C++ 在QtWidget上动态绘制线
下面是一个在小部件上画线的代码。问题是它保持了以前画的线,并且在每次鼠标移动时,它会一次又一次地画。我想像mspaint一样画画,也就是说,只有在鼠标释放事件时,它才会完成线条绘制(否则只需预览线条)。我考虑的一个想法是在每次鼠标移动时删除预览线,另一个想法是绘制一些临时视图并在鼠标释放时完成它。但是很难找到一个合适的方法去做。 谢谢你的帮助C++ 在QtWidget上动态绘制线,c++,qt,qtgui,C++,Qt,Qtgui,下面是一个在小部件上画线的代码。问题是它保持了以前画的线,并且在每次鼠标移动时,它会一次又一次地画。我想像mspaint一样画画,也就是说,只有在鼠标释放事件时,它才会完成线条绘制(否则只需预览线条)。我考虑的一个想法是在每次鼠标移动时删除预览线,另一个想法是绘制一些临时视图并在鼠标释放时完成它。但是很难找到一个合适的方法去做。 谢谢你的帮助 #include "paintwidget.h" #include "ui_paintwidget.h" #include <QtGui>
#include "paintwidget.h"
#include "ui_paintwidget.h"
#include <QtGui>
paintWidget::paintWidget(QWidget* parent)
: QWidget(parent)
, ui(new Ui::paintWidget)
{
ui->setupUi(this);
m_nInitialX = 0;
m_nInitialY = 0;
m_nFinalX = 0;
m_nFinalY = 0;
m_nPTargetPixmap = 0;
m_nPTargetPixmap = new QPixmap(400, 400);
m_nbMousePressed = false;
}
paintWidget::~paintWidget()
{
delete ui;
}
void paintWidget::mousePressEvent(QMouseEvent* event)
{
m_nbMousePressed = true;
m_nInitialX = event->pos().x();
m_nInitialY = event->pos().y();
}
void paintWidget::mouseReleaseEvent(QMouseEvent* event)
{
m_nbMousePressed = false;
//update();
}
void paintWidget::paintEvent(QPaintEvent* e)
{
if (m_nbMousePressed) {
QPainter PixmapPainter(m_nPTargetPixmap);
QPen pen(Qt::green);
PixmapPainter.setPen(pen);
//PixmapPainter.drawLine(m_nInitialX, m_nInitialY, m_nFinalX, m_nFinalY);
}
QPainter painter(this);
painter.drawPixmap(0, 0, *m_nPTargetPixmap);
}
void paintWidget::mouseMoveEvent(QMouseEvent* event)
{
if (event->type() == QEvent::MouseMove) {
QPainter PixmapPainter(m_nPTargetPixmap);
QPen pen(Qt::black);
PixmapPainter.setPen(pen);
PixmapPainter.drawLine(m_nInitialX, m_nInitialY, m_nFinalX, m_nFinalY);
update(); // update your view
m_nFinalX = event->pos().x();
m_nFinalY = event->pos().y();
}
update(); // update your view
}
#包括“paintwidget.h”
#包括“ui_paintwidget.h”
#包括
paintWidget::paintWidget(QWidget*父项)
:QWidget(父项)
,ui(新ui::paintWidget)
{
用户界面->设置用户界面(此);
m_ninitalx=0;
m_nInitialY=0;
m_nFinalX=0;
m_nFinalY=0;
m_nPTargetPixmap=0;
m_nPTargetPixmap=新的QPixmap(400400);
m_nbMousePressed=假;
}
paintWidget::~paintWidget()
{
删除用户界面;
}
void paintWidget::mousePressEvent(QMouseEvent*event)
{
m_nbMousePressed=真;
m_ninitalx=事件->位置();
m_nInitialY=事件->位置();
}
void paintWidget::mouseReleaseEvent(QMouseEvent*事件)
{
m_nbMousePressed=假;
//更新();
}
void paintWidget::paintEvent(QPaintEvent*e)
{
如果(鼠标按下){
QPainter Pixmappainer(m_nPTargetPixmap);
QPen笔(Qt::绿色);
pixmappainer.setPen(笔);
//Pixmappainer.拉丝(m_Ninitalx,m_Ninitaly,m_nFinalX,m_nFinalY);
}
油漆工(本);
painter.drawPixmap(0,0,*m_nPTargetPixmap);
}
void paintWidget::mouseMoveEvent(QMouseEvent*event)
{
如果(事件->类型()==QEvent::MouseMove){
QPainter Pixmappainer(m_nPTargetPixmap);
QPen笔(Qt::黑色);
pixmappainer.setPen(笔);
Pixmappainer.拉丝(m_Ninitalx,m_Ninitaly,m_nFinalX,m_nFinalY);
update();//更新您的视图
m_nFinalX=事件->位置();
m_nfinity=事件->位置();
}
update();//更新您的视图
}
我把我的源代码放在这里:
请注意添加的注释
以下是相关文件:
#include "paintwidget.h"
#include <QPainter>
#include <QPen>
#include <QBrush>
#include <QDebug>
PaintWidget::PaintWidget(QWidget *parent) : QWidget(parent)
{
// the ui form wasn't needed here, so I added it without it.
