Update TextArea in QML from C++ - qt

Question

My question is pretty simple I think. Nevertheless I was not able to figure it out. I have a TextArea defined in my .qml file, which needs to be updated dynamically from the C++ code.
Unfortunately, I don't know how to access/update the TextArea from within the imserver.cpp class.
Can anyone help me out please?
Here is the .qml file:
import QtQuick 2.2
import QtQuick.Controls 1.1
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("IMServer")
menuBar: MenuBar {
Menu {
title: qsTr("File")
MenuItem {
text: qsTr("Exit")
onTriggered: Qt.quit();
}
}
}
TextArea {
id: serverInformation
x: 0
y: 0
width: 247
height: 279
}
}
My main.cpp:
#include <QApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QQmlEngine>
#include <QtQml>
#include "imserver.h"
int main(int argc, char *argv[]) {
QApplication app(argc, argv);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
IMServer server(2000);
qmlRegisterUncreatableType<IMServer>("App", 1, 0, "IMServer", "");
engine.rootContext()->setContextProperty("imserver", &server);
server.startServer();
return app.exec();
}
imserver.h
#ifndef IMSERVER_H
#define IMSERVER_H
#include <QTcpServer>
#include <QTcpSocket>
#include <QAbstractSocket>
#include <QThreadPool>
class IMServer : public QTcpServer {
Q_OBJECT
Q_PROPERTY(QString text WRITE setText NOTIFY textChanged)
public:
explicit IMServer(int port, QObject *parent = 0);
void startServer();
void setText(const QString &txt);
signals:
void textChanged();
public slots:
protected:
void incomingConnection(qintptr fd);
private:
int port;
QThreadPool *pool;
QString m_text;
};
#endif // IMSERVER_H
imserver.cpp:
#include "imserver.h"
#include "clienthandler.h"
IMServer::IMServer(int port, QObject *parent) : QTcpServer(parent) {
this->pool = new QThreadPool(this);
this->pool->setMaxThreadCount(100);
this->port = port;
}
void IMServer::startServer() {
setText("TEST");
if (!this->listen(QHostAddress::Any, this->port)) {
qDebug() << "Server could not be started";
} else {
qDebug() << "Server started, listening...";
}
}
void IMServer::setText(const QString &txt) {
m_text = txt;
emit textChanged();
}
void IMServer::incomingConnection(qintptr fd) {
ClientHandler *client = new ClientHandler();
client->setAutoDelete(true);
client->fd = fd;
this->pool->start(client);
}

Answer 1

There are several ways. Here is how I'd do it.
First you should register your IMServer class:
qmlRegisterUncreatableType<IMServer>("App", 1, 0, "IMServer", "");
Then you add your IMServer instance to QML:
enigne.rootContext()->setContextProperty("imserver", &server);
Your IMServer class then needs a signal, that your TextArea can be connected to, or even better add a property (you need to add the getText() function and textChanged() signal here as well, for a read-only property):
Updated:
Q_PROPERTY(QString text READ getText NOTIFY textChanged)
In the TextArea you can then create a binding:
TextArea {
text: imserver.text
}
Then whenever you emit textChanged in your IMServer class, the TextArea's text will be updated.
For more information: http://doc.qt.io/qt-5/qtqml-cppintegration-topic.html