corresponding events. For example:

barcodeSelection.SelectionUpdated += (object sender, BarcodeSelectionEventArgs args) =>
{
IList<Barcode> newlySelectedBarcodes = args.Session.NewlySelectedBarcodes;
IList<Barcode> selectedBarcodes = args.Session.SelectedBarcodes;
IList<Barcode> newlyUnselectedBarcodes = args.Session.NewlyUnselectedBarcodes;
// Do something with the retrieved barcodes.
}

Use the Built-in Camera​

The data capture context supports using different frame sources to perform recognition on. Most applications will use the built-in camera of the device, e.g. the world-facing camera of a device. The remainder of this tutorial will assume that you use the built-in camera.

important

In iOS, the user must explicitly grant permission for each app to access cameras. Your app needs to provide static messages to display to the user when the system asks for camera permission. To do that include the NSCameraUsageDescription key in your app’s Info.plist file.

When using the built-in camera there are recommended settings for each capture mode. These should be used to achieve the best performance and user experience for the respective mode. The following couple of lines show how to get the recommended settings and create the camera from it:

var cameraSettings = BarcodeSelection.RecommendedCameraSettings;

// Depending on the use case further camera settings adjustments can be made here.

camera = Camera.GetDefaultCamera();
camera?.ApplySettingsAsync(cameraSettings);

Because the frame source is configurable, the data capture context must be told which frame source to use. This is done with a call to DataCaptureContext.SetFrameSourceAsync():

context.SetFrameSourceAsync(camera);

The camera is off by default and must be turned on. This is done by calling IFrameSource.SwitchToDesiredState() with a value of FrameSourceState.On:

camera?.SwitchToDesiredStateAsync(FrameSourceState.On);

Disabling Barcode Selection​

To disable barcode selection, for instance when the selection is complete, set BarcodeSelection.Enabled to false. The effect is immediate: no more frames will be processed after the change. However, if a frame is currently being processed, this frame will be completely processed and deliver any results/callbacks to the registered listeners. Note that disabling the capture mode does not stop the camera, the camera continues to stream frames until it is turned off.