I have an embedded touch screen running linux and my app is Qt/C++.
I start the app with the function main which looks like this:
#include <QApplication>
#include <QThread>
#include <stdlib.h>
int main(int argc, char *argv[])
{
// Create the app
QApplication app(argc, argv);
// Hide the pointer
app.setOverrideCursor( QCursor( Qt::BlankCursor ) );
// Create main window
MainWindow *window = new MainWindow;
// Set up the UI and execute the App
window->show();
app.exec();
// tidy up
delete(window);
return 0;
}
The problem that I have is that when I run the program the cursor is showing. But as soon as I touch the screen (the app is a full-screen app) the cursor then disappears.
I have read that it may be a simple focus issue - i.e. that my app is not in focus or some-such. How can I make sure that my app is the focus at startup?
Or
Is there anything I am doing wrong to hide the mouse pointer?
---EDIT---
If I remove the line app.setOverrideCursor( QCursor( Qt::BlankCursor ) ); then I have focus on my app. So this line somehow makes my app lose focus.
So as a quick hack I put a QTimer in the MainWindow and set it for 100ms (just so that it will only get handled once the event processing starts - i.e. after app.execute()). Then I connected the timer event to a slot function that I call "getFocusOnMeNow()" which in which I have:
this->activateWindow();
this->setFocus();
And this works.
So now I would like to tidy this up. What function/slot can I call AFTER app.execute() within the MainWindow to get focus? I don't see a MainWindow::start() slot that I can overload...?
try
app.setCursorVisible(false);
may this help u.
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 need to implement custom completer, similar to QCompleter but containing customized widgets. I got stuck at the very beginning, I can't make the popup work as it should work. In the following example I attach a completer (well, just a plain widget) to the first line edit. The second line edit is there just to test the focus in/out behavior. The problem is that when the popup displays, it steals the focus from the line edit. But this is not what I want, I want to be able to keep typing in the line edit. I tried several other options as commented out in the code below, but non of them worked.
#include <QApplication>
#include <QLineEdit>
#include <QHBoxLayout>
#include <QWidget>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QWidget container;
QLineEdit editor;
QLineEdit editor2;
QHBoxLayout layout(&container);
layout.addWidget(&editor);
layout.addWidget(&editor2);
QWidget completer; // or QWidget completer(&editor);?
//completer.setFocusProxy(&editor); // tried this, but it does not help
completer.setWindowFlags(Qt::Popup);
// the following lines are an alternative to Qt::Popup but the window
// does not close automatically, which is a problem
// e.g. when moving or resizing the parent window
//completer.setAttribute(Qt::WA_ShowWithoutActivating);
//completer.setWindowFlags(Qt::Tool | Qt::FramelessWindowHint);
QObject::connect(&editor, &QLineEdit::textEdited,
[&] {
completer.resize(editor.width(), 100);
completer.move(editor.mapToGlobal(QPoint(0, editor.height())));
completer.show();
// editor.setFocus(); // does not help either
});
container.show();
return a.exec();
}
How to implement custom completer?
UPDATE: From the docs, I read that "A popup widget is a special top-level widget that sets the Qt::WType_Popup widget flag, e.g. the QMenu widget. When the application opens a popup widget, all events are sent to the popup. Normal widgets and modal widgets cannot be accessed before the popup widget is closed."
So it seems that when I open a popup it automatically receives the events and therefore I have to forward the events to the line edit using QCoreApplication::sendEvent(editor, event); inside my Completer::keyPressEvent. This seems to work fine except the fact that the cursor in the line edit is not visible or not blinking.
Just apply this method to your completer widget:
setWindowFlags(Qt::Tool | Qt::FramelessWindowHint|Qt::WindowStaysOnTopHint);
It works for me.
I'm working on an QT HTML5 application and I was wondering how i could add an top menu just like normal program ( with the default file, tools, help... options ).
I think that I've to change something in the html5applicationviewer.cpp, but I've got 0 knowledge of that ( I'm learning this... )
Even if you could point me a little bit in the right direction, I'm grateful. I've searched around, but found absolutely nothing about this topic ( but maybe i didn't search right... )
If you need more info, please ask.
Simplest way to add normal "desktop"-style menus to a Qt app is to use QMainWindow which has good support for menus.
Here's something to get you started. First I created the default HTML5 Qt application with Qt Creator (SDK version 5.2.1). Then I edited the main.cpp and added some lines. Result is below, original lines without comment and all added lines with comment.
#include <QApplication>
#include <QMainWindow> // added
#include <QMenuBar> // added
#include <QMenu> // added
#include <QAction> // added
#include "html5applicationviewer.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QMainWindow w; // important, viewer is in stack so w must be before it!
