Object creation: I want to create an object of class Note, that is a QWidget. How can I do this? I am only able to show the Note bla that has been declared as a private member of class Traymenu. This goes by clicking on "new Note" in the context Menu of the trayMenu. I want to create a new note for each click on this and add it to a list of Notes in trayMenu to keep the note alive, but don't have an idea how to define a list of elements of objects of my own class Note.
So my 2 problems are: How to create a new note on runtime and how to keep it alive in a list that belongs to trayMenu.
If i comment out the 2 lines Note nwNtand nwNt.show() the compiler says that something in qglobals.h is private.
traymenu.h:
#ifndef TRAYMENU_H
#define TRAYMENU_H
#include <QSystemTrayIcon>
#include <QIcon>
#include <QPixmap>
#include <QMenu> //in use for context menu
#include "note.h"
class Traymenu : public QSystemTrayIcon
{
public:
Traymenu();
~Traymenu();
void createMainContextMenu();
void newNote();
private:
QSystemTrayIcon mainIcon;
QMenu mainContextMenu;
Note bla;
};
#endif // TRAYMENU_H
traymenu.cpp:
#include "traymenu.h"
#include <QDebug>
Traymenu::Traymenu(){
mainIcon.setIcon(QIcon(QPixmap("C:\\papersavers.png")));
mainIcon.setVisible(true);
mainIcon.show();
createMainContextMenu();
}
Traymenu::~Traymenu(){
}
void Traymenu::createMainContextMenu(){
QAction *actionNewNote = mainContextMenu.addAction("Neue Notiz");
QObject::connect(actionNewNote,&QAction::triggered,this,&Traymenu::newNote);
mainIcon.setContextMenu(&mainContextMenu);
}
void Traymenu::newNote(){
qDebug() << "in newNote()" << endl;
//Note nwNt;
//nwNt.show();
bla.show()
}
note.h:
#ifndef NOTE_H
#define NOTE_H
#include <QWidget>
namespace Ui{
class Note;
}
class Note : public QWidget
{
public:
Note(QWidget *parent = 0);
~Note();
private:
Q_OBJECT
Ui::Note *ui;
};
#endif // NOTE_H
note.cpp:
#include "note.h"
#include "ui_note.h"
Note::Note(QWidget *parent) :
QWidget(parent),
ui(new Ui::Note)
{
ui->setupUi(this);
}
Note::~Note()
{
delete ui;
}
Related
I am new in C++ Qt and struggling with the correct use of forward declarations and #include.
What I want to do:
I have a Qt Gui (Class Ui::Gui) where we can set values.
I want to save these values in Gui Class variables.
As soon as a button (Generate Xml) is clicked, I want to pass the object
'ui' to the XmlGeneratorClass, So i can use the values to generate a Xml.
gui.h
#ifndef GUI_H
#define GUI_H
#include <QMainWindow>
#include <QDebug>
#include "xmlgeneratorqobject.h"
namespace Ui {
class Gui;
}
class Gui : public QMainWindow
{
Q_OBJECT
public:
explicit Gui(QWidget *parent = nullptr);
~Gui();
qint8 testvalue = 1;
signals:
void transmitToXmlGen(Ui::Gui*);
private slots:
void on_pushButtonGenerateXml_clicked();
private:
Ui::Gui *ui;
XmlGeneratorQObject *xmlgenerator = new XmlGeneratorQObject();
};
#endif // GUI_H
gui.cpp
#include "gui.h"
#include "ui_gui.h"
Gui::Gui(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Gui)
{
ui->setupUi(this);
connect(this,SIGNAL(transmitToXmlGen(Ui::Gui*)),xmlgenerator,SLOT(receiveFromGui(Ui::Gui*)));
}
Gui::~Gui()
{
delete ui;
}
void Gui::on_pushButtonGenerateXml_clicked()
{
emit transmitToXmlGen(ui);
}
xmlgeneratorqobject.h
#ifndef XMLGENERATORQOBJECT_H
#define XMLGENERATORQOBJECT_H
#include <QObject>
#include <QDebug>
namespace Ui {
class XmlGeneratorQObject;
class Gui;
}
class XmlGeneratorQObject : public QObject {
Q_OBJECT
public:
explicit XmlGeneratorQObject(QObject * parent = nullptr);
private slots:
void receiveFromGui(Ui::Gui*);
};
#endif // XMLGENERATORQOBJECT_H
xmlgeneratorqobject.cpp
#include "xmlgeneratorqobject.h"
XmlGeneratorQObject::XmlGeneratorQObject(QObject *parent){}
void XmlGeneratorQObject::receiveFromGui(Ui::Gui* objectFromGui)
{
qDebug() << objectFromGui->testvalue; // ERROR member access into incomplete type 'Ui::Gui'
}
Expected result:
Access to public variables from passed gui-object should be possible
Actual result:
member access into incomplete type 'Ui::Gui'
Can you please help me learn forward declaration / include?
