Animation on qwidget is not working - c++

Question

I want a widget to animate its opacity when it is shown/hidden. I used the below code, but it does not work.
If I animate the property "maximumHeight", it gets animated in show(), but not in hide(). Could someone tell me where I am going wrong?
Header file
byeform.h
#include <QWidget>
#include <QPropertyAnimation>
namespace Ui {
class ByeForm;
}
class ByeForm : public QWidget
{
Q_OBJECT
public:
explicit ByeForm(QWidget *parent = 0);
~ByeForm();
private:
Ui::ByeForm *ui;
QPropertyAnimation *mpTransition;
protected:
bool eventFilter(QObject *obj, QEvent *event);
};
Source file
byeform.cpp
#include "byeform.h"
#include "ui_byeform.h"
#include <QDebug>
ByeForm::ByeForm(QWidget *parent) :
QWidget(parent),
ui(new Ui::ByeForm)
{
ui->setupUi(this);
this->installEventFilter(this);
mpTransition = new QPropertyAnimation(this, "windowOpacity");
mpTransition->setDuration(1000);
mpTransition->setStartValue(0.00);
mpTransition->setEndValue(1.00);
}
ByeForm::~ByeForm()
{
delete ui;
}
bool ByeForm::eventFilter(QObject *obj, QEvent *event)
{
if (this == obj && QEvent::Show == event->type())
{
qDebug() << Q_FUNC_INFO << "in show";
mpTransition->setDirection(QAbstractAnimation::Forward);
mpTransition->start();
}
else if (this == obj && (QEvent::Hide == event->type() ||
QEvent::Close == event->type()))
{
mpTransition->setDirection(QAbstractAnimation::Backward);
mpTransition->start();
}
return false;
}

Answer 1

Does this fix it?
bool ByeForm::eventFilter(QObject *obj, QEvent *event)
{
if (this == obj && QEvent::Show == event->type())
{
qDebug() << Q_FUNC_INFO << "in show";
mpTransition->setDirection(QAbstractAnimation::Forward);
mpTransition->start();
return true; // you might want to remove this line
}
else if (this == obj && (QEvent::Hide == event->type() ||
QEvent::Close == event->type()))
{
mpTransition->setDirection(QAbstractAnimation::Backward);
mpTransition->start();
return true; // you might want to remove this line
}
return QWidget::eventFilter(obj, event);
}
Ofcourse, it doesn't work because it's already hidden when you start the animation. You need to prolong the visibility until your animation has finished.
Like this, maybe:
void ByeForm::setVisible(bool visible)
{
if(isVisible() && !visible) // transition to hide
{
// m_bHideCalled = true;
mpTransition->setDirection(QAbstractAnimation::Backward);
mpTransition->start();
QTimer::singleShot(1000, this, SLOT(hide());
}
if(!isVisible() && visible) // transition to show
{
mpTransition->setDirection(QAbstractAnimation::Forward);
mpTransition->start();
show();
}
// if(m_bHideCalled)
// {
// m_bHideCalled = false;
// hide();
// }
}
Note that you MIGHT need the m_bHideCalled. Set it to false in the constructor. The name could be better though.

Answer 2

It works, but I think that it not good way to do this (I think that you should be do animate before close event will coming)
bool ByeForm::eventFilter(QObject *obj, QEvent *event)
{
if (this == obj && QEvent::Show == event->type())
{
qDebug() << Q_FUNC_INFO << "in show";
mpTransition->setDirection(QAbstractAnimation::Forward);
mpTransition->start();
}
else if (this == obj && (QEvent::Hide == event->type() ||
QEvent::Close == event->type()))
{
mpTransition->setDirection(QAbstractAnimation::Backward);
mpTransition->start();
while (mpTransition->state() == QAbstractAnimation::Running)
{
QApplication::processEvents();
}
}
return false;
}
Other method
Also you can override closeEvent method like this:
void MainWindow::closeEvent(QCloseEvent* e)
{
mpTransition->setDirection(QAbstractAnimation::Backward);
mpTransition->start();
e->ignore();
}
but in this case you should do something after animate will finished (for example connect on signal finished and call some method for closing window/application/etc).
Also you should be check, would manually call close event or by user operations.