[wpeview] Track the current Java VM and Activity instances

Add WPEApplication, a subclass of android.app.Application which
registers a WKActivityObserver to track activity lifecycle. For now the
observer only tracks the last started android.app.Activity and forwards
it to its native handleActivity{Started,Stopped}() methods.

The current VM instance and Activity are exposed to native code through
the following functions, which have C linkage and are publicly exposed
by libWPEAndroidCommon:

  JavaVM* wpe_android_runtime_get_current_java_vm()
  jobject wpe_android_runtime_get_current_activity()

The intention is that WebKit will use dlsym() to resolve those, thus
avoiding a circular dependency at build time.

Due to WPEApplication being instantiated much earlier than other classes
with native methods, it must take care itself of issuing the needed
System.loadLibrary() calls. Moreover, application services also get to
use the same application class declared in the manifest, which means
WPEApplication must now handle loading the native libraries needed by
services as well. Fortunately, the static Application.getProcessName()
method may be used to determine in which kind of process we are, and
act accordingly.

Author: aperezdc

README.md

@@ -40,6 +40,9 @@ override fun onCreate(savedInstanceState: Bundle?) {
 }
 ```
 
+Note that applications that want to subclass `android.app.Application`
+*must* use `org.wpewebkit.WPEApplication` as their base class instead.
+
 To see WPEView in action check the [tools](tools) folder.
 
 ## Setting up your environment

wpeview/src/main/AndroidManifest.xml

@@ -3,7 +3,7 @@
 
     <uses-permission android:name="android.permission.INTERNET" />
 
-    <application android:extractNativeLibs="true">
+    <application android:name=".WPEApplication" android:extractNativeLibs="true">
         <!-- Do not remove this section. Service definition is generated at build time -->
         <!-- SERVICES PLACEHOLDER -->
     </application>

wpeview/src/main/cpp/Common/Init.cpp

@@ -46,9 +46,45 @@ static void initializeWKVersions()
     Logging::logVerbose("WKRuntime::Init: WPE WebKit %s, GStreamer %s", webkitVersion, gstVersion);
 }
 
+DECLARE_JNI_CLASS_SIGNATURE(JNIActivity, "android/app/Activity");
+
+static jobject s_currentActivity {nullptr};
+
+extern "C" __attribute__((visibility("default"))) jobject wpe_android_runtime_get_current_activity()
+{
+    Logging::logDebug("wpe_android_runtime_get_current_activity -> %p", s_currentActivity);
+    return s_currentActivity;
+}
+
+static void initializeWKActivityObserver()
+{
+    auto klass = JNI::Class("org/wpewebkit/wpe/WKActivityObserver");
+    if (!klass) {
+        Logging::logDebug("Init::initializeWKActivityObserver: No observer class, skipping.");
+        return;
+    }
+
+    klass.registerNativeMethods(JNI::StaticNativeMethod<void(JNIActivity)>(
+                                    "handleActivityStarted",
+                                    +[](JNIEnv*, jclass, JNIActivity activity) {
+                                        Logging::logDebug(
+                                            "WKActivityObserver::handleActivityStarted(%p) current=%p [tid %d]",
+                                            activity, s_currentActivity, gettid());
+                                        s_currentActivity = activity;
+                                    }),
+        JNI::StaticNativeMethod<void(JNIActivity)>(
+            "handleActivityStopped", +[](JNIEnv*, jclass, JNIActivity activity) {
+                Logging::logDebug("WKActivityObserver::handleActivityStopped(%p) current=%p [tid %d]", activity,
+                    s_currentActivity, gettid());
+                if (s_currentActivity == activity)
+                    s_currentActivity = nullptr;