// QLine neatly keeps track of both the two points, m_line in this case
// m_nInitialX = 0;
// m_nInitialY = 0;
// m_nFinalX = 0;
// m_nFinalY = 0;
// m_nPTargetPixmap = 0;
// m_nPTargetPixmap = new QPixmap(400,400);
m_nPTargetPixmap = QPixmap(400,400);// put the pixmap on the stack instead of the heap
m_nPTargetPixmap.fill();
m_nbMousePressed = false;
}
PaintWidget::~PaintWidget()
{
// delete ui;
}
void PaintWidget::mousePressEvent(QMouseEvent* event)
{
m_nbMousePressed = true;
// m_nInitialX = event->pos().x();
// m_nInitialY = event->pos().y();
m_line.setP1(event->pos());
m_line.setP2(event->pos());
}
void PaintWidget::mouseReleaseEvent(QMouseEvent *event)
{
m_nbMousePressed = false;
update();
}
void PaintWidget::paintEvent(QPaintEvent *e)
{
static bool wasPressed = false;
QPainter painter(this);
if(m_nbMousePressed)
{
painter.drawPixmap(0, 0, m_nPTargetPixmap);
painter.drawLine(m_line);
wasPressed = true;
}
else if(wasPressed)
{
// Note that this painting only needs to happen once,
// right when the mouse is released.
QPainter PixmapPainter(&m_nPTargetPixmap);
QPen pen(Qt::green);
PixmapPainter.setPen(pen);
PixmapPainter.drawLine(m_line);
painter.drawPixmap(0, 0, m_nPTargetPixmap);
wasPressed = false;
}
}
void PaintWidget::mouseMoveEvent(QMouseEvent *event)
{
if (event->type() == QEvent::MouseMove)
{
// QPainter PixmapPainter(m_nPTargetPixmap);
// QPen pen(Qt::black);
// PixmapPainter.setPen(pen);
// PixmapPainter.drawLine(m_nInitialX, m_nInitialY, m_nFinalX, m_nFinalY);
// m_nFinalX = event->pos().x();
// m_nFinalY = event->pos().y();
m_line.setP2(event->pos());
// update(); // update your view
}
update(); // update your view
}
#包括“paintwidget.h”
#包括
#包括
#包括
#包括
PaintWidget::PaintWidget(QWidget*parent):QWidget(parent)
{
//这里不需要ui表单,所以我添加了它而没有它。
//QLine整齐地跟踪这两个点,在本例中为m_线
//m_ninitalx=0;
//m_nInitialY=0;
//m_nFinalX=0;
//m_nFinalY=0;
//m_nPTargetPixmap=0;
//m_nPTargetPixmap=新的QPixmap(400400);
m_nPTargetPixmap=QPixmap(400400);//将pixmap放在堆栈而不是堆上
m_nPTargetPixmap.fill();
m_nbMousePressed=假;
}
PaintWidget::~PaintWidget()
{
//删除用户界面;
}
void PaintWidget::mousePressEvent(QMouseEvent*event)
{
m_nbMousePressed=真;
//m_ninitalx=事件->位置();
//m_nInitialY=事件->位置();
m_line.setP1(事件->位置());
m_line.setP2(事件->位置());
}
void PaintWidget::mouseReleaseEvent(QMouseEvent*事件)
{
m_nbMousePressed=假;
更新();
}
void PaintWidget::paintEvent(QPaintEvent*e)
{
静态布尔值被按下=假;
油漆工(本);
如果(鼠标按下)
{
painter.drawPixmap(0,0,m_nPTargetPixmap);
油漆工。拉丝(m_线);
wasPressed=true;
}
否则,如果(已按下)
{
//注意这幅画只需要画一次,
//鼠标松开的时候。
QPainter Pixmappainer(&m_nPTargetPixmap);
QPen笔(Qt::绿色);
pixmappainer.setPen(笔);
Pixmappainer.拉线(m_线);
painter.drawPixmap(0,0,m_nPTargetPixmap);
wasPressed=false;
}
}
void PaintWidget::mouseMoveEvent(QMouseEvent*event)
{
如果(事件->类型()==QEvent::MouseMove)
{
//QPainter Pixmappainer(m_nPTargetPixmap);
//QPen笔(Qt::黑色);
//pixmappainer.setPen(笔);
//Pixmappainer.拉丝(m_Ninitalx,m_Ninitaly,m_nFinalX,m_nFinalY);
//m_nFinalX=事件->位置();
//m_nfinity=事件->位置();
m_line.setP2(事件->位置());
//update();//更新您的视图
}
update();//更新您的视图
}
更新:使用QGraphicscene和绘制线和椭圆的其他信息: QGraphicscene具有可以在单击场景时添加的线条和椭圆 这个例子似乎特别相似:
希望能有所帮助。据我所知,m_nPTargetPixmap是一个额外的绘图层,当鼠标被释放时,它正在画家身上绘制。是吗?是的。先画的在底部,最后画的在顶部。