RecycleView 水平滑动并等分屏幕宽度实现

最近需要实现一个可以水平滑动且每屏显示是个item 的效果，具体看下图：

滑动的显示效果： 具体子item布局：

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp"
    android:gravity="center"
    android:orientation="vertical">

    "@+id/iv_honor_cup_pic"
        android:layout_width="@dimen/base40dp"
        android:layout_height="@dimen/base40dp"
        android:layout_gravity="center_horizontal"
        />
    "@+id/tv_honor_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/base6dp"
        android:layout_gravity="center_horizontal"
        android:textColor="@color/black"
        />


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由于滑动使用RecycleView 做的，所以这里默认是针对 RecycleView 实现，代码如下：

public class HorizontalLayoutManager extends RecyclerView.LayoutManager {
    @Override
    public RecyclerView.LayoutParams generateDefaultLayoutParams() {
        return null;
    }

    private int totalWidth = 0;
    private int offsetY = 0;
    private int offsetX = 0;

    public HorizontalLayoutManager(int rows, int columns) {
        this.rows = rows;
        this.columns = columns;
        this.onePageSize = rows * columns;
    }

    @Override
    public boolean canScrollHorizontally() {
        return true;
    }


    @Override
    public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
        detachAndScrapAttachedViews(recycler);
        int newX = offsetX + dx;
        int result = dx;
        if (newX > totalWidth) {
            result = totalWidth - offsetX;
        } else if (newX < 0) {
            result = 0 - offsetX;
        }
        offsetX += result;
        offsetChildrenHorizontal(-result);
        recycleAndFillItems(recycler, state);
        return result;
    }

    private SparseArray allItemFrames = new SparseArray<>();

    private int getUsableWidth() {
        return getWidth() - getPaddingLeft() - getPaddingRight();
    }

    private int getUsableHeight() {
        return getHeight() - getPaddingTop() - getPaddingBottom();
    }

    private int rows = 0;
    private int columns = 0;
    private int pageSize = 0;
    private int itemWidth = 0;
    private int itemHeight = 0;
    private int onePageSize = 0;
    private int itemWidthUsed;
    private int itemHeightUsed;


    @Override
    public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {

        if (getItemCount() == 0) {
            removeAndRecycleAllViews(recycler);
            return;
        }
        if (state.isPreLayout()) {
            return;
        }
        //获取每个Item的平均宽高
        itemWidth = getUsableWidth() / columns;
        itemHeight = getUsableHeight() / rows;

        //计算宽高已经使用的量，主要用于后期测量
        itemWidthUsed = (columns - 1) * itemWidth;
        itemHeightUsed = (rows - 1) * itemHeight;

        //计算总的页数
        computePageSize(state);
        //计算可以横向滚动的最大值
        totalWidth = (pageSize - 1) * getWidth();

        //分离view
        detachAndScrapAttachedViews(recycler);

        int count = getItemCount();
        for (int p = 0; p < pageSize; p++) {
            for (int r = 0; r < rows; r++) {
                for (int c = 0; c < columns; c++) {
                    int index = p * onePageSize + r * columns + c;
                    if (index == count) {
                        //跳出多重循环
                        c = columns;
                        r = rows;
                        p = pageSize;
                        break;
                    }

                    View view = recycler.getViewForPosition(index);
                    addView(view);
                    //测量item
                    measureChildWithMargins(view, itemWidthUsed, itemHeightUsed);

                    int width = getDecoratedMeasuredWidth(view);
                    int height = getDecoratedMeasuredHeight(view);
                    //记录显示范围
                    Rect rect = allItemFrames.get(index);
                    if (rect == null) {
                        rect = new Rect();
                    }
                    int x = p * getUsableWidth() + c * itemWidth;
                    int y = r * itemHeight;
                    rect.set(x, y, width + x, height + y);
                    allItemFrames.put(index, rect);


                }
            }
            //每一页循环以后就回收一页的View用于下一页的使用
            removeAndRecycleAllViews(recycler);
        }

        recycleAndFillItems(recycler, state);
    }

    private void computePageSize(RecyclerView.State state) {
        pageSize = state.getItemCount() / onePageSize + (state.getItemCount() % onePageSize == 0 ? 0 : 1);
    }

    @Override
    public void onDetachedFromWindow(RecyclerView view, RecyclerView.Recycler recycler) {
        super.onDetachedFromWindow(view, recycler);
        offsetX = 0;
        offsetY = 0;
    }

    private void recycleAndFillItems(RecyclerView.Recycler recycler, RecyclerView.State state) {
        if (state.isPreLayout()) {
            return;
        }

        Rect displayRect = new Rect(getPaddingLeft() + offsetX, getPaddingTop(), getWidth() - getPaddingLeft() - getPaddingRight() + offsetX, getHeight() - getPaddingTop() - getPaddingBottom());
        Rect childRect = new Rect();
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            childRect.left = getDecoratedLeft(child);
            childRect.top = getDecoratedTop(child);
            childRect.right = getDecoratedRight(child);
            childRect.bottom = getDecoratedBottom(child);
            if (!Rect.intersects(displayRect, childRect)) {
                removeAndRecycleView(child, recycler);
            }
        }

        for (int i = 0; i < getItemCount(); i++) {
            if (Rect.intersects(displayRect, allItemFrames.get(i))) {
                View view = recycler.getViewForPosition(i);
                addView(view);
                measureChildWithMargins(view, itemWidthUsed, itemHeightUsed);
                Rect rect = allItemFrames.get(i);
                layoutDecorated(view, rect.left - offsetX, rect.top, rect.right - offsetX, rect.bottom);
            }
        }

    }

    @Override
    public int computeHorizontalScrollRange(RecyclerView.State state) {
        computePageSize(state);
        return pageSize * getWidth();
    }

    @Override
    public int computeHorizontalScrollOffset(RecyclerView.State state) {
        return offsetX;
    }

    @Override
    public int computeHorizontalScrollExtent(RecyclerView.State state) {
        return getWidth();
    }
}
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参考地址