I'm new at Qt. I've created small application and I created second page help.cpp. On MainWindow.cpp I have a button, that switches to help.cpp page.
Function which switches to "help" page:
void MainWindow::on_box1button_clicked()
{
helpwindow = new help(this);
helpwindow->show();
}
This code works properly.
On the "help" page I've got a QButton, which will switch back to mainwindow.cpp. How Can I code that button to actually make this action?
If your intention by "switching" is hiding one window and showing another one, so you can simply pass a reference of the main window to your help window and there when you want to switch back, you can hide/close itself and show the main window.
MainWindow (this code is fine)
helpwindow = new help(this);
helpwindow->show();
HelpWindow
When you want to switch back to the main window, you can do this:
// Hide the HelpWindow itself
// or this->close()
this->hide()
// Show the MainWindow (i.e. the parent window)
QWidget *parent = this->parentWidget();
parent->show();
Since you are creating a new help(this); on mainwindow it is better to close the help window
Use
this->close();
Related
I'm trying to create a C++ Widget Application in QT with multiple windows where you can return to the mainwindow by clicking a Pushbutton.
I'm a complete noobie so I try to follow YouTube tutorial and for opening windows by pushbuttons I watched this one (minute 8:00): https://youtu.be/tP70B-pdTH0
It works when opening secondary windows from the main one but if I try to do the same from a secondary windows to the mainwindow it doesn't. It appears an error "cannot initialize object parameter of type 'Widget' with an expression of type 'MainWindow'"
in the source file I wrote:
void Crediti::on_pushButton_clicked()
{
close();
mainwindow = new MainWindow(this);
mainwindow->show();
}
mainwindow->show(); is the incriminated part
I also included mainwindow in the header of the secondary window and specified the class
MainWindow *mainwindow
in the header so It recognizes mainwindow initially in the source.
I'm doubting if doing this thing is possible at all, and if not so how can I make a pushbutton that, when clicked, can redirect me to the mainwindow?
Please I need this for a school application, thanks
So here you're creating a new main window each time you click on the button. From your description that's not the behaviour you want. I understand you have an application with a main window and other secondary windows and want to bring up the main window when clicking on the button, assuming the main window still exists somewhere and hasn't been deleted.
What I would try is to find the main window when hitting the push button and show / raise it, something along the line of:
#include <QApplication>
#include "MainWindow.h" // Adapt that one to you main window header
// ... some code of your secondary window
void SecondaryWindow::on_pushButton_clicked()
{
for(auto widget : QApplication::topLevelWidgets())
{
// This will return a nullptr if the widget is not the main window
auto mainWindow = dynamic_cast<MainWindow*>(widget);
// skip if not the main window
if(!mainWindow)
continue;
// Show it if hidden
if(mainWindow->isHidden())
mainWindow->show();
// raise it, as in bring it forward, over all other windows
mainWindow->raise();
}
// eventually close the current window if that's what you want
close();
// if you close it and don't need it any more you might also want to delete it
deleteLater();
}
Note that this function won't do anything if the main window has been deleted in the meantime, which might be the case if you closed it and the Qt::WA_DeleteOnClose attribute is set.
Hope that helps.
I have multiple UI windows in my QT project. When a new UI window opens, the previous UI window must be closed, that is, at every point of time only one UI window must be open. How can this be done?
I did that before and i suggest you to not close(delete) UI.
just hide it and when you need it show it again.
check this code:
when user click to see second UI:
void MainApp::on_btnSettings_clicked()
{
this->hide();
settingsManager = new SettingsManager(); // put this line in constructor
settingsManager->show();
}
on second UI on closing form(or back button) emit a signal:
void SettingsManager::closeEvent(QCloseEvent *event)
{
emit settingsBackToMainApp();
}
on main hide second class and show main:
void MainApp::settingsBackToMainApp()
{
settingsManager->hide();
this->show();
}
connect signal to slot:
connect(settingsManager,&SettingsManager::settingsBackToMainApp,this,&MainApp::settingsBackToMainApp); // put this line in constructor
In my Qt Program, there is a menu bar where one of the menu options is Settings. When the user click on the Settings window, it should open a Settings window. The settings window gets opened with a openSettingsWindow() function. This is how I made the Settings menu in the main window:
QMenu settingsMenu("&Settings");
QAction *settings = toolsMenu.addAction("&Settings");
Window::connect(settings,&QAction::triggered,&mainWindow,[&mainWindow](){
openSettingsWindow();
});
menuBar.addMenu(&toolsMenu);
mainWindow is the main window and Window is the class used to create windows which inherits from QWidget. Its constructor takes two arguments: the title of the window and the icon of the window. This is the openSettingsWindow() function:
void openSettingsWindow(){
Window settingsWindow("Settings","icon.png");
settingsWindow.show();
}
The problem is that when I click ont he Settings option in the Settings menu, the Settings window opens as it should, but it closes directly after less than a second. What should I do to keep the Settings window opened?
The local variable settingsWindow gets destructed when your function openSettingsWindow goes out of scope, you need to keep the object valid as long as you want to show your settingsWindow.
one solution would be to allocate the Window object on the heap, and use the Qt::WA_DeleteOnClose to make Qt delete the Window object for you when it is closed, here is how your openSettingsWindow would look like:
void openSettingsWindow(){
Window* settingsWindow = new Window("Settings","icon.png");
settingsWindow->setAttribute(Qt::WA_DeleteOnClose);
settingsWindow->show();
}
You need to return a reference to that Window and keep it until you're no longer using it.
