In this project we will learn how to use Qt designer in Raspberry Pi 3, at first Make a new project namely Widget in form creator from Qt designer. After it's done you can see your Main window there, then we will make a simple counter with 3 Button (1 for exit button) and 1 Label for display counter so we need several component below.
You can drag & drop the widget that you need from widget box available on the left side panel
if you press the + button then counter value will increased by 10, if you press the - button then counter value will decreased by 10. You can see the value in display label or terminal.
if your design has been finish then you must convert it to Python code using pyuic5 -x yourfile.ui -o yourfile.py then you can execute with Python Open your lxterminal then type python3 yourfile.py
The source code from this project can be found here