Is my approach in general okay?
Your xmlgeneratorqobject.cpp needs the line
#include "ui_gui.h"
This gives it the details of the ui widgets. This file is generated by the Qt build system.
Hi i have 3 classes that i want to use. but i dont want to create object of one class more than once. I directly want to use the object (in third class) of one class declared and initialized in second class.
To understand the problem please focus on NetworkConnection members and class defined in example below.
Class Mainwindow header
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "secondscreen.h"
#include "networkconnection.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
NetworkConnection *NetworkConnectionObject;
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
SecondScreen* SecondScreenObject;
};
#endif // MAINWINDOW_H
Class Main Window cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QMessageBox"
#include "networkconnection.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
NetworkConnectionObject = new NetworkConnection();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
int Error = NetworkConnectionObject->Connect(Username,Password);
///////////////
// This Works
//////////////
NetworkConnectionObject->LogInToken = "";
}
Class NetworkConnection Header
#ifndef NETWORKCONNECTION_H
#define NETWORKCONNECTION_H
#include <QString>
class NetworkConnection
{
public:
NetworkConnection();
int Connect(QString Username, QString Passwd);
QString LogInToken;
};
#endif // NETWORKCONNECTION_H
Now i want to use Networkclassobject directly in SeconScreenclass so that i can access LogInToken Member of MainWindowInstance.
#include "secondscreen.h"
#include "ui_secondscreen.h"
#include "mainwindow.cpp"
SecondScreen::SecondScreen(QWidget *parent) :
QDialog(parent),
ui(new Ui::SecondScreen)
{
ui->setupUi(this);
///////////////
// This doesnot work
//////////////
MainWindow::NetworkConnectionObject->LogInToken = "";
}
SecondScreen::~SecondScreen()
{
delete ui;
}
However, when i try this compiler says
Invalid use of non-static data member "MainWindow::NetworkConnectionObject" Problem is i dont want to declare it static. Is there any way to do it.
Without seeing secondscreen.h I can't say for sure but MainWindow::NetworkConnectionObject" doesn't reference a specific instance of MainWindow class, you must reference a specific instance to modify.
If in your SecondScreen header you have something like
class SecondScreen {
// . . .
MainWindow window;
// . . .
}
then in your constructor for SecondScreen you must use the initialized instance of MainWindow, i.e.
SecondScreen::SecondScreen(QWidget* parent) : QDialog(parent) {
window.NetworkConnectionObject->LogInToken = "";
}
i'm trying to change the label text of Class A via Class B using Qt but i can't get it working, here's my codes:
Class A:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "loldata.h"
using namespace std;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
LoLData *lold = new LoLData();
QObject::connect(ui->pushButton, SIGNAL(clicked()), this, SLOT(updateData()));
QObject::connect(lold, SIGNAL(updatePlayerID(QString)), ui->label, SLOT(setText(QString)));
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::updateData()
{
LoLData summoner;
summoner.getSummonerData("Snylerr");
}
Class A: (.h)
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QObject>
#include <string>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void updateData();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
Class B:
#include "loldata.h"
#include "mainwindow.h"
using namespace std;
int LoLData::getSummonerData(QString playerName)
{
emit updatePlayerID("playerName");
return 0;
}
Class B: (.h)
#ifndef DEF_LOLDATA
#define DEF_LOLDATA
#include <QApplication>
#include <QObject>
#include <string>
class LoLData : public QObject
{
Q_OBJECT
public:
int getSummonerData(QString playerName);
signals:
void updatePlayerID(QString playerName);
private:
};
#endif
You can see that i tried to use slots and signals but the text of the label is not changing, i saw a lot of examples on internet but i can't get them working
Thanks for your reply.
You are creating a new instance of LoLData here:
void MainWindow::updateData()
{
LoLData summoner;
summoner.getSummonerData("Snylerr");
}
This instance of LoLData named summoner is not connected to your label's setText slot.
LoLData *lold = new LoLData(); - this instance of LolData is connected to you label's setText slot.
What should yo do?
It depends on what you want to accomplish:
either connect your summoner instance to the label by inserting a QObject::connect(&summoner...) inside yourupdateData` method;
or you don't instantiate a new LolData variable and use lold inside your updateData function:
void MainWindow::updateData()
{
lold->getSummonerData("Snylerr");
}
Also in this case you have to put lold as a member variable.
In your MainWindow constructor, you connect your lold object to the setText slot.
But in updateData, you use an other object (summoner) which is not connect to anything. So when you use getSummonerData on summoner, the signal updatePlayerID is emitted nut they is no slot connected to it.
