How to save whole listView in onSaveInstance? I'm trying to save it but it's not saving

Question

I'm making a mobile music player app and i'm using listView to show the files from the directory. But as soon as I go to another activity and come back to the listView activity, it again takes time to open all the files.

I thought there must be a way to save an activity as it is and then show it to the user quickly when he presses the back button.

This method uses list view to get files from another method read files.

This is the read files method to read files from the android storage

I used an ASYNC TASK to load files in the background. I thought it was a heavy task.

After this i added onItemClickListener to the ListView so that when the item is clicked, the playerActivty is opened.

This is the player..

But as soon as i tap the back button in the player activity. It again takes time to open the first activity. I want to show the files real quick so that when the back button is pressed, the user don't have to wait for seconds to see the existing files.

PLEASE HELP!!! Thank You!