Demonstration of dynamic switching between languages in QML application.
Note, that Qt versions before 5.10 do not yet have QQmlEngine::retranslate(), and then you'll have to use the empty string magic trick.
Beside buiding the app, you also need to compile translation files .ts into .qm wtih Qt Translator or lrelease tool and then place them into i18n folder within the build directory.
For more details read the following article: https://retifrav.github.io/blog/2017/01/04/translating-qml-app/