If you follow this note, you will learn that we can set the in cell space using decoration. If we want to dynamically change the space based on the view’s (cell) size, then we will need to get the view.height property from the * getItemOffsets* function. However, I sometimes get a 0 when I visit view.height .

I saw the same problem in stackoverflow. So here is what I learned.

Solution

Write a fix layout class. You can probably copy and paste this class into your decorator.

/**
 * This function gets from here
 * https://stackoverflow.com/a/53848159/2581637
 *
 * Reason: In `getItemOffsets:` the view do not have a correct
 * height for me to calculate the math. After search on web, I
 * found this solution. Calling before getting the height from
 * the view will fix the problem.
 *
 * @param view: View to calculate the size
 * @param parent: Parent for the view
 */
private fun fixLayoutSize(view: View, parent: ViewGroup) {
    if (view.layoutParams == null) {
        view.layoutParams = ViewGroup.LayoutParams(
                ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT
        )
    }
    val widthSpec = View.MeasureSpec.makeMeasureSpec(parent.width, View.MeasureSpec.EXACTLY)
    val heightSpec = View.MeasureSpec.makeMeasureSpec(parent.height, View.MeasureSpec.UNSPECIFIED)
    val childWidth = ViewGroup.getChildMeasureSpec(
            widthSpec, parent.paddingLeft + parent.paddingRight, view.layoutParams.width
    )
    val childHeight = ViewGroup.getChildMeasureSpec(
            heightSpec, parent.paddingTop + parent.paddingBottom, view.layoutParams.height
    )
    view.measure(childWidth, childHeight)
    view.layout(0, 0, view.measuredWidth, view.measuredHeight)
}

Now call this function once before you get the width/height from the view.

override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
	fixLayoutSize(view, parent)
	print(view.height) // correct height
}

Note that if you don’t notice any number that is wrong, but just some times have a 0 on height, call fixLayoutSize(view, parent) under if (view.height == 0) to speed up process.

Wrong View Size In Decoration

Solution

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