Qt5 Tutorial Resource Files - 2020

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Qt Resource Files

In this tutorial, we will learn Qt Resource Files. We'll set our .pro file as a resource, and then in the run time, we'll read it back and display it into the console.

Picture source: The Qt Resource System.

As we see in the picture, we (application.exe) can access the resources during the run time.

The Qt resource system is a platform-independent mechanism for storing binary files in the application's executable. This is useful if our application always needs a certain set of files (icons, translation files, etc.) and we don't want to run the risk of losing the files.

The resource system is based on tight cooperation between qmake, rcc (Qt's resource compiler), and QFile.

The resources associated with an application are specified in a .qrc file, an XML-based file format that lists files on the disk and optionally assigns them a resource name that the application must use to access the resource.

Here's an example .qrc file:

<!DOCTYPE RCC><RCC version="1.0">
<qresource>
    <file>images/copy.png</file>
    <file>images/cut.png</file>
    <file>images/new.png</file>
    <file>images/open.png</file>
    <file>images/paste.png</file>
    <file>images/save.png</file>
</qresource>
</RCC>

Let's make our resource file.

Right click on the Project->Add New...

Choose...

Hit Next

Finish. Then, the Designer will provide us with resource editor.

Let's make our resource file.

Add->Add Prefix

We can change the name but keep forward slash('/'). Then, Add->Add Files.

We'll use our .pro file as a resource.

We can change the name but keep forward slash('/'). Then, Add->Add Files.

We can put the path to the resource by right click on the file into a clipboard. Then, we can retrieve it from the clipboard.

In the code below, we set our .pro file as a resource. In the run time, we'll read it back and display it into the console. Here is the code:

#include <QCoreApplication>
#include <QFile>
#include <QString>
#include <QDebug>
#include <QTextStream>

void read(QString filename)
{
    QFile file(filename);
    if(!file.open(QFile::ReadOnly |
                  QFile::Text))
    {
        qDebug() << " Could not open the file for reading";
        return;
    }

    QTextStream in(&file);
    QString myText = in.readAll();

    // put QString into qDebug stream
    qDebug() << myText;

    file.close();
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    read(":/MyPreciousRes/MyResources.pro");

    return a.exec();
}

Run and we get the output which is our .pro file:

"#-------------------------------------------------
#
# Project created by QtCreator 2013-09-13T11:02:43
#
#-------------------------------------------------

QT       += core

QT       -= gui

TARGET = MyResources
CONFIG   += console
CONFIG   -= app_bundle

TEMPLATE = app


SOURCES += main.cpp

RESOURCES += \
    MyRes.qrc
"

Note the lines highlighted. Our .pro added lines for the resource!