And now the zooming works fine.
So this is my explanation of my problem: "The screen was not refreshed after double tapped"
Dose this help you for understanding my case?
Do you have better solution then what I did (adding m_view.invalidate())?
English is not my native language and I have done my best, hope you can understand what I have tried to say.
Anyway, I solved this problem with my way, unless you have any opinion about this.