Android: how to check if a View inside of ScrollView is visible?

Question

I have a ScrollView which holds a series of Views. I would like to be able to determine if a view is currently visible (if any part of it is curre

Answer 1

I ended up implementing a combination of two of the Java answers ( @bill-mote https://stackoverflow.com/a/12428154/3686125 and @denys-vasylenko https://stackoverflow.com/a/25528434/3686125 ) in my project as a set of Kotlin extensions, which support either standard vertial ScrollView or HorizontalScrollView controls.

I just tossed these in a Kotlin file named Extensions.kt, no class, just methods.

I used these to determine which item to snap to when a user stops scrolling in various scrollviews in my project:

fun View.isPartiallyOrFullyVisible(horizontalScrollView: HorizontalScrollView) : Boolean {
    val scrollBounds = Rect()
    horizontalScrollView.getHitRect(scrollBounds)
    return getLocalVisibleRect(scrollBounds)
}

fun View.isPartiallyOrFullyVisible(scrollView: ScrollView) : Boolean {
    val scrollBounds = Rect()
    scrollView.getHitRect(scrollBounds)
    return getLocalVisibleRect(scrollBounds)
}

fun View.isFullyVisible(horizontalScrollView: HorizontalScrollView) : Boolean {
    val scrollBounds = Rect()
    horizontalScrollView.getDrawingRect(scrollBounds)
    val left = x
    val right = left + width
    return scrollBounds.left < left && scrollBounds.right > right
}

fun View.isFullyVisible(scrollView: ScrollView) : Boolean {
    val scrollBounds = Rect()
    scrollView.getDrawingRect(scrollBounds)
    val top = y
    val bottom = top + height
    return scrollBounds.top < top && scrollBounds.bottom > bottom
}

fun View.isPartiallyVisible(horizontalScrollView: HorizontalScrollView) : Boolean = isPartiallyOrFullyVisible(horizontalScrollView) && !isFullyVisible(horizontalScrollView)
fun View.isPartiallyVisible(scrollView: ScrollView) : Boolean = isPartiallyOrFullyVisible(scrollView) && !isFullyVisible(scrollView)

Example usage, iterating through scrollview's LinearLayout children and logging outputs:

val linearLayoutChild: LinearLayout = getChildAt(0) as LinearLayout
val scrollView = findViewById(R.id.scroll_view) //Replace with your scrollview control or synthetic accessor
for (i in 0 until linearLayoutChild.childCount) {
    with (linearLayoutChild.getChildAt(i)) {
        Log.d("ScrollView", "child$i left=$left width=$width isPartiallyOrFullyVisible=${isPartiallyOrFullyVisible(scrollView)} isFullyVisible=${isFullyVisible(scrollView)} isPartiallyVisible=${isPartiallyVisible(scrollView)}")
    }
}