I am getting two errors but I cannot identify them

Question

I am a novice to c++, but I am doing my best to learn. I am getting two errors and I don't know why, these are:

1. In constructor 'MyLabel::MyLabel(QWidget*)':
2. Qualified-id in declaration before '(' token -line 7
3. Qualified-id in declaration before '(' token -line20

My code is as follows:

mylabel.cpp:

#include "mylabel.h"
#include "ui_mainwindow.h"

MyLabel::MyLabel(QWidget *parent) :
    QWidget(parent)
{
    void MyLabel::MyLabel()
    {
        this->setAlignment(Qt::AlignCenter);

        //Default Label Value
        this->setText("No Value");

        //set MouseTracking true to capture mouse event even its key is not pressed
        this->setMouseTracking(true);
    }



    void MyLabel::mouseMoveEvent(QMouseEvent * event)
    {
        //Show x and y coordinate values of mouse cursor here
        this->setText("X:" + QString::number(event->x()) + "-- Y:" + QString::number(event->y()));
    }


}        

mylabel.h:

#ifndef MYLABEL_H
#define MYLABEL_H

#include <QObject>
#include <QApplication>
#include <QMainWindow>
#include <QMouseEvent>

class MyLabel : public QWidget
{
    Q_OBJECT
public:
    explicit MyLabel(QWidget *parent = 0);
    ~MyLabel();

    void mouseMoveEvent(QMouseEvent * event);

signals:

};

#endif // MYLABEL_H 

main.cpp

#include "mainwindow.h"
#include "mylabel.h"
#include <QApplication>
#include <QHBoxLayout>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QMainWindow *window = new QMainWindow();

    window->setWindowTitle(QString::fromUtf8("QT - Capture Mouse Move"));
    window->resize(300, 250);

    QWidget *centralWidget = new QWidget(window);
    QHBoxLayout* layout = new QHBoxLayout(centralWidget);

    MyLabel* CoordinateLabel = new MyLabel();
    layout->addWidget(CoordinateLabel);

    window->setCentralWidget(centralWidget);

    window->show();
    return app.exec();
}

mainwindow.cpp is blank

Answer 1

In order to implement your custom label you have to derive your class from Qt's standard QLabel class as:

class MyLabel : public QLabel
{
    Q_OBJECT
public:
    explicit MyLabel(QWidget *parent = 0);
    ~MyLabel();
protected:
    void mouseMoveEvent(QMouseEvent * event);
};

Unfortunately in C++ you can not define a function inside another function as you did in MyLabel::MyLabel() constructor. Just write it in the following way:

MyLabel::MyLabel(QWidget *parent) : QLabel(parent)
{
    setAlignment(Qt::AlignCenter);

    //Default Label Value
    setText("No Value");

    //set MouseTracking true to capture mouse event even its key is not pressed
    setMouseTracking(true);
}

UPDATE

I would implement the handling of the mouse move event in this way:

void MyLabel::mouseMoveEvent(QMouseEvent * event)
{
    // Show x and y coordinate values of mouse cursor here
    QString txt = QString("X:%1 -- Y:%2").arg(event->x()).arg(event->y());
    setText(txt);
}

Answer 2

You are getting error are you are trying to define functions inside your constructor. MyLabel::MyLabel(QWidget *parent) so be

MyLabel::MyLabel(QWidget *parent) : QWidget(parent)
{
    this->setAlignment(Qt::AlignCenter);

    //Default Label Value
    this->setText("No Value");

    //set MouseTracking true to capture mouse event even its key is not pressed
    this->setMouseTracking(true);
}

And then the definition for mouseMoveEvent should follow after the constructor

void MyLabel::mouseMoveEvent(QMouseEvent * event)
{
    //Show x and y coordinate values of mouse cursor here
    this->setText("X:" + QString::number(event->x()) + "-- Y:" + QString::number(event->y()));
}

EDIT:

As pointed out in the comments setAlignment and setText are not members of QWidget so if they are not members of MyLable then you will need to remove those otherwise it will not compile.