Reading a line from a .txt or .csv file in qml (Qt Quick)

Question

I need to display a string on a simulation screen. For that I'm supposed to read the text from an existing Filename.txt/Filename.csv file. The text parameter is updated as shown in the below piece of code. I need to access the string from a text file and use it in MarqueeText element. The Accessed string shall be used in the text field of the MarqueeText element.

MarqueeText {
     id:scrolltext
     width: 255
     height: 48
     anchors.verticalCenter: parent.horizontalCenter
     text:   //i need to access the string in text file to be displayed
}

Please help me with this. Thank you.

Answer 1

Follow the wiki page to read about accessing files in QML. Nokia Wiki Forum http://web.archive.org/web/20150227025348/http://developer.nokia.com/community/wiki/Reading_and_writing_files_in_QML

Summary:

Create a custom QML type, FileIO:

fileio.h

#ifndef FILEIO_H
#define FILEIO_H

#include <QObject>

class FileIO : public QObject
{
    Q_OBJECT

public:
    Q_PROPERTY(QString source
               READ source
               WRITE setSource
               NOTIFY sourceChanged)
    explicit FileIO(QObject *parent = 0);

    Q_INVOKABLE QString read();
    Q_INVOKABLE bool write(const QString& data);

    QString source() { return mSource; };

public slots:
    void setSource(const QString& source) { mSource = source; };

signals:
    void sourceChanged(const QString& source);
    void error(const QString& msg);

private:
    QString mSource;
};

#endif // FILEIO_H

fileio.cpp

#include "fileio.h"
#include <QFile>
#include <QTextStream>

FileIO::FileIO(QObject *parent) :
    QObject(parent)
{

}

QString FileIO::read()
{
    if (mSource.isEmpty()){
        emit error("source is empty");
        return QString();
    }

    QFile file(mSource);
    QString fileContent;
    if ( file.open(QIODevice::ReadOnly) ) {
        QString line;
        QTextStream t( &file );
        do {
            line = t.readLine();
            fileContent += line;
         } while (!line.isNull());

        file.close();
    } else {
        emit error("Unable to open the file");
        return QString();
    }
    return fileContent;
}

bool FileIO::write(const QString& data)
{
    if (mSource.isEmpty())
        return false;

    QFile file(mSource);
    if (!file.open(QFile::WriteOnly | QFile::Truncate))
        return false;

    QTextStream out(&file);
    out << data;

    file.close();

    return true;
}

Register the new QML type:

#include "fileio.h"

Q_DECL_EXPORT int main(int argc, char *argv[])
{
   ...
    qmlRegisterType<FileIO, 1>("FileIO", 1, 0, "FileIO");
    ...
}

Actual QML Usage:

import QtQuick 1.1
import FileIO 1.0

Rectangle {
    width: 360
    height: 360
    Text {
        id: myText
        text: "Hello World"
        anchors.centerIn: parent
    }

    FileIO {
        id: myFile
        source: "my_file.txt"
        onError: console.log(msg)
    }

    Component.onCompleted: {
        console.log( "WRITE"+ myFile.write("TEST"));
        myText.text =  myFile.read();
    }
}