Html5ApplicationViewer viewer;
w.setCentralWidget(&viewer); // set viewer as the central widget
QMenu *fileMenu = w.menuBar()->addMenu("&File"); // create file menu
QAction *exitAction = fileMenu->addAction("&Exit"); // create exit action
QObject::connect(exitAction, SIGNAL(triggered()), qApp, SLOT(quit())); // make the action do something
viewer.setOrientation(Html5ApplicationViewer::ScreenOrientationAuto);
//viewer.showExpanded(); // will be shown by main window
viewer.loadFile(QLatin1String("html/index.html"));
w.show(); // show main window
return app.exec();
}
I´ve beeing programming Java for some time right now...Now that I got into C++ and Qt I am a bit lost about GUI Thread (EDT Thread) and Worker Thread
I am trying to make the main window of my application open only when the configuration window is closed.
I dont want to put the code for creating the main window in the OK button of my configuration window.
I tryed to make them modal but the main window still opens.....
Afther configuration is complete I still have to see if there is an application update...So its something like
EDIT: This is my main:
ConfigurationWindow *cw = new ConfigurationWindow();
//if there is no text file - configuration
cw->show();
//**I need to stop here until user fills the configuration
MainWindow *mw = new MainWindow();
ApplicationUpdateThread *t = new ApplicationUpdateThread();
//connect app update thread with main window and starts it
mw->show();
Try something like this:
#include <QtGui>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QDialog *dialog = new QDialog;
QSlider *slider = new QSlider(dialog);
QHBoxLayout *layout = new QHBoxLayout(dialog);
layout->addWidget(slider);
dialog->setLayout(layout);
dialog->exec();
qDebug() << slider->value(); // prints the slider's value when dialog is closed
QMainWindow mw; // in your version this could be MainWindow mw(slider->value());
w.show();
return a.exec();
}
The idea is that your main window's constructor could accept parameters from the QDialog. In this contrived example I'm just using qDebug() to print the value of the slider in the QDialog when it's closed, not passing it as a parameter, but you get the point.
EDIT: You might also want to "delete" the dialog before creating the main window in order to save memory. In that case you would need to store the parameters for the main window constructor as separate variables before deleting the dialog.
You have to learn about signals and slots. The basic idea is that you would send a signal when you configuration is finished. You put your QMainWindow in a member variable and call mw->show() in a slot of your main programm that is connected with the configurationFinished signal.
If your ConfigurationWindow is a QDialog, you could connect the finished(int) signal to the MainWindow's show() slot (and omit the show() call from main).
I am having a qt question. I want the QLineEdit widget to have the focus at application startup. Take the following code for example:
#include <QtGui/QApplication>
#include <QtGui/QHBoxLayout>
#include <QtGui/QPushButton>
#include <QtGui/QLineEdit>
#include <QtGui/QFont>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWidget *window = new QWidget();
window->setWindowIcon(QIcon("qtest16.ico"));
window->setWindowTitle("QtTest");
QHBoxLayout *layout = new QHBoxLayout(window);
// Add some widgets.
QLineEdit *line = new QLineEdit();
QPushButton *hello = new QPushButton(window);
hello->setText("Select all");
hello->resize(150, 25);
hello->setFont(QFont("Droid Sans Mono", 12, QFont::Normal));
// Add the widgets to the layout.
layout->addWidget(line);
layout->addWidget(hello);
line->setFocus();
QObject::connect(hello, SIGNAL(clicked()), line, SLOT(selectAll()));
QObject::connect(line, SIGNAL(returnPressed()), line, SLOT(selectAll()));
window->show();
return app.exec();
}
Why does line->setFocus() sets the focus on the line widget #app startup only if it is placed after laying out the widgets and if used before it's not working?
Keyboard focus is related to widget tab order, and the default tab order is based on the order in which widgets are constructed. Therefore, creating more widgets changes the keyboard focus. That is why you must make the QWidget::setFocus call last.
I would consider using a sub-class of QWidget for your main window that overrides the showEvent virtual function and then sets keyboard focus to the lineEdit. This will have the effect of always giving the lineEdit focus when the window is shown.
Another trick that might work is by using the singleshot timer:
QTimer::singleShot(0, line, SLOT(setFocus()));
Effectively, this invokes the setFocus() slot of the QLineEdit instance right after the event system is "free" to do so, i.e. sometime after the widget is completely constructed.
Perhaps this is an update as the last answer was in 2012 and the OP last edited the question in 2014. They way I got this to work was to change the policy and then set the focus.
line->setFocusPolicy(Qt::StrongFocus);
line->setFocus();
In Qt setFocus() is a slot, you can try other overloaded method which takes a Qt::FocusReason parameter like the line shown below:
line->setFocus(Qt::OtherFocusReason);
You can read about focus reason options in the following link:
http://doc.trolltech.com/4.4/qt.html#FocusReason-enum