I want to be able to double click a QPushbutton instead of a single click.
What I tried:
connect(pb, SIGNAL(doubleClicked()), this, SLOT(comBtnPressed()));
Error says "QObject::connect: No such signal QPushButton::doubleClicked()"
I chose QPushButton initially, but for my purpose, you can suggest change to other object if it can make a doubleclick event. Not necessarily be a push button.
Thank you Masters of Qt and C++.
A simple solution is to create our own widget so we overwrite the mouseDoubleClickEvent method, and you could overwrite paintEvent to draw the widget:
#ifndef DOUBLECLICKEDWIDGET_H
#define DOUBLECLICKEDWIDGET_H
#include <QWidget>
#include <QPainter>
class DoubleClickedWidget : public QWidget
{
Q_OBJECT
public:
explicit DoubleClickedWidget(QWidget *parent = nullptr):QWidget(parent){
setFixedSize(20, 20);
}
signals:
void doubleClicked();
protected:
void mouseDoubleClickEvent(QMouseEvent *){
emit doubleClicked();
}
void paintEvent(QPaintEvent *){
QPainter painter(this);
painter.fillRect(rect(), Qt::green);
}
};
#endif // DOUBLECLICKEDWIDGET_H
If you want to use it with Qt Designer you can promote as shown in the following link.
and then connect:
//new style
connect(ui->widget, &DoubleClickedWidget::doubleClicked, this, &MainWindow::onDoubleClicked);
//old style
connect(ui->widget, SIGNAL(doubleClicked), this, SLOT(onDoubleClicked));
In the following link there is an example.
Related
I am beginner in Qt, now I want to make my label clickable, I have searched so much online, but no one gives my a real example of how they made it. So can someone teach me step by step? Now my basic thinking is creating a new .c file and new .h file respectively and then include them into my mainwindow.c and then connect it with the existing label in ui form. These are what I was trying to do, but can not make it. Hope someone can teach and better put the step picture in the command, thanks.
Here is the clicklabel.h code:
#ifndef CLICKEDLABEL_H
#define CLICKEDLABEL_H
#include <QWidget>
#include <QLabel>
class ClickedLabel : public QLabel
{
Q_OBJECT
public:
ClickedLabel(QWidget *parent=0): QLabel(parent){}
~ClickedLabel() {}
signals:
void clicked(ClickedLabel* click);
protected:
void mouseReleaseEvent(QMouseEvent*);
};
#endif // CLICKEDLABEL_H
This the clicklabel.c code:
#include "clicklabel.h"
void ClickedLabel::mouseReleaseEvent(QMouseEvent *)
{
emit clicked(this);
}
These are what I added into my mainwindow.c( the name of the label is click_test):
void data_labeling::on_label_clicked()
{
QString path="/home/j/Pictures/images.jpeg";
QPixmap cat(path);
connect(ui->click_test, SIGNAL(clicked()), this,
SLOT(on_label_clicked()));
ui->click_test->setPixmap(cat);
ui->click_test->resize(cat.width(),cat.height());
}
Of course I have promoted it to clicklabel.h and also I have added void on_label_click() to my mainwindow.h under private slots, but nothing happened.
Create a new class derived from QLabel, reimplement mousePressEvent to emit custom pressed() signal (or any other functionality you need)
If you need to use your clickable label in ui files, follow these steps:
Add QLabel to the form
Right-click on added label and select Promote to...
Enter your clickable label class name and its header file name
Press add, than select your label in the tree and select promote
Now you can use your subclassed label (this tutorial actually works for any subclassed widget) as any QWidget using ui->
You can use QPushButton instead, but if you desperately need QLabel, you can do this:
clickable.h
class Clickable :public QLabel
{
Q_OBJECT
signals:
void clicked();
public:
void mousePressEvent(QMouseEvent* event);
using QLabel::QLabel;
};
clickable.cpp
void Clickable::mousePressEvent(QMouseEvent* event)
{
emit clicked();
}
UPDATE:
This implementation I used in my source code. I can't paste complete code, but here is the part where I used it.
source.h
...
private:
QLabel* label1;
QLabel* label2;
...
source.cpp
...
label1 = new Clickable("label1 text", this);
label2 = new Clickable("label2 text", this);
...
connect(label1 , SIGNAL(clicked()), this, SLOT(label1clicked()));
connect(label2 , SIGNAL(clicked()), this, SLOT(label1clicked()));
...
