how to make a button resets a slider to 0?

[lunar]

hello ^_^
i have been programming in QT since yesterday and i got a question how do i reset slider to 0?

void setValue ( int )
Changing the value also changes the sliderPosition.

but it didnt work :confused:

connect(resetButton, SIGNAL(clicked() ), slider, SLOT(setValue(0) ) );



#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLCDNumber>
#include <QSlider>
#include <QVBoxLayout>

#include <iostream>

class MyWidget : public QWidget
{
public:
MyWidget(QWidget *parent);
~MyWidget() { std::cout << "abc" << std::endl; }
};

MyWidget::MyWidget(QWidget *parent = 0) : QWidget(parent)
{
setFixedSize(320, 200);

QPushButton *resetButton = new QPushButton("Reset");

QLCDNumber *lcd = new QLCDNumber(2);
lcd->setSegmentStyle(QLCDNumber::Filled);

QSlider *slider = new QSlider(Qt::Horizontal);
slider->setValue(0);
slider->setRange(0, 99);

connect(resetButton, SIGNAL(clicked() ), slider, SLOT(setValue(0) ) );
connect(slider, SIGNAL(valueChanged(int) ), lcd, SLOT(display(int) ) );

QVBoxLayout *layout = new QVBoxLayout();
layout->addWidget(resetButton);
layout->addWidget(lcd);
layout->addWidget(slider);
setLayout(layout);
}

int main(int argc, char *argv[] )
{
QApplication app(argc, argv);

MyWidget widget;
widget.show();

app.exec();
}

[wagmare]

connect(resetButton, SIGNAL(clicked() ), slider, SLOT(setValue(0) ) );
connect(slider, SIGNAL(valueChanged(int) ), lcd, SLOT(display(int) ) );




u cannot connect a void SIGNAL to int SLOT
clicked() ->setValue(0) connection is not possible .. but reverse is possible ..

so create a private slot


private slot:
void sliderValue();

connect(resetButton, SIGNAL(clicked()), this, SLOT(sliderValue()));

MyWidget::sliderValue()
{
slider->setValue(0);
}

[lunar]

hey thx for help but iam running a little error:

In member function `void MyWidget::SetSliderValue()':|
error: `slider' was not declared in this scope|
warning: unused variable 'slider'|
||=== Build finished: 1 errors, 1 warnings ===|



class MyWidget : public QWidget
{
public:
MyWidget(QWidget *parent);
~MyWidget() { std::cout << "abc" << std::endl; }

private slots:
void SetSliderValue() { slider->setValue(0); }
};




connect(resetButton, SIGNAL(clicked() ), this, SLOT(SetSliderValue() ) );

[wagmare]

hey thx for help but iam running a little error:





connect(resetButton, SIGNAL(clicked() ), this, SLOT(SetSliderValue() ) );



declare slider in private (global)


private :
QSlider *slider;



use it like this


class MyWidget : public QWidget
{
public:
MyWidget(QWidget *parent);
~MyWidget() { std::cout << "abc" << std::endl; }


private slots:
void SetSliderValue() { slider->setValue(0); }

private:
QSlider *slider;
};



otherwise u cant use it in separate function of the class ...

[lunar]

damn :mad: didnt work

http://img34.imageshack.us/img34/5822/asdasdasdn.th.jpg (http://img34.imageshack.us/my.php?image=asdasdasdn.jpg)



#include <QApplication>
#include <QWidget>
#include <QPushButton>
#include <QLCDNumber>
#include <QSlider>
#include <QVBoxLayout>

#include <iostream>

class MyWidget : public QWidget
{
public:
MyWidget(QWidget *parent);
~MyWidget() { std::cout << "abc" << std::endl; }

private:
QSlider *slider;

private slots:
void SetSliderValue() { slider->setValue(0); }
};

MyWidget::MyWidget(QWidget *parent = 0) : QWidget(parent)
{
setFixedSize(320, 200);

QPushButton *resetButton = new QPushButton("Reset");

QLCDNumber *lcd = new QLCDNumber(2);
lcd->setSegmentStyle(QLCDNumber::Filled);

QSlider *slider = new QSlider(Qt::Horizontal);
slider->setValue(0);
slider->setRange(0, 99);

connect(resetButton, SIGNAL(clicked() ), this, SLOT(SetSliderValue() ) );
connect(slider, SIGNAL(valueChanged(int) ), lcd, SLOT(display(int) ) );

QVBoxLayout *layout = new QVBoxLayout();
layout->addWidget(resetButton);
layout->addWidget(lcd);
layout->addWidget(slider);
setLayout(layout);
}

int main(int argc, char *argv[] )
{
QApplication app(argc, argv);

MyWidget widget;
widget.show();

app.exec();
}

[wagmare]

relax ................ u are new ...


change this ..
QSlider *slider = new QSlider(Qt::Horizontal);
to
slider = new QSlider(Qt::Horizontal);

because u have already defined it in private:

private:
QSlider *slider;

[wagmare]

i think u need the macro Q_OBJECT to connect ... it is giving error n connect .. how stupid i am not to mention it earlier ..

[lunar]

hmm didnt work i think something is wrong with the button :)

i have also added #include <QObject> and Q_OBJECT yesterday but didnt work
QObject: No such file or directory|
||=== Build finished: 1 errors, 0 warnings ===|


what about " emit "



void Counter::setValue(int value)
{
if (value != m_value) {
m_value = value;
emit valueChanged(value);
}
}

[wagmare]

see the code i attached with this thread ... i cant set the setValue(0) to slider .... its giving seg fault ...

[wagmare]

yipeeee i completed this one .... its working .. your logic is right .. use this attachment

[lunar]

i believe it will work but:

|7|QObject: No such file or directory|
||=== Build finished: 1 errors, 0 warnings ===| :eek:

looks like its gonna be more complicated than WinApi :D:D
do u know what mistake does show this error? :mad:

[Lykurg]

|7|QObject: No such file or directory|
||=== Build finished: 1 errors, 0 warnings ===|

May you have to explicit add a #include <QObject> in the header file or more likely clean your directory before you build the new files.

[wagmare]

which os u are using .. i compiled it in linux .... ok make clean then give make ...
else qmake again the .pro file ...

did u see what are the error u done .. ? in the code ...

[vonCZ]

FYI- it worked for me, too. WinXP, Visual Studio 2005 Command Prompt:

C:\prompt> qmake
C:\prompt> nmake release