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目的:从此示例中了解QChart中曲线的绘制方法 和 插图的生成方法。本博文主要侧重于插图的生成方法。
本示例中有View和Callout两个类
View类:继承自QGraphicsView
添加两个曲线,series和series2,并各自关联了两个事件,鼠标的点击事件(对应KeepCallout)和悬停事件(对应tooltip)
KeepCallout中将Callout图元添加到Scene(场景)中,代码实现如下
m_callouts.append(m_tooltip);
m_tooltip = new Callout(m_chart);
tooltip中,若鼠标悬停在曲线上,则显示Callout图元;若不悬停在曲线上,则隐藏Callout图元。代码实现如下
if (m_tooltip == 0)
m_tooltip = new Callout(m_chart);
if (state) {
m_tooltip->setText(QString("X: %1 \nY: %2 ").arg(point.x()).arg(point.y()));
m_tooltip->setAnchor(point);
m_tooltip->setZValue(11);
m_tooltip->updateGeometry();
m_tooltip->show();
} else {
m_tooltip->hide();
}
Callout类:继承自QGraphicsItem
涉及到Qt QGraphicsView中的知识点:
1. setDragMode主要用于设置鼠标的拖拽方式
//没有任何反应,鼠标事件将被忽略
setDragMode(QGraphicsView::NoDrag)
//光标变为指向手,然后拖动鼠标将滚动滚动条,此模式在交互和非交互模式下均有效
setDragMode(QGraphicsView::ScrollHandDrag)
//将出现矩形块,拖动鼠标将设置矩形的大小,并选中矩形覆盖的所有项目,非交互视图禁用此模式
setDragMode(QGraphicsView::RubberBandDrag)
2. 隐藏滚动条
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
3. 防止走样(反走样)
//Qt默认关闭反走样,反走样比不反走样质量高
setRenderHint(QPainter::Antialiasing,true);//默认为True
4. 鼠标追踪开始事件
setMouseTracking(false);//鼠标追踪事件从按下左键后开始追踪
setMouseTracking(true);//鼠标追踪开始
最后给出程序中的两个主要类:
Callout.h
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Charts module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#ifndef CALLOUT_H
#define CALLOUT_H
#include <QtCharts/QChartGlobal>
#include <QtWidgets/QGraphicsItem>
#include <QtGui/QFont>
QT_BEGIN_NAMESPACE
class QGraphicsSceneMouseEvent;
QT_END_NAMESPACE
QT_CHARTS_BEGIN_NAMESPACE
class QChart;
QT_CHARTS_END_NAMESPACE
QT_CHARTS_USE_NAMESPACE
class Callout : public QGraphicsItem
{
public:
Callout(QChart *parent);
void setText(const QString &text);
void setAnchor(QPointF point);
void updateGeometry();
QRectF boundingRect() const;
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,QWidget *widget);
protected:
void mousePressEvent(QGraphicsSceneMouseEvent *event);
void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
private:
QString m_text;
QRectF m_textRect;
QRectF m_rect;
QPointF m_anchor;
QFont m_font;
QChart *m_chart;
};
#endif // CALLOUT_H
Callout.cpp
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Charts module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "callout.h"
#include <QtGui/QPainter>
#include <QtGui/QFontMetrics>
#include <QtWidgets/QGraphicsSceneMouseEvent>
#include <QtGui/QMouseEvent>
#include <QtCharts/QChart>
Callout::Callout(QChart *chart):
QGraphicsItem(chart),
m_chart(chart)
{
}
QRectF Callout::boundingRect() const
{
QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
QRectF rect;
rect.setLeft(qMin(m_rect.left(), anchor.x()));
rect.setRight(qMax(m_rect.right(), anchor.x()));
rect.setTop(qMin(m_rect.top(), anchor.y()));
rect.setBottom(qMax(m_rect.bottom(), anchor.y()));
return rect;
}
void Callout::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
Q_UNUSED(option)
Q_UNUSED(widget)
QPainterPath path;
path.addRoundedRect(m_rect, 5, 5);
QPointF anchor = mapFromParent(m_chart->mapToPosition(m_anchor));
if (!m_rect.contains(anchor)) {
QPointF point1, point2;
// establish the position of the anchor point in relation to m_rect
bool above = anchor.y() <= m_rect.top();
bool aboveCenter = anchor.y() > m_rect.top() && anchor.y() <= m_rect.center().y();
bool belowCenter = anchor.y() > m_rect.center().y() && anchor.y() <= m_rect.bottom();
bool below = anchor.y() > m_rect.bottom();
bool onLeft = anchor.x() <= m_rect.left();
bool leftOfCenter = anchor.x() > m_rect.left() && anchor.x() <= m_rect.center().x();
bool rightOfCenter = anchor.x() > m_rect.center().x() && anchor.x() <= m_rect.right();
bool onRight = anchor.x() > m_rect.right();
// get the nearest m_rect corner.
