Baby likes to play with the mobile screen while watching cartoons; how to disable touch? Device: Sony Xperia Z Ultra

Whenever baby is watching cartoons he likes to pick up the phone and his touch then stops the video or if he slides, it changes the app. How can I disable touch screen while the video is playing so even if he is playing with the screen the video keeps on going and nothing happens?

P.S: He probably thinks I have to burst these guys too, just like he does on bubble burst type games. He is 8 months.
You can use MX Player (adware or pro version), which has a "Kids lock" feature under
Settings &gt; Player &gt; Controls &gt; Lock mode.

P.S. you should not give your phone to 8 months old.