I'm really stuck on one problem that I want to solve. the problem is that I have a Class for QMainWindow which holds the Ui variable for that form. Now I want to be able to edit that Form using the Ui variable in that class on a QDialog cpp file. I probably sound really stupid and I really have no idea how I should explain this, but I have code which maybe can help.
MainWindow.h:
#include "ui_mainwindow.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
protected:
Ui::MainWindow *ui;
}
MainWindow.cpp:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "dialog.h"
Dialog *dialog;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
dialog = new Dialog(this);
dialog->show();
}
QDialog.cpp:
#include "ui_mainwindow.h"
#include "mainwindow.h"
#include "dialog.h"
#include "ui_dialog.h"
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
}
Dialog::~Dialog()
{
delete ui;
}
Ui::MainWindow *mainui;
void Dialog::on_pushbutton_clicked(){
mainui->label->setText("test");
}
So as you can see from the above code, it shows that I have a pointer to the Ui variable however its uninitialised, therefore it would lead to a SIGSEGV error, so how to do Initialize this pointer? any help here is highly appreciated, and even though this is probably really simple I just don't know what to do. (I have looked at other questions but I couldn't quite grasp what to do, so please explain what I am to do before linking me to a similar question. Also, I have left out the Dialog.h file as I didn't think it was needed, please tell me if I need to show it, thanks!).
Generally in C++ you should practice what is called encapsulation - keep data inside a class hidden from others that don't need to know about it. It's not good to have multiple pointers to the UI object as now all those other objects have to know how the main window UI is implemented.
In this case, what I would recommend is to use Qt's signals and slots mechanism to allow the dialog to tell the main window what you need it to do. That has the advantage that if you add more dialogs, or change how things are implemented in the main window, you don't need to alter the signal slot mechanism, and the details are hidden cleanly.
So - for your dialog, add a signal like this in the header file
class Dialog : QDialog
{
Q_OBJECT
signals:
void setTextSignal(QString text);
}
and in your main window header, add a slot.
class MainWindow : public QMainWindow
{
Q_OBJECT
public slots:
void setTextSlot(const QString &text);
}
now in your method where the button is pressed,
void Dialog::on_pushbutton_clicked()
{
emit setTextSignal("test");
}
and in your main window
void MainWindow::setTextSlot(const QString &text)
{
mainUi->label->setText(text);
}
The final part is to connect the signal and slot together, which you would do in your main window function where you create the dialog:
void MainWindow::on_pushButton_clicked()
{
dialog = new Dialog(this);
connect(dialog, SIGNAL(setTextSignal(QString)), this, SLOT(setTextSlot(QString)));
dialog->show();
}
You can see there are many advantages to this; the Dialog no longer needs a pointer to the main window UI, and it makes your code much more flexible (you can have other objects connected to the signals and slots as well).
Short answere - your can't! If you want to create a new instance of the ui, you would have to do:
MainWindow::Ui *ui = new MainWindow::UI();
ui->setupUi(this);
However, the this-pointer for a UI created for a QMainWindow based class must inherit QMainWindow - thus, you can't.
In general, it is possible if you create your Ui based on a QWidget instead of a QMainWindow, since both inherit QWidget.
Alternativly, you could try the following:
QMainWindow *subWindow = new QMainWindow(this);
subWindow->setWindowFlags(Qt::Widget);
MainWindow::Ui *ui = new MainWindow::UI();
ui->setupUi(subWindow );
//... add the mainwindow as a widget to some layout
But I would guess the result will look weird and may not even work in the first place.
This might come off as a very stupid question, but I have to write a very simple program, consisting of a line edit and push button.
This program has to be able to take inputs(numbers) from the user in the line edit area and every time the push button is pressed, store the number values within an array of size 10.
I have some experience with C++ but am just generally very confused with the GUI aspects of Qt. The GUI stuff is just way over my head so I apologize again if this is trivial! But if anyone could help me figure out how to do this you would be the coolest.
Thanks!
