首页 > 代码库 > QGraphicsView的paintEvent双缓存绘画
QGraphicsView的paintEvent双缓存绘画
MyGraphicsView.h
1 #ifndef MYGRAPHICSVIEW_H 2 #define MYGRAPHICSVIEW_H 3 4 #include <QGraphicsView> 5 #include <QMouseEvent> 6 #include <QPaintEvent> 7 #include <QKeyEvent> 8 #include <QPainter> 9 #include <QPixmap> 10 #include <QDebug> 11 12 class MyGraphicsView : public QGraphicsView 13 { 14 Q_OBJECT 15 16 public: 17 MyGraphicsView(QWidget *parent); 18 ~MyGraphicsView(); 19 20 protected: 21 void mousePressEvent(QMouseEvent *event); 22 void mouseDoubleClickEvent(QMouseEvent *event); 23 void mouseMoveEvent(QMouseEvent *event); 24 void mouseReleaseEvent(QMouseEvent *event); 25 void paintEvent(QPaintEvent *event); 26 void keyPressEvent(QKeyEvent *event); 27 28 private: 29 QPixmap pix; 30 QPoint lasetPoint; 31 QPoint endPoint; 32 QPixmap tempPix; 33 bool isDrawing; 34 bool isDoubleClick; 35 }; 36 37 #endif // MYGRAPHICSVIEW_H
MyGraphicsView.cpp
#include "MyGraphicsView.h" MyGraphicsView::MyGraphicsView(QWidget *parent) : QGraphicsView(parent) { pix = QPixmap(1024, 768); pix.fill(Qt::white); isDrawing = false; isDoubleClick = false; } MyGraphicsView::~MyGraphicsView() { } void MyGraphicsView::mousePressEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) { lasetPoint = event->pos(); isDrawing = true; isDoubleClick = false; } QGraphicsView::mousePressEvent(event); } void MyGraphicsView::mouseDoubleClickEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) { isDoubleClick = true; } QGraphicsView::mouseDoubleClickEvent(event); } void MyGraphicsView::mouseMoveEvent(QMouseEvent *event) { if (event->buttons() & Qt::LeftButton) { if (!isDoubleClick) { endPoint = event->pos(); this->viewport()->update(); } } QGraphicsView::mouseMoveEvent(event); } void MyGraphicsView::mouseReleaseEvent(QMouseEvent *event) { if (event->button() == Qt::LeftButton) { if (!isDoubleClick) { endPoint = event->pos(); isDrawing = false; this->viewport()->update(); } } QGraphicsView::mouseReleaseEvent(event); } void MyGraphicsView::paintEvent(QPaintEvent *event) { /// 直接在窗体上绘图,前1次画的矩形是不能保存住的 // QPainter painter(this->viewport()); // int x, y, w, h; // x = lasetPoint.x(); // y = lasetPoint.y(); // w = endPoint.x() - x; // h = endPoint.y() - y; // painter.drawRect(x, y, w, h); /// 直接在pix上绘图,前1次前2次前3次...画的都保存住了(鼠标每移动一点就会触发paintEvent函数而画一次),所以在pix上会呈现好多矩形 // int x, y, w, h; // x = lasetPoint.x(); // y = lasetPoint.y(); // w = endPoint.x() - x; // h = endPoint.y() - y; // QPainter pp(&pix); // pp.drawRect(x, y, w, h); // QPainter painter(this->viewport()); // painter.drawPixmap(0, 0, pix); /// 双缓冲绘图,原理是在拖动过程中先把原来的图形复制到tempPix里面并在tempPix里面画,我们此时看到的就是在tempPix里的图形。只在鼠标释放的时候才在pix绘一次。 int x, y, w, h; x = lasetPoint.x(); y = lasetPoint.y(); w = endPoint.x() - x; h = endPoint.y() - y; QPainter painter(this->viewport()); if (isDrawing) { tempPix = pix; QPainter pp(&tempPix); pp.drawRect(x, y, w, h); painter.drawPixmap(0, 0, tempPix); } else { QPainter pp(&pix); pp.drawRect(x, y, w, h); painter.drawPixmap(0, 0, pix); } QGraphicsView::paintEvent(event); } void MyGraphicsView::keyPressEvent(QKeyEvent *event) { QGraphicsView::keyPressEvent(event); }
三种绘制方法效果图:
QGraphicsView的paintEvent双缓存绘画
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。