For my GUI i would like to have two pairs of buttons that scroll up and down a scrollarea. The first set of buttons should work on say scrollarea1 and the second set of buttons should work on a scrollarea2. The widgets that I put in the scrollarea are called viewport1 and viewport2. Since both both set of buttons should do the same (scrolling up and down) I thought I would make two slots called scrollUp and scrollDown that would handle the scrolling for both sets of buttons. Unfortunately I cannot make this work and need some help. I have tried the following:
QPushButton up;
QPushButton down;
QPushButton up2;
QPushButton down2;
connect(&up,SIGNAL(clicked()),&up,SLOT(scrollUp()));
connect(&up2,SIGNAL(clicked()),&up,SLOT(scrollUp()));
connect(&down,SIGNAL(clicked()),&down,SLOT(scrollDown()));
connect(&down2,SIGNAL(clicked()),&down,SLOT(scrollDown()));
void MainWindow::scrollDown()
{
QScrollArea area;
QWidget view;
if((QPushButton) &sender = down)
{
area=scrollArea;
view=viewport;
}
if((QPushButton) &sender = down2)
{
area=scrollArea;
view=viewport;
}
int curpos = area.verticalScrollBar()->value();
area.verticalScrollBar()->setValue(curpos+15);
int newpos = area.verticalScrollBar()->value();
QPoint topLeft = area.viewport()->rect().topLeft();
view.move(topLeft.x(),topLeft.y()-(newpos));
}
void MainWindow::scrollUp()
{
QScrollArea area;
QWidget view;
if((QPushButton) &sender = up)
{
area=scrollArea;
view=viewport;
}
if((QPushButton) &sender = up2)
{
area=scrollArea2;
view=viewport2;
}
int curpos = area.verticalScrollBar()->value();
area.verticalScrollBar()->setValue(curpos-15);
int newpos = area.verticalScrollBar()->value();
QPoint topLeft = area.viewport()->rect().topLeft();
view.move(topLeft.x(),topLeft.y()-(newpos));
}
But this doesn´t work for several reasons. I also tried giving the slot some arguments, something like:
connect(&up,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea1,viewport1)));
connect(&up2,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea2,viewport2)));
But again, no succes. Can anybody help me?
First of all, "It doesn't work" does not mean anything, and it is hard to help you if you do not say what errors you get. Then, there are few problems.
All QObject's derived classes are not copiable, it means you can not do
QWidget a;
QWidget b;
b = a; // Wrong
You should use pointers (or perhaps references).
QWidget a;
QWidget * b = new QWidget(...);
QWidget * c;
c = & a; // Ok
c = b; // Ok
Then your connect
calls are wrong:
connect(&up, SIGNAL(clicked()), &up, SLOT(scrollUp()));
The third argument is the object who has the slot. up
is a QPushButton, it does not have a scrollUp()
slot, it is your MainWindow who does:
connect(&up, SIGNAL(clicked()), this, SLOT(scrollUp()));
(since connect
is called in MainWindow's constructor this
points to the current MainWindow object).
Also in C++ the single =
sign means assignment, for equality comparison use =='. And
sender` is a function.
Your approach should work if implemented in the right way:
class MainWindow: public QWidget
{
QScrollArea * scroll1;
QScrollArea * scroll2;
QWidget * view1;
QWidget * view2;
QPushButton * up1;
QPushButton * up2;
QPushButton * down1;
QPushButton * down2;
public:
MainWindow()
{
// Here initialize member variables.
...
connect(up1, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(up2, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(down1, SIGNAL(clicked()), this, SLOT(scrollDown()));
connect(down2, SIGNAL(clicked()), this, SLOT(scrollDown()));
}
public slots:
void scrollDown()
{
QScrollArea * area;
QWidget * view;
if(qobject_cast<QPushButton>(sender()) == down1) {
area = & scroll1;
view = & view1;
} else if(qobject_cast<QPushButton>(sender()) == down2) {
area = & scroll2;
view = & view2;
} else {
// Error.
}
// Now `area` and `view` point to the right widgets.
...
}
void scrollUp()
{
// The same as before.
}
};
Another approach would be to extract the actual scrolling instructions to a separate function:
class MainWindow: public QWidget
{
// Same variables as before
...
public:
MainWindow()
{
// Here initialize member variables.
...
connect(up1, SIGNAL(clicked()), this, SLOT(scrollUp1()));
connect(up2, SIGNAL(clicked()), this, SLOT(scrollUp2()));
connect(down1, SIGNAL(clicked()), this, SLOT(scrollDown1()));
connect(down2, SIGNAL(clicked()), this, SLOT(scrollDown2()));
}
public slots:
void scrollDown(QScrollArea * area, QWidget * view)
{
// Here you scroll over `area` and `view`.
}
void scrollDown1()
{
scrollDown(scroll1, area1);
}
void scrollDown2()
{
scrollDown(scroll2, area2);
}
// Again, the same for `scrollUp`.
};