I want to get the currentIndex of combobox in the main Widget, then send this value to another class. I tried to make a function to return the currentIndex, however, I always get '0'. Could someone explain me why, or give me an example? Plus, I think it's because I create a new object in another class, but how can I get the actived Widget's pointer? Here are the codes:
widget.h
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
namespace Ui { class Widget; }
class Widget : public QWidget {
Q_OBJECT
public:
explicit Widget(QWidget *parent = 0);
~Widget();
int comboboxText();
private slots:
void on_pushButton_clicked();
private:
Ui::Widget *ui; };
#endif // WIDGET_H
widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include <QDebug>
#include "database.h"
Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
}
Widget::~Widget()
{
delete ui;
}
int Widget::comboboxText(){
return ui->comboBox->currentIndex();
}
void Widget::on_pushButton_clicked()
{
qDebug() << "from Widget: " << comboboxText();
Database database;
database.getIndex();
}
database.h
#ifndef DATABASE_H
#define DATABASE_H
#include <QObject>
#include <QDebug>
class Database : public QObject
{
Q_OBJECT
public:
explicit Database(QObject *parent = 0);
void getIndex();
signals:
public slots:
};
#endif // DATABASE_H
database.cpp
#include "database.h"
#include <widget.h>
Database::Database(QObject *parent) : QObject(parent)
{
}
void Database::getIndex(){
Widget a;
qDebug()<< "from database: " << a.comboboxText();
}
I am new to qt and I am trying to create a program where the MainWindow calls a QDialog to enter some data.
The problem is that the parent() at my QDialog does not have any access to the public methods of the MainWindow in our case the
void save_city(const City *city); //public method of MainWindow
The code is actually big so here is some of the code.Thanks.
mainwindow.h
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QMainWindow>
#include <QTextStream>
#include <QVector>
#include <QDebug>
#include <QFile>
#include "dialog_add_city.h"
#include "street.h"
#include "city.h"
#include "map.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
//main Window constructor
explicit MainWindow(QWidget *parent = 0);
//main Window deconstructor
~MainWindow();
/*utility function to save the city
*the function is public so that also QDialogs
*data saves can */
//////////////
//here is the public function
void save_city(const City *city);
private slots:
private:
Map mainMap;
Ui::MainWindow *ui;
QGraphicsView view;
QGraphicsScene scene;
};
dialog_add_city.h
#ifndef DIALOG_ADD_CITY_H
#define DIALOG_ADD_CITY_H
#include <QDialog>
#include "mainwindow.h"
#include "City.h"
namespace Ui {
class Dialog_Add_City;
}
class Dialog_Add_City : public QDialog
{
Q_OBJECT
public:
explicit Dialog_Add_City(QWidget *parent = 0);
~Dialog_Add_City();
private slots:
//Add New City Button clicked-Adds an new city to our city_locations.txt
void on_PushButton_Add_New_City_clicked();
private:
Ui::Dialog_Add_City *ui;
};
#endif // DIALOG_ADD_CITY_H
dialog_add_city.cpp
#include "dialog_add_city.h"
#include "ui_dialog_add_city.h"
Dialog_Add_City::Dialog_Add_City(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog_Add_City)
{
ui->setupUi(this);
}
Dialog_Add_City::~Dialog_Add_City()
{
delete ui;
}
void Dialog_Add_City::on_PushButton_Add_New_City_clicked()
{
City *city=new City(ui->lineEdit_cityName->text(),
ui->lineEdit_X_Ko->text().toDouble(),
ui->lineEdit_Y_Ko->text().toDouble());
qDebug() << ui->lineEdit_cityName->text()
<< ui->lineEdit_X_Ko->text()
<< ui->lineEdit_Y_Ko->text();
/////////////////////////////
//HERE IS THE PROBLEM
parent()->save_city(city);
}
Any other suggestions are welcomed!
The Problem is that parent() will return a pointer the parent object as QObject.
QObject Documentation
As dreschrjm pointed out you could try to cast the object via
MyWidget *myWidget = qobject_cast<MyWidget *>(obj);
from The Meta-Object System
Suggestion: Use Qt's signal/slot mechanism to avoid a backward reference to the parent.
Declare save_city as signal in Dialog_Add_City.
Declare save_city in MainWindow as slot
Connect both where the dialog is created:
e.g.
void MainWindow::show_add_city_dialog()
{
Dialog_Add_city dialog;
connect(&dialog, &Dialog_Add_city::save_city, this, &MainWindow::save_city);
dialog.exec();
}
Replace parent()->save_city(city); in Dialog_Add_City with emit save_city(city);
Ensure that the new city object doesn't leak, I think a better design would be to create the City object elsewhere not in the dialog.
so
emit save_city(ui->lineEdit_cityName->text(),
ui->lineEdit_X_Ko->text().toDouble(),
ui->lineEdit_Y_Ko->text().toDouble());
and the slot
void MainWindow::save_city(const QString &cityName, double x, double y)
{
City *city=new City(cityName, x, y);
// do some interresting things with city.
}