Android: Fix application state tracking

- Make sure we don't process state changes before the platform plugin
is completely created and registered.
- Protect shared data with mutexes.
- Don't update the application state from different threads.

This was causing issues when testing run-time permission checks, when
the application quickly switches state due to permission dialog being
shown. In this case the states would be incorrectly delivered when the
application was made active again.

Change-Id: I3446eab9414ee5437cd788c27d65f808d1314aa5
Reviewed-by: BogDan Vatra <bogdan@kdab.com>

src/plugins/platforms/android/androidjnimain.cpp

@@ -82,8 +82,8 @@ static jobject m_serviceObject = nullptr;
 static jmethodID m_setSurfaceGeometryMethodID = nullptr;
 static jmethodID m_destroySurfaceMethodID = nullptr;
 
-static bool m_activityActive = true; // defaults to true because when the platform plugin is
-                                     // initialized, QtActivity::onResume() has already been called
+static int m_pendingApplicationState = -1;
+static QBasicMutex m_pendingAppStateMtx;
 
 static jclass m_bitmapClass  = nullptr;
 static jmethodID m_createBitmapMethodID = nullptr;
@@ -130,13 +130,22 @@ static const char m_qtTag[] = "Qt";
 static const char m_classErrorMsg[] = "Can't find class \"%s\"";
 static const char m_methodErrorMsg[] = "Can't find method \"%s%s\"";
 
+static void flushPendingApplicationState();
+
 namespace QtAndroid
 {
     void setAndroidPlatformIntegration(QAndroidPlatformIntegration *androidPlatformIntegration)
     {
-        m_surfacesMutex.lock();
+        QMutexLocker lock(&m_surfacesMutex);
         m_androidPlatformIntegration = androidPlatformIntegration;
-        m_surfacesMutex.unlock();
+
+        // flush the pending state if necessary.
+        if (m_androidPlatformIntegration) {
+            flushPendingApplicationState();
+        } else {
+            QMutexLocker locker(&m_pendingAppStateMtx);
+            m_pendingApplicationState = -1;
+        }
     }
 
     QAndroidPlatformIntegration *androidPlatformIntegration()
@@ -215,12 +224,6 @@ namespace QtAndroid
         m_statusBarShowing = false;
     }
 
-    void setApplicationActive()
-    {
-        if (m_activityActive)
-            QWindowSystemInterface::handleApplicationStateChanged(Qt::ApplicationActive);
-    }
-
     jobject createBitmap(QImage img, JNIEnv *env)
     {
         if (!m_bitmapClass)
@@ -446,6 +449,16 @@ namespace QtAndroid
 
 } // namespace QtAndroid
 
+// Force an update of the pending application state (state set before the platform plugin was created)
+static void flushPendingApplicationState()
+{
+    QMutexLocker locker(&m_pendingAppStateMtx);
+    if (m_pendingApplicationState == -1)
+        return;
+
+    QWindowSystemInterface::handleApplicationStateChanged(Qt::ApplicationState(m_pendingApplicationState));
+    m_pendingApplicationState = -1;
+}
 
 static jboolean startQtAndroidPlugin(JNIEnv* /*env*/, jobject /*object*//*, jobject applicationAssetManager*/)
 {
@@ -655,13 +668,14 @@ static void updateWindow(JNIEnv */*env*/, jobject /*thiz*/)
 
 static void updateApplicationState(JNIEnv */*env*/, jobject /*thiz*/, jint state)
 {
-    m_activityActive = (state == Qt::ApplicationActive);
-
-    if (!m_main || !m_androidPlatformIntegration || !QGuiApplicationPrivate::platformIntegration()) {
-        QAndroidPlatformIntegration::setDefaultApplicationState(Qt::ApplicationState(state));
+    if (!m_main || !QtAndroid::androidPlatformIntegration()) {
+        QMutexLocker locker(&m_pendingAppStateMtx);
+        m_pendingApplicationState = Qt::ApplicationState(state);
         return;
     }
 
+    flushPendingApplicationState();
+
     if (state == Qt::ApplicationActive)
         QtAndroidPrivate::handleResume();
     else if (state == Qt::ApplicationInactive)

src/plugins/platforms/android/androidjnimain.h

@@ -85,8 +85,6 @@ namespace QtAndroid
     jobject activity();
     jobject service();
 
