Integrating Augmented Reality Features in XML Apps

Augmented Reality (AR) is transforming the mobile app landscape by seamlessly blending digital content with the real world. While modern frameworks like ARCore and Sceneform have simplified AR development, many developers still work with traditional XML-based Android apps. Integrating AR features into these apps presents unique challenges but offers significant opportunities to enhance user engagement and utility.

Understanding the Basics of Augmented Reality

Augmented Reality overlays computer-generated images onto the real world as seen through a device’s camera. This technology differs from Virtual Reality (VR), which creates an entirely virtual environment. AR apps use a device’s camera, sensors, and processing power to recognize the environment and place digital objects realistically.

Why Integrate AR in XML-Based Android Apps?

• Enhanced User Experience: Provides immersive and interactive experiences.
• Increased Engagement: Captures users’ attention and encourages prolonged app usage.
• Innovative Functionality: Introduces new features like virtual try-ons, interactive manuals, and enhanced navigation.

Challenges of Integrating AR in XML Apps

• Complexity: AR implementation requires knowledge of computer vision, sensor data processing, and 3D graphics.
• Performance: AR can be resource-intensive, potentially leading to performance issues on older devices.
• Compatibility: Ensuring compatibility with various Android devices and AR platforms.

Step-by-Step Guide to Integrating AR Features

Step 1: Set Up Your Development Environment

Before diving into AR development, set up your development environment with Android Studio and ensure that the Android SDK is up-to-date.

Step 2: Add ARCore Dependency

ARCore is Google’s platform for building AR experiences. To use ARCore, add the necessary dependency to your app’s build.gradle file:

dependencies {
    implementation "com.google.ar:core:1.40.0"  // Use the latest version
}

Step 3: Declare AR Permissions and Features in AndroidManifest.xml

Declare the necessary permissions and features in your app’s AndroidManifest.xml file to enable ARCore:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="your.package.name">

    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-feature android:name="android.hardware.camera.ar" android:required="true"/>

    <application
        ...
        <meta-data
            android:name="com.google.ar.core"
            android:value="required" />
    </application>
</manifest>

Explanation:

• <uses-permission android:name="android.permission.CAMERA"/>: Grants the app access to the device’s camera.
• <uses-feature android:name="android.hardware.camera.ar" android:required="true"/>: Indicates that the app requires AR capabilities. If the device doesn’t support AR, the app won’t be available in the Google Play Store.
• <meta-data android:name="com.google.ar.core" android:value="required" />: Installs ARCore on the device when the app is installed if it’s not already present.

Step 4: Create an AR Activity

Create a new Activity that handles the AR logic. This Activity will display the camera feed and overlay the AR elements. Here’s an example using Java:

package your.package.name;

import android.os.Bundle;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.google.ar.core.ArCoreApk;
import com.google.ar.core.Session;
import com.google.ar.core.Config;
import com.google.ar.core.exceptions.UnavailableException;
import android.opengl.GLSurfaceView;
import android.util.Log;

public class ARActivity extends AppCompatActivity {

    private GLSurfaceView surfaceView;
    private Session arSession;
    private boolean installRequested;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ar);

        surfaceView = findViewById(R.id.surfaceView);
        installRequested = false;

        // Check AR availability and install if needed
        checkARAvailability();
    }

    private void checkARAvailability() {
        ArCoreApk.Availability availability = ArCoreApk.getInstance().checkAvailability(this);
        if (availability.isTransient()) {
            // Re-query at 5Hz while being transient.
            new android.os.Handler().postDelayed(() -> {
                checkARAvailability();
            }, 200);
        }

        if (availability.isSupported()) {
            // AR is supported, proceed to create session
            createARSession();
        } else {
            // AR is not supported, handle accordingly
            Toast.makeText(this, "ARCore not supported on this device", Toast.LENGTH_LONG).show();
            finish();
        }
    }

    private void createARSession() {
        try {
            // Create a new AR session
            arSession = new Session(this);

            // Configure the session
            Config config = new Config(arSession);
            config.setUpdateMode(Config.UpdateMode.LATEST_CAMERA_IMAGE);
            arSession.configure(config);

            // Set up the OpenGL surface view
            surfaceView.setPreserveEGLContextOnPause(true);
            surfaceView.setEGLContextClientVersion(2);

            // Set the renderer
            surfaceView.setRenderer(new ARRenderer(this, arSession));
            surfaceView.setRenderMode(GLSurfaceView.RENDERMODE_CONTINUOUSLY);

