How to lock and unlock a folder in android

I am just starting with Android. And my boss told me to find some good way to lock/unlock a folder with password in Android. Does an开发者_开发知识库ybody know how to implement this. Any help will be greatly appreciated.

Thank you

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In Android you only have "one user", (you have root too, but here doesnt count), so you cant lock a folder, because its your self. But if you are use one file with permisson to write, other app cant write. And if you want make something that you only open with a pass, like a FoldeGuard, you can make a file, that have your information with some Formatter, and You are the only person that can open that file, you can too asociate the file with you app and open automatically your app. So the simple way for me is, make a BD, that there you have all information you need and put password in the bd, or make a file that you asociate your app, and later when you open a file and put the pass you extract all information for a folder... I hope that ideas help you :)