Android: QtActivityDelegateBase listens to focus events from child views

In order to detect gaining/losing and moving focus between windows,
implement GlobalFocusChangeListener for the root View.

Add a surfaceFocusChanged native function in QAndroidPlatformWindow in
order to follow these focus changes.

Task-number: QTBUG-118139
Change-Id: Ia9bf6249c28a420f42793a9829aef31b12757630
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>
(cherry picked from commit 2c192c6f5fe08b014bfa90ea0452258e649d3183)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

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

@@ -138,6 +138,7 @@ class QtActivityDelegate extends QtActivityDelegateBase
                                              r.width(), kbHeight);
             return true;
         });
+        registerGlobalFocusChangeListener(m_layout);
         m_inputDelegate.setEditPopupMenu(new EditPopupMenu(m_activity, m_layout));
     }
 

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

@@ -133,6 +133,26 @@ abstract class QtActivityDelegateBase
         setUpLayout();
     }
 
+    protected void registerGlobalFocusChangeListener(final View view) {
+        view.getViewTreeObserver().addOnGlobalFocusChangeListener(this::onGlobalFocusChanged);
+    }
+
+    private void onGlobalFocusChanged(View oldFocus, View newFocus) {
+        if (newFocus instanceof QtEditText) {
+            final QtWindow newWindow = (QtWindow) newFocus.getParent();
+            QtWindow.windowFocusChanged(true, newWindow.getId());
+            m_inputDelegate.setFocusedView((QtEditText) newFocus);
+        } else {
+            int id = -1;
+            if (oldFocus instanceof QtEditText) {
+                final QtWindow oldWindow = (QtWindow) oldFocus.getParent();
+                id = oldWindow.getId();
+            }
+            QtWindow.windowFocusChanged(false, id);
+            m_inputDelegate.setFocusedView(null);
+        }
+    }
+
     public void hideSplashScreen()
     {
         hideSplashScreen(0);

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

@@ -135,6 +135,7 @@ class QtEmbeddedDelegate extends QtActivityDelegateBase implements QtNative.AppS
 
     void setView(QtView view) {
         m_view = view;
+        registerGlobalFocusChangeListener(m_view);
     }
 
     public void setRootWindowRef(long ref) {

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

@@ -24,6 +24,7 @@ class QtWindow extends QtLayout implements QtSurfaceInterface {
     private final QtEditText m_editText;
 
     private static native void setSurface(int windowId, Surface surface);
+    static native void windowFocusChanged(boolean hasFocus, int id);
 
     public QtWindow(Context context, QtWindow parentWindow)
     {
@@ -31,6 +32,7 @@ class QtWindow extends QtLayout implements QtSurfaceInterface {
         setId(View.generateViewId());
         m_editText = new QtEditText(context);
         setParent(parentWindow);
+        setFocusableInTouchMode(true);
 
         QtNative.runAction(() -> {
             m_gestureDetector =

src/plugins/platforms/android/qandroidplatformwindow.cpp

@@ -342,10 +342,28 @@ void QAndroidPlatformWindow::setSurface(JNIEnv *env, jobject object, jint window
     }
 }
 
+void QAndroidPlatformWindow::windowFocusChanged(JNIEnv *env, jobject object,
+                                          jboolean focus, jint windowId)
+{
+    Q_UNUSED(env)
+    Q_UNUSED(object)
+    QWindow* window = QtAndroid::windowFromId(windowId);
+    Q_ASSERT_X(window, "QAndroidPlatformWindow", "windowFocusChanged event window should exist");
+    if (focus) {
+        QWindowSystemInterface::handleFocusWindowChanged(window);
+    } else if (!focus && window == qGuiApp->focusWindow()) {
+        // Clear focus if current window has lost focus
+        QWindowSystemInterface::handleFocusWindowChanged(nullptr);
+    }
+}
+
 bool QAndroidPlatformWindow::registerNatives(QJniEnvironment &env)
 {
     if (!env.registerNativeMethods(QtJniTypes::Traits<QtJniTypes::QtWindow>::className(),
-                                  {Q_JNI_NATIVE_SCOPED_METHOD(setSurface, QAndroidPlatformWindow)})) {
+                                {
+                                    Q_JNI_NATIVE_SCOPED_METHOD(setSurface, QAndroidPlatformWindow),
+                                    Q_JNI_NATIVE_SCOPED_METHOD(windowFocusChanged, QAndroidPlatformWindow)
+                                })) {
         qCCritical(lcQpaWindow) << "RegisterNatives failed for"
                                 << QtJniTypes::Traits<QtJniTypes::QtWindow>::className();
         return false;

src/plugins/platforms/android/qandroidplatformwindow.h

@@ -93,6 +93,8 @@ protected:
 private:
     static void setSurface(JNIEnv *env, jobject obj, jint windowId, QtJniTypes::Surface surface);
     Q_DECLARE_JNI_NATIVE_METHOD_IN_CURRENT_SCOPE(setSurface)
+    static void windowFocusChanged(JNIEnv *env, jobject object, jboolean focus, jint windowId);
+    Q_DECLARE_JNI_NATIVE_METHOD_IN_CURRENT_SCOPE(windowFocusChanged)
 };
 
 QT_END_NAMESPACE