QPushButton not clickable in MainWindow

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?

Kuba hasn't forgotten Monica · Accepted Answer · 2017-01-18T21:43:42.693

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"

thanks for the help it worked, what exactly does setupUI do? http://stackoverflow.com/questions/5692991/qt-setupui here it says it creates the actual instances of the objects but aren't we already initializing it manually? — johndoesnow, Jan 18 '17 at 21:22

QPushButton not clickable in MainWindow

1 Answers1