fix(android): forward back key event

mobilewebview/android/src/org/mobilewebview/MobileWebView.java

@@ -82,7 +82,18 @@ public MobileWebView(Context context, long nativePtr, View rootView) {
 
     private void initializeWebViewOnMainThread(Context context) {
         try {
-            mWebView = new WebView(context);
+            mWebView = new WebView(context) {
+                @Override
+                public boolean dispatchKeyEvent(android.view.KeyEvent event) {
+                    if (event.getKeyCode() == android.view.KeyEvent.KEYCODE_BACK) {
+                        if (event.getAction() == android.view.KeyEvent.ACTION_UP) {
+                            withNativePtr(MobileWebView.this::nativeOnBackRequested);
+                        }
+                        return true;
+                    }
+                    return super.dispatchKeyEvent(event);
+                }
+            };
             setupWebView();
         } catch (RuntimeException e) {
             Log.e(TAG, "Failed to initialize WebView on main thread", e);
@@ -410,6 +421,12 @@ public void setVisible(boolean visible) {
         runOnMainThread(() -> {
             if (mWebView == null) return;
             mWebView.setVisibility(visible ? View.VISIBLE : View.GONE);
+            // Grab focus when shown so the WebView receives key events
+            // (notably KEYCODE_BACK). Without focus, dispatchKeyEvent is not
+            // called and Back is never forwarded to QML.
+            if (visible) {
+                mWebView.requestFocus();
+            }
         });
     }
 
@@ -684,6 +701,7 @@ private native void nativeOnWebMessageReceived(long nativePtr, String message,
     private native void nativeOnJavaScriptResult(long nativePtr, String result, String error);
     private native void nativeOnTitleChanged(long nativePtr, String title);
     private native void nativeOnNavigationStateChanged(long nativePtr, boolean canGoBack, boolean canGoForward);
+    private native void nativeOnBackRequested(long nativePtr);
     private native void nativeOnHistoryChanged(long nativePtr, String[] urls, String[] titles, int currentHistoryIndex);
     private native void nativeOnNewWindowRequested(long nativePtr, String url, boolean userInitiated);
     private native void nativeOnLoadProgressChanged(long nativePtr, int progress);

mobilewebview/src/android/mobilewebviewbackend_android.cpp

@@ -7,6 +7,8 @@
 
 #include <QDebug>
 #include <QQuickWindow>
+#include <QKeyEvent>
+#include <QCoreApplication>
 #include <QFile>
 #include <QGuiApplication>
 #include <QJniObject>
@@ -988,6 +990,22 @@ Java_org_mobilewebview_MobileWebView_nativeOnNavigationStateChanged(JNIEnv *env,
     }, Qt::QueuedConnection);
 }
 
+JNIEXPORT void JNICALL
+Java_org_mobilewebview_MobileWebView_nativeOnBackRequested(JNIEnv *env, jobject obj, jlong nativePtr)
+{
+    Q_UNUSED(env)
+    Q_UNUSED(obj)
+    if (nativePtr == 0) return;
+
+    AndroidWebViewPrivate *backend = reinterpret_cast<AndroidWebViewPrivate*>(nativePtr);
+    QMetaObject::invokeMethod(backend->q_ptr, [backend]() {
+        QQuickWindow *win = backend->q_ptr->window();
+        if (!win) return;
+        QCoreApplication::postEvent(win, new QKeyEvent(QEvent::KeyPress, Qt::Key_Back, Qt::NoModifier));
+        QCoreApplication::postEvent(win, new QKeyEvent(QEvent::KeyRelease, Qt::Key_Back, Qt::NoModifier));
+    }, Qt::QueuedConnection);
+}
+
 JNIEXPORT void JNICALL
 Java_org_mobilewebview_MobileWebView_nativeOnHistoryChanged(JNIEnv *env, jobject obj,
                                                             jlong nativePtr, jobjectArray urls,