Modify a QML Text from C++

neda

Hi,
I'm using Qt version 5.5.1 from windows 8.1.
I can not bind data to text control.
My program stopped working and the result was this error:

Unable to assign QQuickText to QString
The program has unexpectedly finished.

Please guide me.
Thanks

main.cpp:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    MySerialPort iSerialPort;
    iSerialPort.myText= engine.rootObjects().at(0)->findChild<QObject*>("text1Text");    
    iSerialPort.openSerialPort();
	
	QThread* thread;
	iSerialPort.moveToThread(thread);
    thread->start();
	
    return app.exec();
}

serialport.cpp:

void MySerialPort::readData()
{
    QByteArray data = serial->readAll();

    qDebug() << data;


    myText->setProperty("text", data);
}

myserialport.h:

#ifndef MYSERIALPORT_H
#define MYSERIALPORT_H
#include <QtSerialPort/QtSerialPort>
#include <QObject>
#include <QApplication>
#include <QQmlApplicationEngine>

class MySerialPort: public QSerialPort
{
     Q_OBJECT
public:
    MySerialPort();
    QObject *myText;

public slots:
    void openSerialPort();
    void closeSerialPort();

    void writeData(const QByteArray &data);
    void readData();

    void handleError(QSerialPort::SerialPortError error);

private:
    void showStatusMessage(const QString &message);

    QSerialPort *serial;

};

#endif // MYSERIALPORT_H

main.qml:

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")


    Text {
        id: text1Text
        objectName: text1Text
        width: 400
        height: 29
        color: "red"
        text: "This text should change..."
        font.pixelSize: 12
    }

}

neda

My problem is solved.
But
Is this the best code?
What do you think?
Can you suggest a better method?

main.cpp:

#include <QApplication>
#include <QQmlApplicationEngine>
#include <myserialport.h>
#include <QQmlContext>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    MyDisplay myDisplay;
	myDisplay.setText("neda");
    engine.rootContext()->setContextProperty("myDisplay", &myDisplay);
	
    MySerialPort iSerialPort;
 iSerialPort.setDisplay(&myDisplay);
    iSerialPort.openSerialPort();

    return app.exec();
}

mydisplay.h:

#include <QObject>

#ifndef MYDISPLAY_H
#define MYDISPLAY_H

class MyDisplay : public QObject
{
    Q_OBJECT
    Q_PROPERTY(QString newText READ getText WRITE setText NOTIFY textChanged)

public:
    MyDisplay();

    MyDisplay(QString);

    Q_INVOKABLE QString getText() const;
public slots:
    void setText(QString text);

signals:
    void textChanged(QString);

private:
    QString newText;
};

#endif // MYDISPLAY_H

mydisplay.cpp:

#include "mydisplay.h"
#include "qstring.h"
MyDisplay::MyDisplay()
{
    newText = "";
}

MyDisplay::MyDisplay(QString text)
{
    newText = text;
}

QString MyDisplay::getText() const
{
    return newText;
}

void MyDisplay::setText(QString text)
{
    if (text != newText)
    {
        newText = text;
        emit textChanged(text);
    }
}

serialport.cpp:

void MySerialPort::readData()
{

    QByteArray data = serial->readAll();


    qDebug() << data;

    QString dataString=data;

    myDisplay->setText(dataString);
}
void MySerialPort::setDisplay(MyDisplay * m_display)
{
myDisplay = m_display;
}

myserialport.h:

class MySerialPort: public QSerialPort
{
     Q_OBJECT
public:
    MySerialPort();

public slots:
    void openSerialPort();
    void closeSerialPort();
void setDisplay(MyDisplay * m_display);
    void writeData(const QByteArray &data);
    void readData();

    void handleError(QSerialPort::SerialPortError error);

private:
    void showStatusMessage(const QString &message);
    MyDisplay * myDisplay;
    QSerialPort *serial;

};

main.qml:

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")

    Text {
            id: text1Text
            //objectName: text1Text
            width: 400
            height: 29
            color: "red"
            text: myDisplay.newText
            font.pixelSize: 12
        }
}

BrianDavis

@neda What was the data type of myText in serialport.h?
I have had luck with passing the result of

findChild<QQuickItem*>("Lorem")

to another class, and then using

setProperty("text", "Ipsum")

In some cases you may even find it valuable to check that findChild returns what you expected

if (theFoundChild && theFoundChild->inherits("QQuickText"))

The error makes it sound like you were passing a the QObject* to be stored as a QString. If that is not the case, then perhaps trying QQuickItem* instead of QObject* would help.

I realize your question is a bit dated, but others will stumble on it as well.

Using contextProperties as you did in your solution makes the code more difficult to understand and less encapsulated.

neda

@BrianDavis Thank you