Android在RecyclerView中获得可见子对象的计数

我试图知道用户在recyclerview中可以看到多少项，在某些设备中，此计数不同，我无法使用以下代码计算：

private int countVisibleRow() {
    if (messagesView.getLayoutManager() != null) {
       LinearLayoutManager layoutManager = (LinearLayoutManager) messagesView.getLayoutManager();
       int                 first         = layoutManager.findFirstVisibleItemPosition();
       int                 last          = layoutManager.findLastVisibleItemPosition();
       return last - first;
    } else {
       return 0;
    }
}

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无论何时滚动recylerView，都将代码放入onScroll listner方法中此方法将被激发（将此代码放入构造函数中的适配器类中）

---

无论何时滚动recylerView，都将代码放入onScroll listner方法中此方法将被激发（将此代码放入构造函数中的适配器类中）

尝试以下方法：

public class LinearLayoutManagerWithSmoothScroller extends LinearLayoutManager {

    public LinearLayoutManagerWithSmoothScroller(Context context) {
        super(context, HORIZONTAL, false);
    }

    @Override
    public int findFirstVisibleItemPosition() {
        return super.findFirstVisibleItemPosition();
    }

    @Override
    public int findLastVisibleItemPosition() {
        return super.findLastVisibleItemPosition();
    }

    public LinearLayoutManagerWithSmoothScroller(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return LinearLayoutManagerWithSmoothScroller.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }
    }
}

   layoutmanager = new LinearLayoutManagerWithSmoothScroller(QuestionsActivity.this);
  paginationRV.setLayoutManager(layoutmanager);

使用方法如下：

public class LinearLayoutManagerWithSmoothScroller extends LinearLayoutManager {

    public LinearLayoutManagerWithSmoothScroller(Context context) {
        super(context, HORIZONTAL, false);
    }

    @Override
    public int findFirstVisibleItemPosition() {
        return super.findFirstVisibleItemPosition();
    }

    @Override
    public int findLastVisibleItemPosition() {
        return super.findLastVisibleItemPosition();
    }

    public LinearLayoutManagerWithSmoothScroller(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return LinearLayoutManagerWithSmoothScroller.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }
    }
}

   layoutmanager = new LinearLayoutManagerWithSmoothScroller(QuestionsActivity.this);
  paginationRV.setLayoutManager(layoutmanager);

尝试以下方法：

public class LinearLayoutManagerWithSmoothScroller extends LinearLayoutManager {

    public LinearLayoutManagerWithSmoothScroller(Context context) {
        super(context, HORIZONTAL, false);
    }

    @Override
    public int findFirstVisibleItemPosition() {
        return super.findFirstVisibleItemPosition();
    }

    @Override
    public int findLastVisibleItemPosition() {
        return super.findLastVisibleItemPosition();
    }

    public LinearLayoutManagerWithSmoothScroller(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return LinearLayoutManagerWithSmoothScroller.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }
    }
}

   layoutmanager = new LinearLayoutManagerWithSmoothScroller(QuestionsActivity.this);
  paginationRV.setLayoutManager(layoutmanager);

使用方法如下：

public class LinearLayoutManagerWithSmoothScroller extends LinearLayoutManager {

    public LinearLayoutManagerWithSmoothScroller(Context context) {
        super(context, HORIZONTAL, false);
    }

    @Override
    public int findFirstVisibleItemPosition() {
        return super.findFirstVisibleItemPosition();
    }

    @Override
    public int findLastVisibleItemPosition() {
        return super.findLastVisibleItemPosition();
    }

    public LinearLayoutManagerWithSmoothScroller(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state,
                                       int position) {
        RecyclerView.SmoothScroller smoothScroller = new TopSnappedSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private class TopSnappedSmoothScroller extends LinearSmoothScroller {
        public TopSnappedSmoothScroller(Context context) {
            super(context);

        }

        @Override
        public PointF computeScrollVectorForPosition(int targetPosition) {
            return LinearLayoutManagerWithSmoothScroller.this
                    .computeScrollVectorForPosition(targetPosition);
        }

        @Override
        protected int getVerticalSnapPreference() {
            return SNAP_TO_START;
        }
    }
}

   layoutmanager = new LinearLayoutManagerWithSmoothScroller(QuestionsActivity.this);
  paginationRV.setLayoutManager(layoutmanager);

---

---

结果是什么？recyclerview的整个概念是，你不必担心有多少是可见的。LayoutManager为每个设备相应地处理它，还可以缓存更多的行。你为什么需要可见的计数？@OrkunKoçyiğit我明白了zero@Mahdi.Pishguy试试我的解决方案结果如何？recyclerview的整个概念是，你不必担心有多少是可见的。LayoutManager为每个设备相应地处理它，还可以缓存更多的行。你为什么需要可见的计数？@OrkunKoçyiğit我明白了zero@Mahdi.Pishguy请尝试我的解决方案，以便在项目对用户可见时如何获取项目的计数？使用与获取layoutmanger.findLastVisibleItemPosition（）相同的方法但请确保layoutmanager是LinearLayoutManager的实例，带有SmoothScroller类默认情况下，我在recyclerView上有两个可见项，但我得到

-1

always@Mahdi.Pishguy你在LayoutManager.findLastVisibleItemPosition（）中得到了什么那个么，当项目对用户可见时，如何获取项目的数量呢？使用与获取layoutmanger.findLastVisibleItemPosition（）相同的方法但请确保layoutmanager是LinearLayoutManager的实例，带有SmoothScroller类默认情况下，我在recyclerView上有两个可见项，但我得到

-1

always@Mahdi.Pishguylayoutmanger.findLastVisibleItemPosition（）@shahis17june不滚动项目怎么样？@shahis17june不滚动项目怎么样？