BarcodePicker

BarcodePicker reads barcodes/QR codes from live camera frames, filtering by format. It is an abstract class: the consumer implements onBarcode(BarcodeFormat format, String code). It follows the picker pattern (see Picker) — it returns the read payload via getAnswer().

🔴 · Package: dev.crossfly.ui.picker · Extends: Picker implements GdxCamera.Listener (abstract) · Hardware: camera

ℹ️ This BarcodePicker is the camera-based reader and still exists. Do not confuse it with the old barcode generation utility (util/barcode), which was removed during modernization.

When to use

• Scan barcodes (products, tickets) or QR codes.

When NOT to use

• Take a photo/record video → use PhotoPicker.

Appearance

Full-screen camera preview (black background), title at the top, a central red crosshair for aiming, and a white “X” close button in the bottom-right corner.

Complete example (copy, paste and run)

BarcodePicker is abstract: instantiate it with a body implementing onBarcode. Since it is a camera overlay, trigger it from a Button. The example reuses the basic usage (1D formats, closes on the 1st read) and writes the payload into a Label. BarcodeFormat comes from com.google.zxing.

package com.exemplo;

import com.google.zxing.BarcodeFormat;

import dev.crossfly.ui.*;
import dev.crossfly.ui.layout.*;
import dev.crossfly.ui.picker.*;

/** Runnable main screen. Point the launcher (classname) and run: gradlew :lwjgl3:run */
public class MainWindow extends Window
{
   @Override
   public void onShow() throws Exception
   {
      super.onShow();
      setLayout(new VerticalLayout());

      Label saida = new Label("Nenhum código lido");
      add(LAY_AUTO, saida);

      Button escanear = new Button("Escanear código")
         .onAction(c ->
         {
            BarcodePicker scanner = new BarcodePicker("Aponte para o código", BarcodePicker.formats1D)
            {
               protected void onBarcode(BarcodeFormat format, String code)
               {
                  onUI(() -> saida.setText(format + ": " + code)); // back to the paint thread
                  hide(); // closes after the 1st read (doesn't close on its own)
               }
            };
            scanner.show(answer -> {});
         });
      add(LAY_AUTO, escanear);
   }
}

The snippets below show only the core (what goes inside onShow()). To run them, place them in the MainWindow skeleton above.

Basic usage

BarcodePicker scanner = new BarcodePicker("Aponte para o código", BarcodePicker.formats1D)
{
   protected void onBarcode(BarcodeFormat format, String code)
   {
      Debug.log(format + ": " + code);
      hide(); // closes after the 1st read
   }
};
scanner.show(answer -> campoCodigo.setText((String) answer));

Constructors

Properties and customization

Callbacks and events

getAnswer() returns the last decoded payload, or null if canceled.

States

• There is no automatic hide() on detection — you decide when to close in your onBarcode (by calling hide()). Without it, the scanner keeps reading (useful for continuous reading).
• Consecutive repeated codes (same lastCode) are ignored.
• onAppPause/onAppResume manage the camera; onRemove stops the decoding thread.

Accept only QR and close on the first read

BarcodePicker scanner = new BarcodePicker("Leia o QR", BarcodePicker.formats2D)
{
   protected void onBarcode(BarcodeFormat format, String code)
   {
      onUI(() -> campoCodigo.setText(code)); // UI update on the paint thread
      hide();
   }
};
scanner.show(answer -> Debug.log("Lido: " + answer));

Best practices

• Call hide() in onBarcode for a single read; omit it for continuous reading.
• Decoding runs on a background thread — wrap UI updates in onUI(...).

Common mistakes

• Forgetting hide() when you wanted a single read — the scanner stays active.
• Updating the UI directly in onBarcode — respect the paint thread with onUI(...).

See also

• Area guide: ui/ · Recipes: cookbook/
• Pattern base: Picker
• Related components: PhotoPicker