Chrobalt Java Bridge

b/372558900

cobalt/android/BUILD.gn

@@ -56,6 +56,9 @@ android_library("cobalt_apk_java") {
     "apk/app/src/main/java/dev/cobalt/coat/CaptionSettings.java",
     "apk/app/src/main/java/dev/cobalt/coat/CobaltActivity.java",
     "apk/app/src/main/java/dev/cobalt/coat/CobaltHttpHelper.java",
+    "apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptAndroidObject.java",
+    "apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptAndroidObjectExample.java",
+    "apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptInterface.java",
 
     # "apk/app/src/main/java/dev/cobalt/coat/CobaltMediaSession.java",
     "apk/app/src/main/java/dev/cobalt/coat/CobaltService.java",
@@ -92,6 +95,7 @@ android_library("cobalt_apk_java") {
 
     # "apk/app/src/main/java/dev/cobalt/storage/CobaltStorageLoader.java",
     # "apk/app/src/main/java/dev/cobalt/storage/StorageProto.java",
+    "apk/app/src/main/java/dev/cobalt/util/AssetLoader.java",
     "apk/app/src/main/java/dev/cobalt/util/DisplayUtil.java",
     "apk/app/src/main/java/dev/cobalt/util/Holder.java",
     "apk/app/src/main/java/dev/cobalt/util/IsEmulator.java",
@@ -105,6 +109,7 @@ android_library("cobalt_apk_java") {
 android_assets("cobalt_apk_assets") {
   testonly = true
   sources = [
+    "apk/app/src/app/assets/example.js",
     "apk/app/src/app/assets/not_empty.txt",
     "apk/app/src/app/assets/test/not_empty.txt",
     "apk/app/src/app/assets/web/cobalt_blue_splash_screen.css",

cobalt/android/apk/app/src/app/assets/example.js

@@ -0,0 +1 @@
+AndroidExample.testJavaScriptMethod();

cobalt/android/apk/app/src/main/java/dev/cobalt/coat/CobaltActivity.java

@@ -23,13 +23,19 @@
 import android.media.AudioManager;
 import android.net.Uri;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
 import android.util.Pair;
 import android.view.View;
 import android.view.ViewGroup.LayoutParams;
 import android.view.ViewParent;
 import android.widget.FrameLayout;
+import dev.cobalt.coat.javabridge.CobaltJavaScriptAndroidObject;
+import dev.cobalt.coat.javabridge.CobaltJavaScriptAndroidObjectExample;
+import dev.cobalt.coat.javabridge.CobaltJavaScriptInterface;
 import dev.cobalt.media.MediaCodecCapabilitiesLogger;
 import dev.cobalt.media.VideoSurfaceView;
+import dev.cobalt.util.AssetLoader;
 import dev.cobalt.util.DisplayUtil;
 import dev.cobalt.util.Log;
 import dev.cobalt.util.UsedByNative;
@@ -38,7 +44,10 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.regex.Pattern;
+import org.chromium.content_public.browser.JavascriptInjector;
+import org.chromium.content_public.browser.WebContents;
 import org.chromium.content_shell_apk.ContentShellActivity;
+
 // import dev.cobalt.media.AudioOutputManager;
 
 /** Native activity that has the required JNI methods called by the Starboard implementation. */
@@ -66,6 +75,8 @@ public abstract class CobaltActivity extends ContentShellActivity {
 
   private static final Pattern URL_PARAM_PATTERN = Pattern.compile("^[a-zA-Z0-9_=]*$");
 
+  public static final int JAVA_BRIDGE_INITIALIZATION_DELAY_MILLI_SECONDS = 100;
+
   private VideoSurfaceView videoSurfaceView;
 
   private boolean forceCreateNewVideoSurfaceView = false;
@@ -105,6 +116,55 @@ protected void onCreate(Bundle savedInstanceState) {
     videoSurfaceView = new VideoSurfaceView(this);
     addContentView(
         videoSurfaceView, new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
+
+    initializeJavaBridge();
+  }
+
+  /**
+   * Initializes the Java Bridge to allow communication between Java and JavaScript.
+   * This method injects Java objects into the WebView and loads corresponding JavaScript code.
+   */
+  private void initializeJavaBridge() {
+
+    WebContents webContents = getActiveWebContents();
+    if (webContents == null) {
+        // WebContents not initialized yet, post a delayed runnable to check again
+        new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
+            @Override
+            public void run() {
+                initializeJavaBridge(); // Recursive call to check again
+            }
+        }, JAVA_BRIDGE_INITIALIZATION_DELAY_MILLI_SECONDS);
+        return;
+    }
+
+    // --- Initialize the Java Bridge ---
+
+    // 1. Gather all Java objects that need to be exposed to JavaScript.
+    List<CobaltJavaScriptAndroidObject> javaScriptAndroidObjectList = new ArrayList<>();
+    javaScriptAndroidObjectList.add(new CobaltJavaScriptAndroidObjectExample());
+
+    // 2. Use JavascriptInjector to inject Java objects into the WebView.
+    //    This makes the annotated methods in these objects accessible from JavaScript.
+    JavascriptInjector javascriptInjector = JavascriptInjector.fromWebContents(webContents, false);
+    if (javascriptInjector == null) {
+      Log.w(TAG, "javascriptInjector is null, failed to init Java Bridge.");
+      return;
+    }
+
+    javascriptInjector.setAllowInspection(true);
+    for (CobaltJavaScriptAndroidObject javascriptAndroidObject : javaScriptAndroidObjectList) {
+      javascriptInjector.addPossiblyUnsafeInterface(javascriptAndroidObject, javascriptAndroidObject.getJavaScriptInterfaceName(), CobaltJavaScriptInterface.class);
+    }
+
+    // 3. Load and evaluate JavaScript code that interacts with the injected Java objects.
+    for (CobaltJavaScriptAndroidObject javaScriptAndroidObject : javaScriptAndroidObjectList) {
+      String jsFileName = javaScriptAndroidObject.getJavaScriptAssetName();
+      if (jsFileName != null) {
+        String jsCode = AssetLoader.loadJavaScriptFromAssets(this, jsFileName);
+        webContents.evaluateJavaScript(jsCode, null);
+      }
+    }
   }
 
