Android: Implement accessibility backend interface

This will provide the JNI API used by QtAndroidAccessibility namespace
via QtAndroid namespace.

Removed unnecessary functions like createAccessibilityDelegate from
QtEmbeddedDelegate, moved the interface extension to where it is
actually supported: QtActivityDelegate.

Until now, QtActivityDelegateBase has called the QtEmbeddedDelegate
implementation on createAccessibilityDelegate() in order to create a
QtAccessibilityDelegate - which has not actually created the delegate -
and then done a null check before trying to call the - always null -
QtAccessibilityDelegate member.

The embedding and service-embedding usecases are now dealt with via the
interface validity checks on the C++ side, until an actual
implementation for those is completed.

Task-number: QTBUG-118874
Change-Id: Iea3db0e17ae80c0443e9027bdfe36bba311eed2b
Reviewed-by: Tinja Paavoseppä <tinja.paavoseppa@qt.io>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

src/android/jar/CMakeLists.txt

@@ -42,6 +42,7 @@ set(java_sources
     src/org/qtproject/qt/android/QtServiceEmbeddedDelegate.java
     src/org/qtproject/qt/android/BackendRegister.java
     src/org/qtproject/qt/android/QtWindowInterface.java
+    src/org/qtproject/qt/android/QtAccessibilityInterface.java
 )
 
 qt_internal_add_jar(Qt${QtBase_VERSION_MAJOR}Android

src/android/jar/src/org/qtproject/qt/android/QtAccessibilityDelegate.java

@@ -61,6 +61,8 @@ class QtAccessibilityDelegate extends View.AccessibilityDelegate
     }
     // TODO do we want to have one QtAccessibilityDelegate for the whole app (QtRootLayout) or
     // e.g. one per window?
+    // FIXME make QtAccessibilityDelegate window based or verify current way works
+    // also for child windows: QTBUG-120685
     public QtAccessibilityDelegate(QtLayout layout)
     {
         m_layout = layout;

src/android/jar/src/org/qtproject/qt/android/QtAccessibilityInterface.java

@@ -0,0 +1,14 @@
+// Copyright (C) 2024 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+package org.qtproject.qt.android;
+
+@UsedFromNativeCode
+public interface QtAccessibilityInterface {
+    default void initializeAccessibility() { }
+    default void notifyLocationChange(int viewId) { }
+    default void notifyObjectHide(int viewId, int parentId) { }
+    default void notifyObjectFocus(int viewId) { }
+    default void notifyScrolledEvent(int viewId) { }
+    default void notifyValueChanged(int viewId, String value) { }
+    default void notifyObjectShow(int parentId) { }
+}

src/android/jar/src/org/qtproject/qt/android/QtActivityDelegate.java

@@ -31,7 +31,8 @@ import android.widget.PopupMenu;
 
 import java.util.HashMap;
 
-class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInterface
+class QtActivityDelegate
+        extends QtActivityDelegateBase implements QtWindowInterface, QtAccessibilityInterface
 {
     private static final String QtTAG = "QtActivityDelegate";
 
@@ -42,7 +43,7 @@ class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInter
 
     private View m_dummyView = null;
     private HashMap<Integer, View> m_nativeViews = new HashMap<Integer, View>();
-
+    private QtAccessibilityDelegate m_accessibilityDelegate = null;
 
     QtActivityDelegate(Activity activity)
     {
@@ -58,6 +59,8 @@ class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInter
             m_backendsRegistered = true;
             BackendRegister.registerBackend(QtWindowInterface.class,
                                             (QtWindowInterface)QtActivityDelegate.this);
+            BackendRegister.registerBackend(QtAccessibilityInterface.class,
+                                            (QtAccessibilityInterface)QtActivityDelegate.this);
         }
     }
 
@@ -66,6 +69,7 @@ class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInter
         if (m_backendsRegistered) {
             m_backendsRegistered = false;
             BackendRegister.unregisterBackend(QtWindowInterface.class);
+            BackendRegister.unregisterBackend(QtAccessibilityInterface.class);
         }
     }
 
@@ -226,7 +230,55 @@ class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInter
         });
     }
 
