[英]How to draw a Rectangle in Qgraphicsview dynamically (runtime), using Qt4
使用QT Creator版本2.4.1。
我只是QT平台上的入門者,正在嘗試動態繪制矩形。 該程序使用3個鼠標事件
問題是mouseMoveEvent永遠不會被調用。
這是代碼片段
main.cpp
#include <QtGui/QApplication>
#include "dialog.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Dialog w;
w.show();
return a.exec();
}
對話框.cpp
#include "dialog.h"
#include "ui_dialog.h"
#include "mysquare.h"
Dialog::Dialog(QWidget *parent) :
QDialog(parent),
ui(new Ui::Dialog)
{
ui->setupUi(this);
setMouseTracking(true);
scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);
scene->setBackgroundBrush(Qt::black);
square = new mySquare;
scene->addItem(square);
square->mPix = QPixmap(200,200);
square->mPix.fill(Qt::white);
scene->addPixmap(square->mPix);
}
Dialog::~Dialog()
{
delete ui;
}
void Dialog::on_pushButton_clicked()
{
square->selectedTool = 1;
}
對話框
#ifndef DIALOG_H
#define DIALOG_H
#include <QDialog>
#include <QtCore>
#include <QtGui>
#include "mysquare.h"
namespace Ui {
class Dialog;
}
class Dialog : public QDialog
{
Q_OBJECT
public:
explicit Dialog(QWidget *parent = 0);
~Dialog();
private slots:
void on_pushButton_clicked();
private:
Ui::Dialog *ui;
QGraphicsScene *scene;
mySquare *square;
};
#endif // DIALOG_H
mysquare.cpp
#include "mysquare.h"
using namespace std;
mySquare::mySquare()
{
pressed = false;
selectedTool = 1;
mPix = QPixmap(200,200);
mPix.fill(Qt::white);
}
void mySquare::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
painter->begin(this);
if(pressed)
{
painter->drawPixmap(0,0,mPix);
painter->drawRect(mRect);
drawStarted = true;
}
else if (drawStarted)
{
QPainter tempPainter(&mPix);
tempPainter.drawRect(mRect);
painter->drawPixmap(0,0,mPix);
}
painter->end();
}
void mySquare::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
pressed = true;
y = event->pos();
cout<<"Pos X : "<<y.x() <<endl;
cout<<"Pos Y : "<<y.y() <<endl;
if(selectedTool == 1)
{
mRect.setTopLeft(event->pos());
mRect.setBottomRight(event->pos());
cout << "Value of x_start axis " << X_1 <<endl;
cout << "Value of y_start axis " << Y_1 <<endl;
}
else if (selectedTool == 2)
{
}
update();
}
void mySquare::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
cout<<"Inside mouseMoveEvent \n";
if(event->type() == QEvent::MouseMove)
{
if(selectedTool == 1){
mRect.setBottomRight(event->pos());
}
else if (selectedTool == 2){
//mLine.setP2(event->pos());
}
}
update();
}
void mySquare::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
{
pressed = false;
update();
cout<<"Inside mouseReleaseEvent \n";
}
mysquare.h
#ifndef MYSQUARE_H
#define MYSQUARE_H
#include <QPainter>
#include <QGraphicsItem>
#include <QDebug>
#include <QPainter>
#include <iostream>
#include <QPixmap>
#include <QPaintEvent>
#include <QGraphicsSceneMouseEvent>
class mySquare: public QGraphicsItem
{
public:
mySquare();
int selectedTool;
QPixmap mPix;
QRectF boundingRect() const;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
bool pressed;
bool drawStarted;
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
private:
QRectF mRect;
QPointF y;
private slots:
};
#endif // MYSQUARE_H
請指導我,謝謝。
嘗試將屬性mouseTracking
設置為true。 你可以在這里閱讀它
您的代碼中也有一些問題。 例如,使用square = new mySquare;
創建mySquare
對象square = new mySquare;
。 但是我看不到您將代碼稱為delete square
代碼。
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