Things need to do
set a button and a lineedit either in ui or in constructor of mywindows.
set validator for int.
declare a slot for button, to pass the int in lineEdit to your data structure.
fixed array is not enough to store all the user input, you need to think about whether you need is a list, a dynamic array, a fixed array of stack or queue.
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QList>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
QList<int> m_list;
};
#endif // MAINWINDOW_H
mainwindows.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
ui->lineEdit->setValidator(new QIntValidator(0, 9999, this));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
m_list.append(ui->lineEdit->displayText().toInt());
qDebug() << m_list;
}
Put lineEdit and button on form in Qt Designer or create it by yourself:
Create slot in header:
private slots:
void mySlot();
//do connection in dialog's constructor
connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(mySlot()));
//Write slot
void Dialog::mySlot()
{
QString str = ui->lineEdit->text()
//now str contains all your text you can put it in different arrays.
}
text() return QString, but if you sure that it is double, then call toDouble() method
QString str = ui->lineEdit->text().replace(",",".")
double var = str.toDouble();
Moreover you can set QDoubleValidator to lineEdit and user can input only double in this lineEdit. Search in web what validator is and use setValidator() method to set it to lineEdit.
I will start off by explaining my main goal. I have a main window with 7 buttons on it(amongst other things), when you hit each button, it closes out the current window and opens up a new window. All the windows will have the same 7 buttons, so you can go between each window. With all windows having the exact same 7 buttons, I wanted to set up a function that each class can call to set up each button and connect to a slot() in my mainwindow.cpp(called setupSubsystemButtons in example below). However, I can't seem to get the window to close using the standard "this->close()"...it works when I go from the main window to another window(the main window closes) but when I go from a different window to say the home window, the different window doesn't close. Suggestions would be greatly appreciated. My guess is that my understanding of "this" when it comes to calling slots in another class is wrong.
mainwindow.cpp( the parts that are relevant)
void MainWindow::ECSgeneralScreen()
{
ECSgeneralCommand *ECSgeneral = new ECSgeneralCommand;
this->close();
ECSgeneral->show();
//opens up the ECS screen
}
void MainWindow::homeScreen()
{
MainWindow *home = new MainWindow;
this->close();
home->show();
//opens up the ECS screen
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::setupSubsystemButtons(QGridLayout *layout)
{
//Push Button Layout
homeScreenButton = new QPushButton("Home");
layout->addWidget(homeScreenButton, 3, 11);
connect(homeScreenButton, SIGNAL(clicked()), this, SLOT(homeScreen()));
ECSgeneralScreenButton = new QPushButton("General");
layout->addWidget(ECSgeneralScreenButton,5,11);
connect(ECSgeneralScreenButton, SIGNAL(clicked()), this, SLOT(ECSgeneralScreen()));
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QtWidgets>
#include <QDialog>
namespace Ui {
class MainWindow;
}
class MainWindow : public QDialog
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
QWidget *window;
void setupSubsystemButtons(QGridLayout *layout);
~MainWindow();
private slots:
public slots:
void ECSgeneralScreen();
void homeScreen();
};
#endif // MAINWINDOW_H
ecsgeneralcommandWindow
include "ecsgeneralcommand.h"
#include "mainwindow.h"
#include <QtWidgets>
#include <QtCore>
ECSgeneralCommand::ECSgeneralCommand(MainWindow *parent) : QDialog(parent)
{
QGridLayout *layout = new QGridLayout;
QWidget::setFixedHeight(600);
QWidget::setFixedWidth(650);
...
//Setup Subsystem Buttons
test.setupSubsystemButtons(layout);
setLayout(layout);
}
ecsgeneralcommandWindow header
#ifndef ECSGENERALCOMMAND_H
#define ECSGENERALCOMMAND_H
#include <QDialog>
#include <QMainWindow>
#include <QtWidgets>
#include <QObject>
#include "mainwindow.h"
class ECSgeneralCommand : public QDialog
{
Q_OBJECT
public:
explicit ECSgeneralCommand(MainWindow *parent = 0);
private:
MainWindow test;
public slots:
};
#endif // ECSGENERALCOMMAND_H
Slots are just normal functions. When Qt invokes a slot, it ends up calling the appropriate receiver's method. In other words, this equals to the value of the 3rd argument of your connect statements. You passed this there, so the receiver is MainWindow object. E.g. MainWindow::homeScreen method always tries to close MainWindow. If it is already hidden, this action takes no effect.
