QT c++和qml交互实例

一、demo效果图

该实例，主要是在已有的QWidget工程中，加入qml工程，方便qml项目的开发与维护，让qml开发者更好的上手qml。

（1）展示了c++和qml常见的交互方式。
（2）qwidget工程如何加载qml工程，如何加载自己实现的qml tool库。
（3）创建无边框qml界面，支持拖拽，窗口的缩小与展开，界面的分段实现。
（4）展示一个简单的堆栈窗口（SwipeView），相当于QStackedWidget，管理多个子窗口页面。
（5）实现一个简单的列表框（ListView），相当于QListWidget，定时请求网络数据，展示学生信息，将view和model进行分离，降低界面与数据的耦合。
（6）点击学号、年龄，实现了列表数据的排序。

二、c++和qml交互的基本方式

两者的交互是核心，简单学习后，可以快速上手。方式有很多种，有的比较繁杂，不易理解，此处只使用了最方便使用的方法，满足基本的交互。基本的方式不外乎有四种。

• qml 调用 C++ 类对象
• C++ 类对象调用 qml
• qml 给 C++ 发送信号
• C++ 给 qml 发送信号

1、qml 调用 C++ 类对象

需要先将C++类（MainQuickView、MyWindow）注册。和qml相关的C++类，最好都进行注册。

// cpp
class MainQuickView : public QQuickView
{Q_OBJECT
public:MainQuickView(QQuickView *parent = nullptr);~MainQuickView() override;void initialzeUI();
protected:
};void MainQuickView ::initialzeUI()
{// 注册，为了qml中可以直接访问C++对象this->rootContext()->setContextProperty("myQuickView", this);MyWindow *w = new MyWindow();this->rootContext()->setContextProperty("myWindow", w);...
}

这样C++的信号，public槽函数，Q_INVOKABLE 修饰的类成员函数

// cpp
class MyWindow : public QWidget
{Q_OBJECTpublic:MyWindow();// Q_INVOKABLE可以将C++函数暴漏给qml引擎，注册到元对象系统Q_INVOKABLE void invokableMethod();signals:void dataChanged();public slots:void refresh();
};

就可以在qml中调用

// main.qml
Rectangle {id: rootwidth: 1200height: 800onClicked: {myWindow.showNormal(); // showNormal是QWidget父类的槽函数}
}

2、C++ 类对象调用 qml

需要先找到你想访问的qml中，名为"topRect"的QQuickItem对象

// cpp
QQuickItem* topRect = this->rootObject()->findChild<QQuickItem*>("topRect");

然后再访问qml实现的函数，“setTitleText”，该函数标题3展示(qml 给 C++ 发送信号)

// cpp
QMetaObject::invokeMethod(topRect, "setTitleText", Q_ARG(QVariant, QString::fromLocal8Bit("Qml窗口标题")));

3、qml 给 C++ 发送信号

qml发送信号

// qml
Rectangle {id: rootsignal sendTopRectPos(var x, var y)  // 定义信号function setTitleText(text) {titleText.text = text}MouseArea {// ... property point clickPos: "0, 0"onPressed: {clickPos = Qt.point(mouse.x, mouse.y)}onPositionChanged: {var delta = Qt.point(mouse.x - clickPos.x, mouse.y - clickPos.y)sendTopRectPos(delta.x, delta.y)  // 发送信号}}
}

C++绑定槽函数，该操作可以实现无边框窗口的拖拽

// cpp
QQuickItem* topRect = this->rootObject()->findChild<QQuickItem*>("topRect");if (topRect) {connect(topRect, SIGNAL(sendTopRectPos(QVariant, QVariant)),this, SLOT(onSendTopRectPos(QVariant, QVariant)));

4、C++ 给 qml 发送信号

C++发送信号

// cpp
void MainQuickView::minMaxQmlWindow()
{int nStudent = 10;emit refreshStuCount(nStudent); // 发送信号
}

qml绑定槽函数

// qml
Rectangle {id: rootfunction onRefreshStuCount(nStudent){// ...}Component.onCompleted: {mainQuickView.refreshStuCount.connect(onRefreshStuCount)  // 绑定qml函数}

