Qt- Don't show QWidget if it has been already shown

Question

I want to use Animation which toggled by clicking on specific button. Here is my code:

source:

    void MainWindow::menuClicked()
    {
    //if animation is shown , try to hide it 
        if (m_menuOpend){
            m_animation = new QPropertyAnimation(widgetAnimate, "geometry");
            m_animation->setDuration(200);
            m_animation->setStartValue(QRect(0, 43, 400, 5*windowsHeight/6));
            m_animation->setEndValue(QRect(-300, 43, 400, 5*windowsHeight/6));
            m_animation->setEasingCurve(QEasingCurve::Linear);
            m_animation->start(QPropertyAnimation::DeleteWhenStopped);
            m_menuOpend = false;
        }else{
            //if widget has not created
            if (!widgetAnimate){
               widgetAnimate = new QWidget (this);
            }
        widgetAnimate->show();
        m_animation = new QPropertyAnimation(widgetAnimate, "geometry");
        m_animation->setDuration(200);
        m_animation->setStartValue(QRect(-300, 43, 400, 5*windowsHeight/6));
        m_animation->setEndValue(QRect(0, 43, 400, 5*windowsHeight/6));
        m_animation->setEasingCurve(QEasingCurve::Linear);
        m_animation->start(QPropertyAnimation::DeleteWhenStopped);    
        m_menuOpend = true;
    } 
}

header:

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

    private:
        QWidget *widgetAnimate;
};

Actually I give an error on

widgetAnimate->show();

because it's skip

if (!widgetAnimate)

condition every time. Any suggestion to avoid creating multiple widget?

How is initialized your widgetAnimate variable? It is global? in the class? what is the starting value? — Adrian Maire, Oct 28 '15 at 07:21
Have you initialized `widgetAnimate` to `0` or `nullptr`? You can't use `if (!widgetAnimate)` otherwise. — yzn-pku, Oct 28 '15 at 07:49
Initialize `widgetAnimate` variable in the `MainWindow` constructor. — vahancho, Oct 28 '15 at 08:53
Alternatively, if you're using [C++11](http://stackoverflow.com/questions/19398438/c-qt-how-to-add-std-c11-to-the-makefile-which-is-generated-by-qmake/19398489#19398489), you can initialise the variable when you declare it in the header *QWidget *widgetAnimate = nullptr;* — TheDarkKnight, Oct 28 '15 at 09:24

Qt- Don't show QWidget if it has been already shown

0 Answers0