   /**

cobalt/android/apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptAndroidObject.java

@@ -0,0 +1,25 @@
+package dev.cobalt.coat.javabridge;
+
+import androidx.annotation.Nullable;
+
+/**
+ * Interface for Android objects that are exposed to JavaScript.
+ */
+public interface CobaltJavaScriptAndroidObject {
+
+    /**
+     * Gets the name used to expose this object to JavaScript.
+     * This name is used in the `addJavascriptInterface` method of the WebView.
+     *
+     * @return The JavaScript interface name.
+     */
+    public String getJavaScriptInterfaceName();
+
+    /**
+     * Gets the name of the JavaScript asset file that uses this interface.
+     * This allows the JavaScript code to be loaded and interact with this object.
+     *
+     * @return The name of the JavaScript asset file, or null if not applicable.
+     */
+    public @Nullable String getJavaScriptAssetName();
+}

cobalt/android/apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptAndroidObjectExample.java

@@ -0,0 +1,26 @@
+package dev.cobalt.coat.javabridge;
+
+import static dev.cobalt.util.Log.TAG;
+
+import android.util.Log;
+
+/**
+ * A simple example of implement CobaltJavaScriptAndroidObject.
+ */
+public class CobaltJavaScriptAndroidObjectExample implements CobaltJavaScriptAndroidObject {
+
+    @Override
+    public String getJavaScriptInterfaceName() {
+        return "AndroidExample";
+    }
+
+    @Override
+    public String getJavaScriptAssetName() {
+        return "example.js";
+    }
+
+    @CobaltJavaScriptInterface
+    public void testJavaScriptMethod() {
+        Log.w(TAG, "Hello world");
+    }
+}

cobalt/android/apk/app/src/main/java/dev/cobalt/coat/javabridge/CobaltJavaScriptInterface.java

@@ -0,0 +1,17 @@
+package dev.cobalt.coat.javabridge;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation that allows exposing methods to JavaScript. Starting from API level
+ * {@link android.os.Build.VERSION_CODES#JELLY_BEAN_MR1} and above, methods explicitly
+ * marked with this annotation are available to the Javascript code.
+ */
+@SuppressWarnings("javadoc")
+@Retention(RetentionPolicy.RUNTIME)
+@Target({ElementType.METHOD})
+public @interface CobaltJavaScriptInterface {
+}

cobalt/android/apk/app/src/main/java/dev/cobalt/util/AssetLoader.java

@@ -0,0 +1,29 @@
+package dev.cobalt.util;
+
+import static dev.cobalt.util.Log.TAG;
+
+import android.content.Context;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+import java.io.IOException;
+
+/** Utility functions for read asset. */
+public class AssetLoader {
+
+    private AssetLoader() {}
+
+    public static String loadJavaScriptFromAssets(Context context, String filename) {
+        try {
+            InputStream is = context.getAssets().open(filename);
+            int size = is.available();
+            byte[] buffer = new byte[size];
+            is.read(buffer);
+            is.close();
+            return new String(buffer, StandardCharsets.UTF_8);
+        } catch (IOException ex) {
+            String error = "asset " + filename + " failed to load";
+            Log.e(TAG, error);
+            return String.format("console.error('%s');", error);
+        }
+    }
+}

content/app/content_main_runner_impl.cc

@@ -675,6 +675,8 @@ int NO_STACK_PROTECTOR RunZygote(ContentMainDelegate* delegate) {
       return kMainFunctions[i].function(std::move(main_params));
   }
 
+  content::RenderFrameHost::AllowInjectingJavaScript();
+
   auto exit_code = delegate->RunProcess(process_type, std::move(main_params));
   DCHECK(absl::holds_alternative<int>(exit_code));
   DCHECK_GE(absl::get<int>(exit_code), 0);