三、关键代码

1、工程结构图

2、c++代码

MainWindow.cpp

MainWindow::MainWindow(QWidget *parent): QWidget(parent), ui(new Ui::MainWindow), m_pQuickVew(nullptr)
{ui->setupUi(this);
}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::on_pushButton_clicked()
{if (!m_pQuickVew){// 加载qml包含两种方式，一种是QQuickView，一种是QQmlApplicationEngine// 当前使用第一种方式，MainQuickView继承自QQuickViewm_pQuickVew = new MainQuickView();m_pQuickVew->setObjectName("quickView");}m_pQuickVew->show();
}

MainQuickView.cpp

static const char* s_mainPath = "qrc:/qml/main.qml";MainQuickView::MainQuickView(QQuickView *parent): QQuickView(parent), m_bMin(false)
{this->setFlags(Qt::Window | Qt::FramelessWindowHint);this->setTitle(QString::fromLocal8Bit("图书馆"));initialize();setMoveable();setTitleData();
}MainQuickView::~MainQuickView()
{
}void MainQuickView::initialize()
{// 初始化view 和 model，降低耦合，提高可维护性if (!m_pStudentInfoView)m_pStudentInfoView = new StudentInfoView();if (!m_pStudentInfoModel)m_pStudentInfoModel = m_pStudentInfoView->getStudentInfoMode();// ...其他功能initialzeUI();
}void MainQuickView::initialzeUI()
{// 注册，qml中可以直接访问C++对象this->rootContext()->setContextProperty("mainQuickView", this);// qml可以通过"studentInfoView"，去使用其实现的函数this->rootContext()->setContextProperty("studentInfoView", m_pStudentInfoView);this->rootContext()->setContextProperty("studentInfoModel", m_pStudentInfoModel);// qml根对象大小随窗口大小改变而改变this->setResizeMode(QQuickView::SizeRootObjectToView);// 导入自定义模块工具this->engine()->addImportPath(":/qmlTools");// 设置准备加载得qml文件，相当于c++的main函数入口this->setSource(QUrl(s_mainPath));
}void MainQuickView::minMaxQmlWindow()
{m_bMin = !m_bMin;emit minQmlWindow(m_bMin);
}void MainQuickView::onSendTopRectPos(QVariant pX, QVariant pY)
{this->setX(this->x() + pX.toInt());this->setY(this->y() + pY.toInt());
}void MainQuickView::onCloseQuickView()
{close();
}void MainQuickView::onShowMinimized()
{showMinimized();
}void MainQuickView::setMoveable()
{// 当移动qml窗口时，将移动坐标告诉C++// 找到对象名叫topRect的qml，C++绑定qml的信号QQuickItem* topRect = this->rootObject()->findChild<QQuickItem*>("topRect");if (topRect) {connect(topRect, SIGNAL(sendTopRectPos(QVariant, QVariant)),this, SLOT(onSendTopRectPos(QVariant, QVariant)));}
}void MainQuickView::setTitleData()
{// 找到对象名叫topRect的qml，C++向qml发送消息，触发qml中实现的setTitleText函数QQuickItem* topRect = this->rootObject()->findChild<QQuickItem*>("topRect");QMetaObject::invokeMethod(topRect, "setTitleText", Q_ARG(QVariant, QString::fromLocal8Bit("Qml窗口标题")));
}

