Integrazione QML / C++

Integrazione

QML / C++

Paolo Sereno

Chi Sono ?

…un informatico

Seguo l’evoluzione del Qt Application Framework dal

lontano 2003

Nell’ottobre 2009 ho fondato la web community

www.qt-italia.org (chi vuol collaborare… serve aiuto!)

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http://www.qt-italia.org/

Dove va il mondo?

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prototipazione (sempre più) rapida

interaction design

user experience

Internet of things

Sempre più velocemente…

E quindi ?

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…ma da solo non basta…

In diverse occasioni si rende necessario estendere

QML con C++

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Fonte: Qt Assistant 5.4

QML è stato progettato per essere esteso mediante C++

Le funzionalità C++ possono essere invocate da QML

Gli oggetti QML possono essere caricati e modificati da

C++

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Esportare oggetti C++ verso QML

Esportare oggetti C++ a QML

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The QQmlContext class defines a context within a QML engine.

proviamo a capire…


The QQmlContext class defines a context within a QML engine.

#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();

}

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#include <QQmlContext>

#include "label.h"


{



QQmlContext *context=engine.rootContext();

Label label("Pippo");

context->setContextProperty("label",&label);


return app.exec();

}

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The QQmlContext class defines a

context within a QML engine.

label.h

class Label : public QObject

{

Q_OBJECT

Q_PROPERTY(QString name READ name WRITE setName NOTIFY nameChanged)

public:

explicit Label(QString name, QObject *parent = 0);

~Label();

QString name(){return m_name;};

void setName(QString newName){m_name=newName; emit nameChanged();};

signals:

void nameChanged();

public slots:

private:

QString m_name;

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label.cpp

#include "label.h“

Label::Label(QString name, QObject *parent) : QObject(parent)

{

setName(name);

}

Label::~Label()

{

}

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MainForm.ui.qml

Item {

width: 320

height: 240

property alias button1: button1

RowLayout {

anchors.centerIn: parent

Button {

id: button1

text: label.name

}

}

}

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Q_PROPERTY(QString name READ name WRITE setName

NOTIFY nameChanged)

main.qml

import QtQuick 2.4

import QtQuick.Controls 1.3

import QtQuick.Window 2.2

ApplicationWindow {

title: qsTr("Hello World")

width: 320

height: 240

visible: true

MainForm {

anchors.fill: parent

button1.onClicked:label.name="Paperino";

}

}

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Q_PROPERTY(QString name READ name WRITE setName

NOTIFY nameChanged)

Risultato

prima

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Risultato

dopo

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Esportare classi C++ verso QML

Classi «NON GUI»

Esportare classi a QML

Types can be registered by calling qmlRegisterType() with an

appropriate type namespace and version number.


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Esportare classi a QML

#include <QApplication>

#include <QQmlApplicationEngine>

#include <QtQml>

#include "label.h"


{


qmlRegisterType <Label>("com.helloworld.qmlcomponents",1,0,"Label");



return app.exec();

}

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MainForm.ui.qml

import com.helloworld.qmlcomponents 1.0

Item {

width: 320

height: 240


property alias label:label

Label {

id:label

name: "Pluto"

}

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main.qml

…

MainForm {

anchors.fill: parent

button1.onClicked: {

label.name="Paperino"

button1.text=label

}

}

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Risultato

prima

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Risultato

dopo

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E se facessi così ?

Item {

width: 320

height: 240


//property alias label:label

Label {

id:label

name: "Pluto"

}

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Questo il risultato…

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Esportare classi C++ verso QML

Classi «GUI»

Esportare classi (GUI) a QML

The QQuickPaintedItem class provides a way to use the QPainter API

in the QML Scene Graph.


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main.cpp

#include "rettangolo.h"


{



qmlRegisterType <Rettangolo>("com.helloworld.qmlcomponents",1,0,"Rettangolo");


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rettangolo.h

#include <QQuickPaintedItem>

#include <QPainter>

class Rettangolo : public QQuickPaintedItem

{

Q_OBJECT

public:

explicit Rettangolo(QQuickItem *parent = 0);

void paint(QPainter *painter);

signals:

public slots:

};

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rettangolo.cpp

void Rettangolo::paint(QPainter *painter)

{

QLinearGradient linearGrad(QPointF(0,0), QPointF(0,height()));

linearGrad.setColorAt(0, QColor(90,180,90,255));

linearGrad.setColorAt(1, QColor(10,120,10,255));

QBrush brush=QBrush(linearGrad);

painter->fillRect(boundingRect(),brush);

}

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MainForm.ui.qml

Item {

width: 320

height: 240

RowLayout {

anchors.centerIn: parent

Rettangolo {

id: rect;

width: 100

height: 100

}

}

}

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Risultato

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Model View Delegate

C++/QML

Model-View-Delegate

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StringListModelclass StringListModel : public QAbstractListModel

{

Q_OBJECT

public:

explicit StringListModel (QObject *parent = 0);

int rowCount(const QModelIndex &parent = QModelIndex()) const;

int columnCount(const QModelIndex &parent) const;

Qt::ItemFlags flags(const QModelIndex &index) const;

QVariant data(const QModelIndex &index, int role) const;

bool setData(const QModelIndex &index, const QVariant &value, int role =

Qt::EditRole);

bool insertRows(int position, int rows, const QModelIndex &parent);

bool removeRows(int position, int rows, const QModelIndex &parent);

QVariant headerData(int section, Qt::Orientation orientation, int role) const;

private:

QStringList mItemsList;

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stringlistmodel.cpp

StringListModel::StringListModel(QObject *parent)

:QAbstractListModel(parent)

{

mItemsList <<"Pippo"<<"Pluto"<<"Paperino";

}

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stringlistmodel.cpp

QVariant StringListModel::data(const QModelIndex &index, int role)

const

{

if(index.isValid() && index.row() < this->mItemsList.size() &&

role == Qt::DisplayRole)

return this->mItemsList.at(index.row());

return QVariant();

}

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main.cpp


{



qmlRegisterType<StringListModel>("com.helloworld.Models", 1, 0,

"StringListModel");


return app.exec();

}

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MainForm.ui.qml

StringListModel{

id:myModel

}

ListView {

id: listView

model: myModel

delegate: Item {

Row {

id: row1

Text {

text: display

}

}

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Risultato

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Q_INVOKABLE

class StringListModel : public QAbstractListModel

{

Q_OBJECT

public:

…

Q_INVOKABLE QString getSomething ();

private:

QStringList mItemsList;

QString mSomething;

}

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getSomething()

QString StringListModel::getSomething()

{

return mSomething;

}

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stringlistmodel.cpp

StringListModel::StringListModel(QObject *parent)

:QAbstractListModel(parent)

{

mItemsList <<"Pippo"<<"Pluto"<<"Paperino";

mSomething="La mia lista";

}

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Uso di getSomething

Text {

id: text1

x: 105

y: 20

width: 110

height: 24

text: myModel.getSomething()

horizontalAlignment: Text.AlignHCenter

font.pixelSize: 12

}

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Risultato

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Esportare oggetti QML verso C++

main.qml

ApplicationWindow {

…

Button {

x:110

y:80

objectName: "button1"

width:100

height:40

text: "QML"

}

}

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main.cpp


{



QQmlComponent component(&engine, QUrl(QStringLiteral("qrc:/main.qml")));

QObject *object = component.create();

QObject *button = object->findChild<QObject *>("button1");

if(button)

button->setProperty("text","c++");

return app.exec();

}

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Risultato

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E’ quasi finito!

…lo troverete su AmazonQt day 2015 51

DOMANDE ???

Integrazione QML / C++

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