使用图形视图框架(Graphics View Framework)在QML中创建交互式图形界面
- 使用图形视图框架(Graphics View Framework)在QML中创建交互式图形界面
- 使用图形视图框架(Graphics View Framework)在QML中创建交互式图形界面
- 什么是图形视图框架(Graphics View Framework)?
- 在QML中使用图形视图框架
- 步骤1:项目配置
- 步骤2:创建QmlGraphicsView类
- 步骤3:注册自定义类型
- 步骤4:创建QML界面
- 步骤5:运行应用程序
- 完整代码
- 总结
使用图形视图框架(Graphics View Framework)在QML中创建交互式图形界面
在现代应用程序开发中,图形界面是用户体验的关键。Qt框架为我们提供了一种强大而灵活的方式来创建各种图形界面,而QML(Qt Meta-Object Language)是Qt的一部分,用于设计和构建现代、响应式的用户界面。本文将介绍如何在QML中使用图形视图框架,以创建交互式的图形界面。
什么是图形视图框架(Graphics View Framework)?
图形视图框架是Qt中的一个核心组件,它允许开发者创建和管理2D图形场景。这个框架提供了一个强大的工具集,用于在应用程序中显示和处理图形元素,例如矩形、文本、线条等。它不仅支持静态图形展示,还支持交互和动画效果。
在QML中使用图形视图框架
在QML中使用图形视图框架需要进行一些设置和配置。下面是一些步骤,帮助您在项目中集成图形视图框架:
步骤1:项目配置
首先,确保您的Qt项目已正确配置。在项目的.pro文件中,确保已添加QT += quick widgets
,并且设置了正确的Qt版本。还要配置文件的字符集,确保使用UTF-8编码。
步骤2:创建QmlGraphicsView类
在项目中,您需要创建一个自定义的QmlGraphicsView类,该类继承自QQuickPaintedItem
,用于在QML中显示图形内容。这个类将充当图形视图的容器。
// QmlGraphicsView.h
#pragma once// Include necessary Qt headersclass QmlGraphicsView : public QQuickPaintedItem
{Q_OBJECTpublic:QmlGraphicsView(QQuickItem* parent = nullptr): QQuickPaintedItem(parent) {// 初始化图形场景并添加图形元素// 设置交互选项}// 实现绘制函数void paint(QPainter* painter) override {// 绘制图形内容}signals:// 自定义信号private slots:// 自定义槽函数protected:// 处理鼠标和交互事件的函数
};
步骤3:注册自定义类型
在main.cpp
中,使用qmlRegisterType
函数将自定义的QmlGraphicsView
类注册为QML类型,以便在QML文件中使用。
qmlRegisterType<QmlGraphicsView>("QmlWidgets", 1, 0, "QmlGraphicsView");
步骤4:创建QML界面
在QML文件(例如main.qml
)中,导入所需的Qt Quick模块和自定义类型,然后创建界面并将自定义的QmlGraphicsView
作为子项嵌套在其中。
import QtQuick 2.15
import QtQuick.Window 2.15
import QmlWidgets 1.0Window {width: 640height: 480visible: truetitle: qsTr("QmlWidgets")QmlGraphicsView {anchors.fill: parent}
}
步骤5:运行应用程序
最后,在main.cpp
中启动应用程序,加载QML界面,并在需要时添加国际化支持。
完整代码
#pragma once#include <QApplication>
#include <QDebug>
#include <QEvent>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QQuickPaintedItem>
#include <QQuickWindow>
#include <QPainter>
#include <QGraphicsSceneMouseEvent>/*#
ref https://het.as.utexas.edu/HET/Software/html/qtdeclarative.html
ref https://doc.qt.io/qt-5/qtquick-porting-qt5.html
ref https://github.com/KDABLabs/DeclarativeWidgets
ref https://www.qt.io/blog/2017/01/19/should-you-be-using-qgraphicsviewhttps://qmlbook.github.io/#
https://github.com/machinekit/QtQuickVcp
https://github.com/FabriceSalvaire/qt5-vector-graphic-shaders
https://box2d.org/https://www.learnqt.guide/working-with-events# 可参考 qtcharts QML 组件,它使用图形视图框架移植到QML图表。
https://github.com/qt/qtcharts/tree/dev*/
class QmlGraphicsView : public QQuickPaintedItem
{Q_OBJECTpublic:QmlGraphicsView(QQuickItem* parent = nullptr): QQuickPaintedItem(parent) {// Set item flagssetFlag(ItemHasContents, true);// Initialize the GraphicsScenem_scene = new QGraphicsScene(this);setAntialiasing(QQuickItem::antialiasing());connect(m_scene, &QGraphicsScene::changed, this, &QmlGraphicsView::sceneChanged);connect(this, &QmlGraphicsView::needRender, this, &QmlGraphicsView::renderScene, Qt::QueuedConnection);connect(this, SIGNAL(antialiasingChanged(bool)), this, SLOT(handleAntialiasingChanged(bool)));// add Textm_scene->addText("Hello, world!\ncheungxiongwei");m_scene->addRect(1, 1, 85, 32);setAcceptedMouseButtons(Qt::AllButtons);setAcceptHoverEvents(true);}~QmlGraphicsView() { delete m_sceneImage; }signals:public:void paint(QPainter* painter) override {if(m_sceneImage && painter) {auto pos = boundingRect().center() - m_scene->sceneRect().center();painter->drawImage(pos, *m_sceneImage);}}Q_SIGNALS:void needRender();
