This app checks the app that has a "SYSTEM_ALERT_WINDOW permission" in running.
Overview
This app lists the apps that have SYSTEM_ALERT_WINDOW permission called screen overlay app.
If the screen overlay apps are running, a phenomenon that cannot press some buttons may occur by Android security.
By stopping the apps that are shown in the list, it is possible to find the app that is running security.
Note: Because it can not find automatically the app that is blocking the button, please make sure by one by one stop.
How to use
The manual can be displayed in the following operation.
1. The dialog appears when the app starts in the first, then select the OK button.
2. Select the "Manual" on the setting icon in top right corner of the app screen.
Install Button Unlocker
By installing the this app at the same time with this app, you will be able to unlock the lock button of without stopping the screen overlay app.
https://play.google.com/store/apps/details?id=jp.sfapps.installbuttonunlocker