Can not activate trayicon when dialog is open - qt

Question

(Update on 2019-01-02: Simplify my example)
I am working on a program that can minimize to tray and hide the main window. I expect the mainwindow to show when I click on the tray icon. This usually works, but I find that if the program minimizes to tray when I call QFileDialog::getOpenFileName() to select file without closing the dialog, I cannot activate the trayicon. Does anyone know how to solve it? I am using Qt 5.12.0 (was using Qt 5.9.0) on Manjaro Linux.
Minimal, Complete, and Verifiable example:
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.h:
class MainWindow : public QMainWindow
{
Q_OBJECT
QSystemTrayIcon *trayIcon;
QMenu *trayContextMenu;
QAction *actShow;
QPushButton *button;
public:
MainWindow(QWidget *parent = 0);
protected:
void changeEvent(QEvent *);
private slots:
void click();
void trayIcon_activated(QSystemTrayIcon::ActivationReason reason);
void actShow_Triggered();
};
#endif // MAINWINDOW_H
mainwindow.cpp:
#include "mainwindow.h"
#include <QFileDialog>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent)
{
QPushButton *button = new QPushButton("button", this);
setCentralWidget(button);
connect(button,&QPushButton::clicked,
this,&MainWindow::click);
trayIcon=new QSystemTrayIcon;
trayIcon->setIcon(QIcon("hmtimer.png"));
trayContextMenu=new QMenu;
actShow=trayContextMenu->addAction(tr("Show"));
trayIcon->setContextMenu(trayContextMenu);
connect(actShow,&QAction::triggered,
this,&MainWindow::actShow_Triggered);
connect(trayIcon,&QSystemTrayIcon::activated,
this,&MainWindow::trayIcon_activated);
}
void MainWindow::changeEvent(QEvent *event)
{
if(event->type()==QEvent::WindowStateChange){
if(isMinimized()){
this->hide();
trayIcon->show();
}
}
else{
QMainWindow::changeEvent(event);
}
}
void MainWindow::click()
{
QFileDialog::getOpenFileName(this,QString());
}
void MainWindow::trayIcon_activated(QSystemTrayIcon::ActivationReason reason)
{
if(reason==3){ //reason==Trigger
this->show();
trayIcon->hide();
}
}
void MainWindow::actShow_Triggered()
{
this->show();
trayIcon->hide();
}
The example can be downloaded here
It seems that if the program minimizes to tray when QFileDialog::getOpenFileName(this,QString()) is not closed, I cannot make the mainwindow appear by click on the tray icon or right click to show the context menu.
How to reproduce:
Open the program
Click on the button to open file dialog
Minimize to tray
Try clicking and right-clicking on the tray icon

Answer 1

I found a way to show the main window. I can do this by double clicking the icon with the following code of MainWindow::trayIcon_activated:
void MainWindow::trayIcon_activated(QSystemTrayIcon::ActivationReason reason)
{
if(reason==QSystemTrayIcon::DoubleClick){
this->show();
trayIcon->hide();
}
}
I still don't know how to show the mainwindow with single click or show the context menu with right click. If anyone knows, please tell me.
EDIT: Seems that this no longer works. I tried both my previous example and new example. Don't know what is going wrong.