可移动的橡皮筋从一点移动到另一点

Question

我在QLabel上画了一个QRubberband。我可以使用QSizeGrip来调整它的大小。现在我想使用QMouseevents将它从一个点移动到另一个点。有人能帮我吗?

void CropImage::mousePressEvent(QMouseEvent *event)
{
    QLabel::mousePressEvent(event);
    lastPoint = event->pos();
    rubberband = new QRubberBand(QRubberBand::Rectangle,this);
    rubberband->setGeometry(QRect(lastPoint, QSize()));
    rubberband->show();
}
void CropImage::mouseReleaseEvent(QMouseEvent *event)
{
    newPoint = event->pos();
}

这是我的子类部分，用于鼠标事件。代码如下:

Resizable_rubber_band::Resizable_rubber_band(QWidget *parent) : QWidget(parent)
{
 //tell QSizeGrip to resize this widget instead of top-level window
 setWindowFlags(Qt::SubWindow);
 QHBoxLayout* layout = new QHBoxLayout(this);
 layout->setContentsMargins(0, 0, 0, 0);
 QSizeGrip* grip1 = new QSizeGrip(this);
 QSizeGrip* grip2 = new QSizeGrip(this);
 layout->addWidget(grip1, 0, Qt::AlignLeft | Qt::AlignTop);
 layout->addWidget(grip2, 0, Qt::AlignRight | Qt::AlignBottom);
 rubberband = new QRubberBand(QRubberBand::Rectangle, this);
 rubberband->move(0, 0);
 rubberband->show();
}
 void Resizable_rubber_band::resizeEvent(QResizeEvent *)
 {
    rubberband->resize(size());
 }
 void Resizable_rubber_band::mousePressEvent(QMouseEvent *event)
 {
    lastPoint = event->pos();
    rubberband->childAt(lastPoint);
 }
 void Resizable_rubber_band::mouseReleaseEvent(QMouseEvent *event)
 {
   newpoint = event->pos();
   int dragx=newpoint.x()-lastPoint.x();
   int dragy=newpoint.y()-lastPoint.y();
   band->move(0+dragx,0+dragy);
 }

在这个代码中，我的问题是我没有得到确切的坐标后拖动

谢谢。

阿施施

Answer 1

这里是我做的一个快速示例，您可以使用鼠标事件移动QRubberBand:

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QRubberBand>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
protected:
    void mousePressEvent(QMouseEvent *e);
    void mouseMoveEvent(QMouseEvent *e);
    void mouseReleaseEvent(QMouseEvent *e);
private:
    Ui::MainWindow *ui;
    QRubberBand *rubberBand;
    bool move_rubberband;
    QPoint rubberband_offset;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMouseEvent>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    move_rubberband = false;
    rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
    rubberBand->setGeometry(0,0,50,50);
    rubberBand->show();
}
MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::mousePressEvent(QMouseEvent *e)
{
    if(rubberBand->geometry().contains(e->pos()))
    {
        rubberband_offset = e->pos() - rubberBand->pos();
        move_rubberband = true;
    }
}
void MainWindow::mouseMoveEvent(QMouseEvent *e)
{
    if(move_rubberband)
    {
        rubberBand->move(e->pos() - rubberband_offset);
    }
}
void MainWindow::mouseReleaseEvent(QMouseEvent *e)
{
    move_rubberband = false;
}