Permission slide behavior

[iffa]

When granting permissions, the button does not disappear until I interact with the slide: swipe/press a button etc. If you press the button a second time (after granting the permissions already), this happens:
java.lang.NullPointerException: permission cannot be null or empty at android.content.pm.PackageManager.buildRequestPermissionsIntent(PackageManager.java:3058) at android.app.Activity.requestPermissions(Activity.java:4166) at android.support.v4.app.ActivityCompatApi23.requestPermissions(ActivityCompat23.java:32) at android.support.v4.app.ActivityCompat.requestPermissions(ActivityCompat.java:316) at com.heinrichreimersoftware.materialintro.slide.SimpleSlide$1.onClick(SimpleSlide.java:130) at android.view.View.performClick(View.java:5697) at android.widget.TextView.performClick(TextView.java:10814) at android.view.View$PerformClick.run(View.java:22526) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:158) at android.app.ActivityThread.main(ActivityThread.java:7229) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

the button could also be animated and look pretty when showing up or disappearing

[heinrichreimer]

The button normally hides and shows with a simple alpha transition when you scroll to the next slide.
The problem here is that the permission slide can only update its permissions when it's in focus. That has something to do with how an Activity attaches and detaches from a Fragment.