移动到另一个片段时视图高度返回 0 然后导航回来 android kotlin

Question

I have two fragments . In fragment A there is a RecyclerView , when I click on the element of which I get to another fragment B . In fragment A I have a MaterialToolbar which can have different heights, so in onViewCreated() I call materialToolbar.height to get its height. When I open fragment A everything works fine, however when I click on an element in the RecyclerView , I get to fragment B , in which on pressing the back button I will go back to the fragment A and the height of my materialToolbar will already be 0. Why does it return 0? And how can I make it return the value I need?

Answer 1

There's an observer which listens to view-heirarchy of any given view.

toolbar.viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            binding.mbSelect.viewTreeObserver.removeOnGlobalLayoutListener(this)
            val height = materialToolbar.height
        }
    })

Try this above code in you fragment A, you will get the actual height toolbar