Handle destruction of activity more gracefully

Since Qt will put the app in a state where it can't recover from (the UI
can never be shown again) we have to terminate everything else as well.
Otherwise Go threads and the service/notification would still be around but
one could never access the UI again.

This is of course not ideal. Ideally, the activity lifecycle should be
independent from the service livecycle and the service should be able to
outlive the activity. The activity should be able to re-create itself once
destroyed.

tray/android/src/io/github/martchus/syncthingtray/Activity.java

@@ -148,7 +148,13 @@ public void onStop() {
     }
 
     public void onDestroy() {
+        // stop service and libsyncthing
+        // note: QtActivity will exit the main thread in super.onDestroy() so we cannot keep the service running.
+        //       It would not stop the service and Go threads but it would be impossible to re-enter the UI leaving
+        //       the app in some kind of zombie state.
         Log.i(TAG, "Destroying");
+        stopLibSyncthing();
+        stopSyncthingService();
         super.onDestroy();
     }
 
@@ -161,11 +167,12 @@ protected void onNewIntent(Intent intent) {
 
     private void sendAndroidIntentToQtQuickApp(String page, boolean fromNotification) {
         try {
-            onAndroidIntent(page, fromNotification);
+            handleAndroidIntent(page, fromNotification);
         } catch (java.lang.UnsatisfiedLinkError e) {
             showToast("Unable to open in Syncthing Tray app right now.");
         }
     }
 
-    private static native void onAndroidIntent(String page, boolean fromNotification);
+    private static native void handleAndroidIntent(String page, boolean fromNotification);
+    private static native void stopLibSyncthing();
 }

tray/gui/quick/app.cpp

@@ -81,14 +81,21 @@ static void deletePipelineCache()
 }
 
 #ifdef Q_OS_ANDROID
-// define functions called from Java
+/// \brief The JniFn namespace defines functions called from Java.
+namespace JniFn {
 static App *appObjectForJava = nullptr;
 
-static void onAndroidIntent(JNIEnv *, jobject, jstring page, jboolean fromNotification)
+static void stopLibSyncthing(JNIEnv *, jobject)
+{
+    QMetaObject::invokeMethod(appObjectForJava, "stopLibSyncthing", Qt::QueuedConnection);
+}
+
+static void handleAndroidIntent(JNIEnv *, jobject, jstring page, jboolean fromNotification)
 {
     QMetaObject::invokeMethod(appObjectForJava, "handleAndroidIntent", Qt::QueuedConnection,
         Q_ARG(QString, QJniObject::fromLocalRef(page).toString()), Q_ARG(bool, fromNotification));
 }
+}
 #endif
 
 App::App(bool insecure, QObject *parent)
@@ -178,14 +185,15 @@ App::App(bool insecure, QObject *parent)
 
 #ifdef Q_OS_ANDROID
     // register native methods of Android activity
-    if (!appObjectForJava) {
-        appObjectForJava = this;
+    if (!JniFn::appObjectForJava) {
+        JniFn::appObjectForJava = this;
         auto env = QJniEnvironment();
         auto registeredMethods = true;
         static const JNINativeMethod activityMethods[] = {
-            { "onAndroidIntent", "(Ljava/lang/String;Z)V", reinterpret_cast<void *>(onAndroidIntent) },
+            { "handleAndroidIntent", "(Ljava/lang/String;Z)V", reinterpret_cast<void *>(JniFn::handleAndroidIntent) },
+            { "stopLibSyncthing", "()V", reinterpret_cast<void *>(JniFn::stopLibSyncthing) },
         };
-        registeredMethods = env.registerNativeMethods("io/github/martchus/syncthingtray/Activity", activityMethods, 1) && registeredMethods;
+        registeredMethods = env.registerNativeMethods("io/github/martchus/syncthingtray/Activity", activityMethods, 2) && registeredMethods;
         if (!registeredMethods) {
             qWarning() << "Unable to register all native methods in JNI environment.";
         }
@@ -695,6 +703,11 @@ void App::handleNewErrors(const std::vector<Data::SyncthingError> &errors)
 {
     Q_UNUSED(errors)
     invalidateStatus();
+#ifdef Q_OS_ANDROID
+    if (errors.empty()) {
+        clearSyncthingErrorsNotification();
+    }
+#endif
 }
 
 void App::handleStateChanged(Qt::ApplicationState state)
@@ -766,27 +779,22 @@ void App::clearAndroidExtraNotifications(int firstId, int lastId)
 
 void App::updateSyncthingErrorsNotification(CppUtilities::DateTime when, const QString &message)
 {
-    auto whenString = when.toString();
-    m_syncthingErrors.reserve(m_syncthingErrors.size() + 1 + whenString.size() + 2 + message.size());
-    if (!m_syncthingErrors.isEmpty()) {
-        m_syncthingErrors += QChar('\n');
-    }
-    m_syncthingErrors += std::move(whenString);
-    m_syncthingErrors += QChar(':');
-    m_syncthingErrors += QChar(' ');
-    m_syncthingErrors += message;
-
-    const auto title = QJniObject::fromString(tr("Syncthing errors/notifications"));
-    static const auto text = QJniObject::fromString(QString());
-    const auto subText = QJniObject::fromString(m_syncthingErrors);
+    ++m_syncthingErrors;
+    const auto title = QJniObject::fromString(m_syncthingErrors == 1
+        ? tr("Syncthing error/notification")
+        : tr("%1 Syncthing errors/notifications").arg(m_syncthingErrors));
+    const auto text = QJniObject::fromString(m_syncthingErrors == 1
+        ? message
+        : tr("most recent: ") + message);
+    const auto subText = QJniObject::fromString(QString::fromStdString(when.toString()));
     static const auto page = QJniObject::fromString(QStringLiteral("connectionErrors"));
     const auto &icon = makeAndroidIcon(commonForkAwesomeIcons().exclamation);
     updateExtraAndroidNotification(title, text, subText, page, icon, 2);
 }
 
 void App::clearSyncthingErrorsNotification()
 {
-    m_syncthingErrors.clear();
+    m_syncthingErrors = 0;
     clearAndroidExtraNotifications(2, -1);
 }
 
@@ -857,6 +865,11 @@ void App::handleAndroidIntent(const QString &data, bool fromNotification)
         emit newDirTriggered(folderRef.deviceId.toString(), folderRef.folderId.toString(), folderRef.folderLabel.toString());
     }
 }
+
+void App::stopLibSyncthing()
+{
+    m_launcher.stopLibSyncthing();
+}
 #endif
 
 void App::clearInternalErrors()

tray/gui/quick/app.h

@@ -292,6 +292,7 @@ private Q_SLOTS:
     void showNewDevice(const QString &devId, const QString &message);
     void showNewDir(const QString &devId, const QString &dirId, const QString &dirLabel, const QString &message);
     void handleAndroidIntent(const QString &page, bool fromNotification);
+    void stopLibSyncthing();
 #endif
 
 private:
@@ -315,7 +316,7 @@ private Q_SLOTS:
     QVariantList m_internalErrors;
     StatusInfo m_statusInfo;
 #ifdef Q_OS_ANDROID
-    QString m_syncthingErrors;
+    int m_syncthingErrors = 0;
     QHash<const QIcon *, QJniObject> m_androidIconCache;
     int m_androidNotificationId = 100000000;
 #endif