1. 頭文件?

#include <QWidget> #include <QPainter> #include <QMouseEvent> #include <QDebug>class MainWidget : public QWidget {Q_OBJECTpublic:MainWidget(QWidget *parent = 0);~MainWidget(); private:QPixmap pix;QPoint lastPoint;QPoint endPoint; protected:void paintEvent(QPaintEvent *event);void mouseMoveEvent(QMouseEvent *event);void mousePressEvent(QMouseEvent *event);void mouseReleaseEvent(QMouseEvent *event); };

2. cpp文件

#include "mainwidget.h"MainWidget::MainWidget(QWidget *parent): QWidget(parent) {resize(600, 500); //窗口大小設置為600*500pix = QPixmap(200, 200);pix.fill(Qt::white);}MainWidget::~MainWidget() {}void MainWidget::paintEvent(QPaintEvent *event) {QPainter pp(&pix); // 根據鼠標指針前后兩個位置就行繪制直線pp.drawLine(lastPoint, endPoint); // 讓前一個坐標值等于后一個坐標值，這樣就能實現畫出連續的線lastPoint = endPoint;QPainter painter(this);painter.drawPixmap(0, 0, pix); }void MainWidget::mouseMoveEvent(QMouseEvent *event) {if (event->buttons() == Qt::LeftButton){endPoint = event->pos();update();} }void MainWidget::mousePressEvent(QMouseEvent *event) {if (event->button() == Qt::LeftButton) {lastPoint = event->pos();} }void MainWidget::mouseReleaseEvent(QMouseEvent *event) {if (event->button() == Qt::LeftButton){endPoint = event->pos();update();} }

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?參考資料：

1.?http://shouce.jb51.net/qt-beginning/21.html

2.?mouseMoveEvent中判斷鼠標狀態

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