-    @UsedFromNativeCode
+    @Override
+    public void notifyLocationChange(int viewId)
+    {
+        if (m_accessibilityDelegate == null)
+            return;
+        m_accessibilityDelegate.notifyLocationChange(viewId);
+    }
+
+    @Override
+    public void notifyObjectHide(int viewId, int parentId)
+    {
+        if (m_accessibilityDelegate == null)
+            return;
+        m_accessibilityDelegate.notifyObjectHide(viewId, parentId);
+    }
+
+    @Override
+    public void notifyObjectShow(int parentId)
+    {
+        if (m_accessibilityDelegate == null)
+           return;
+        m_accessibilityDelegate.notifyObjectShow(parentId);
+    }
+
+    @Override
+    public void notifyObjectFocus(int viewId)
+    {
+        if (m_accessibilityDelegate == null)
+            return;
+        m_accessibilityDelegate.notifyObjectFocus(viewId);
+    }
+
+    @Override
+    public void notifyValueChanged(int viewId, String value)
+    {
+        if (m_accessibilityDelegate == null)
+            return;
+        m_accessibilityDelegate.notifyValueChanged(viewId, value);
+    }
+
+    @Override
+    public void notifyScrolledEvent(int viewId)
+    {
+        if (m_accessibilityDelegate == null)
+            return;
+        m_accessibilityDelegate.notifyScrolledEvent(viewId);
+    }
+
+    @Override
     public void initializeAccessibility()
     {
         QtNative.runAction(() -> {
@@ -362,16 +414,6 @@ class QtActivityDelegate extends QtActivityDelegateBase implements QtWindowInter
         });
     }
 
-    @Override
-    QtAccessibilityDelegate createAccessibilityDelegate()
-    {
-        if (m_layout != null)
-            return new QtAccessibilityDelegate(m_layout);
-
-        Log.w(QtTAG, "Null layout, failed to initialize accessibility delegate.");
-        return null;
-    }
-
     private void setActivityBackgroundDrawable()
     {
         TypedValue attr = new TypedValue();

src/android/jar/src/org/qtproject/qt/android/QtActivityDelegateBase.java

@@ -37,7 +37,6 @@ abstract class QtActivityDelegateBase
 {
     protected Activity m_activity;
     protected HashMap<Integer, QtWindow> m_topLevelWindows;
-    protected QtAccessibilityDelegate m_accessibilityDelegate = null;
     protected QtDisplayManager m_displayManager = null;
     protected QtInputDelegate m_inputDelegate = null;
 
@@ -46,7 +45,6 @@ abstract class QtActivityDelegateBase
 
     // Subclass must implement these
     abstract void startNativeApplicationImpl(String appParams, String mainLib);
-    abstract QtAccessibilityDelegate createAccessibilityDelegate();
     abstract QtLayout getQtLayout();
 
     // With these we are okay with default implementation doing nothing
@@ -153,62 +151,6 @@ abstract class QtActivityDelegateBase
         hideSplashScreen(0);
     }
 
-    @UsedFromNativeCode
-    public void notifyLocationChange(int viewId)
-    {
-        if (m_accessibilityDelegate == null)
-            return;
-        m_accessibilityDelegate.notifyLocationChange(viewId);
-    }
-
-    @UsedFromNativeCode
-    public void notifyObjectHide(int viewId, int parentId)
-    {
-        if (m_accessibilityDelegate == null)
-            return;
-        m_accessibilityDelegate.notifyObjectHide(viewId, parentId);
-    }
-
-    @UsedFromNativeCode
-    public void notifyObjectShow(int parentId)
-    {
-        if (m_accessibilityDelegate == null)
-           return;
-        m_accessibilityDelegate.notifyObjectShow(parentId);
-    }
-
-    @UsedFromNativeCode
-    public void notifyObjectFocus(int viewId)
-    {
-        if (m_accessibilityDelegate == null)
-            return;
-        m_accessibilityDelegate.notifyObjectFocus(viewId);
-    }
-
-    @UsedFromNativeCode
-    public void notifyValueChanged(int viewId, String value)
-    {
-        if (m_accessibilityDelegate == null)
-            return;
-        m_accessibilityDelegate.notifyValueChanged(viewId, value);
-    }
-
-    @UsedFromNativeCode
-    public void notifyScrolledEvent(int viewId)
-    {
-        if (m_accessibilityDelegate == null)
-            return;
-        m_accessibilityDelegate.notifyScrolledEvent(viewId);
-    }
-
-    @UsedFromNativeCode
-    public void initializeAccessibility()
-    {
-        QtNative.runAction(() -> {
-            m_accessibilityDelegate = createAccessibilityDelegate();
-        });
-    }
-
     void handleUiModeChange(int uiMode)
     {
         // QTBUG-108365

src/android/jar/src/org/qtproject/qt/android/QtEmbeddedDelegate.java

@@ -122,14 +122,6 @@ class QtEmbeddedDelegate extends QtActivityDelegateBase
         QtNative.startApplication(appParams, mainLib);
     }
 
