feat: Add QR code generation to Receiver UI for instant mobile pairing

app/build.gradle

@@ -32,6 +32,7 @@ dependencies {
     implementation 'androidx.appcompat:appcompat:1.3.1'
     implementation 'androidx.core:core:1.6.0'
     implementation 'org.java-websocket:Java-WebSocket:1.5.4'
+    implementation 'com.google.zxing:core:3.3.3'
 
     testImplementation 'junit:junit:4.13.2'
 }

app/src/main/java/com/m5dev/librecast/MainActivity.java

@@ -6,6 +6,7 @@
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.ServiceConnection;
+import android.graphics.Bitmap;
 import android.media.MediaFormat;
 import android.os.Bundle;
 import android.os.IBinder;
@@ -14,6 +15,7 @@
 import android.view.SurfaceView;
 import android.view.View;
 import android.view.WindowManager;
+import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 import androidx.appcompat.app.AppCompatActivity;
@@ -26,6 +28,7 @@ public class MainActivity extends AppCompatActivity implements SurfaceHolder.Cal
 
     private SurfaceView surfaceView;
     private LinearLayout layoutStatus;
+    private ImageView imageQrCode;
     private TextView textServerStatus;
     private TextView textConnectionStatus;
 
@@ -75,6 +78,7 @@ protected void onCreate(Bundle savedInstanceState) {
 
         surfaceView = findViewById(R.id.surface_view);
         layoutStatus = findViewById(R.id.layout_status);
+        imageQrCode = findViewById(R.id.image_qr_code);
         textServerStatus = findViewById(R.id.text_server_status);
         textConnectionStatus = findViewById(R.id.text_connection_status);
 
@@ -138,8 +142,20 @@ private void updateUI(Intent intent) {
                 serverIp = NetworkUtils.getLocalIpAddress(this);
             }
             textServerStatus.setText(getString(R.string.server_ready_format, serverIp, serverPort));
+
+            if (serverIp != null && !serverIp.isEmpty() && !"0.0.0.0".equals(serverIp)) {
+                String wsUri = "ws://" + serverIp + ":" + serverPort;
+                Bitmap qrBitmap = QRCodeUtils.generateQRCode(wsUri, 250, 250);
+                if (qrBitmap != null && imageQrCode != null) {
+                    imageQrCode.setImageBitmap(qrBitmap);
+                    imageQrCode.setVisibility(View.VISIBLE);
+                }
+            }
         } else {
             textServerStatus.setText(getString(R.string.server_stopped));
+            if (imageQrCode != null) {
+                imageQrCode.setVisibility(View.GONE);
+            }
         }
 
         if (isClientConnected) {

app/src/main/java/com/m5dev/librecast/QRCodeUtils.java

@@ -0,0 +1,60 @@
+package com.m5dev.librecast;
+
+import android.graphics.Bitmap;
+import android.util.Log;
+
+import com.google.zxing.BarcodeFormat;
+import com.google.zxing.EncodeHintType;
+import com.google.zxing.WriterException;
+import com.google.zxing.common.BitMatrix;
+import com.google.zxing.qrcode.QRCodeWriter;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class QRCodeUtils {
+
+    private static final String TAG = "QRCodeUtils";
+
+    /**
+     * Generates an Android Bitmap containing a QR code for the specified text.
+     *
+     * @param text   The content string to encode in the QR code (e.g. "ws://192.168.1.100:8080")
+     * @param width  Desired bitmap width in pixels
+     * @param height Desired bitmap height in pixels
+     * @return Bitmap containing the QR code, or null if generation fails or input is empty.
+     */
+    public static Bitmap generateQRCode(String text, int width, int height) {
+        if (text == null || text.trim().isEmpty() || width <= 0 || height <= 0) {
+            return null;
+        }
+
+        try {
+            QRCodeWriter writer = new QRCodeWriter();
+            Map<EncodeHintType, Object> hints = new HashMap<>();
+            hints.put(EncodeHintType.MARGIN, 1);
+
+            BitMatrix bitMatrix = writer.encode(text, BarcodeFormat.QR_CODE, width, height, hints);
+            int matrixWidth = bitMatrix.getWidth();
+            int matrixHeight = bitMatrix.getHeight();
+
+            int[] pixels = new int[matrixWidth * matrixHeight];
+            for (int y = 0; y < matrixHeight; y++) {
+                int offset = y * matrixWidth;
+                for (int x = 0; x < matrixWidth; x++) {
+                    pixels[offset + x] = bitMatrix.get(x, y) ? 0xFF000000 : 0xFFFFFFFF;
+                }
+            }
+
+            Bitmap bitmap = Bitmap.createBitmap(matrixWidth, matrixHeight, Bitmap.Config.ARGB_8888);
+            bitmap.setPixels(pixels, 0, matrixWidth, 0, 0, matrixWidth, matrixHeight);
+            return bitmap;
+        } catch (WriterException e) {
+            Log.e(TAG, "Failed to encode QR code", e);
+            return null;
+        } catch (Exception e) {
+            Log.e(TAG, "Unexpected error generating QR code", e);
+            return null;
+        }
+    }
+}

app/src/main/res/layout/activity_main.xml

@@ -27,6 +27,14 @@
             android:textSize="36sp"
             android:textStyle="bold" />
 
+        <ImageView
+            android:id="@+id/image_qr_code"
+            android:layout_width="250dp"
+            android:layout_height="250dp"
+            android:layout_marginTop="20dp"
+            android:contentDescription="QR Code"
+            android:visibility="gone" />
+
         <TextView
             android:id="@+id/text_server_status"
             android:layout_width="wrap_content"

app/src/test/java/com/m5dev/librecast/QRCodeUtilsTest.java

@@ -0,0 +1,41 @@
+package com.m5dev.librecast;
+
+import com.google.zxing.BarcodeFormat;
+import com.google.zxing.EncodeHintType;
+import com.google.zxing.common.BitMatrix;
+import com.google.zxing.qrcode.QRCodeWriter;
+
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+public class QRCodeUtilsTest {
+
+    @Test
+    public void testQRCodeBitMatrixEncoding() throws Exception {
+        String testUrl = "ws://192.168.1.100:8080";
+        QRCodeWriter writer = new QRCodeWriter();
+        Map<EncodeHintType, Object> hints = new HashMap<>();
+        hints.put(EncodeHintType.MARGIN, 1);
+
+        BitMatrix bitMatrix = writer.encode(testUrl, BarcodeFormat.QR_CODE, 250, 250, hints);
+        assertNotNull("BitMatrix should not be null", bitMatrix);
+        assertTrue("Width should be positive", bitMatrix.getWidth() > 0);
+        assertTrue("Height should be positive", bitMatrix.getHeight() > 0);
+    }
+
+    @Test
+    public void testQRCodeUtilsNullOrEmptyHandling() {
+        assertNull("Null text should return null", QRCodeUtils.generateQRCode(null, 250, 250));
+        assertNull("Empty text should return null", QRCodeUtils.generateQRCode("", 250, 250));
+        assertNull("Whitespace text should return null", QRCodeUtils.generateQRCode("   ", 250, 250));
+        assertNull("Invalid width should return null", QRCodeUtils.generateQRCode("ws://192.168.1.1:8080", 0, 250));
+        assertNull("Invalid height should return null", QRCodeUtils.generateQRCode("ws://192.168.1.1:8080", 250, -1));
+    }
+}