        } catch (UnavailableException e) {
            handleARException(e);
        } catch (Exception e) {
            Log.e("ARActivity", "Failed to create AR session", e);
        }
    }

    private void handleARException(UnavailableException e) {
        String message = "Please install ARCore to run this application";
        Log.e("ARActivity", "ARCore error", e);
        switch (e.reason) {
            case INSTALL_REQUESTED:
                installRequested = true;
                try {
                    ArCoreApk.getInstance().requestInstall(this, !installRequested);
                } catch (UnavailableException ex) {
                    ex.printStackTrace();
                }
                return;
            case UNSUPPORTED_DEVICE_CONFIGURATION:
                message = "This device does not support ARCore.";
                break;
            case ANDROID_VERSION_UNSUPPORTED:
                message = "This version of Android is not supported for AR.";
                break;
            case DEVICE_NOT_CAPABLE:
                message = "This device is not ARCore capable.";
                break;
            case UNKNOWN_ERROR:
                message = "Failed to create AR session.";
                break;
        }
        Toast.makeText(this, message, Toast.LENGTH_LONG).show();
        finish();
    }

    @Override
    protected void onResume() {
        super.onResume();
        
        if (arSession == null) {
             checkARAvailability();
             return;
        }
        
        try {
            arSession.resume();
            surfaceView.onResume();
        } catch (Exception e) {
            Log.e("ARActivity", "Session resume failed", e);
            Toast.makeText(this, "Failed to resume AR session", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        if (arSession != null) {
            surfaceView.onPause();
            arSession.pause();
        }
    }
}

Explanation:

• GLSurfaceView: Used to render OpenGL graphics, which is essential for displaying AR elements.
• Session: Represents an ARCore session, managing the AR state.
• Config: Configuration settings for the AR session, such as the update mode.
• checkARAvailability(): Checks if ARCore is available and supported on the device. If not, it prompts the user to install it.
• createARSession(): Creates and configures the AR session, setting up the OpenGL surface view and renderer.
• handleARException(): Handles various exceptions that may occur during ARCore initialization, providing user-friendly messages.
• onResume() and onPause(): Lifecycle methods to properly manage the AR session and surface view when the activity is resumed or paused.

Step 5: Create the Layout for AR Activity

Create a simple layout file named `activity_ar.xml` with a `GLSurfaceView` in your `res/layout` directory:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.opengl.GLSurfaceView
        android:id="@+id/surfaceView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</RelativeLayout>

Step 6: Implement the AR Renderer

The ARRenderer class is responsible for rendering the AR scene. Create a new class named ARRenderer:

package your.package.name;

import android.content.Context;
import android.opengl.GLES20;
import android.opengl.GLSurfaceView;

import com.google.ar.core.Frame;
import com.google.ar.core.Session;
import com.google.ar.core.Camera;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

public class ARRenderer implements GLSurfaceView.Renderer {

    private final Context context;
    private final Session arSession;
    private final BackgroundRenderer backgroundRenderer = new BackgroundRenderer();

    public ARRenderer(Context context, Session session) {
        this.context = context;
        this.arSession = session;
    }

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        GLES20.glClearColor(0.1f, 0.1f, 0.1f, 1.0f);

        // Prepare the rendering objects. This involves reading shaders, so may throw an IOException.
        try {
            // Create the texture and pass it to ARCore session to be filled during update.
            backgroundRenderer.createOnGlThread(context);
            arSession.setCameraTextureName(backgroundRenderer.getTextureId());
        } catch (Exception e) {
            Log.e("ARRenderer", "Failed to initialize renderer", e);
        }
    }

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        GLES20.glViewport(0, 0, width, height);
        backgroundRenderer.onDisplayChanged(width, height);
    }

    @Override
    public void onDrawFrame(GL10 gl) {
        // Clear screen to notify driver it should not load any pixels from previous frame.
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);

        if (arSession == null) {
            return;
        }
        // Notify ARCore session that the view size changed so that the perspective matrix and
        // the video display rotation can be updated.
        
        try {
             // Update session to grab the latest frame data
            arSession.update();
            Frame frame = arSession.getCurrentFrame();

            // If frame is ready, render camera preview image to the GL surface.
            backgroundRenderer.draw(frame);

        } catch (Throwable t) {
            // Avoid crashing the application due to unhandled exceptions.
            Log.e("ARRenderer", "Exception on the OpenGL thread", t);
        }

    }
}

Explanation:

• Context and Session: The context and ARCore session are passed to the renderer for access to resources and AR functionality.
• BackgroundRenderer: Manages the rendering of the camera feed as the background of the AR scene.
• onSurfaceCreated(): Called when the GLSurfaceView is created. It initializes the background renderer and sets the camera texture name for the ARCore session.
• onSurfaceChanged(): Called when the surface changes (e.g., on rotation). It updates the viewport and background renderer dimensions.
• onDrawFrame(): Called on each frame. It updates the AR session, gets the current frame, and draws the background using the camera feed.

