1 files changed, 77 insertions, 0 deletions
diff --git a/src/main/ui/widgets/QRPanel.java b/src/main/ui/widgets/QRPanel.java
new file mode 100644
index 0000000..d72d0d0
--- /dev/null
+++ b/src/main/ui/widgets/QRPanel.java
@@ -0,0 +1,77 @@
+package ui.widgets;
+
+import com.google.zxing.BarcodeFormat;
+import com.google.zxing.WriterException;
+import com.google.zxing.common.BitMatrix;
+import com.google.zxing.qrcode.QRCodeWriter;
+
+import javax.swing.*;
+import java.awt.*;
+import java.util.Collections;
+
+import static com.google.zxing.EncodeHintType.ERROR_CORRECTION;
+import static com.google.zxing.qrcode.decoder.ErrorCorrectionLevel.L;
+
+/**
+ * A fixed-size panel displaying a QR code.
+ */
+public class QRPanel extends JPanel {
+    private final int size;
+
+    private BitMatrix data;
+
+    /**
+     * EFFECTS: Init with the specific rectangular size. Min size = max size = preferred size.
+     */
+    public QRPanel(int size) {
+        super();
+        setSize(new Dimension(size, size));
+        setMaximumSize(new Dimension(size, size));
+        setMinimumSize(new Dimension(size, size));
+        setPreferredSize(new Dimension(size, size));
+        this.size = size;
+    }
+
+    /**
+     * EFFECTS: Draw the QR code. Leave white if no data is set.
+     * MODIFIES: this
+     */
+    @Override
+    protected void paintComponent(Graphics graphics) {
+        super.paintComponent(graphics);
+        graphics.setColor(Color.WHITE);
+        graphics.fillRect(0, 0, size, size);
+
+        if (data == null) {
+            return;
+        }
+
+        graphics.setColor(Color.BLACK);
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                if (data.get(i, j)) {
+                    graphics.fillRect(i, j, 1, 1);
+                }
+            }
+        }
+    }
+
+    /**
+     * EFFECTS: Set data and repaint. Nullable.
+     * MODIFIES: this
+     */
+    public void setData(String data) {
+        if (data == null) {
+            this.data = null;
+            invalidate();
+            return;
+        }
+        try {
+            this.data = new QRCodeWriter().encode(data, BarcodeFormat.QR_CODE, size, size,
+                    Collections.singletonMap(ERROR_CORRECTION, L));
+        } catch (WriterException e) {
+            e.printStackTrace();
+        }
+        invalidate();
+    }
+}