I'm getting the undefined reference to vtable for CustomProgressBar' error when trying to launch following code:
customprogressbar.h
#ifndef CUSTOMPROGRESSBAR_H
#define CUSTOMPROGRESSBAR_H
#include <QProgressBar>
#include "task.h"
class CustomProgressBar : public QProgressBar
{
Q_OBJECT
public:
CustomProgressBar(DayTask, QWidget* parent = 0);
protected:
void paintEvent(QPaintEvent *) Q_DECL_OVERRIDE;
private:
DayTask task;
};
#endif // CUSTOMPROGRESSBAR_H
customprogressbar.cpp
#include "customprogressbar.h"
#include <QPainter>
CustomProgressBar::CustomProgressBar(DayTask task, QWidget* parent) :
task{task},
QProgressBar(parent)
{
}
//paintevent
What could cause the problem?
Maybe moc (meta object compiler) is not being run for your header?
Anyway, it's duplicate for this question
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.
I got two errors in Qt, I wish you can help me with this. This is my first time I post something, please me help. This is the code:
#include <QMainWindow>
#include "mainwindow.h"
#include <QThread>
#include <QtCore>
#include "ui_mainwindow.h"
class HiloPrincipal : public QThread
{
Q_OBJECT
public:
explicit HiloPrincipal( MainWindow* parent = 0); // First error
MainWindow * _parent; // Second error
void run(); // Sacar Botella y poner botella.
signals:
public slots:
};
#endif // HILOS_H
I almost sure you have created include cycle.
Fix it like this:
#ifndef HILOS_H // this was missing! Probably when you did copy paste to question
#define HILOS_H
#include <QMainWindow>
// remove line: #include "mainwindow.h"
#include <QThread>
#include <QtCore>
// remove line: #include "ui_mainwindow.h"
// forward declaration
class MainWindow;
class HiloPrincipal : public QThread
{
Q_OBJECT
public:
explicit HiloPrincipal( MainWindow* parent = 0); // First error
MainWindow * _parent; // Second error
void run(); // Sacar Botella y poner botella.
signals:
public slots:
};
#endif // HILOS_H
Than include this headers files mainwindow.h in HiloPrincipal.cpp. This should solve build issue, but not actual problem.
Note problem is caused by invalid design of classes. Your HiloPrincipal thread shouldn't have any knowledge about MainWindow.
Also you're doing that wrong - this is invalid use of QThread.
I've encountered an error which I cannot seem to find a solution to anywhere else.
The error occurs when I'm trying to declare an instance of the "EncodeWindow" class.The compiler is giving errors C2143,C4430 and C2238. I am simply trying to give the "MainWindow" class an instance of "EncodeWindow".
File mainWindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QString>
#include <QLabel>
#include "Image.h"
#include "encodewindow.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
/*Check whether a given file path is valid*/
bool CheckFilePath(QString);
/*Sets UI widgets*/
void setOriginalImage_Label(const char*);
void setEncodedImage_Label(const char*);
void setDebug_TextBox(QString);
/*Saves all information about current encoding/decoding*/
void saveFile();
private slots:
void on_Encode_Button_clicked();
void on_Reset_Button_clicked();
void on_Save_Button_clicked();
void on_AddEncodeImage_Debug_Button_clicked();
void on_AddImage_Button_clicked();
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
EncodeWindow *CurrentEncodeWindow = new EncodeWindow; //ERROR HERE!! C2143
int fileNumber = 0;
};
#endif // MAINWINDOW_H
File encodeWindow.h:
#ifndef ENCODEWINDOW_H
#define ENCODEWINDOW_H
#include <QMainWindow>
#include "mainwindow.h"
namespace Ui {
class EncodeWindow;
}
class EncodeWindow : public QMainWindow
{
Q_OBJECT
public:
explicit EncodeWindow(QWidget *parent = 0);
~EncodeWindow();
/*Get filepaths from 'result' object (For access to filepaths without 'encode' Window)*/
const char* getOriginalFilePath();
const char* getEncodeFilePath();
const char* getSaveFilePath();
bool checkUI(const char*,const char*,const char*,bool*);
bool CheckFilePath(const char*);
std::string readInText(const char*);
private slots:
void on_RedChannel_CheckBox_clicked(bool);
void on_GreenChannel_CheckBox_clicked(bool);
void on_BlueChannel_CheckBox_clicked(bool);
void on_AlphaChannel_CheckBox_clicked(bool);
void on_BitDepth_Slider_sliderMoved(int);
void on_BitDepth_SpinBox_valueChanged(int);
void on_Encode_Button_clicked();
private:
Ui::EncodeWindow *ui;
Encoded result; //Enocoded object (child of Image class)
};
#endif // ENCODEWINDOW_H
Any help would be great. The code was done in Qt for an image steganography project.
Thanks.
You have circular includes. "mainwindow.h" includes "encodewindow.h" and "encodewindow.h" includes "mainwindow.h". The include guards stop the cycle, but the class definitions for whichever header is included first won't be complete in the second include file, which will result in your errors.
