功能
实现QtCharts曲线图移动和缩放：
- 按住鼠标左键拖动曲线可移动曲线；
- 滚动鼠标滚轮实现图形X轴方向的缩放；
- 按住Ctrl，滚动鼠标滚轮实现图形Y轴方向的缩放；
- 按鼠标右键恢复图形初始状态;
- 缩放过程以鼠标当前位置为缩放中心；
- 鼠标移动过程中会在左上角显示当前坐标。
实现
继承QChartView，主要重新实现鼠标事件和键盘事件。
- 移动图形利用QChart的scroll函数；
void scroll(qreal dx, qreal dy, const QRectF &rect = QRectF());
鼠标按下时，记录按下状态，并记录当前坐标位置，在移动事件内计算鼠标移动的距离，以此设置图形滚动的距离，即可实现移动 - 缩放则设置当前坐标轴的显示范围；
void setRange(const QVariant &min, const QVariant &max);
代码
.cpp文件
实现移动
CSDN QT技术栈大纲：Qt开发必备技术栈学习路线和资料
1 void ChartView::mousePressEvent(QMouseEvent *event)
2 {
3 if (event->button() == Qt::LeftButton)
4 {
5 m_lastPoint = event->pos();
6 m_isPress = true;
7 }
8 }
9
10 void ChartView::mouseMoveEvent(QMouseEvent *event)
11 {
12 if (!m_coordItem)
13 {
14 m_coordItem = new QGraphicsSimpleTextItem(this->chart());
15 m_coordItem->setZValue(5);
16 m_coordItem->setPos(100, 60);
17 m_coordItem->show();
18 }
19 const QPoint curPos = event->pos();
20 QPointF curVal = this->chart()->mapToValue(QPointF(curPos));
21 QString coordStr = QString("X = %1, Y = %2").arg(curVal.x()).arg(curVal.y());
22 m_coordItem->setText(coordStr);
23
24 if (m_isPress)
25 {
26 QPoint offset = curPos - m_lastPoint;
27 m_lastPoint = curPos;
28 if (!m_alreadySaveRange)
29 {
30 this->saveAxisRange();
31 m_alreadySaveRange = true;
32 }
33 this->chart()->scroll(-offset.x(), offset.y());
34 }
35 }
36
37 void ChartView::mouseReleaseEvent(QMouseEvent *event)
38 {
39 m_isPress = false;
40 if (event->button() == Qt::RightButton)
41 {
42 if (m_alreadySaveRange)
43 {
44 this->chart()->axisX()->setRange(m_xMin, m_xMax);
45 this->chart()->axisY()->setRange(m_yMin, m_yMax);
46 }
47 }
48 }
49
50 //保存原始位置
51 void ChartView::saveAxisRange()
52 {
53 QValueAxis *axisX = dynamic_cast<QValueAxis*>(this->chart()->axisX());
54 m_xMin = axisX->min();
55 m_xMax = axisX->max();
56 QValueAxis *axisY = dynamic_cast<QValueAxis*>(this->chart()->axisY());
57 m_yMin = axisY->min();
58 m_yMax = axisY->max();
59 }实现缩放
1 void ChartView::wheelEvent(QWheelEvent *event)
2 {
3 const QPoint curPos = event->pos();
4 QPointF curVal = this->chart()->mapToValue(QPointF(curPos));
5
6 if (!m_alreadySaveRange)
7 {
8 this->saveAxisRange();
9 m_alreadySaveRange = true;
10 }
11 const double factor = 1.5;//缩放比例
12 if (m_ctrlPress)
13 {//Y轴
14 QValueAxis *axisY = dynamic_cast<QValueAxis*>(this->chart()->axisY());
15 const double yMin = axisY->min();
16 const double yMax = axisY->max();
17 const double yCentral = curVal.y();
18
19 double bottomOffset;
20 double topOffset;
21 if (event->delta() > 0)
22 {//放大
23 bottomOffset = 1.0 / factor * (yCentral - yMin);
24 topOffset = 1.0 / factor * (yMax - yCentral);
25 }
26 else
27 {//缩小
28 bottomOffset = 1.0 * factor * (yCentral - yMin);
29 topOffset = 1.0 * factor * (yMax - yCentral);
30 }
31
32 this->chart()->axisY()->setRange(yCentral - bottomOffset, yCentral + topOffset);
33 }
34 else
35 {//X轴
36 QValueAxis *axisX = dynamic_cast<QValueAxis*>(this->chart()->axisX());
37 const double xMin = axisX->min();
38 const double xMax = axisX->max();
39 const double xCentral = curVal.x();
40
41 double leftOffset;
42 double rightOffset;
43 if (event->delta() > 0)
44 {//放大
45 leftOffset = 1.0 / factor * (xCentral - xMin);
46 rightOffset = 1.0 / factor * (xMax - xCentral);
47 }
48 else
49 {//缩小
50 leftOffset = 1.0 * factor * (xCentral - xMin);
51 rightOffset = 1.0 * factor * (xMax - xCentral);
52 }
53 this->chart()->axisX()->setRange(xCentral - leftOffset, xCentral + rightOffset);
54 }
55 }
56 }以下为Qt Android下使用手势实现Qchart的缩放
要使用手势，先在构造函数中注册允许使用手势
1 //this->setAttribute(Qt::WA_AcceptTouchEvents); //设置接收触摸事件
2 grabGesture(Qt::PinchGesture); //这里只grabGesture了PinchGesture 1 //监听事件类型
2 bool ChartView::event(QEvent *event)
3 {
4 switch(event->type())
5 {
6 // case QEvent::TouchBegin:
7 // //accepting touch begin allows us to get touch updates
8 // return true;
9 // break;
10 case QEvent::Gesture: //如果是手势事件就交给手势事件处理
11 return gestureEvent(static_cast<QGestureEvent*>(event));
12 break;
13 default: //默认为鼠标事件