qreal x = (onRight + rightOfCenter) * m_rect.width();
qreal y = (below + belowCenter) * m_rect.height();
bool cornerCase = (above && onLeft) || (above && onRight) || (below && onLeft) || (below && onRight);
bool vertical = qAbs(anchor.x() - x) > qAbs(anchor.y() - y);
qreal x1 = x + leftOfCenter * 10 - rightOfCenter * 20 + cornerCase * !vertical * (onLeft * 10 - onRight * 20);
qreal y1 = y + aboveCenter * 10 - belowCenter * 20 + cornerCase * vertical * (above * 10 - below * 20);;
point1.setX(x1);
point1.setY(y1);
qreal x2 = x + leftOfCenter * 20 - rightOfCenter * 10 + cornerCase * !vertical * (onLeft * 20 - onRight * 10);;
qreal y2 = y + aboveCenter * 20 - belowCenter * 10 + cornerCase * vertical * (above * 20 - below * 10);;
point2.setX(x2);
point2.setY(y2);
path.moveTo(point1);
path.lineTo(anchor);
path.lineTo(point2);
path = path.simplified();
}
painter->setBrush(QColor(255, 255, 255));
painter->drawPath(path);
painter->drawText(m_textRect, m_text);
}
void Callout::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
event->setAccepted(true);
}
void Callout::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
if (event->buttons() & Qt::LeftButton){
setPos(mapToParent(event->pos() - event->buttonDownPos(Qt::LeftButton)));
event->setAccepted(true);
} else {
event->setAccepted(false);
}
}
void Callout::setText(const QString &text)
{
m_text = text;
QFontMetrics metrics(m_font);
m_textRect = metrics.boundingRect(QRect(0, 0, 150, 150), Qt::AlignLeft, m_text);
m_textRect.translate(5, 5);
prepareGeometryChange();
m_rect = m_textRect.adjusted(-5, -5, 5, 5);
}
void Callout::setAnchor(QPointF point)
{
m_anchor = point;
}
void Callout::updateGeometry()
{
prepareGeometryChange();
setPos(m_chart->mapToPosition(m_anchor) + QPoint(10, -50));
View.h
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the Qt Charts module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:GPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
** approved by the KDE Free Qt Foundation. The licenses are as published by
** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "view.h"
#include <QtGui/QResizeEvent>
#include <QtWidgets/QGraphicsScene>
#include <QtCharts/QChart>
#include <QtCharts/QLineSeries>
#include <QtCharts/QSplineSeries>
#include <QtWidgets/QGraphicsTextItem>
#include "callout.h"
#include <QtGui/QMouseEvent>
View::View(QWidget *parent)
: QGraphicsView(new QGraphicsScene, parent),
m_coordX(0),
m_coordY(0),
m_chart(0),
m_tooltip(0)
{
setDragMode(QGraphicsView::NoDrag);
setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
// chart
m_chart = new QChart;
m_chart->setMinimumSize(640, 480);
m_chart->setTitle("Hover the line to show callout. Click the line to make it stay");
m_chart->legend()->hide();
QLineSeries *series = new QLineSeries;
series->append(1, 3);
series->append(4, 5);
series->append(5, 4.5);
series->append(7, 1);
series->append(11, 2);
m_chart->addSeries(series);
QSplineSeries *series2 = new QSplineSeries;
series2->append(1.6, 1.4);
series2->append(2.4, 3.5);
series2->append(3.7, 2.5);
series2->append(7, 4);
series2->append(10, 2);
m_chart->addSeries(series2);
m_chart->createDefaultAxes();
m_chart->setAcceptHoverEvents(true);
setRenderHint(QPainter::Antialiasing,true);
scene()->addItem(m_chart);
m_coordX = new QGraphicsSimpleTextItem(m_chart);
m_coordX->setPos(m_chart->size().width()/2 - 50, m_chart->size().height());
m_coordX->setText("X: ");
m_coordY = new QGraphicsSimpleTextItem(m_chart);
m_coordY->setPos(m_chart->size().width()/2 + 50, m_chart->size().height());
m_coordY->setText("Y: ");
connect(series, &QLineSeries::clicked, this, &View::keepCallout);
connect(series, &QLineSeries::hovered, this, &View::tooltip);
connect(series2, &QSplineSeries::clicked, this, &View::keepCallout);
connect(series2, &QSplineSeries::hovered, this, &View::tooltip);
this->setMouseTracking(true);
}
void View::resizeEvent(QResizeEvent *event)
{
if (scene()) {
scene()->setSceneRect(QRect(QPoint(0, 0), event->size()));
m_chart->resize(event->size());
m_coordX->setPos(m_chart->size().width()/2 - 50, m_chart->size().height() - 20);
m_coordY->setPos(m_chart->size().width()/2 + 50, m_chart->size().height() - 20);
const auto callouts = m_callouts;
for (Callout *callout : callouts)
callout->updateGeometry();
}
QGraphicsView::resizeEvent(event);
}
void View::mouseMoveEvent(QMouseEvent *event)
{
m_coordX->setText(QString("X: %1").arg(m_chart->mapToValue(event->pos()).x()));
m_coordY->setText(QString("Y: %1").arg(m_chart->mapToValue(event->pos()).y()));
QGraphicsView::mouseMoveEvent(event);
}
void View::keepCallout()
{
m_callouts.append(m_tooltip);
m_tooltip = new Callout(m_chart);
}
void View::tooltip(QPointF point, bool state)
{
if (m_tooltip == 0)
m_tooltip = new Callout(m_chart);
if (state) {
m_tooltip->setText(QString("X: %1 \nY: %2 ").arg(point.x()).arg(point.y()));
m_tooltip->setAnchor(point);
m_tooltip->setZValue(11);
m_tooltip->updateGeometry();
m_tooltip->show();
} else {
m_tooltip->hide();
}
}
main.cpp
#include <QtWidgets/QApplication>
#include "view.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
View w;
w.show();
return a.exec();
}
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