He was walking home (фоновое действие) when somebody called his name.
She was reading a book and suddenly came across an interesting phrase.
When I came home, she was watching TV
When she called me, I was driving a car
When the telephone rang, I was having breakfast
When I came into the room my younger brother was watching a cartoon film.
My sister was watching TV while his husband played with the children
Tom burnt his hand when he was cooking the dinner.
It was raining when I got up.
While I was working in the garden, I hurt my back.
When Tom arrived, we were having dinner.