Step 7: Creating BackgroundRenderer
Create the class:

package your.package.name;

import android.content.Context;
import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLES20;
import android.opengl.GLUtils;
import android.util.Log;

import com.google.ar.core.Frame;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

public class BackgroundRenderer {
    private static final String TAG = BackgroundRenderer.class.getSimpleName();

    private static final int COORDS_PER_VERTEX = 3;
    private static final int TEXCOORDS_PER_VERTEX = 2;

    private static final float[] QUAD_COORDS = new float[] {
            //   x,    y,   z
            -1.0f, -1.0f, 0.0f,
            -1.0f, +1.0f, 0.0f,
            +1.0f, -1.0f, 0.0f,
            +1.0f, +1.0f, 0.0f,
    };

    private static final float[] QUAD_TEXCOORDS = new float[] {
            // Texture 0
            0.0f, 1.0f,
            0.0f, 0.0f,
            1.0f, 1.0f,
            1.0f, 0.0f,
    };

    private int quadProgram;
    private int quadPositionParam;
    private int quadTexCoordParam;
    private int textureId = -1;
    private int quadTexUniform;
    private int videoWidth;
    private int videoHeight;

    private FloatBuffer quadCoords;
    private FloatBuffer quadTexCoords;


    public void createOnGlThread(Context context) throws IOException {

        quadProgram = ShaderUtil.loadGLShader(TAG, context, GLES20.GL_VERTEX_SHADER, "shaders/screenquad.vert");
        int fragmentShader = ShaderUtil.loadGLShader(TAG, context, GLES20.GL_FRAGMENT_SHADER, "shaders/screenquad.frag");

        quadProgram = GLES20.glCreateProgram();
        GLES20.glAttachShader(quadProgram, quadProgram);
        GLES20.glAttachShader(quadProgram, fragmentShader);
        GLES20.glLinkProgram(quadProgram);
        GLES20.glUseProgram(quadProgram);

        ShaderUtil.checkGLError(TAG, "Program creation");

        quadPositionParam = GLES20.glGetAttribLocation(quadProgram, "a_Position");
        quadTexCoordParam = GLES20.glGetAttribLocation(quadProgram, "a_TexCoord");
        quadTexUniform = GLES20.glGetUniformLocation(quadProgram, "u_Texture");

        ShaderUtil.checkGLError(TAG, "Program parameters");

        // Texture id
        int[] textures = new int[1];
        GLES20.glGenTextures(1, textures, 0);
        textureId = textures[0];
        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, GLES20.GL_CLAMP_TO_EDGE);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, GLES20.GL_CLAMP_TO_EDGE);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR);
        GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR);

        ShaderUtil.checkGLError(TAG, "Texture loading");

        ByteBuffer bbTexCoords = ByteBuffer.allocateDirect(QUAD_TEXCOORDS.length * 4);
        bbTexCoords.order(ByteOrder.nativeOrder());
        quadTexCoords = bbTexCoords.asFloatBuffer();
        quadTexCoords.put(QUAD_TEXCOORDS);
        quadTexCoords.position(0);

        ByteBuffer bbCoords = ByteBuffer.allocateDirect(QUAD_COORDS.length * 4);
        bbCoords.order(ByteOrder.nativeOrder());
        quadCoords = bbCoords.asFloatBuffer();
        quadCoords.put(QUAD_COORDS);
        quadCoords.position(0);
    }
    

    public int getTextureId() {
        return textureId;
    }

    /**
     *  Calculates the inverse matrix of frame.get pose and passes it to the shader.
     *
     * @param frame The last AR frame
     */
    public void draw(Frame frame) {
        if (textureId == -1) {
            return;
        }

        // Ensure that video texture is displayed full screen
        videoWidth = frame.getCamera().getImageIntrinsics().getImageDimensions()[0];
        videoHeight = frame.getCamera().getImageIntrinsics().getImageDimensions()[1];

        GLES20.glDisable(GLES20.GL_DEPTH_TEST);
        GLES20.glDepthMask(false);

        GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId);

        GLES20.glUseProgram(quadProgram);

        // Set the vertex positions.
        GLES20.glVertexAttribPointer(quadPositionParam, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, 0, quadCoords);

        // Set the texture coordinates.
        GLES20.glVertexAttribPointer(quadTexCoordParam, TEXCOORDS_PER_VERTEX, GLES20.GL_FLOAT, false, 0, quadTexCoords);

        // Enable vertex arrays
        GLES20.glEnableVertexAttribArray(quadPositionParam);
        GLES20.glEnableVertexAttribArray(quadTexCoordParam);

        GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
        GLES20.glUniform1i(quadTexUniform, 0);

        GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

        // Disable vertex arrays
        GLES20.glDisableVertexAttribArray(quadPositionParam);
        GLES20.glDisableVertexAttribArray(quadTexCoordParam);

