QML其实是对ECMAScript的扩展,融合了Qt object系统,它是一种新的解释性语言,QML引擎虽然由Qt C++实现,但QML对象的运行环境说到底和C++对象的上下文环境是不通的,是平行的两个世界,如果想在QML中访问C++对象,那么必然要找到一种途径在两个运行环境之间建立沟通的桥梁。
Qt提供了两种在QML环境中使用C++对象的方式:
(1)在C++中实现一个类,注册为QML环境的一个类型,在QML环境中使用该类型创建对象
(2)在C++中构造一个对象,将这个对象设置为QML的上下文属性,在QML环境中直接使用该属性
一 类的方式实现在QML中使用C++对象
1. 定义可以导出的C++类
要想将一个类或对象导出到QML中,必须满足以下几个条件:
(1)从QObject或QObject的派生类继承
(2)使用Q_OBJECT宏
(3)Q_INVOKABLE宏
在定义一个类的成员函数时使用Q_INVOKABLE宏来修饰,就可以让该方法被元对象系统调用,这个宏必须放在返回类型前面
(4)Q_ENUMS宏
如果要导出的类定义了想在QML中使用的枚举类型,可以使用Q_ENUM宏将该枚举注册到元对象系统中
(5)Q_PROPERTY宏
Q_PROPERTY宏用来定义可以通过元对象系统访问的属性,通过它定义的属性,可以在QML中访问,修改,也可以在属性变化时发射特定的信号
例子:
#ifndef COLORMAKER_H
#define COLORMAKER_H
#include <QObject>
#include <QColor>
class ColorMaker : public QObject
{
Q_OBJECT
Q_ENUMS(GenerateAlgorithm)
Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
Q_PROPERTY(QColor timeColor READ timeColor)
public:
explicit ColorMaker(QObject *parent = nullptr);
~ColorMaker();
enum GenerateAlgorithm
{
RandomRGB,
RandomRed,
RandomGreen,
RandomBlue,
LinearIcrease
};
QColor color() const {return m_currentColor;}
void setColor(const QColor& color);
QColor timeColor() const;
Q_INVOKABLE GenerateAlgorithm alorithm() const;
Q_INVOKABLE void serAlgorithm(GenerateAlgorithm algorithm);
signals:
void colorChanged(const QColor& color);
void currentTime(const QString& strTime);
public slots:
void start();
void stop();
protected:
void timerEvent(QTimerEvent *e);
private:
GenerateAlgorithm m_algorithm;
QColor m_currentColor;
int m_nColorTimer;
};
#endif // COLORMAKER_H
#include "colormaker.h"
#include <QTime>
#include <QTimerEvent>
#include <QDebug>
ColorMaker::ColorMaker(QObject *parent)
: QObject(parent)
,m_algorithm(RandomRGB)
,m_currentColor(Qt::black)
,m_nColorTimer(0)
{
qsrand(QDateTime::currentDateTime().toTime_t());
}
ColorMaker::~ColorMaker()
{
}
void ColorMaker::setColor(const QColor &color)
{
m_currentColor = color;
emit colorChanged(color);
}
QColor ColorMaker::timeColor() const
{
QTime time = QTime::currentTime();
qDebug() << time.toString("yyyy-MM-dd hh:mm:ss");
int r = time.hour();
int g = time.minute() * 2;
int b = time.second() * 4;
qDebug() << r << ":"<< g << ":"<< b;
return QColor(r,g,b);
}
ColorMaker::GenerateAlgorithm ColorMaker::alorithm() const
{
return m_algorithm;
}
void ColorMaker::serAlgorithm(ColorMaker::GenerateAlgorithm algorithm)
{
m_algorithm = algorithm;
}
void ColorMaker::start()
{
qDebug() << "ColorMaker start";
if (m_nColorTimer == 0)
{
m_nColorTimer = startTimer(1000);
}
}
void ColorMaker::stop()
{
if (m_nColorTimer > 0)
{
killTimer(m_nColorTimer);
m_nColorTimer = 0;
}
}
void ColorMaker::timerEvent(QTimerEvent *e)
{
if (e->timerId() == m_nColorTimer)
{
switch (m_algorithm) {
case RandomRGB:
m_currentColor.setRgb(qrand()%255, qrand()%255,qrand()%255);
break;
case RandomRed:
m_currentColor.setRed(qrand()%255);
break;
case RandomGreen:
m_currentColor.setGreen(qrand()%255);
break;
case RandomBlue:
m_currentColor.setBlue(qrand()%255);
break;
case LinearIcrease:
{
int r = m_currentColor.red() + 10;
int g = m_currentColor.green() + 10;
int b = m_currentColor.blue() + 10;
m_currentColor.setRgb(r%255,g%255,b%255);
}
break;
default:
break;
}
emit colorChanged(m_currentColor);
emit currentTime(QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss"));