StudentInfoView.cpp

StudentInfoView::StudentInfoView(QObject *parent): QObject(parent), m_sortType(StudentInfoSort::sortNone)
{if (!m_pStudentInfoModel)m_pStudentInfoModel = new StudentInfoModel(this);// 如果数据来自网络，就需要定时请求接口，并更新界面m_timer = new QTimer(this);m_timer->setInterval(10 * 1000);QObject::connect(m_timer, &QTimer::timeout, this, &StudentInfoView::onUpdateInfoData);onUpdateInfoData();m_timer->start();
}StudentInfoModel *StudentInfoView::getStudentInfoMode()
{return m_pStudentInfoModel;
}// qSort()比较函数不能定义为类成员函数（参数包含隐藏的this指针），会导致参数不符
// 可以定义为static类成员函数、static函数、普通函数
bool StudentInfoView::idAscend(const StudentInfoItem &stu1, const StudentInfoItem &stu2)
{return stu1.stuId < stu2.stuId; //学号升序
}// 普通函数
bool idDescend(const StudentInfoItem &stu1, const StudentInfoItem &stu2)
{return stu1.stuId > stu2.stuId; //学号降序
}bool ageAscend(const StudentInfoItem &stu1, const StudentInfoItem &stu2)
{return stu1.age < stu2.age; //年龄升序
}void StudentInfoView::setSort(StudentInfoSort sortType)
{m_sortType = sortType;if (m_sortType == StudentInfoSort::sortIdAscend){qSort(m_allDatas.begin(), m_allDatas.end(), idAscend);}else if (m_sortType == StudentInfoSort::sortIdDescend){qSort(m_allDatas.begin(), m_allDatas.end(), idDescend);}else if (m_sortType == StudentInfoSort::sortAgeAscend){// 比较函数也可以写为lambda表达式qSort(m_allDatas.begin(), m_allDatas.end(),[](const StudentInfoItem& stu1, const StudentInfoItem& stu2){return stu1.age < stu2.age;});}
}void StudentInfoView::updateSort(int sortType)
{// qml调用，执行哪一种排序方式，并刷新数据setSort((StudentInfoSort)sortType);if (m_pStudentInfoModel)m_pStudentInfoModel->clear();for (auto studentInfo : m_allDatas) {if (m_pStudentInfoModel) {m_pStudentInfoModel->AddModel(studentInfo);}}
}void StudentInfoView::onUpdateInfoData()
{// 每隔十秒请求网络接口，根据返回的数据刷新model，该实例模拟网络数据m_allDatas.clear();if (m_pStudentInfoModel)m_pStudentInfoModel->clear();QVector<StudentInfoItem> studentInfos;StudentInfoItem item1;item1.stuId = 9704;item1.stuName = QString::fromLocal8Bit("百里");item1.sex = 1;item1.age = 14;StudentInfoItem item2;item2.stuId = 9207;item2.stuName = QString::fromLocal8Bit("黄忠");item2.sex = 1;item2.age = 26;StudentInfoItem item3;item3.stuId = 9206;item3.stuName = QString::fromLocal8Bit("鲁班");item3.sex = 1;item3.age = 17;StudentInfoItem item4;item4.stuId = 9787;item4.stuName = QString::fromLocal8Bit("女娲");item4.sex = 0;item4.age = 33;studentInfos << item1 << item2 << item3 << item4;m_allDatas = studentInfos;setSort(m_sortType); //每一次网络数据刷新后，执行保存的排序方式for (auto studentInfo : m_allDatas) {if (m_pStudentInfoModel) {m_pStudentInfoModel->AddModel(studentInfo);}}
}