private Q_SLOTS:void handleAntialiasingChanged(bool enable) {setAntialiasing(enable);emit needRender();}void sceneChanged(QList<QRectF> region) {const int count = region.size();const qreal limitSize = 0.01;if(count && !m_updatePending) {qreal totalSize = 0.0;for(int i = 0; i < count; i++) {const QRectF& reg = region.at(i);totalSize += (reg.height() * reg.width());if(totalSize >= limitSize) break;}// Ignore region updates that change less than small fraction of a pixel,// as there is little point regenerating the image in these cases. These// are typically cases where OpenGL series are drawn to otherwise static// view.if(totalSize >= limitSize) {m_updatePending = true;// Do async render to avoid some unnecessary renders.emit needRender();} else {// We do want to call update to trigger possible gl series updates.update();}}}void renderScene() {m_updatePending = false;QSize viewSize = size().toSize();if(!m_sceneImage || viewSize != m_sceneImage->size()) {delete m_sceneImage;qreal dpr = window() ? window()->devicePixelRatio() : 1.0;m_sceneImage = new QImage(viewSize * dpr, QImage::Format_ARGB32);m_sceneImage->setDevicePixelRatio(dpr);m_sceneImageNeedsClear = true;}if(m_sceneImageNeedsClear) {m_sceneImage->fill(Qt::transparent);}QPainter painter(m_sceneImage);if(antialiasing()) {painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing | QPainter::SmoothPixmapTransform);}QRect renderRect(QPoint(0, 0), viewSize);m_scene->render(&painter, renderRect, renderRect);update();}protected:void mousePressEvent(QMouseEvent* event) override {m_mousePressScenePoint = event->pos();m_mousePressScreenPoint = event->globalPos();m_lastMouseMoveScenePoint = m_mousePressScenePoint;m_lastMouseMoveScreenPoint = m_mousePressScreenPoint;m_mousePressButton = event->button();m_mousePressButtons = event->buttons();QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMousePress);mouseEvent.setWidget(0);mouseEvent.setButtonDownScenePos(m_mousePressButton, m_mousePressScenePoint);mouseEvent.setButtonDownScreenPos(m_mousePressButton, m_mousePressScreenPoint);mouseEvent.setScenePos(m_mousePressScenePoint);mouseEvent.setScreenPos(m_mousePressScreenPoint);mouseEvent.setLastScenePos(m_lastMouseMoveScenePoint);mouseEvent.setLastScreenPos(m_lastMouseMoveScreenPoint);mouseEvent.setButtons(m_mousePressButtons);mouseEvent.setButton(m_mousePressButton);mouseEvent.setModifiers(event->modifiers());mouseEvent.setAccepted(false);QApplication::sendEvent(m_scene, &mouseEvent);update();}void mouseReleaseEvent(QMouseEvent* event) override {QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseRelease);mouseEvent.setWidget(0);mouseEvent.setButtonDownScenePos(m_mousePressButton, m_mousePressScenePoint);mouseEvent.setButtonDownScreenPos(m_mousePressButton, m_mousePressScreenPoint);mouseEvent.setScenePos(event->pos());mouseEvent.setScreenPos(event->globalPos());mouseEvent.setLastScenePos(m_lastMouseMoveScenePoint);mouseEvent.setLastScreenPos(m_lastMouseMoveScreenPoint);mouseEvent.setButtons(event->buttons());mouseEvent.setButton(event->button());mouseEvent.setModifiers(event->modifiers());mouseEvent.setAccepted(false);QApplication::sendEvent(m_scene, &mouseEvent);m_mousePressButtons = event->buttons();m_mousePressButton = Qt::NoButton;update();}void hoverMoveEvent(QHoverEvent* event) override {QPointF previousLastScenePoint = m_lastMouseMoveScenePoint;// Convert hover move to mouse move, since we don't seem to get actual mouse move events.