You should either have a slot in each window class and connect buttons to appropriate receivers, or use a pointer to the currently active window instead of this when calling close(). But your architecture is strange in the first place. Why would you need to create these buttons for each window? It is reasonable to create them once and use in all windows. Also hiding and showing windows is not necessary. You can create one main window with buttons and a QStackedWidget that will contain the content of all other windows. Maybe you can even use QTabWidget instead of these buttons.
I'm a very beginnner at C++ /Qt programming. I've made this simple dialog box that check the QLineEdit, if the text entered is "bob" should enable the OK button.
I can't get it to compile successfully, it gives me:
dialog.cpp|31|undefined reference to `Dialogmio::send()'
What am I doing wrong?
This is dialog.h:
//dialog.h
#ifndef DIALOG_H_INCLUDED
#define DIALOG_H_INCLUDED
#include <QDialog>
class QPushButton;
class QLineEdit;
class Dialogmio : public QWidget
{
public:
Dialogmio(QWidget *parent =0);
signals:
void send ();
public slots:
void recip(QString &text);
private:
QLineEdit *linedit;
QPushButton *buttonOK;
};
#endif
This is dialog.cpp:
//dialog.cpp
#include <QtGui>
#include "dialog.h"
Dialogmio::Dialogmio(QWidget *parent)
: QWidget(parent)
{
linedit = new QLineEdit();
buttonOK = new QPushButton("OK");
buttonOK->setEnabled(FALSE);
connect( linedit, SIGNAL( textChanged(const QString &) ), this, SLOT( recip(const QString &) ));
connect (this,SIGNAL( send()), this, SLOT( buttonOK->setEnabled(true)) );
QHBoxLayout *layout = new QHBoxLayout();
layout->addWidget(linedit);
layout->addWidget(buttonOK);
setLayout(layout);
}
void Dialogmio::recip(QString &text)
{
QString a = linedit->text();
if (a == "bob"){
emit send(); //here it gives me the error
}
}
This is main.cpp:
#include <QApplication>
#include "dialog.h"
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
Dialogmio *dialog = new Dialogmio;
dialog->show();
return app.exec();
}
I've inserted the Q_OBJECT macro as suggested, now I get one more errors on line 7:
dialog.cpp|7|undefined reference to `vtable for Dialogmio'|
You start by including the Qt file for QDialog, but then go on to inherit from QWidget. While inheriting from QWidget is not a problem, was your intention to actually inherit from QDialog(?), in which case you should define your class this way: -
class Dialogmio : public QDialog
{
Q_OBJECT
public:
Dialog(QWidget* parent);
private slots:
void aSlotFunction();
}
The signals and slots mechanism are C++ extensions that are unique to Qt and in order for a class to use it, the class must include the Q_OBJECT macro, which adds all the necessary functionality. During the build stages, Qt parses the header and creates the code required for the extensions, including run-time type information, the dynamic property system and of-course the signals and slots.
As you state you're using codeblocks as the IDE, if it doesn't automatically run qmake before building, you'll need to do that whenever you add any signals or slots to a class in order for the moc (meta-object-compiler) to see them.
Another thing is that the call to connect signals and slots is wrong: -
connect (this,SIGNAL( send()), this, SLOT( buttonOK->setEnabled(true)) );
The parameter in the SLOT macro takes a slot function, so you need to create a slot and connect it to the send signal: -
connect(this, SIGNAL(send()), this, SLOT(aSlotFunction());
Inside the aSlotFunction, you can then call the set enabled for the button: -
void Dialogmio::aSlotFunction()
{
buttonOK->setEnabled(true);
}
If you're using Qt 5, there's an easier syntax of handling the connection: -
connect(this, &Dialogmio::send, this, &Dialogmio::aSlotFunction);
As this syntax accepts pointers to the functions that will be called, they don't actually have to be declared as slots to work. In addition, you do not provide the arguments, so if they change, you won't have to update the connect calls too.