StudentInfoModel.cpp

#include "StudentInfoModel.h"StudentInfoModel::StudentInfoModel(QObject *parent): QAbstractListModel(parent)
{roleNames();
}StudentInfoModel::~StudentInfoModel()
{}void StudentInfoModel::clear()
{if (m_allDatas.size() <= 0)return;beginRemoveRows(QModelIndex(), 0, m_allDatas.size() - 1);m_allDatas.clear();endRemoveRows();
}void StudentInfoModel::mremove(int index)
{beginRemoveRows(QModelIndex(), index, index);m_allDatas.erase(m_allDatas.begin() + index);endRemoveRows();
}void StudentInfoModel::update(int index, const StudentInfoItem &infoModel)
{if (index < 0 || m_allDatas.size() < index)return;StudentInfoItem &srcModel = m_allDatas[index];srcModel = infoModel;
}void StudentInfoModel::AddModel(const StudentInfoItem &md)
{beginInsertRows(QModelIndex(), rowCount(), rowCount());m_allDatas.push_back(md);endInsertRows();
}QVariant StudentInfoModel::data(const QModelIndex &index, int role) const
{if (index.row() < 0 || index.row() >= m_allDatas.size()) {return QVariant();}const StudentInfoItem &itemInfo = m_allDatas.at(index.row());StudentInfoRoles infoRole = static_cast<StudentInfoRoles>(role);switch (infoRole) {case StudentInfoRoles::stuIdRole :return itemInfo.stuId;break;case StudentInfoRoles::stuNameRole :return itemInfo.stuName;break;case StudentInfoRoles::stuSexRole :return itemInfo.sex;break;case StudentInfoRoles::stuAgeRole :return itemInfo.age;break;default:return QVariant();break;}
}int StudentInfoModel::rowCount(const QModelIndex &parent) const
{return m_allDatas.size();
}QHash<int, QByteArray> StudentInfoModel::roleNames() const
{// 映射C++端的枚举与QML端的字符串QHash<int, QByteArray> data;data[int(StudentInfoRoles::stuIdRole)]   = "stuId";data[int(StudentInfoRoles::stuNameRole)] = "stuName";data[int(StudentInfoRoles::stuSexRole)]  = "sex";data[int(StudentInfoRoles::stuAgeRole)]  = "age";return data;
}

3、qml代码

main.qml

import QtQuick 2.0
import QtQuick.Layouts 1.0Item {id: rootwidth: 1200height: 800Rectangle {anchors.fill: parentcolor: "red"ColumnLayout {spacing: 0MainQuickTopRect {id: topRectobjectName: "topRect"width: root.widthheight: 50}MainQuickMiddleRect {id: middleRectobjectName: "middleRect"width: root.widthheight: root.height - topRect.height}}}
}

MainQuickTopRect.qml

import QtQuick 2.12
import QtQuick.Layouts 1.0
import QtQuick.Controls 2.12
import "../qmlTools/ButtonTools"Rectangle {id: rootcolor: "#181D33"signal sendTopRectPos(var x, var y)function setTitleText(text) {titleText.text = text}function onMinQmlWindow(bMin){if (bMin)narrowBtn.clicked() // narrowBtn是最小化按钮，当然也可以直接mainQuickView.onShowMinimized()elsemainQuickView.showNormal()}Component.onCompleted: {mainQuickView.minQmlWindow.connect(onMinQmlWindow)}RowLayout {id: rowLayoutanchors.fill: rootanchors.leftMargin: 16anchors.rightMargin: 16Text {id: titleTextanchors.fill: rootanchors.left: rowLayout.leftverticalAlignment: Text.AlignVCenterhorizontalAlignment: Text.AlignHCentercolor: "white"font.pixelSize: 18font.family: "Microsoft YaHei UI"font.bold: truetext: ""// 设置文本框背景颜色Rectangle {id: titleTextBackanchors.fill: titleTextcolor: "#000000"z: -1}}// 最小化ImageBtn {id: narrowBtnwidth: 24height: 24anchors.right: closeBtn.leftnormalUrl: "qrc:/resource/minNormal.png"hoveredUrl: "qrc:/resource/minHover.png"pressedUrl: "qrc:/resource/minHover.png"onClicked: {mainQuickView.onShowMinimized();console.log("min");}}// 关闭ImageBtn {id: closeBtnwidth: 24height: 24anchors.right: rowLayout.rightnormalUrl: "qrc:/resource/closeNormal.png"hoveredUrl: "qrc:/resource/closeHover.png"pressedUrl: "qrc:/resource/closeHover.png"onClicked: {mainQuickView.onCloseQuickView();}}}MouseArea {anchors.fill: parentacceptedButtons: Qt.LeftButtonpropagateComposedEvents: true  //传递鼠标事件property point clickPos: "0, 0"onPressed: {clickPos = Qt.point(mouse.x, mouse.y)console.log("onPressed " + clickPos);}onPositionChanged: {var delta = Qt.point(mouse.x - clickPos.x, mouse.y - clickPos.y)sendTopRectPos(delta.x, delta.y)}}
}

