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Qt示例解析 【Callout】

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出16170入6148汤圆

发表于 2022-7-1 12:44:14 来自手机 | 显示全部楼层 |阅读模式
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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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