        GLES20.glDepthMask(true);
        GLES20.glEnable(GLES20.GL_DEPTH_TEST);
    }

    /**
     * Allocates and initializes GL resources needed for rendering the background.
     */
    public void onDisplayChanged(int width, int height) {
        GLES20.glViewport(0, 0, width, height);
    }
}

Then, creating a helper class ShderUtil.java for loading shader GL:

package your.package.name;

import android.content.Context;
import android.opengl.GLES20;
import android.util.Log;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class ShaderUtil {
    private static final String TAG = "ShaderUtil";

    /**
     * Loads a GL shader from the raw resource.
     *
     * @param tag               The tag to use for logging.
     * @param context           The context to use for accessing the resource.
     * @param shaderType        The type of shader to load (GLES20.GL_VERTEX_SHADER or
     *                          GLES20.GL_FRAGMENT_SHADER).
     * @param resourceId The resource ID of the raw resource to load the shader from.
     * @return The shader program.
     */
    public static int loadGLShader(String tag, Context context, int shaderType, String filename) throws IOException {
        String shaderCode = readShaderFileFromAssets(context, filename);
        int shader = GLES20.glCreateShader(shaderType);
        GLES20.glShaderSource(shader, shaderCode);
        GLES20.glCompileShader(shader);
        final int[] compileStatus = new int[1];
        GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
        if (compileStatus[0] == 0) {
            Log.e(tag, "Error compiling shader: " + GLES20.glGetShaderInfoLog(shader));
            GLES20.glDeleteShader(shader);
            shader = 0;
        }
        if (shader == 0) {
            throw new RuntimeException("Error creating shader.");
        }
        return shader;
    }

    /**
     * Checks if any GL error occurred.
     *
     * @param tag Used for logging the error.
     */
    public static void checkGLError(String tag, String label) {
        while (GLES20.glGetError() != GLES20.GL_NO_ERROR) {
            Log.e(tag, label + ": glError " + GLES20.glGetError());
            throw new RuntimeException(label + ": glError " + GLES20.glGetError());
        }
    }
    private static String readShaderFileFromAssets(Context context, String filename) throws IOException {
        StringBuilder shaderCode = new StringBuilder();
        try (InputStream inputStream = context.getAssets().open(filename);
             BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream))) {
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                shaderCode.append(line).append("\n");
            }
        } catch (IOException e) {
            Log.e(TAG, "Could not read shader file from assets: " + filename);
            throw e;
        }
        return shaderCode.toString();
    }
}

Add two shaders under the `assets/shaders` with name` screenquad.vert`:

attribute vec4 a_Position;
attribute vec2 a_TexCoord;
varying vec2 v_TexCoord;
void main() {
  v_TexCoord = a_TexCoord;
  gl_Position = a_Position;
}

and` screenquad.frag`:

precision mediump float;
varying vec2 v_TexCoord;
uniform sampler2D u_Texture;
void main() {
  gl_FragColor = texture2D(u_Texture, v_TexCoord);
}

Step 8: Run Your AR App

Connect your Android device to your development machine and run the app. Ensure that the device has ARCore installed. If ARCore is not installed, the app will prompt you to install it.

Advanced AR Features

After setting up a basic AR app, you can integrate more advanced features:

Object Placement and Interaction

Enable users to place 3D objects in the real world and interact with them using touch gestures. This requires implementing hit testing to determine the intersection point of a touch event with real-world surfaces.

// Example code snippet for hit testing
Frame frame = arSession.getCurrentFrame();
MotionEvent tap = ... // User tap event

List<HitResult> results = frame.hitTest(tap);
for (HitResult hit : results) {
    Trackable trackable = hit.getTrackable();
    if (trackable instanceof Plane &&
        ((Plane) trackable).isPoseInPolygon(hit.getHitPose())) {
        // Place your 3D object here
        break;
    }
}

Image Recognition and Tracking

Implement image recognition to detect specific images in the real world and overlay them with AR content. This can be used to create interactive print media or enhance brand experiences.

// Example code snippet for image recognition
AugmentedImageDatabase imageDatabase = new AugmentedImageDatabase(arSession);
Bitmap bitmap = ... // Your image bitmap

imageDatabase.addImage("your_image_name", bitmap);
Config config = arSession.getConfig();
config.setAugmentedImageDatabase(imageDatabase);
arSession.configure(config);

Conclusion

Integrating AR features into XML-based Android apps enhances user experiences and opens new avenues for innovation. While the integration process may seem complex, breaking it down into manageable steps simplifies the development. By using ARCore, developers can create immersive and interactive AR apps that push the boundaries of mobile technology. Embracing AR can provide a competitive edge and enrich the way users interact with their devices.