MainQuickMiddleRect.qml

import QtQuick 2.0
import QtQuick 2.12
import QtQuick.Controls 1.2
import QtQuick.Controls 2.5
import QtQuick.Layouts 1.1
import QtQuick.Controls.Styles 1.2
import "../qmlTools/ButtonTools"Rectangle {id: rootcolor: "#2E3449"property int oneCount: 50property int twoCount: 50property int threeCount: 50readonly property int pageWidth  : 400Rectangle {id: titleSwitchBtnwidth: parent.width / 2anchors.top: parent.topanchors.topMargin: 30anchors.left: parent.leftanchors.leftMargin: width - width / 2height: 46color: "#2C5CA5"RowLayout {spacing: 20anchors.bottom: parent.bottomanchors.bottomMargin: 0anchors.left: parent.leftanchors.leftMargin: 40DownLineBtn { // qmlTool中自定义实现的下划线按钮id: cover_one_btnbtn_width: 100btn_string: qsTr("一班") + oneCount + qsTr("人")onMyClicked: {coverBtnStat(cover_one_btn, true)coverBtnStat(cover_two_btn, false)coverBtnStat(cover_three_btn, false)swipeView.currentIndex = 0}}DownLineBtn {id: cover_two_btnbtn_width: 100btn_string: qsTr("二班") + twoCount + qsTr("人")onMyClicked: {coverBtnStat(cover_one_btn, false)coverBtnStat(cover_two_btn, true)coverBtnStat(cover_three_btn, false)swipeView.currentIndex = 1}}DownLineBtn {id: cover_three_btnbtn_width: 100btn_string: qsTr("三班") + threeCount + qsTr("人")onMyClicked: {coverBtnStat(cover_one_btn, false)coverBtnStat(cover_two_btn, false)coverBtnStat(cover_three_btn, true)swipeView.currentIndex = 2}}}}Rectangle {id: viewanchors.top: titleSwitchBtn.bottomanchors.topMargin: 4anchors.left: titleSwitchBtn.leftwidth: titleSwitchBtn.widthheight: pageWidthcolor: "white"radius: 4SwipeView {id: swipeViewobjectName: "outSideSwipView"anchors.fill: parentcurrentIndex: 0clip: true  //隐藏未选中的界面interactive: false  //鼠标能否滑动Item {  //St: 0，第一页id: onePageRectangle {id: oneViewanchors.fill: parentcolor: "#D7B9A1"}}Item {  //St: 1，第二页id: twoPageMainQuickMiddleTableRect {id: tableViewcolor: "green"width: titleSwitchBtn.widthheight: pageWidth}}Item { //St: 2，第三页id: defaultPageRectangle {anchors.fill: parentcolor: "#E6EC12"radius: 4Text {text: qsTr("没有数据")font.pixelSize:16color: "red"font.family: "Microsoft YaHei"verticalAlignment: Text.AlignVCenterhorizontalAlignment: Text.AlignHCenteranchors.verticalCenter: parent.verticalCenteranchors.horizontalCenter: parent.horizontalCenter}}}}}Component.onCompleted: {// 初始化按钮状态coverBtnStat(cover_one_btn, true)coverBtnStat(cover_two_btn, false)coverBtnStat(cover_three_btn, false)}/*  btn: object*  st : modify state*/function coverBtnStat(btn, st) {btn.bold_st = stbtn.show_line = st}
}

