ListView+RealSmoothScroll.kt

ListView+RealSmoothScroll.kt

import android.os.Handler
import android.view.View
import android.widget.AbsListView
import android.widget.AdapterView

// workaround for scrolling issue
// refer: https://stackoverflow.com/questions/11431832/android-smoothscrolltoposition-not-working-correctly
fun AbsListView.realSmoothScrollToPosition(position: Int) {
    fun getChildAtPosition(view: AdapterView<*>, position: Int): View? {
        val index = position - view.firstVisiblePosition
        if (index >= 0 && index < view.childCount) {
            return view.getChildAt(index)
        } else {
            return null
        }
    }

    val child = getChildAtPosition(this, position)
    // There's no need to scroll if child is already at top or view is already scrolled to its end
    if (child != null && (child.top == 0 || child.top > 0 && !this.canScrollVertically(1))) {
        return
    }

    this.setOnScrollListener(object : AbsListView.OnScrollListener {
        override fun onScrollStateChanged(view: AbsListView, scrollState: Int) {
            if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
                view.setOnScrollListener(null)

                // Fix for scrolling bug
                Handler().post { view.setSelection(position) }
            }
        }

        override fun onScroll(view: AbsListView, firstVisibleItem: Int, visibleItemCount: Int, totalItemCount: Int) {
        }
    })

    // Perform scrolling to position
    Handler().post { this.smoothScrollToPositionFromTop(position, 0) }
}