一个插槽的多个信号

Question

对于我的GUI,我希望有两对按钮可以在滚动条上下滚动.第一组按钮应该在说scrollarea1上工作,第二组按钮应该在scrollarea2上工作.我放在scrollarea中的小部件称为viewport1和viewport2.由于两组按钮都应该相同(向上和向下滚动),我想我会创建两个名为scrollUp和scrollDown的插槽来处理两组按钮的滚动.不幸的是,我无法完成这项工作,需要一些帮助.我尝试过以下方法:

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));
}

但这不起作用有几个原因.我也尝试给插槽一些参数,例如:

connect(&up,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea1,viewport1)));
connect(&up2,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea2,viewport2)));

但同样,没有成功.有谁能够帮我？

Answer 1

首先,"它不起作用"并不意味着什么,如果你没有说出你得到的错误,很难帮助你.然后,几乎没有问题.

所有QObject的派生类都不可复制,这意味着你无法做到

QWidget a;
QWidget b;
b = a; // Wrong

你应该使用指针(或者可能是引用).

QWidget a;
QWidget * b = new QWidget(...);
QWidget * c;
c = & a; // Ok
c = b; // Ok

那你的connect电话是错的:

connect(&up, SIGNAL(clicked()), &up, SLOT(scrollUp()));

第三个参数是具有槽的对象.up是一个QPushButton,它没有scrollUp()插槽,你的MainWindow是谁:

connect(&up, SIGNAL(clicked()), this, SLOT(scrollUp()));

(因为connect在MainWindow的构造函数中调用this指向当前的MainWindow对象).

同样在C++中,单=符号表示赋值,对于相等比较,使用=='. Andsender`是一个函数.

如果以正确的方式实施,您的方法应该有效:

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.
    }
};

另一种方法是将实际滚动指令提取到单独的函数:

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`.
};

Answer 2

您的代码中存在多个错误:

• 关于信号的发送者:没有被QObject称为" sender"的方法QObject * QObject::sender() const;,而是一种在信号发送者上返回指针的方法.
• 在if条件:你是铸造QPushButton**成QPushButton((QPushButton) &sender),你不要比较你的按钮那个东西up(2)和down(2).
• 在插槽和信号之间的连接中:插槽scrollUp和scrollDown插槽不属于QPushButton类,而是属于您的MainWindow类.

最后,你应该写这样的东西:

connect(&up,    SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(&up2,   SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(&down,  SIGNAL(clicked()), this, SLOT(scrollDown()));
connect(&down2, SIGNAL(clicked()), this, SLOT(scrollDown()));

void MainVindow::scrollDown() {
    // [...]

    QPushButton * senderButton = qobject_cast<QPushButton *>(this->sender()); 
    // QPushButton * senderButton = (QPushButton *) this->sender(); works too

    if (senderButton == &down) {
        // [...]
    }

    if (senderButton == &down2) {
        // [...]
    }

    // [...]
}

void MainVindow::scrollUp() {
    // [...]

    QPushButton * senderButton = qobject_cast<QPushButton *>(this->sender());
    // QPushButton * senderButton = (QPushButton *) this->sender(); works too

    if (senderButton == &up) {
        // [...]
    }

    if (senderButton == &up2) {
        // [...]
    }
    // [...]
}