我需要知道哪些元素目前显示在我的RecyclerView。ListViews上没有与OnScrollListener.onScroll(…)方法等价的方法。我试图与view . getglobalvisibl勃起(…)工作,但黑客是太丑陋,并不总是工作太。
有人有什么想法吗?
我需要知道哪些元素目前显示在我的RecyclerView。ListViews上没有与OnScrollListener.onScroll(…)方法等价的方法。我试图与view . getglobalvisibl勃起(…)工作,但黑客是太丑陋,并不总是工作太。
有人有什么想法吗?
当前回答
你可以找到recycle视图的第一个和最后一个可见的子视图,并检查你正在寻找的视图是否在范围内:
var visibleChild: View = rv.getChildAt(0)
val firstChild: Int = rv.getChildAdapterPosition(visibleChild)
visibleChild = rv.getChildAt(rv.childCount - 1)
val lastChild: Int = rv.getChildAdapterPosition(visibleChild)
println("first visible child is: $firstChild")
println("last visible child is: $lastChild")
其他回答
您可以使用recyclerView.getChildAt()来获取每个可见的子视图,并在适配器代码中对这些视图设置一些convertview.setTag(index)标记将帮助您将其与适配器数据关联起来。
Addendum: The proposed functions findLast...Position() do not work correctly in a scenario with a collapsing toolbar while the toolbar is expanded. It seems that the recycler view has a fixed height, and while the toolbar is expanded, the recycler is moved down, partially out of the screen. As a consequence the results of the proposed functions are too high. Example: The last visible item is told to be #9, but in fact item #7 is the last one that is on screen. This behaviour is also the reason why my view often failed to scroll to the correct position, i.e. scrollToPosition() did not work correctly (I finally collapsed the toolbar programmatically).
最后,我找到了一个解决方案,从适配器中的onBindViewHolder事件了解当前项是否可见。
关键是来自LayoutManager的isViewPartiallyVisible方法。
在您的适配器中,您可以从RecyclerView中获得LayoutManager,它作为参数从onAttachedToRecyclerView事件中获得。
你可以找到recycle视图的第一个和最后一个可见的子视图,并检查你正在寻找的视图是否在范围内:
var visibleChild: View = rv.getChildAt(0)
val firstChild: Int = rv.getChildAdapterPosition(visibleChild)
visibleChild = rv.getChildAt(rv.childCount - 1)
val lastChild: Int = rv.getChildAdapterPosition(visibleChild)
println("first visible child is: $firstChild")
println("last visible child is: $lastChild")
对于StaggeredGridLayoutManager执行以下操作:
RecyclerView rv = findViewById(...);
StaggeredGridLayoutManager lm = new StaggeredGridLayoutManager(...);
rv.setLayoutManager(lm);
要获得可见的项目视图:
int[] viewsIds = lm.findFirstCompletelyVisibleItemPositions(null);
ViewHolder firstViewHolder = rvPlantios.findViewHolderForLayoutPosition(viewsIds[0]);
View itemView = viewHolder.itemView;
记得检查它是否为空。