Prevent Swiping of ViewPager2 when onTouch of inner view

Question

I have a ViewPager2 with a fragment inside,

in the fragment, I have a custom view with certain touch logic that involves moving the finger.

how do I prevent the ViewPager from swiping while the inner view intercepts the touch event?

override fun onTouchEvent(event: MotionEvent?): Boolean {
    if (event?.action == MotionEvent.ACTION_DOWN || event?.action == MotionEvent.ACTION_MOVE) {
       //Do some stuff here
    }
    return true
}

while swiping this view the view pager still swipes to other pages.

Answer 1

Set OnTouchListener for inner view. In onTouch() method, call:

viewPager.requestDisallowInterceptTouchEvent(true)

ViewPager handles its swiping motion in onInterceptTouchEvent(). Above code prevents ViewPager from calling onInterceptTouchEvent(). When you're swiping, ViewPager returns true in onInterceptTouchEvent() which also prevents touch events to be passed to child views. Therefore disallowing intercept allows child views to handle touch events.

Set back to false when the inner view is not being touched.

From my experience, onInterceptTouchEvent() prevents onTouchEvent(). It does not prevent OnTouchListener. So the key here is to set up OnTouchListener for the inner view.

Answer 2

To fix this, you should extend the ViewPager2 like this:

fun ViewPager2.reduceDragSensitivity() {
    val recyclerViewField = ViewPager2::class.java.getDeclaredField("mRecyclerView")
    recyclerViewField.isAccessible = true
    val recyclerView = recyclerViewField.get(this) as RecyclerView

    val touchSlopField = RecyclerView::class.java.getDeclaredField("mTouchSlop")
    touchSlopField.isAccessible = true
    val touchSlop = touchSlopField.get(recyclerView) as Int
    touchSlopField.set(recyclerView, touchSlop * 6) // "6" was obtained experimentally
}

and call reduceDragSensitivity. So the viewpager2 will look like this:

view_pager.reduceDragSensitivity()

Example: https://github.com/ali-sardari/ViewPager2Example