设置可拖动线段的限制
To set limit to draggable line segments
我正在尝试实现可以通过鼠标在两点之间拖动的线段(如下所示,其中绿色和红色线必须可以在黑色虚线之间拖动)。
示例图片
我可以用鼠标拖动线条。
作为下一步,我想为这个可拖动区域设置一个限制,但我在实施时遇到了问题。如果有人可以帮助我做到这一点,我真的很感激。我现在详细解释一下情况:
.h
是:
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
void paintEvent(QPaintEvent *e);
public slots:
void changeP1value(int);
private:
Ui::MainWindow *ui;
bool dragging = false;
QPoint p1 = QPoint(400,100);
QPoint p2 = QPoint(450,100);
QPoint p3 = QPoint(450,100);
QPoint p4 = QPoint(500,100);
QPoint *CurPoint1=nullptr;
QPoint *CurPoint2=nullptr;
protected:
virtual void mousePressEvent(QMouseEvent *event) override;
virtual void mouseReleaseEvent(QMouseEvent *event) override;
virtual void mouseMoveEvent(QMouseEvent *event) override;
};
#endif // MAINWINDOW_H
并在 .cpp
文件中:
// small helper to give us the distance
int distance(QPoint x1, QPoint x2)
{
return abs(x2.y() - x1.y());
}
// the Paint event to draw lines
void MainWindow::paintEvent(QPaintEvent *e)
{
QPainter painter1(this);
QPen pointpen(Qt::black);
pointpen.setWidth(5);
QPen linepen1(Qt::red);
linepen1.setWidth(2);
QPen linepen2(Qt::green);
linepen2.setWidth(2);
painter1.setPen(linepen1);
painter1.drawLine(p1,p2);
painter1.setPen(linepen2);
painter1.drawLine(p3,p4);
}
// when user clicks
void MainWindow::mousePressEvent(QMouseEvent *event)
{
QPoint mp = event->pos(); // where is mouse
// test if we hit the line. give user 20 pixels slack as its hard to hit one pixel
if (distance ( mp, p1) < 20 && ( mp.x() > p1.x() && mp.x() < p2.x() ) ) {
dragging = true; // flag we are dragging
CurPoint1 = &p1;
CurPoint2 = &p2;
}
else if (distance ( mp, p3) < 20 && ( mp.x() > p3.x() && mp.x() < p4.x() ) ) {
dragging = true;
CurPoint1 = &p3;
CurPoint2 = &p4;
}
}
void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
dragging = false; // if user release mouse we are not draggign anymore
}
// then when mouse move
void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
// If we are dragging, call your normal slider changed function to update your points.
if (dragging)
{
if(CurPoint1->y()>50 && CurPoint1->y()<150)
{
changeP1value(event->y());
}
else
update();
}
}
void MainWindow::changeP1value(int value)
{
CurPoint1->setY(value);
CurPoint2->setY(value);
update();
}
在 mouseMoveEvent
中,我有条件检查我是否正在拖动一条线以及高度是否在 50 到 150 之间:
if (dragging)
{
if(CurPoint1->y()>50 && CurPoint1->y()<150) //----> it get stucked and cannot be dragged down again
{
changeP1value(event->y());
}
else
update();
}
在这种情况下我可以拖动,线在设置的限制处停止但我不能再向下拖动。你能发现问题吗?
提前致谢
您需要检查 新 y 值,而不是当前值:
void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
if (dragging)
{
if(event->y() > 50 && event->y() < 150)
{
changeP1value(event->y());
}
else
update();
}
}
我正在尝试实现可以通过鼠标在两点之间拖动的线段(如下所示,其中绿色和红色线必须可以在黑色虚线之间拖动)。
示例图片
我可以用鼠标拖动线条。
作为下一步,我想为这个可拖动区域设置一个限制,但我在实施时遇到了问题。如果有人可以帮助我做到这一点,我真的很感激。我现在详细解释一下情况:
.h
是:
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
void paintEvent(QPaintEvent *e);
public slots:
void changeP1value(int);
private:
Ui::MainWindow *ui;
bool dragging = false;
QPoint p1 = QPoint(400,100);
QPoint p2 = QPoint(450,100);
QPoint p3 = QPoint(450,100);
QPoint p4 = QPoint(500,100);
QPoint *CurPoint1=nullptr;
QPoint *CurPoint2=nullptr;
protected:
virtual void mousePressEvent(QMouseEvent *event) override;
virtual void mouseReleaseEvent(QMouseEvent *event) override;
virtual void mouseMoveEvent(QMouseEvent *event) override;
};
#endif // MAINWINDOW_H
并在 .cpp
文件中:
// small helper to give us the distance
int distance(QPoint x1, QPoint x2)
{
return abs(x2.y() - x1.y());
}
// the Paint event to draw lines
void MainWindow::paintEvent(QPaintEvent *e)
{
QPainter painter1(this);
QPen pointpen(Qt::black);
pointpen.setWidth(5);
QPen linepen1(Qt::red);
linepen1.setWidth(2);
QPen linepen2(Qt::green);
linepen2.setWidth(2);
painter1.setPen(linepen1);
painter1.drawLine(p1,p2);
painter1.setPen(linepen2);
painter1.drawLine(p3,p4);
}
// when user clicks
void MainWindow::mousePressEvent(QMouseEvent *event)
{
QPoint mp = event->pos(); // where is mouse
// test if we hit the line. give user 20 pixels slack as its hard to hit one pixel
if (distance ( mp, p1) < 20 && ( mp.x() > p1.x() && mp.x() < p2.x() ) ) {
dragging = true; // flag we are dragging
CurPoint1 = &p1;
CurPoint2 = &p2;
}
else if (distance ( mp, p3) < 20 && ( mp.x() > p3.x() && mp.x() < p4.x() ) ) {
dragging = true;
CurPoint1 = &p3;
CurPoint2 = &p4;
}
}
void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
dragging = false; // if user release mouse we are not draggign anymore
}
// then when mouse move
void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
// If we are dragging, call your normal slider changed function to update your points.
if (dragging)
{
if(CurPoint1->y()>50 && CurPoint1->y()<150)
{
changeP1value(event->y());
}
else
update();
}
}
void MainWindow::changeP1value(int value)
{
CurPoint1->setY(value);
CurPoint2->setY(value);
update();
}
在 mouseMoveEvent
中,我有条件检查我是否正在拖动一条线以及高度是否在 50 到 150 之间:
if (dragging)
{
if(CurPoint1->y()>50 && CurPoint1->y()<150) //----> it get stucked and cannot be dragged down again
{
changeP1value(event->y());
}
else
update();
}
在这种情况下我可以拖动,线在设置的限制处停止但我不能再向下拖动。你能发现问题吗?
提前致谢
您需要检查 新 y 值,而不是当前值:
void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
if (dragging)
{
if(event->y() > 50 && event->y() < 150)
{
changeP1value(event->y());
}
else
update();
}
}