RecyclerView smoothScroll位于中心位置。安卓 _recyclerview

别裁伪体亲风雅，转益多师是汝师。这篇文章主要讲述RecyclerView smoothScroll位于中心位置。安卓相关的知识，希望能为你提供帮助。
我正在为我的RecyclerView使用水平布局管理器。我需要以下一种方式制作RecyclerView：当点击某个项目时 - 将smoothScrool放到该位置并将该项目放在RecyclerView的中心（如果可能，例如20中的10项）。
【RecyclerView smoothScroll位于中心位置。安卓】所以，我对smoothScrollToPosition()没有问题，但如何把项目放在RecyclerView的中心???
谢谢！
答案是的，这是可能的。
通过实施RecyclerView.SmoothScroller的方法onTargetFound(View, State, Action)。

/** * Called when the target position is laid out. This is the last callback SmoothScroller * will receive and it should update the provided {@link Action} to define the scroll * details towards the target view. * @param targetViewThe view element which render the target position. * @param stateTransient state of RecyclerView * @param actionAction instance that you should update to define final scroll action *towards the targetView */ abstract protected void onTargetFound(View targetView, State state, Action action);

特别是在LinearLayoutManager与LinearSmoothScroller：

public class CenterLayoutManager extends LinearLayoutManager {public CenterLayoutManager(Context context) { super(context); }public CenterLayoutManager(Context context, int orientation, boolean reverseLayout) { super(context, orientation, reverseLayout); }public CenterLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); }@Override public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) { RecyclerView.SmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext()); smoothScroller.setTargetPosition(position); startSmoothScroll(smoothScroller); }private static class CenterSmoothScroller extends LinearSmoothScroller {CenterSmoothScroller(Context context) { super(context); }@Override public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) { return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2); } } }

另一答案对答案的改进 - 没有必要覆盖LinearLayoutManager
从上一个答案：

public class CenterSmoothScroller extends LinearSmoothScroller {CenterSmoothScroller(Context context) { super(context); }@Override public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) { return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2); } }

在这里如何使用它：

RecyclerView.LayoutManager lm = new GridLayoutManager(...): // or whatever layout manager you need...RecyclerView.SmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext()); smoothScroller.setTargetPosition(position); lm.startSmoothScroll(smoothScroller);

另一答案以防有人在接受的答案中需要Kotlin相当于班级。

class CenterLayoutManager : LinearLayoutManager { constructor(context: Context) : super(context) constructor(context: Context, orientation: Int, reverseLayout: Boolean) : super(context, orientation, reverseLayout) constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes)override fun smoothScrollToPosition(recyclerView: RecyclerView, state: RecyclerView.State, position: Int) { val centerSmoothScroller = CenterSmoothScroller(recyclerView.context) centerSmoothScroller.targetPosition = position startSmoothScroll(centerSmoothScroller) }private class CenterSmoothScroller(context: Context) : LinearSmoothScroller(context) { override fun calculateDtToFit(viewStart: Int, viewEnd: Int, boxStart: Int, boxEnd: Int, snapPreference: Int): Int = (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2) } }

另一答案从现在开始（2019年2月），我可以轻松地在ListView中使用此代码