How to avoid clicking button twice in Qt

LeonSu

Hello !

I want to avoid clicking button twice during sometime.

I tried some method in the following
Method 1

int clicktime = 0;
void start()
{
   ui->button->setEnabled(false);
   clicktime++;
   qDebug() << clicktime ;
   QThread::msleep(1000);
   ui->button->setEnabled(true);
}

when I clicked the button many times quickly, the function will run many times slowly.

now I try to block the signals of button

Method 2

int clicktime = 0;
void start()
{
   ui->button->blocksignals(true);
   ui->button->setEnabled(false);
   clicktime++;
   qDebug() << clicktime ;
   QThread::msleep(1000);
   ui->button->setEnabled(true);
   ui->button->blocksignals(false);

}

After I push the button many times, quickly, the function also run many times.
The result of Method 1 is the same with Method 2

I tried to disconnected the button from function start.
It is not work.

Could any one can help me or get me some suggestions?
Thanks in advance.

Devopia53

@LeonSu

If possible, do not use the sleep () function in the GUI. Thereby causing the GUI to be blocked.

See the following sample:

connect(ui->button, &QPushButton::clicked, [&]{
    qDebug() << "clicked";
    ui->button->setEnabled(false);
    QTimer::singleShot(1000, [&]{ ui->button->setEnabled(true); });
});

LeonSu

@Devopia53

Thank you for your solution.

Your solution is work well in Qt 5.9.3, but there are some errors in Qt 5.3.2.

I find another solution is work OK, also

int clicktime = 0;
void start()
{
   ui->button->blocksignals(true);
   ui->button->setEnabled(false);
   clicktime++;
   qDebug() << clicktime ;
   QThread::msleep(1000);
   ui->button->setEnabled(true);
   ui->button->blocksignals(false);
   QCoreApplication::processEvents(QEventLoop::AllEvents, 1000);
}

I think your method is batter.
I will study how to using your method in Qt 5.3.2

thanks again.
LeonSu

JonB

@LeonSu said in How to avoid clicking button twice in Qt:

QThread::msleep(1000);

Sorry, but anything which involves QThread::msleep(); or ::sleep(), regardless of Qt version, is just wrong/bad/unusable/interferes unacceptably with user interaction.

jsulm

@LeonSu said in How to avoid clicking button twice in Qt:

I will study how to using your method in Qt 5.3.2

Just don't use lambda, use normal slot in older Qt versions instead...

JonB

@LeonSu
BTW, what is so special about preventing another click within 1 second? Why not half a second or 2 seconds or whatever? Is your actual intention to prevent a second click while the code for the first click is still executing? In which case, your re-enablement of the button should not be on some kind of timer but rather when the first click handler's code has completed?

Devopia53

@LeonSu

Your solution is work well in Qt 5.9.3, but there are some errors in Qt 5.3.2.

Qt 5.3.2 supports C++11. If the compiler supports it, add the following directive in your .pro file. I tested it with the Qt 5.3.2 / MinGW 4.8.2 version.

like this: CONFIG += c++11

LeonSu

@jsulm
lambda can be compiled with C++11.
but I get the error message : "no matching function for call to 'QTimer::singleShot(int, MainWindow::bigbuttontest()<lambda()>'.....

The Qt 5.3.2 does not support this method.
There are only two overloaded functions.

/
 void	singleShot(int msec, const QObject * receiver, const char * member)
 void      singleShot(int msec, Qt::TimerType timerType, const QObject * receiver, const char * member)

In Qt 5.9.3 had ten overloaded functions

void  singleShot(int msec, const QObject *receiver, const char *member)
void  singleShot(int msec, Qt::TimerType timerType, const QObject *receiver, const char *member)
void  singleShot(int msec, const QObject *receiver, PointerToMemberFunction method)
void  singleShot(int msec, Qt::TimerType timerType, const QObject *receiver, PointerToMemberFunction method)
void singleShot(int msec, Functor functor)
void singleShot(int msec, Qt::TimerType timerType, Functor functor)
void singleShot(int msec, const QObject *context, Functor functor)
void singleShot(int msec, Qt::TimerType timerType, const QObject *context, Functor functor)
void singleShot(std::chrono::milliseconds msec, const QObject *receiver, const char *member)
void singleShot(std::chrono::milliseconds msec, Qt::TimerType timerType, const QObject *receiver, const char *member)

@JonB
I try to avoid to clicking button twice during 1 second.

@Devopia53
Qt 5.3.2 does not support this method.

Devopia53

@LeonSu

As suggested by @jsulm, use an alternative string-based SLOT () macro.