}
else
{
return QObject::timerEvent(e);
}
}
2. 注册QML类型
要注册一个QML类型,有多种方法:
qmlRegisterSingletonType()注册一个单例类型
qmlRegisterType()注册一个非单例类型
qmlRegisterTypeNotAvaliable()注册一个类型用来占位
qmlRegisterUncreatableType()通常用来注册一个具有附加属性的附加类型,具体参考Qt SDK
template<typename T>
int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);
template<typename T, int metaObjectRevision>
int qmlRegisterType(const char *uri, int versionMajor, int versionMinor, const char *qmlName);
uri 指定唯一的包名
qmlname 是QML中可以使用的类名
qmlRegisterType<ColorMaker>("an.qt.ColorMaker", 1, 0, "ColorMaker");
3. 在QML中导入类型
一旦你在C++中注册好了QML类型,就可以在QML文档中引入你注册的包,然后使用注册的类型了
import an.qt.ColorMaker 1.0
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickView>
#include <QtQml>
#include "colormaker.h"
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
//QQmlApplicationEngine engine;
//engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
//if (engine.rootObjects().isEmpty())
// return -1;
qmlRegisterType<ColorMaker>("an.qt.ColorMaker", 1, 0, "ColorMaker");
QQuickView viewer;
viewer.setResizeMode(QQuickView::SizeRootObjectToView);
viewer.setSource(QUrl("qrc:///main.qml"));
viewer.show();
return app.exec();
}
4. 在QML中创建由C++导出的类型的实例并使用
引入包后,你可以在QML中创建 C++导入类型的对象了,与QML内建类型的使用完全一样。
Rectangle
{
width: 360;
height: 360;
ColorMaker
{
id:colorMaker;
color:Qt.green;
}
}
例:
import QtQuick 2.2
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
import QtQuick.Controls.Styles 1.4
import QtQuick.Dialogs 1.3
import QtQml 2.11
import an.qt.ColorMaker 1.0
Rectangle
{
width: 360;
height: 360;
Text {
id: timeLabel;
anchors.left: parent.left;
anchors.leftMargin: 4;
anchors.top : parent.top;
anchors.topMargin: 4;
font.pixelSize: 26;
}
ColorMaker
{
id:colorMaker;
color:Qt.green;
}
Rectangle
{
id:colorRect;
anchors.centerIn: parent;
width: 200;
height: 200;
color: "blue";
}
Button
{
id:start;
text:"start";
anchors.left: parent.left;
anchors.leftMargin: 4;
anchors.bottom: parent.bottom;
anchors.bottomMargin: 4;
onClicked:
{
console.log("start onClicked");
colorMaker.start();
}
}
Button
{
id:stop;
text:"stop";
anchors.left: start.right;
anchors.leftMargin: 4;
anchors.bottom: start.bottom;
anchors.bottomMargin: 4;
onClicked:
{
colorMaker.stop();
}
}
function changeAlgorithm(button, algorithm)
{
switch(algorithm)
{
case 0:
button.text = "RandomRGB"
break;
case 1:
button.text ="RandomRed";
break;
case 2:
button.text ="RandomGreen";
break;
case 3:
button.text ="RandomBlue";
break;
case 4:
button.text ="LinearIncrease";
break;
}
}
Button
{
id:colorAlgorithm;
text:"RandomRGB";
anchors.left:stop.right;
anchors.leftMargin: 4;
anchors.bottom: stop.bottom;
onClicked:
{
var algorithm = (colorMaker.alorithm() + 1 ) % 5;
changeAlgorithm(colorAlgorithm,algorithm);
colorMaker.serAlgorithm(algorithm);
}
}
Button
{
id:quit
text:"quit"
anchors.left: colorAlgorithm.right;
anchors.leftMargin: 4;
anchors.bottom: colorAlgorithm.bottom;
onClicked:
{
Qt.quit();
}
}
Component.onCompleted:
{
colorMaker.color = Qt.rgba(0,180,120,255);
colorMaker.serAlgorithm(colorMaker.LinearIcrease);
changeAlgorithm(colorAlgorithm,colorMaker.alorithm());
}
Connections
{
target: colorMaker;
onCurrentTime:
{
timeLabel.text = strTime;
console.log("onCurrentTime");
// timeLabel.color = colorMaker.timeColor;
