Crash due to NPE

[firefinchdev]

The following is the stack trace from my crashlytics console

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.VelocityTracker.addMovement(android.view.MotionEvent)' on a null object reference
       at androidx.viewpager.widget.ViewPager.fakeDragBy(ViewPager.java:2626)
       at com.heinrichreimersoftware.materialintro.app.IntroActivity$5.fakeDragToPosition(IntroActivity.java:402)
       at com.heinrichreimersoftware.materialintro.app.IntroActivity$5.onAnimationUpdate(IntroActivity.java:384)
       at android.animation.ValueAnimator.animateValue(ValueAnimator.java:1522)
       at android.animation.ValueAnimator.animateBasedOnTime(ValueAnimator.java:1316)
       at android.animation.ValueAnimator.doAnimationFrame(ValueAnimator.java:1446)
       at android.animation.AnimationHandler.doAnimationFrame(AnimationHandler.java:146)
       at android.animation.AnimationHandler.-wrap2(AnimationHandler.java)
       at android.animation.AnimationHandler$1.doFrame(AnimationHandler.java:54)
       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
       at android.view.Choreographer.doCallbacks(Choreographer.java:725)
       at android.view.Choreographer.doFrame(Choreographer.java:657)
       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:899)
       at android.os.Handler.handleCallback(Handler.java:790)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loop(Looper.java:164)
       at android.app.ActivityThread.main(ActivityThread.java:6548)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:857)

[firefinchdev]

Till now, I have received crashes on Oppo, Samsung, Xiaomi, G_TOUCH devices on Android 6, 8, and 9.

[firefinchdev]

I have no idea why this must be happening, and the above stack trace is the only information I have. I was unable to find a solution on the net.

[firefinchdev]

The only conclusion I was able to draw was that when fakeDragToPosition is called by material-intro, then the function calls ViewPager.fakeDragBy, which calls mVelocityTracker.addMovement(ev). For some reason, the mVelocityTracker object is null. Can you please look into this?

[heinrichreimer]

There are some internal issues in ViewPager. Maybe we should move to ViewPager2.

[sds100]

Some of my users are still having this problem so I'm going to work on a fix. Does anyone know how to reproduce it?