Create a custom slot(QLabel)

[Using signal(valueChanged) of QSlider to change text of QLabel]

1. your class inherit from class of QObject's children

2. written the keyword "Q_OBJECT" in your code of class

3. use moc(Meta-Object Compiler) to generate a moc file

example:

--------mylabe.h------------

#ifndef MYLABEL_H

#define MYLABEL_H

#include <QLabel>

class mylabel : public QLabel{

Q_OBJECT

public slots:

void setText(int x){

QLabel::setText(QString::number(x));

}

};

#endif // MYLABEL_H

--------main.cpp------------

#include <QApplication>

#include <QHBoxLayout>

#include <QVBoxLayout>

#include <QSlider>

#include <QSpinBox>

#include <QPushButton>

#include "mylabel.moc" <---generated by moc (moc mylabe.h > mylabel.moc)

#include "mylabel.h"

int main(int argc, char* argv[])

{

QApplication app(argc, argv);

QWidget *window = new QWidget;

window->resize(500,600);

window->setWindowTitle("Qt Slots");

QPushButton *button = new QPushButton();

button->setText(QWidget::tr("quit離開"));

QObject::connect(button, SIGNAL(clicked()),&app, SLOT(quit()));

mylabel *label=new mylabel();

QSpinBox *spinBox = new QSpinBox;

QSlider *slider = new QSlider(Qt::Horizontal);

spinBox->setRange(0, 100);

slider->setRange(0, 100);

QObject::connect(spinBox, SIGNAL(valueChanged(int)),slider, SLOT(setValue(int)));

QObject::connect(slider, SIGNAL(valueChanged(int)),spinBox, SLOT(setValue(int)));

QObject::connect(slider, SIGNAL(valueChanged(int)),label, SLOT(setText(int)));

spinBox->setValue(35);

QHBoxLayout *layout = new QHBoxLayout;

QVBoxLayout *vlayout = new QVBoxLayout;

layout->addWidget(spinBox);

layout->addWidget(slider);

vlayout->addLayout(layout);

vlayout->addWidget(label);

vlayout->addWidget(button);

window->setLayout(vlayout);

window->show();

return app.exec();

}

-----

Ref:https://doc.qt.io/qt-5/signalsandslots.html

#QLabel

#QSlider

#QSpinBox

#QPushButton

#Qt

#slot