14 break;
15 }
16 return QWidget::event(event);
17 }
18
19 //处理手势事件
20 bool ChartView::gestureEvent(QGestureEvent *event)
21 {
22 if (!m_alreadySaveRange) //执行手势事件之前先保存原始位置
23 {
24 this->saveAxisRange();
25 m_alreadySaveRange = true;
26 }
27
28 if (QGesture *pinch = event->gesture(Qt::PinchGesture)) //如果是捏合手势，进行缩放处理
29 {
30 pinchTriggered(static_cast<QPinchGesture *>(pinch));
31 event->accept();
32 }
33 return true;
34 }
35
36 //处理缩放事件
37 void ChartView::pinchTriggered(QPinchGesture *gesture)
38 {
39 QPinchGesture::ChangeFlags changeFlags = gesture->changeFlags();
40 if (changeFlags & QPinchGesture::ScaleFactorChanged)
41 {
42 currentStepScaleFactor = gesture->scaleFactor(); //合计放大系数
43 }
44 if (gesture->state() == Qt::GestureFinished)
45 {
46 scaleFactor = 1;
47 scaleFactor *= currentStepScaleFactor;
48 currentStepScaleFactor = 1;
49 }
50
51 if(scaleFactor >= 1)
52 {
53 this->chart()->zoom(1.05);
54 }
55 else if(scaleFactor < 1)
56 {
57 this->chart()->zoom(0.95);
58 }
59 update();.h文件
1 #pragma once
2
3 #include <QChartView>
4 #include <QMouseEvent>
5 #include <QGraphicsSimpleTextItem>
6
7 QT_CHARTS_USE_NAMESPACE
8
9 class ChartView : public QChartView
10 {
11 Q_OBJECT
12
13 public:
14 ChartView(QChart *chart, QWidget *parent = nullptr);
15 ~ChartView();
16 // 保存坐标区域，用于复位
17 void saveAxisRange();
18
19 protected:
20 void mousePressEvent(QMouseEvent *event);
21 void mouseMoveEvent(QMouseEvent *event);
22 void mouseReleaseEvent(QMouseEvent *event);
23 void wheelEvent(QWheelEvent *event);
24 void keyPressEvent(QKeyEvent *event);
25 void keyReleaseEvent(QKeyEvent *event);
26
27 //以下3个为Qt Android下Qchart的缩放（单指触点时默认为鼠标点击，所以移动功能可正常使用）
28 bool event(QEvent *event) override; //使用手势实现缩放
29 bool gestureEvent(QGestureEvent *event);
30 void pinchTriggered(QPinchGesture *gesture);
31
32 private:
33 QPoint m_lastPoint;
34 bool m_isPress;
35 bool m_ctrlPress;
36 bool m_alreadySaveRange;
37 double m_xMin, m_xMax, m_yMin, m_yMax;
38 QGraphicsSimpleTextItem* m_coordItem;
39 };main文件
1 #include <QApplication>
2 #include <QMainWindow>
3 #include <QLineSeries>
4 #include "ChartView.h"
5
6 int main(int argc, char *argv[])
7 {
8 QApplication a(argc, argv);
9
10 QLineSeries *series = new QLineSeries();
11
12
13 series->append(0, 6);
14 series->append(2, 4);
15 series->append(3, 8);
16 series->append(7, 4);
17 series->append(10, 5);
18 *series << QPointF(11, 1) << QPointF(13, 3) << QPointF(17, 6) << QPointF(18, 3) << QPointF(20, 2);
19
20 QChart *chart = new QChart();
21 chart->legend()->hide();
22 chart->addSeries(series);
23 chart->createDefaultAxes();
24 chart->setTitle("图形移动和缩放");
25
26 auto *chartView = new ChartView(chart);//使用自定义ChartView
27 chartView->setRenderHint(QPainter::Antialiasing);
28
29 QMainWindow window;
30 window.setCentralWidget(chartView);
31 window.resize(400, 300);
32 window.show();
33
34 return a.exec();
35 }.pro文件
1 QT += core gui charts
2
3 greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
4
5 CONFIG += c++11
6
7 # The following define makes your compiler emit warnings if you use
8 # any Qt feature that has been marked deprecated (the exact warnings
9 # depend on your compiler). Please consult the documentation of the
10 # deprecated API in order to know how to port your code away from it.
11 DEFINES += QT_DEPRECATED_WARNINGS
12
13 # You can also make your code fail to compile if it uses deprecated APIs.
14 # In order to do so, uncomment the following line.
15 # You can also select to disable deprecated APIs only up to a certain version of Qt.
16 #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0
17
18 SOURCES += \
19 ChartView.cpp \
20 main.cpp
21
22 HEADERS += \
23 ChartView.h
24
25 FORMS +=
26
27 # Default rules for deployment.
28 qnx: target.path = /tmp/$${TARGET}/bin
29 else: unix:!android: target.path = /opt/$${TARGET}/bin
30 !isEmpty(target.path): INSTALLS += targetps:将文件都放在这，下次要用可以直接来复制，方便点。
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