[英]Calling C++ function from QML code
For example in the following code i have a window with 2 inputs : quantity and price I want to call a c++ function which evaluates the subtotal and adds 5% tax to it. 例如,在下面的代码中我有一个带有2个输入的窗口:数量和价格我想调用一个c ++函数来评估小计并为其增加5%的税。
I have tried searching many places but couldn't get complete working code with this latest version of QT5. 我尝试过搜索很多地方,但无法使用最新版本的QT5获得完整的工作代码。 Please tell me how to call a C++ function from QML.
请告诉我如何从QML调用C ++函数。
main.qml : main.qml:
import QtQuick 2.2
import QtQuick.Controls 1.1
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
menuBar: MenuBar {
Menu {
title: qsTr("File")
MenuItem {
text: qsTr("Exit")
onTriggered: Qt.quit();
}
}
}
Column{
Label {
text: qsTr("Enter the number of items purchased: ")
}
TextField {
id: in1
objectName: "in1"
}
Label {
text: qsTr("Enter the price per item ($):")
}
TextField {
id: in2
objectName: "in2"
}
Button {
id: button
objectName: "button"
text: "Compute"
onClicked: {
total.text = "Final bill, including 5% tax, is $" + clickedButton(in1.text, in2.text); // here i'm calling the c++ function
}
}
Label {
id: total
objectName: "total"
text: "Final bill, including 5% tax, is $____"
}
}
}
main.cpp main.cpp中
#include <QApplication>
#include <QQmlApplicationEngine>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
return app.exec();
}
double clickedButton(int number, int price){
const double TAX_rate = 0.05;
double subtotal;
subtotal = price*number;
return (subtotal + subtotal*TAX_rate);
}
Simply use: 只需使用:
engine.rootContext()->setContextProperty("yourName", new yourClass());
In your qml you can call the function with yourname.yourfunction()
Additional in your class you have to make your Function Q_INVOKABEL
在您的qml中,您可以使用
yourname.yourfunction()
调用该函数。在您的课程中,您必须使您的函数Q_INVOKABEL
You need to declare clickedButton as Q_INVOKABLE like this: 您需要将clickedButton声明为Q_INVOKABLE,如下所示:
public:
Q_INVOKABLE void cppMethod(const QString &msg) {
qDebug() << "Called the C++ method with" << msg;
}
See this sample: http://qt-project.org/doc/qt-4.8/qtbinding.html 请参阅此示例: http : //qt-project.org/doc/qt-4.8/qtbinding.html
Create a class like : 创建一个类,如:
class BillCalculator : public QObject
{
Q_OBJECT
Q_PROPERTY(double totalPrice READ totalPrice WRITE setTotalPrice NOTIFY totalPriceChanged)
public:
BillCalculator(QObject *parent = 0) :
QObject(parent),
mTotalPrice(0.0)
{
}
double totalPrice() const { return mTotalPrice; }
signals:
void totalPriceChanged();
public slots:
void setTotalPrice(const double &arg)
{
if(mTotalPrice != arg)
{
mTotalPrice = arg;
emit totalPriceChanged();
}
}
void calculateTotalPrice(int number, int price)
{
const double TAX_rate = 0.05;
double subtotal;
subtotal = price*number;
setTotalPrice(subtotal + subtotal*TAX_rate);
}
protected:
double mTotalPrice;
};
in your main.cpp, include <QQmlContext>
and modify as below 在你的main.cpp中,包含
<QQmlContext>
并修改如下
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("billCalculator", new BillCalculator);
engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
modify your main.qml file as below 修改你的main.qml文件,如下所示
Button {
id: button
objectName: "button"
text: "Compute"
onClicked: {
billCalculator.calculateTotalPrice(parseInt(in1.text), parseInt(in2.text));
}
}
Label {
id: total
objectName: "total"
text: "Final bill, including 5% tax, is $" + (billCalculator.totalPrice > 0 ? billCalculator.totalPrice.toFixed(2) : "____")
}
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