In the next article we are going to take a look at how to install Qt Creator and how to compile a basic program in Ubuntu. Qt is an object-oriented, cross-platform working environment. It is used to develop programs that use a graphical user interface or different command line tools and consoles for servers that do not require a graphical user interface.
Qt is a free, open source, cross-platform application development framework. Is compatible with various platforms as; Gnu / Linux, OS X, Windows, Android, iOS and others. More than a programming language, Qt is a framework written in C ++.
In the following lines we will see how install Qt Creator via the command line. Later we will see how to write a simple style program Hello World puedo cambiarlo and how to run it. All this I am going to do on Ubuntu 19.04.
Install Qt Creator
To start we will install Build Essential, if you don't already have it installed. This is a package that will allow users to install and use c ++ tools in Ubuntu. To proceed with the installation, we open a terminal (Ctrl + Alt + T) and first we will update the available software and then install the package by typing:
sudo apt update; sudo apt install build-essential
If you don't have the Qt Creator package installed that contains the UI and command line tools for creating and running the Qt project, write in the same terminal:
sudo apt install qtcreator
If you want Qt 5 to be used as the default version of Qt Creator, run the following command:
sudo apt install qt5-default
To implement more complex projects, you will have to install Qt documentation and samples. This can be done by typing in the terminal:
sudo apt-get install qt5-doc qtbase5-examples qtbase5-doc-html
The package qt5-doc Contains the Qt 5 API documentation. qtbase5-examples contains the Qt Base 5 examples and qtbase5-doc-html Contains the HTML documentation for the Qt 5 base libraries.
Write and compile your first Qt program from the terminal
Everything that is going to be read below can also be done from a graphical environment, but in this case we will do it via the terminal. Writing and compiling Qt programs from the Ubuntu command line is pretty straightforward. The steps to follow are:
Create a project directory
We will start by creating a working directory for host our Qt project. In the terminal (Ctrl + Alt + T) we write:
mkdir ProyectoQt
Create a .cpp file in the project directory
Inside the directory that we just created, we are going to execute the following command to create a .cpp file:
vim mainEjemplo.cpp
In the blank file, just copy the following code. Its only purpose is to print a line in a window with the title 'My first Qt program'.
#include <QApplication>
#include <QLabel>
#include <QWidget>
int main(int argc, char *argv[ ])
{
QApplication app(argc, argv);
QLabel hola("<center>Ejemplo Qt para Ubunlog</center>");
hola.setWindowTitle("Mi primer programa Qt");
hola.resize(600, 400);
hola.show();
return app.exec();
}
Once pasted into the file, it only remains to save and close the editor.
Create the Qt project file
After saving the file and inside the project folder, the following command will have to be executed to create a Qt project file:
qmake -project
We can verify that the previous command has created a file with the name of ProjectQt.pro in the project directory. This project file is the basic skeleton for Qt projects and can be edited.
Settings in the Qt project file
Since we want to compile the project from the command line, we will have to add the following line to the .pro file that we created in the previous step.
QT += gui widgets
To do this, there is only open the SampleProject.pro file and paste inside the previous line:
vim ProyectoQt.pro
Create an executable file for the project
The following command will create a file with the name of 'makefile' in the project directory.
qmake ProyectoQt.pro
Now, we will use make to compile the Makefile in an executable program:
make
As long as there are no errors in the project, this command should create an executable program in the working directory.
The file ProjectQt in green color, it is the executable file Qt.
Test the program
If you have reached this point, you are all set to launch the executable file that we created in the previous step. You can launch the program by typing in the terminal, inside the project folder:
./ProyectoQt
The output of this example is as follows:
This is the basics that any user should know to write, compile, and run a first Qt program. As I mentioned lines above, you can choose between the command line or the UI method, depending on the needs of your project and personal preferences. For more information, consult the official Qt documentation.
A scope, what the article intends is to install and compile a program using QT, on the other hand Qt Creator is a multiplatform IDE, otherwise it is great