How to quickly kill an app in Android
Well there is well prepared app for this function called Gravity Box, for using this app, your device has to be rooted. Here is a tutorial on rooting your Android Phone.
- Install Gravity Box Xposed module
- Under Navigation bar tweaks, Select Custom key settings then Long press action (Kill foreground app) and choose your Icon Style/Set custom image for the icon to be placed always on your Navigation Bar. Simply touch on it to get rid of the unresponsive app
