FakeBlankScreen

Do you own a device with an OLED screen and run a long-running background task on it?
And, do you want that task to keep running while minimizing battery use and avoiding screen burn-in?
This app is perfect for that situation!

This app shows the black screen when it starts, and prevents the device from sleeping by acquiring the screen wake-lock. It is intended for devices that have an OLED display.

By keeping the screen black, processing in the background is not stopped/restricted unlike putting the device to sleep,
Unlike simply keeping the screen on, it also does not cause OLED burn-in.

How to use:

When you launch this app, the black screen will appear.
This app will enable the screen's wake-lock and prevent the device from entering sleep mode. That's all.

To close this app, swipe from the top or bottom edge of the screen to reveal the navigation bar, tap the square button to open the recent-apps list, and close this app from it. This app doesn't have exit function itself.

Removed extra dependencies. As a result, the minimum-targeted version of Android has been lowered to Android 3 (API 11), and the size of the APK has been reduced to about 60KiB. (Thanks to ebraminio!)