简单的QT绘图程序

环境

OS : Ubuntu 11.04

IDE ：Qt Creator 2.2.1

Qt : 4.7.4 (32bit)

Complier: gcc

新建一个空白Qt工程

文件--> 新建工程或项目-->其它项目-->空的Qt项目

比如命名为Qt_Instance_Example

添加一个C++源文件

比如命名为main.cpp，添加如下代码

#include <QApplication>  
#include <mypainterwidget.h>  
  
int main(int argc,char** argv)  
{  
    QApplication a(argc,argv);  
  
    MyPainterWidget w(0);  
    w.show();  
    return a.exec();  
}

这里的MyPainterWidget类是我们自己编写的QWidget类的子类，用来实现绘制的窗口部件。

下面我们添加这个类并编写其代码。

添加C++类，命名为MyPainterWidget

.h 文件如下

#ifndef MYPAINTERWIDGET_H  
#define MYPAINTERWIDGET_H  
  
#include <QWidget>  
#include <QPoint>  
#include<vector>  
  
using namespace std;  
  
  
//线段  
typedef struct myLine{  
    QPoint startPnt;  
    QPoint endPnt;  
}myLine;  
  
class MyPainterWidget: public QWidget  
{  
public:  
    MyPainterWidget(QWidget* parent);  
    ~MyPainterWidget();  
  
    //继承  
    void paintEvent(QPaintEvent* p);  
    void mousePressEvent(QMouseEvent *e);  
    void mouseMoveEvent(QMouseEvent *e);  
    void mouseReleaseEvent(QMouseEvent *e);  
  
    QPoint startPnt;   //起点  
    QPoint endPnt;     //终点  
    bool isPressed;    //鼠标是否按下  
  
    vector<myLine*> lines; //存放所有的线段  
};  
  
#endif // MYPAINTERWIDGET_H

.cpp 文件如下

#include "mypainterwidget.h"  
#include <QString>  
#include <QMessageBox>  
#include <QPainter>  
#include <QPen>  
#include <QMouseEvent>  
  
  
MyPainterWidget::MyPainterWidget(QWidget* parent)  
     :QWidget(parent){  
    setMinimumSize(240,120);  
    setMaximumSize(480,240);  
    this->setMouseTracking(true);  
    this->isPressed = false;  
}  
  
MyPainterWidget::~MyPainterWidget(){  
  
}  
  
void MyPainterWidget::paintEvent(QPaintEvent*p){  
    QPainter painter(this);  
    QPen pen;                                 //创建一个画笔  
    pen.setColor(Qt::darkCyan);  
    pen.setWidth(5);  
    painter.setPen(pen);  
  
    for(int i = 0;i<lines.size();i++){  
        myLine* pLine = lines[i];  
        painter.drawLine(pLine->startPnt,pLine->endPnt);  
    }  
}  
  
void MyPainterWidget::mousePressEvent(QMouseEvent *e){  
    setCursor(Qt::PointingHandCursor);  
    startPnt = e->pos();  
    endPnt = e->pos();  
    this->isPressed = true;  
    //QString msg ="("+QString::number(e->x())+","+QString::number(e->y())+")";  
    //QMessageBox::warning(this,tr("Warning"),msg,QMessageBox::Ok);  
}  
  
void MyPainterWidget::mouseMoveEvent(QMouseEvent *e){  
    if(this->isPressed){  
        endPnt = e->pos();  
  
        myLine* line = new myLine;  //put the new line into vector  
        line->startPnt = startPnt;  
        line->endPnt = endPnt;  
        this->lines.push_back(line);  
  
        update();                                    //repainter，call paintEvent  
        startPnt = endPnt;  
    }  
}  
  
void MyPainterWidget::mouseReleaseEvent(QMouseEvent *e){  
    setCursor(Qt::ArrowCursor);  
    this->isPressed = false;  
}

简单的QT绘图程序

猜你喜欢