how to build simple qt application using yocto?

Yocto provides a great class qmake5 to compile QT projects based on QMake.

In order to use it create a .pro file for the project:

qtexample.pro

QT += core
SOURCES += qtexample.cpp

qtexample.cpp

#include <QCoreApplication>
#include <QDebug>
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    
    qDebug() << "Hello World";

    return a.exec();
}

Now, in your layer, you can add a simple recipe that compiles that project.

For example: meta-custom/recipes-project/qtexample

In qtexample folder create files folder and copy qtexample.pro and qtexample.cpp in it.

In qtexample folder directly create qtexample_0.1.bb recipe:

SUMMARY = "QT Example Recipe"
LICENSE = "CLOSED"

SRC_URI = "file://qtexample.pro \
           file://qtexample.cpp"

DEPENDS += "qtbase"
RDEPENDS_${PN} += "qtwayland"

S = "${WORKDIR}"

inherit qmake5

You can change the version ofcourse (0.1).

The layout should look like this:

meta-custom/
    ├── recipes-project/
        ├── qtexample_0.1.bb
        └── files/
            ├── qtexample.pro
            └── qtexample.cpp

Then, bitbake qtexample should work and create a qtexample binary that you can find in ${WORKDIR}