QPushButton not clickable in MainWindow - c++

Question

I'm writing a QT project in Xcode, I made a Widget application in the QT Editor and used the "qmake -spec macx-xcode" to convert the project into an Xcode project.
I have a standard project:
main.cpp
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow w;
w.show();
return app.exec();
}
main window.cpp
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent), ui(new Ui::MainWindow)
{
m_button = new QPushButton(this);
m_button -> setText("button");
m_button->setGeometry(QRect(QPoint(100, 100),QSize(200, 50)));
QPushButton *workingButton = new QPushButton("Hello");
workingButton -> show();
connect(m_button, SIGNAL(clicked()), this, SLOT(quitButton()));
ui->setupUi(this);
}
void MainWindow::quitButton() {
m_button->setText("Example");
}
MainWindow::~MainWindow()
{
delete ui;
}
main window.h
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void quitButton();
private:
Ui::MainWindow *ui;
QPushButton *m_button;
};
#endif
The m_button shows up in the mainWindow but it is not clickable but the workingButton, shows up in its own separate window, and in the connect, when I replace the m_button with the workingButton, it is able to call the function. Any idea why the m_button is not sending a signal or function not being called?

Answer 1

The reason is quite simple: you have other transparent widgets overlaid on top of m_button. You must ensure that the button is not covered by anything else. E.g. move the creation of the button after the setupUi call or make the button a child of the central widget. Generally speaking, the setupUi call should be the first thing in a widget's constructor.
You also don't need to dynamically allocate the child widgets: prefer holding things by value: less things can go wrong then, and you're having less overhead, too!
Thus, pretending that the Ui_MainWindow class was really generated by uic:
// https://github.com/KubaO/stackoverflown/tree/master/questions/simple-button-main-41729401
#include <QtWidgets>
class Ui_MainWindow {
public:
QWidget *central;
QGridLayout *layout;
QLabel *label;
void setupUi(QMainWindow *parent);
};
class MainWindow : public QMainWindow, private Ui_MainWindow {
Q_OBJECT
QPushButton m_button{"Click Me"};
public:
MainWindow(QWidget *parent = nullptr) : QMainWindow(parent) {
setupUi(this);
m_button.setParent(centralWidget());
m_button.setGeometry({{50, 50}, m_button.sizeHint()});
}
};
void Ui_MainWindow::setupUi(QMainWindow *parent) {
central = new QWidget{parent};
layout = new QGridLayout{central};
label = new QLabel{"Hello"};
label->setAlignment(Qt::AlignCenter);
label->setStyleSheet("background-color:blue; color:white;");
layout->addWidget(label, 0, 0);
parent->setCentralWidget(central);
parent->setMinimumSize(200, 200);
}
int main(int argc, char ** argv) {
QApplication app{argc, argv};
MainWindow w;
w.show();
return app.exec();
}
#include "main.moc"