QT画矩形

第一次发QT的博文，本人对QT接触没多久，还在入门水平，大牛勿喷哈，之前因为C#  (.net framework)做出来的绘制矩形的程序闪的太厉害了，现在用QT重做一个

先上效果图

---

代码贴全了

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QPalette>
#include<Qstring>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    //设置背景色为白色
    QPalette palette(this->palette());
    palette.setColor(QPalette::Background, Qt::white);
    this->setPalette(palette);
    //初始化变量
    this->mousedown=false;
    this->release=false;
    ;
    ;
    //初始化画布
    pix=new QPixmap(w,h);
    pix->fill(Qt::white);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::paintEvent(QPaintEvent *event)
{

    QPainter paintpix(pix);
    QPainter paintform(this);
    if(this->mousedown)//鼠标移动时触发
    {
        paintform.drawPixmap(,,w,h,*pix);
        QRect* rect=new QRect(this->startpoint,this->endpoint);
        paintform.drawRect (*rect);

    }
    else if(!this->mousedown&&this->release)//鼠标释放时触发
    {
        if(this->startpoint.x()==this->endpoint.x()&&this->endpoint.y()==this->startpoint.y())//两点重合时什么也不画
        {
             paintform.drawPixmap(,,w,h,*pix);
            return;
        }

        QRect* rect=new QRect(this->startpoint,this->endpoint);
        paintpix.drawRect (*rect);
         paintform.drawPixmap(,,w,h,*pix);
        this->release=false;
    }
    else
    {
        paintform.drawPixmap(,,w,h,*pix);
    }

}

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if(this->mousedown)
    {
        this->endpoint=event->pos();
        update();
    }

}

void MainWindow::mousePressEvent(QMouseEvent *event)
{
    startpoint=event->pos();
    this->mousedown=true;

}

void MainWindow::mouseReleaseEvent(QMouseEvent *event)
{
    this->endpoint=event->pos();
    this->mousedown=false;
    this->release=true;
    update();
}

void MainWindow::repaint()//重画时
{
    QPainter paintform(this);
    paintform.drawPixmap(,,w,h,*pix);
}

示例代码链接：：http://pan.baidu.com/s/1eQ2TaJw

这个是C#版本的 http://www.cnblogs.com/magicianlyx/p/4979644.html