// QGraphicsScene generates hover events from mouse move events, so we don't need// to pass hover events there.QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseMove);mouseEvent.setWidget(0);mouseEvent.setButtonDownScenePos(m_mousePressButton, m_mousePressScenePoint);mouseEvent.setButtonDownScreenPos(m_mousePressButton, m_mousePressScreenPoint);mouseEvent.setScenePos(event->pos());// Hover events do not have global pos in them, and the screen position doesn't seem to// matter anyway in this use case, so just pass event pos instead of trying to// calculate the real screen position.mouseEvent.setScreenPos(event->pos());mouseEvent.setLastScenePos(m_lastMouseMoveScenePoint);mouseEvent.setLastScreenPos(m_lastMouseMoveScreenPoint);mouseEvent.setButtons(m_mousePressButtons);mouseEvent.setButton(m_mousePressButton);mouseEvent.setModifiers(event->modifiers());m_lastMouseMoveScenePoint = mouseEvent.scenePos();m_lastMouseMoveScreenPoint = mouseEvent.screenPos();mouseEvent.setAccepted(false);QApplication::sendEvent(m_scene, &mouseEvent);// Update triggers another hover event, so let's not handle successive hovers at same// position to avoid infinite loop.if(previousLastScenePoint != m_lastMouseMoveScenePoint) {update();}}void mouseDoubleClickEvent(QMouseEvent* event) override {m_mousePressScenePoint = event->pos();m_mousePressScreenPoint = event->globalPos();m_lastMouseMoveScenePoint = m_mousePressScenePoint;m_lastMouseMoveScreenPoint = m_mousePressScreenPoint;m_mousePressButton = event->button();m_mousePressButtons = event->buttons();QGraphicsSceneMouseEvent mouseEvent(QEvent::GraphicsSceneMouseDoubleClick);mouseEvent.setWidget(0);mouseEvent.setButtonDownScenePos(m_mousePressButton, m_mousePressScenePoint);mouseEvent.setButtonDownScreenPos(m_mousePressButton, m_mousePressScreenPoint);mouseEvent.setScenePos(m_mousePressScenePoint);mouseEvent.setScreenPos(m_mousePressScreenPoint);mouseEvent.setLastScenePos(m_lastMouseMoveScenePoint);mouseEvent.setLastScreenPos(m_lastMouseMoveScreenPoint);mouseEvent.setButtons(m_mousePressButtons);mouseEvent.setButton(m_mousePressButton);mouseEvent.setModifiers(event->modifiers());mouseEvent.setAccepted(false);QApplication::sendEvent(m_scene, &mouseEvent);update();}private:QGraphicsScene* m_scene {nullptr};QPointF m_mousePressScenePoint;QPoint m_mousePressScreenPoint;QPointF m_lastMouseMoveScenePoint;QPoint m_lastMouseMoveScreenPoint;Qt::MouseButton m_mousePressButton;Qt::MouseButtons m_mousePressButtons;QImage* m_sceneImage {nullptr};bool m_updatePending {false};bool m_sceneImageNeedsClear {false};
};
代码仓库
https://gitcode.net/cheungxiongwei/qmlwidgets
总结
通过以上步骤,您可以在QML中成功集成图形视图框架,创建交互式的图形界面。这使您能够轻松地管理和展示2D图形元素,为用户提供出色的图形体验。
无论是游戏开发、数据可视化还是其他需要图形界面的应用程序,Qt的图形视图框架为开发者提供了一个强大的工具,使其能够以直观和交互式的方式与用户进行互动。
希望本文对您理解如何在QML中使用图形视图框架提供了一些帮助。如果您想深入学习和探索这个主题,可以查看Qt官方文档和示例代码。祝您在Qt开发中取得成功!