Android : App crashes with Skipped 480 frames! The application may be doing too much work

I'm currently working on a piano app, and my app acts weirdly at first, and crashes shortly with the error as the title represents.

I've ran my main function, which is playing sounds in a new threat, and I do have an old android device.

Can you guys provide me with an alternative route to get the same results from this app?

Here is the link to two classes