-    void setApplicationActive();
-
     void showStatusBar();
     void hideStatusBar();
 

src/plugins/platforms/android/qandroidplatformintegration.cpp

@@ -80,8 +80,6 @@ int QAndroidPlatformIntegration::m_defaultPhysicalSizeHeight = 71;
 Qt::ScreenOrientation QAndroidPlatformIntegration::m_orientation = Qt::PrimaryOrientation;
 Qt::ScreenOrientation QAndroidPlatformIntegration::m_nativeOrientation = Qt::PrimaryOrientation;
 
-Qt::ApplicationState QAndroidPlatformIntegration::m_defaultApplicationState = Qt::ApplicationActive;
-
 bool QAndroidPlatformIntegration::m_showPasswordEnabled = false;
 
 void *QAndroidPlatformNativeInterface::nativeResourceForIntegration(const QByteArray &resource)
@@ -120,6 +118,12 @@ void *QAndroidPlatformNativeInterface::nativeResourceForIntegration(const QByteA
     return 0;
 }
 
+void QAndroidPlatformNativeInterface::customEvent(QEvent *event)
+{
+    if (event->type() == QEvent::User)
+        QtAndroid::setAndroidPlatformIntegration(static_cast<QAndroidPlatformIntegration *>(QGuiApplicationPrivate::platformIntegration()));
+}
+
 QAndroidPlatformIntegration::QAndroidPlatformIntegration(const QStringList &paramList)
     : m_touchDevice(nullptr)
 #ifndef QT_NO_ACCESSIBILITY
@@ -147,7 +151,6 @@ QAndroidPlatformIntegration::QAndroidPlatformIntegration(const QStringList &para
     m_primaryScreen->setAvailableGeometry(QRect(0, 0, m_defaultGeometryWidth, m_defaultGeometryHeight));
 
     m_mainThread = QThread::currentThread();
-    QtAndroid::setAndroidPlatformIntegration(this);
 
     m_androidFDB = new QAndroidPlatformFontDatabase();
     m_androidPlatformServices = new QAndroidPlatformServices();
@@ -210,7 +213,9 @@ QAndroidPlatformIntegration::QAndroidPlatformIntegration(const QStringList &para
         }
     }
 
-    QGuiApplicationPrivate::instance()->setApplicationState(m_defaultApplicationState);
+    // We can't safely notify the jni bridge that we're up and running just yet, so let's postpone
+    // it for now.
+    QCoreApplication::postEvent(m_androidPlatformNativeInterface, new QEvent(QEvent::User));
 }
 
 static bool needsBasicRenderloopWorkaround()

src/plugins/platforms/android/qandroidplatformintegration.h

@@ -65,6 +65,9 @@ class QAndroidPlatformNativeInterface: public QPlatformNativeInterface
 public:
     void *nativeResourceForIntegration(const QByteArray &resource) override;
     std::shared_ptr<AndroidStyle> m_androidStyle;
+
+protected:
+    void customEvent(QEvent *event) override;
 };
 
 class QAndroidPlatformIntegration : public QPlatformIntegration
@@ -121,7 +124,6 @@ public:
 
     QTouchDevice *touchDevice() const { return m_touchDevice; }
     void setTouchDevice(QTouchDevice *touchDevice) { m_touchDevice = touchDevice; }
-    static void setDefaultApplicationState(Qt::ApplicationState applicationState) { m_defaultApplicationState = applicationState; }
 
 private:
     EGLDisplay m_eglDisplay;
@@ -140,9 +142,6 @@ private:
 
     static Qt::ScreenOrientation m_orientation;
     static Qt::ScreenOrientation m_nativeOrientation;
-
-    static Qt::ApplicationState m_defaultApplicationState;
-
     static bool m_showPasswordEnabled;
 
     QPlatformFontDatabase *m_androidFDB;

src/plugins/platforms/android/qandroidplatformwindow.cpp

@@ -96,11 +96,6 @@ void QAndroidPlatformWindow::setVisible(bool visible)
     QRect availableGeometry = screen()->availableGeometry();
     if (geometry().width() > 0 && geometry().height() > 0 && availableGeometry.width() > 0 && availableGeometry.height() > 0)
         QPlatformWindow::setVisible(visible);
-
-    // The Android Activity is activated before Qt is initialized, causing the application state to
-    // never be set to 'active'. We explicitly set this state when the first window becomes visible.
-    if (visible)
-        QtAndroid::setApplicationActive();
 }
 
 void QAndroidPlatformWindow::setWindowState(Qt::WindowState state)