To have a one-track mind
All Henry thinks about is food. When he is having breakfast, he is already planning lunch. He has a one-track mind!
Wayne Rooney was the perfect football player in his heyday: popular with fans and fast on the pitch, with a one-track mind for scoring goals.
Many people today have a one-track mind when it comes to their career and earning money. They rank their work above their social lives.
“I’m a man with a one-track mind
So much to do in one lifetime” (Queen, I Want it All)