}
}
Connections
{
target: colorMaker;
onColorChanged:
{
colorRect.color = color;
}
}
}
/*Rectangle
{
width: 600
height: 600
Image {
id: imageLabel;
width: 600;
height: 540;
anchors.top: parent.top
anchors.left: parent.left
fillMode: Image.PreserveAspectFit
source: "http://images.cnblogs.com/cnblogs_com/xiaobingqianrui/1185116/o_Image%201.png"
}
Button
{
id:openBtn
width: 100;
height: 40;
text: "Open";
anchors.top:imageLabel.bottom
anchors.topMargin: 10;
anchors.left: parent.left
anchors.leftMargin: 10;
onClicked:fileDialog.open();
}
Label
{
id:pathLabel;
text: "Hello world"
font.pixelSize: 22
font.italic: true
color: "steelblue"
anchors.top:imageLabel.bottom
anchors.topMargin: 10;
anchors.left: openBtn.right
anchors.leftMargin: 10
}
FileDialog
{
id:fileDialog
title: "please choose a file"
nameFilters: ["Image Files (*.jpg *.png *.gif)"]
onAccepted:
{
imageLabel.source=fileDialog.fileUrl;
console.log(fileDialog.fileUrl);
var imageFile = new String(fileDialog.fileUrl);
pathLabel.text=imageFile.slice(8);
}
}
}*/
二 对象的方式实现在QML中使用C++对象
1. 注册属性
viewer.rootContext()->setContextProperty("colorMaker", new ColorMaker);
2. 在QML中使用关联到的C++对象的属性
一旦调用setContextProperty()导出了属性,就可以在QML中使用了,不需要import语句
import QtQuick 2.2
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
import QtQuick.Controls.Styles 1.4
import QtQuick.Dialogs 1.3
import QtQml 2.11
//import an.qt.ColorMaker 1.0
Rectangle
{
width: 360;
height: 360;
Text {
id: timeLabel;
anchors.left: parent.left;
anchors.leftMargin: 4;
anchors.top : parent.top;
anchors.topMargin: 4;
font.pixelSize: 26;
}
/* ColorMaker
{
id:colorMaker;
color:Qt.green;
}*/
Rectangle
{
id:colorRect;
anchors.centerIn: parent;
width: 200;
height: 200;
color: "blue";
}
Button
{
id:start;
text:"start";
anchors.left: parent.left;
anchors.leftMargin: 4;
anchors.bottom: parent.bottom;
anchors.bottomMargin: 4;
onClicked:
{
console.log("start onClicked");
colorMaker.start();
}
}
Button
{
id:stop;
text:"stop";
anchors.left: start.right;
anchors.leftMargin: 4;
anchors.bottom: start.bottom;
anchors.bottomMargin: 4;
onClicked:
{
colorMaker.stop();
}
}
function changeAlgorithm(button, algorithm)
{
switch(algorithm)
{
case 0:
button.text = "RandomRGB"
break;
case 1:
button.text ="RandomRed";
break;
case 2:
button.text ="RandomGreen";
break;
case 3:
button.text ="RandomBlue";
break;
case 4:
button.text ="LinearIncrease";
break;
}
}
Button
{
id:colorAlgorithm;
text:"RandomRGB";
anchors.left:stop.right;
anchors.leftMargin: 4;
anchors.bottom: stop.bottom;
onClicked:
{
var algorithm = (colorMaker.alorithm() + 1 ) % 5;
changeAlgorithm(colorAlgorithm,algorithm);
colorMaker.serAlgorithm(algorithm);
}
}
Button
{
id:quit
text:"quit"
anchors.left: colorAlgorithm.right;
anchors.leftMargin: 4;
anchors.bottom: colorAlgorithm.bottom;
onClicked:
{
Qt.quit();
}
}
Component.onCompleted:
{
colorMaker.color = Qt.rgba(0,180,120,255);
//colorMaker.serAlgorithm(colorMaker.LinearIcrease);
colorMaker.serAlgorithm(2);
changeAlgorithm(colorAlgorithm,colorMaker.alorithm());
}
Connections
{
target: colorMaker;
onCurrentTime:
{
timeLabel.text = strTime;
console.log("onCurrentTime");
// timeLabel.color = colorMaker.timeColor;
}
}
Connections
{
target: colorMaker;
onColorChanged:
{
colorRect.color = color;
}
}
}