In the snippet above, there's nothing that I see in encodewindow.h that uses anything in mainwindow.h, so just remove the include of mainwindow.h from encodewindow.h.
I am implementing a library management system using Qt C++. I have a Material class which is a QMainwindow and when I click Fiction Section in menu bar Fiction form should be opened which is a QDialogbox. But although I implemented this concept I get the error which is "expected class-name before '{'". Please help to find the error. Thank You in advance.
This is material.h
#ifndef MATERIALS_H
#define MATERIALS_H
#include <QMainWindow>
#include "materialinner.h"
#include "fictionsection.h"
namespace Ui {
class Materials;
}
class Materials : public QMainWindow, public MaterialInner
{
Q_OBJECT
public:
explicit Materials(QWidget *parent = 0);
~Materials();
private slots:
void on_btnAdd_clicked();
void on_btnLoad_clicked();
void on_btnEdit_clicked();
void on_tblMaterial_clicked(const QModelIndex &index);
void on_btnSearch_clicked();
void on_actionClear_triggered();
void createAction();
void on_actionEdit_triggered();
void on_actionDelete_Records_triggered();
void on_actionFiction_section_triggered();
private:
Ui::Materials *ui;
FictionSection *fic;
};
#endif // MATERIALS_H
This is material.cpp
#include "materials.h"
#include "ui_materials.h"
#include <QDebug>
#include <QMessageBox>
Materials::Materials(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Materials)
{
ui->setupUi(this);
// QObject ::connect(ui->lneditSearch,SIGNAL(textChanged(const QString &)),this,SLOT(displaySearch()));
}
Materials::~Materials()
{
delete ui;
}
void Materials::on_actionFiction_section_triggered()
{
/* this->hide();
fiction = new FictionSection();
fiction->show();*/
this->hide();
fic = new FictionSection();
fic->show();
}
This is fictionsection.h
#ifndef FICTIONSECTION_H
#define FICTIONSECTION_H
#include <QDialog>
#include "materials.h"
#include "materialinner.h"
namespace Ui {
class FictionSection;
}
class FictionSection : public QDialog, public Materials
**{**
Q_OBJECT
public:
explicit FictionSection(QWidget *parent = 0);
~FictionSection();
private:
Ui::FictionSection *ui;
};
#endif // FICTIONSECTION_H
Error occurs in functionsection.cpp class. And the curly brace where the error occured is bold.
With the following code snippet it gives the error of "request for memeber 'show' is ambiguous"
Material.cpp
#include "materials.h"
#include "ui_materials.h"
#include "fictionsection.h"
#include <QDebug>
#include <QMessageBox>
Materials::Materials(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::Materials)
{
ui->setupUi(this);
// QObject ::connect(ui->lneditSearch,SIGNAL(textChanged(const QString &)),this,SLOT(displaySearch()));
}
void Materials::on_actionFiction_section_triggered()
{
this->hide();
fiction = new FictionSection();
fiction->show();
}
How to solve this?
You have a circular dependency: materials.h includes fictionsection.h and fictionsection.h includes materials.h.
As your header files has routines to prevent multiple inclusion (#ifndef FICTIONSECTION_H and #ifndef MATERIALS_H, which are good), when material.h includes fictionsection.h, this one includes material.h again but this has absolutely no effect due to your multiple inclusion protection....consequence is that fictionsection.h does not get Materials declaration in the end and refuses to declare FictionSection deriving from it!
You need to use a forward declaration to solve that:
In materials.h, replace:
#include "fictionsection.h"
by
class FictionSection;
And add #include "fictionsection.h" in materials.cpp only.
Forward declaration is a common practice to resolve this problem. But, even without this problem occuring, forward declaration remains a good practice because it will speed up your compilation.
Currently using the latest QT Creator and working on a small tutorial application. Was wanting to have a button that all the function could use and placed it in the header file:
#ifndef GAMEBOARD_H
#define GAMEBOARD_H
#include <QWidget>
#include <QtGui/QPushButton>
class QLCDNumber;
class CannonField;
class QPushButton;
class Gameboard : public QWidget
{
Q_OBJECT
public:
Gameboard(QWidget *parent = 0);
private:
QLCDNumber *remaning_shots;
QLCDNumber *hits;
CannonField *cannon_field;
QPushButton *shootb;
public slots:
void shoot();
void hit();
void missed();
void restart();
};
#endif // GAMEBOARD_H
gameboard.cpp:
#include "cannonfield.h"
#include "gameboard.h"
#include "lcdrange.h"
Gameboard::Gameboard(QWidget *parent)
: QWidget(parent) {
shootb = new QPushButton(tr("Shoot"));
And when I'm trying to run the application it just crashes before it even begins. I don't even have to use the button for anything, it crashes anyway. What am I doing wrong?
Or should I just use signals?
QPushButton *shootb = new QPushButton(tr("Shoot"));
connect(this, SIGNAL(disableShoot(bool)), shootb, SLOT(setDisabled(bool)));
And then I call it like this:
void Gameboard::missed() {
emit disableShoot(true);
}
Correct me if that's an ugly solution.