Window *openSettingsWindow() {
Window *settingsWindow = new Window("Settings, "icon.png");
settingsWindow.show();
return settingsWindow;
}
QMenu settingsMenu("&Settings");
QAction *settings = toolsMenu.addAction("&Settings");
Window *settingsWindow = null;
Window::connect(settings,&QAction::triggered,&mainWindow,[&mainWindow, &settingsWindow](){
settingsWindow = openSettingsWindow();
});
menuBar.addMenu(&toolsMenu);
You might want to find a better way of storing the settingsWindow pointer in the main function if you're going to have many possible open windows but this will work.
Remember to call delete() on that pointer when you're done with the settings window (likely on the window close event)
I've stumbled across very strange behaviour during work on my program.
I've written custom changeEvent class, which allows me to hide program to SysTray on minimizing.
But when i double click on taskbar app icon, the function goes crazy. It creates 2 to 4 systray icons and on requesting window show again, it just shows main window borders without any content inside.
Here's my changeEvent code:
void MainWindow::changeEvent(QEvent *e) {
QMainWindow::changeEvent(e);
if(e->type()==QEvent::WindowStateChange)
if(isMinimized()) {
trayIcon=new QSystemTrayIcon(QIcon(":/icon/itime.ico"));
connect(trayIcon,SIGNAL(activated(QSystemTrayIcon::ActivationReason)),this,SLOT(on_show(QSystemTrayIcon::ActivationReason)));
QAction *showAction=new QAction("Pokaż",trayIcon);
connect(showAction,SIGNAL(triggered()),this,SLOT(on_show()));
QMenu *trayIconMenu=new QMenu;
trayIconMenu->addAction(showAction);
trayIcon->setContextMenu(trayIconMenu);
trayIcon->show();
this->hide();
}
}
on_show(QSystemTrayIcon::ActivatioReason) SLOT:
void MainWindow::on_show(QSystemTrayIcon::ActivationReason reason) {
if(reason) {
if(reason!=QSystemTrayIcon::DoubleClick)
return;
}
if(this->isMinimized()) {
this->raise();
this->showNormal();
this->setWindowState(Qt::WindowActive);
trayIcon->hide();
}
}
on_show() SLOT is just the same besides that first if.
Soo, I would like to know whether there is any way to disable minimizing of window by taskbar icon click.
If there's none, then maybe you have any ideas what can go wrong in here when doubleclicking on icon in taskbar?
Thanks for help!
I've managed to work around that problem by overloading closeEvent function and leaving alone changeEvent function.
So, I'm using boolean flag to distinct between closing of program by menu item and by clicking "X" button and the rest stays just the same, as posted in my earlier post with one change.
I've moved this whole block of code to window constructor in order to prevent multiple creation of trayIcon, as pointed out by Nicolas.
trayIcon=new QSystemTrayIcon(QIcon(":/icon/itime.ico"));
connect(trayIcon,SIGNAL(activated(QSystemTrayIcon::ActivationReason)),this,SLOT(on_show(QSystemTrayIcon::ActivationReason)));
QAction *showAction=new QAction("Pokaż",trayIcon);
connect(showAction,SIGNAL(triggered()),this,SLOT(on_show()));
QMenu *trayIconMenu=new QMenu;
trayIconMenu->addAction(showAction);
trayIcon->setContextMenu(trayIconMenu);
Thanks for your help!
Let's say I have 2 windows in my application, and two classes responsible for them:
class MainWindow: public QMainWindow and class SomeDialog: public QWidget.
In my Main Window I have a button. When it is clicked, I need to display the second window. I do it this way:
SomeDialog * dlg = new SomeDialog();
dlg.show();
Now, the user does something in the window, and closes it. At this point I want to get some data from that window, and then, I suppose, I will have to delete dlg. But how do I catch the event of that window being closed?
Or is there another way not to have a memory leak? Maybe It would be better to create an instance of each window on startup, and then just Show()/Hide() them?
How do I manage such a case?
It is advised to use show() / exec() and hide() instead of dynamically creating the dialog every time you want to show it. Also use QDialog instead of QWidget.
In the constructor of your main window create it and hide it
MainWindow::MainWindow()
{
// myDialog is class member. No need to delete it in the destructor
// since Qt will handle its deletion when its parent (MainWindow)
// gets destroyed.
myDialog = new SomeDialog(this);
myDialog->hide();
// connect the accepted signal with a slot that will update values in main window
// when the user presses the Ok button of the dialog
connect (myDialog, SIGNAL(accepted()), this, SLOT(myDialogAccepted()));
// remaining constructor code
}
In the slot connected to the buttons's clicked() event simply show it, and if necessary pass some data to the dialog
void myClickedSlot()
{
myDialog->setData(data);
myDialog->show();
}
void myDialogAccepted()
{
// Get values from the dialog when it closes
}
Subclass from QWidget and reimplement
virtual void QWidget::closeEvent ( QCloseEvent * event )
http://doc.qt.io/qt-4.8/qwidget.html#closeEvent
Also it looks like the widget you want to show is a dialog. So consider using QDialog or it's subclasses. QDialog has useful signals you can connect to:
void accepted ()
void finished ( int result )
void rejected ()
I think you are looking for the Qt::WA_DeleteOnClose window flag: http://doc.qt.io/archives/qt-4.7/qt.html#WidgetAttribute-enum
QDialog *dialog = new QDialog(parent);
dialog->setAttribute(Qt::WA_DeleteOnClose)
// set content, do whatever...
dialog->open();
// safely forget about it, it will be destroyed either when parent is gone or when the user closes it.