[android] Detect home button press in android

Since API 14 you can use the function onTrimMemory() and check for the flag TRIM_MEMORY_UI_HIDDEN. This will tell you that your Application is going to the background.

So in your custom Application class you can write something like:

override fun onTrimMemory(level: Int) {
    if (level == TRIM_MEMORY_UI_HIDDEN) {
        // Application going to background, do something
    }
}

For an in-depth study of this, I invite you to read this article: http://www.developerphil.com/no-you-can-not-override-the-home-button-but-you-dont-have-to/