+            }));
+}
+
 JNIEnv* Init::initialize(JavaVM* javaVM)
 {
     auto* env = JNI::initVM(javaVM);
     initializeWKVersions();
+    initializeWKActivityObserver();
     return env;
 }

wpeview/src/main/cpp/Common/JNI/JNIEnv.cpp

@@ -32,6 +32,11 @@ pthread_key_t globalJNIEnvKey = 0;
 std::atomic_bool globalEnableJavaExceptionDescription = true;
 // NOLINTEND(cppcoreguidelines-avoid-non-const-global-variables)
 
+extern "C" __attribute__((visibility("default"))) JavaVM* wpe_android_runtime_get_current_java_vm()
+{
+    return globalJavaVM;
+}
+
 void detachTerminatedNativeThread(void* /*keyValue*/)
 {
     if (globalJavaVM != nullptr)

wpeview/src/main/cpp/Runtime/EntryPoint.cpp

@@ -18,6 +18,7 @@
  */
 
 #include "Init.h"
+#include "Logging.h"
 #include "WKCallback.h"
 #include "WKCookieManager.h"
 #include "WKNetworkSession.h"
@@ -42,7 +43,8 @@ extern "C" JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* javaVM, void* /*reserved*/)
         WKSettings::configureJNIMappings();
 
         return JNI::VERSION;
-    } catch (...) {
+    } catch (const std::exception& e) {
+        Logging::logError("Runtime: JNI_OnLoad: %s", e.what());
         return JNI_ERR;
     }
 }

wpeview/src/main/cpp/Service/EntryPoint.cpp

@@ -107,7 +107,8 @@ extern "C" JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* javaVM, void* /*reserved*/)
                 JNI::StaticNativeMethod<void(jlong, jint, jint)>("initializeNativeMain", initializeNativeMain));
 
         return JNI::VERSION;
-    } catch (...) {
+    } catch (const std::exception& e) {
+        Logging::logError("Service: JNI_OnLoad: %s", e.what());
         return JNI_ERR;
     }
 }

wpeview/src/main/java/org/wpewebkit/WPEApplication.java

@@ -0,0 +1,92 @@
+/**
+ * Copyright (C) 2025 Igalia S.L. <[email protected]>
+ *   Author: Adrian Perez de Castro <[email protected]>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+package org.wpewebkit;
+
+import android.app.Activity;
+import android.app.Application;
+import android.os.Bundle;
+import android.util.Log;
+
+public class WPEApplication extends Application {
+    static final String LOGTAG = "WPEApplication";
+
+    private enum ProcessKind {
+        MAIN {
+            @Override
+            public String[] getLibraryNames() {
+                return new String[] {"WPEAndroidRuntime"};
+            }
+        },
+        NETWORK {
+            @Override
+            public String[] getLibraryNames() {
+                return new String[] {"WPEAndroidService"};
+            }
+        },
+        WEBCONTENT {
+            @Override
+            public String[] getLibraryNames() {
+                return new String[] {"gstreamer-1.0", "WPEAndroidService"};
+            }
+        },
+        WEBDRIVER {
+            @Override
+            public String[] getLibraryNames() {
+                return new String[] {"WPEWebDriver", "WPEAndroidService"};
+            }
+        };
+
+        abstract public String[] getLibraryNames();
+    }
+
+    private static final ProcessKind getProcessKind() {
+        String name = getProcessName();
+        int colonPosition = name.indexOf(':');
+        if (colonPosition < 0)
+            return ProcessKind.MAIN;
+
+        name = name.substring(colonPosition + 1).replaceAll("[0-9]", "");
+        switch (name) {
+        case "WPEWebProcess":
+            return ProcessKind.WEBCONTENT;
+        case "WPENetworkProcess":
+            return ProcessKind.NETWORK;
+        case "WPEWebDriverProcess":
+            return ProcessKind.WEBDRIVER;
+        default:
+            throw new IllegalStateException("Cannot derive process kind from '" + getProcessName() + "'");
+        }
+    }
+
+    public static final ProcessKind processKind = getProcessKind();