-    @Override
-    QtAccessibilityDelegate createAccessibilityDelegate()
-    {
-        // FIXME make QtAccessibilityDelegate window based or verify current way works
-        // also for child windows: QTBUG-120685
-        return null;
-    }
-
     @UsedFromNativeCode
     @Override
     QtLayout getQtLayout()

src/android/jar/src/org/qtproject/qt/android/QtServiceEmbeddedDelegate.java

@@ -28,6 +28,7 @@ class QtServiceEmbeddedDelegate implements QtEmbeddedViewInterface, QtNative.App
         m_service = service;
         QtNative.registerAppStateListener(this);
         QtNative.setService(service);
+        // QTBUG-122920 TODO Implement accessibility for service UIs
     }
 
     @UsedFromNativeCode

src/plugins/platforms/android/androidjniaccessibility.cpp

@@ -82,7 +82,7 @@ namespace QtAndroidAccessibility
 
     void initialize()
     {
-        QtAndroid::qtActivityDelegate().callMethod<void>("initializeAccessibility");
+        QtAndroid::initializeAccessibility();
     }
 
     bool isActive()

src/plugins/platforms/android/androidjnimain.cpp

@@ -95,6 +95,7 @@ Q_CONSTINIT static QBasicAtomicInt startQtAndroidPluginCalled = Q_BASIC_ATOMIC_I
 
 Q_DECLARE_JNI_CLASS(QtEmbeddedDelegateFactory, "org/qtproject/qt/android/QtEmbeddedDelegateFactory")
 Q_DECLARE_JNI_CLASS(QtWindowInterface, "org/qtproject/qt/android/QtWindowInterface")
+Q_DECLARE_JNI_CLASS(QtAccessibilityInterface, "org/qtproject/qt/android/QtAccessibilityInterface");
 
 namespace QtAndroid
 {
@@ -237,36 +238,46 @@ namespace QtAndroid
         return true;
     }
 
+    void initializeAccessibility()
+    {
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
+                "initializeAccessibility");
+    }
+
     void notifyAccessibilityLocationChange(uint accessibilityObjectId)
     {
-        qtActivityDelegate().callMethod<void>("notifyLocationChange", accessibilityObjectId);
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
+                "notifyLocationChange", accessibilityObjectId);
     }
 
     void notifyObjectHide(uint accessibilityObjectId, uint parentObjectId)
     {
-        qtActivityDelegate().callMethod<void>("notifyObjectHide",
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
-                                              accessibilityObjectId, parentObjectId);
+                "notifyObjectHide", accessibilityObjectId, parentObjectId);
     }
 
     void notifyObjectShow(uint parentObjectId)
     {
-        qtActivityDelegate().callMethod<void>("notifyObjectShow",
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
-                                              parentObjectId);
+                "notifyObjectShow", parentObjectId);
     }
 
     void notifyObjectFocus(uint accessibilityObjectId)
     {
-        qtActivityDelegate().callMethod<void>("notifyObjectFocus", accessibilityObjectId);
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
+                "notifyObjectFocus", accessibilityObjectId);
     }
 
     void notifyValueChanged(uint accessibilityObjectId, jstring value)
     {
-        qtActivityDelegate().callMethod<void>("notifyValueChanged", accessibilityObjectId, value);
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
+                "notifyValueChanged", accessibilityObjectId, value);
     }
 
     void notifyScrolledEvent(uint accessibilityObjectId)
     {
-        qtActivityDelegate().callMethod<void>("notifyScrolledEvent", accessibilityObjectId);
+        m_backendRegister->callInterface<QtJniTypes::QtAccessibilityInterface, void>(
+                "notifyScrolledEvent", accessibilityObjectId);
     }
 
     void notifyNativePluginIntegrationReady(bool ready)

src/plugins/platforms/android/androidjnimain.h

@@ -65,6 +65,7 @@ namespace QtAndroid
     jobject createBitmap(int width, int height, QImage::Format format, JNIEnv *env);
     jobject createBitmapDrawable(jobject bitmap, JNIEnv *env = nullptr);
 
+    void initializeAccessibility();
     void notifyAccessibilityLocationChange(uint accessibilityObjectId);
     void notifyObjectHide(uint accessibilityObjectId, uint parentObjectId);
     void notifyObjectShow(uint parentObjectId);