MainQuickMiddleTableRect.qml

import QtQuick 2.0
import "../qmlTools/ButtonTools"
import QtQuick.Controls 1.4
import QtQuick.Controls 2.5Rectangle {id: winanchors.fill: parentcolor: "green"property var current_numbers      : 0property var stu_id_sort_state    : 1property var stu_id_sort_open     : false// 绘制表头Rectangle {id: table_Headheight: 48anchors.top: titleSwitchBtn.bottomRectangle {id: table_Textheight: 47  // 比整个表头高度小1，为了容纳下划线TextShow {id: name_texttext: qsTr("姓名")anchors.left: table_Text.leftanchors.leftMargin: 68anchors.verticalCenter: table_Text.verticalCenter}TextShow {id: id_text// 学号未点击时，显示"↕"，表示不排序，点击后再判断时升序还是降序text: qsTr("学号") + (!stu_id_sort_open ?qsTr("↕") :(stu_id_sort_state ? qsTr("↓") : qsTr("↑")))anchors.left: table_Text.leftanchors.leftMargin: 150anchors.verticalCenter: table_Text.verticalCenterMouseArea {anchors.fill: parentpropagateComposedEvents: trueonPressed: {console.log("student id clicked")studentInfoView.updateSort(stu_id_sort_state ? 1 : 2) // 通知C++修改排序方式stu_id_sort_state = !stu_id_sort_statestu_id_sort_open = true}}}TextShow {id: sex_texttext: qsTr("性别")anchors.left: table_Text.leftanchors.leftMargin: 220anchors.verticalCenter: table_Text.verticalCenter}TextShow {id: age_texttext: qsTr("年龄")anchors.left: table_Text.leftanchors.leftMargin: 290anchors.verticalCenter: table_Text.verticalCenterMouseArea {anchors.fill: parentpropagateComposedEvents: trueonPressed: {console.log("student age clicked")studentInfoView.updateSort(3)stu_id_sort_open = false}}}LongLine {anchors.top: table_Text.bottom}}}//listViewRectangle {width: parent.widthheight: parent.height - table_Head.heightcolor: "green"anchors.top: table_Head.bottomListView {id: list_viewanchors.rightMargin: 10anchors.bottomMargin: 50anchors.leftMargin: 0anchors.topMargin: 0anchors.fill: parentmaximumFlickVelocity: 800clip: truedelegate: studentInfoDelegatemodel: studentInfoModelboundsBehavior: Flickable.StopAtBoundshighlightMoveDuration: 0ScrollBar.vertical: ScrollBar {id: scrollbar//visible: (current_numbers > 8)visible: trueanchors.right: list_view.rightwidth: 8active: truebackground: Item {Rectangle {anchors.right: parent.rightheight: parent.heightcolor: "yellow"radius: 4}}contentItem: Rectangle {radius: 4color: "red"}}}//studentInfoDelegate 渲染每一个itemComponent {id: studentInfoDelegateRectangle {id: list_itemwidth: parent.widthheight: 46color: "green"Rectangle {width: parent.widthheight: parent.heightcolor: "green"anchors.verticalCenter: parent.verticalCenterRectangle {id: rect_itemcolor: "#333333"height: 45TextShow {id: stu_nametext: model.stuNameanchors.verticalCenter: rect_item.verticalCenteranchors.left: rect_item.leftanchors.leftMargin: 68}TextShow {id: id_typetext: model.stuIdanchors.verticalCenter: rect_item.verticalCenteranchors.left: rect_item.leftanchors.leftMargin: 150}TextShow {id: sex_typetext: (model.sex == 1) ? qsTr("男") : qsTr("女")anchors.verticalCenter: rect_item.verticalCenteranchors.left: rect_item.leftanchors.leftMargin: 220}TextShow {id: age_typetext: model.age + qsTr(" 岁")anchors.verticalCenter: rect_item.verticalCenteranchors.left: rect_item.leftanchors.leftMargin: 290}}LongLine {anchors.top: rect_item.bottom}}}}}Component.onCompleted: {// qml加载完成后，可以获取C++中数据的个数，用来标识是否需要展示滚动条current_numbers = 4}
}