+
+    static {
+        final String libraries[] = processKind.getLibraryNames();
+        Log.d(LOGTAG, "Process: " + processKind.toString() + " - Libraries: " + String.join(", ", libraries));
+        for (String libraryName : libraries)
+            System.loadLibrary(libraryName);
+    }
+
+    public WPEApplication() {
+        super();
+        if (processKind == ProcessKind.MAIN)
+            registerActivityLifecycleCallbacks(new org.wpewebkit.wpe.WKActivityObserver());
+    }
+}

wpeview/src/main/java/org/wpewebkit/wpe/WKActivityObserver.java

@@ -0,0 +1,71 @@
+/**
+ * Copyright (C) 2025 Igalia S.L. <[email protected]>
+ *   Author: Adrian Perez de Castro <[email protected]>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+package org.wpewebkit.wpe;
+
+import android.app.Activity;
+import android.app.Application;
+import android.os.Bundle;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+
+public class WKActivityObserver implements Application.ActivityLifecycleCallbacks {
+    private static final String LOGTAG = "WKActivityObserver";
+
+    @Override
+    public void onActivityCreated(@NonNull Activity a, @NonNull Bundle b) {
+        Log.d(LOGTAG, "activity created: " + a);
+    }
+
+    @Override
+    public void onActivityStarted(@NonNull Activity a) {
+        Log.d(LOGTAG, "activity started: " + a);
+        handleActivityStarted(a);
+    }
+
+    @Override
+    public void onActivityPaused(@NonNull Activity a) {
+        Log.d(LOGTAG, "activity paused: " + a);
+    }
+
+    @Override
+    public void onActivityResumed(@NonNull Activity a) {
+        Log.d(LOGTAG, "activity resumed: " + a);
+    }
+
+    @Override
+    public void onActivityStopped(@NonNull Activity a) {
+        Log.d(LOGTAG, "activity stopped: " + a);
+        handleActivityStopped(a);
+    }
+
+    @Override
+    public void onActivityDestroyed(@NonNull Activity a) {
+        Log.d(LOGTAG, "activity destroyed: " + a);
+    }
+
+    @Override
+    public void onActivitySaveInstanceState(@NonNull Activity a, @NonNull Bundle b) {
+        Log.d(LOGTAG, "activity save state: " + a);
+    }
+
+    private static native void handleActivityStarted(@NonNull Activity a);
+    private static native void handleActivityStopped(@NonNull Activity a);
+}

wpeview/src/main/java/org/wpewebkit/wpe/WKRuntime.java

@@ -48,8 +48,6 @@
 public final class WKRuntime {
     private static final String LOGTAG = "WKRuntime";
 
-    static { System.loadLibrary("WPEAndroidRuntime"); }
-
     protected static native void startNativeLooper();
     private static native void setupNativeEnvironment(@NonNull String[] envStringsArray);
     private native void nativeInit();

wpeview/src/main/java/org/wpewebkit/wpe/services/NetworkProcessService.java

@@ -36,7 +36,7 @@ public class NetworkProcessService extends WPEService {
     private static final String LOGTAG = "WPENetworkProcess";
 
     @Override
-    protected void loadNativeLibraries() {
+    protected void setupServiceEnvironment() {
         // To debug the sub-process with Android Studio (Java and native code), you must:
         // 1- Uncomment the following instruction to wait for the debugger before loading native code.
         // 2- Force the dual debugger (Java + Native) in Run/Debug configuration (the automatic detection won't work).
@@ -45,11 +45,6 @@ protected void loadNativeLibraries() {
 
         // android.os.Debug.waitForDebugger();
 
-        System.loadLibrary("WPEAndroidService");
-    }
-
-    @Override
-    protected void setupServiceEnvironment() {
         final String assetsVersion = WKVersions.versionedAssets("network_process");
         Context context = getApplicationContext();
         if (ServiceUtils.needAssets(context, assetsVersion)) {