Qt/QML: Save and abort settings - save

Question

I am designing a GUI for my 3D printer. At the home screen you can chose between starting a new print or changing the settings (feedrates, acceleration etc.). Fot the settings I was following this example. But unlinke as in the example, my settings are not properties of the GUI (like x postion, width etc.) but raw data that is entered through text fields and is insignificant to the GUI. The settings are saved at the end of the GUI in a .txt file which is later translated into a code for the printer.
My first question is, how do i design a save- and abort-button? The user should be able to change the text fields but the changes should only be terminal when the save button is pressed.
My second question is, should i ALWAYS read out the text fields? The settings usually shouldnt be changed, so is there a more efficient way? (read the text fields only when the save button was clicked, otherwise adopt the previous values?
For the save Button I was trying something like this, but i doesnt work:
Item {
TextField {id: testField}
Button {id: testButton; text: "Accept"; onClicked: settings.state = "inactive"}
Settings {id:settings; property string state: "active"}
state: settings.state
states: [
State {name: "active"}
State {name:"inactive"; property alias test: testField.text}
]
}

Answer 1

File operations must be done on C++ level. Following code will be a good example of showing open, save and edit operation in Qt.
It uses widget so add the following in .pro file.
QT += widgets
qmlfile.h
//qmlfile.h
#ifndef QMLFILE_H
#define QMLFILE_H
#include <QObject>
class QMLFile : public QObject
{
Q_OBJECT
public:
explicit QMLFile(QObject *parent = 0);
Q_INVOKABLE QString getFileContents() const;
Q_INVOKABLE void saveFileContents(QString fileContents) const;
};
#endif
qmlfile.cpp
#include <QFileDialog>
#include <QTextStream>
#include <QDebug>
#include "qmlfile.h"
QMLFile::QMLFile(QObject *parent): QObject(parent)
{
}
QString QMLFile::getFileContents() const
{
QString fileName = QFileDialog::getOpenFileName(NULL, tr("Open File"), "/home", tr("Text Files (*.txt)"));
qDebug() << "fileName:" << fileName;
QFile file(fileName);
if(!file.open(QIODevice::ReadOnly | QIODevice::Text))
return "";
QString content = file.readAll();
file.close();
return content;
}
void QMLFile::saveFileContents(QString fileContents) const
{
QString fileName = QFileDialog::getSaveFileName(NULL, tr("Save File"), "/home/ansh/data.txt", tr("Text Files (*.txt)"));
QFile file(fileName);
if(file.open(QIODevice::WriteOnly | QIODevice::Text))
{
qDebug() << "created file:" << fileName;
QTextStream stream(&file);
stream << fileContents << endl;
file.close();
return;
}
else
{
qDebug() << "could not create file:" << fileName;
return;
}
}
main.cpp
#include <QGuiApplication>
#include <QQuickView>
#include <QQmlContext>
#include <QApplication>
#include "qmlfile.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QQuickView view;
QMLFile qmlFile;
view.rootContext()->setContextProperty("QMLFile", &qmlFile);
QObject::connect((QObject*)view.engine(), SIGNAL(quit()), QApplication::instance(), SLOT(quit()));
view.setSource(QUrl(QLatin1String("qrc:/main.qml")));
view.show();
return app.exec();
}
main.qml
import QtQuick 2.5
import QtQuick.Controls 2.0
Rectangle {
width: 360; height: 360
Rectangle{
id:buttons
height: 50; width: parent.width; anchors.top: parent.top
Row {
Button {
text: "open"
onClicked: txt.text = QMLFile.getFileContents();
}
Button {
text: "save"
onClicked: QMLFile.saveFileContents(txt.text);
}
Button {
text: "Abort"
onClicked: Qt.quit()
}
spacing: 5
}
}
Rectangle{
id:textHandle
width: parent.width; height: parent.height - buttons.height; anchors.bottom: parent.bottom
TextEdit{
id: txt; anchors.fill: parent
}
}
}
For the second question, since the settings are dynamic in nature it has to be read every time.