RecyclerView 实现GridView效果九宫格分割线完美解决

RecyclerView更加优化的复用机制和方便实现UI效果,几乎替代Listview和GridView的使用。但是分割线的实现,需要自己来写。listview的可以再theme中指定listDivider。但是gridView分割线,需要自己继承ItemDecoration来绘制。

《RecyclerView 实现GridView效果九宫格分割线完美解决》

先贴代码

/** * Desc:九宫格分割线 无最右边与最下边线 * Author:zhangcx * Data: 2018/8/1 11:56 */
public class GridDividerItemDecoration extends RecyclerView.ItemDecoration {
    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
    private Drawable mDivider;

    public GridDividerItemDecoration(Context context) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        drawHorizontal(c, parent);
        drawVertical(c, parent);
    }

    private int getSpanCount(RecyclerView parent) {
        // 列数
        int spanCount = -1;
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
        }
        return spanCount;
    }

    public void drawHorizontal(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getLeft() - params.leftMargin;
            final int right = child.getRight() + params.rightMargin
                    + mDivider.getIntrinsicWidth();
            final int top = child.getBottom() + params.bottomMargin;
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    public void drawVertical(Canvas c, RecyclerView parent) {
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);

            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getTop() - params.topMargin;
            final int bottom = child.getBottom() + params.bottomMargin;
            final int left = child.getRight() + params.rightMargin;
            final int right = left + mDivider.getIntrinsicWidth();

            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    /** * 是否是最后一行 */
    private boolean isLastRow(int itemPosition, RecyclerView parent) {
        int spanCount = getSpanCount(parent);
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        //有多少列
        if (layoutManager instanceof GridLayoutManager) {
            int childCount = parent.getAdapter().getItemCount();

            double count = Math.ceil((double) childCount / (double) spanCount);//总行数
            double currentCount = Math.ceil((double) (itemPosition + 1) / spanCount);//当前行数

            //最后当前数量小于总的
            if (currentCount < count) {
                return false;
            }
        }
        return true;
    }


    /** * 判断是否是最后一列 */
    private boolean isLastColum(int itemPosition, RecyclerView parent) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        //有多少列
        if (layoutManager instanceof GridLayoutManager) {
            int spanCount = getSpanCount(parent);
            if ((itemPosition + 1) % spanCount == 0) {//因为是从0可以所以要将ItemPosition先加1
                return true;
            }
        }
        return false;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State
            state) {
        super.getItemOffsets(outRect, view, parent, state);
        LogUtil.out("++++++++++++++条目," + parent.getChildLayoutPosition(view) + "是否最后一行" + isLastRow(parent.getChildLayoutPosition(view), parent));
        LogUtil.out("++++++++++++++条目," + parent.getChildLayoutPosition(view) + "是否最后一列" + isLastColum(parent.getChildLayoutPosition(view), parent));
        if (isLastRow(parent.getChildLayoutPosition(view), parent))// 如果是最后一行,则不需要绘制底部
        {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        }

        if (isLastColum(parent.getChildLayoutPosition(view), parent))// 如果是最后一列,则不需要绘制右边
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}

我们调用mRecyclerView.addItemDecoration()方法添加decoration的时候,RecyclerView在绘制的时候,去会绘制decorator,即调用该类的onDraw和onDrawOver方法,

  • onDraw方法先于drawChildren
  • onDrawOver在drawChildren之后,一般我们选择复写其中一个即可。
  • getItemOffsets 可以通过outRect.set()为每个Item设置一定的偏移量,主要用于绘制Decorator。

判断最后一行的方法

①条目总数 /列数 向上取整 拿到总行数
②当前条目位置/ 列数 取到当前位于的行数
③ 当前行数,小于总行数 那就不是最后一行

  private boolean isLastRow(int itemPosition, RecyclerView parent) {
        int spanCount = getSpanCount(parent);
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        //有多少列
        if (layoutManager instanceof GridLayoutManager) {
            int childCount = parent.getAdapter().getItemCount();

            double count = Math.ceil((double) childCount / (double) spanCount);//总行数
            double currentCount = Math.ceil((double) (itemPosition + 1) / spanCount);//当前行数

            //最后当前数量小于总的
            if (currentCount < count) {
                return false;
            }
        }
        return true;
    }

判断是否为最后一列

当前位置 取余 列数 为0时,就是最后一列

 private boolean isLastColum(int itemPosition, RecyclerView parent) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        //有多少列
        if (layoutManager instanceof GridLayoutManager) {
            int spanCount = getSpanCount(parent);
            if ((itemPosition + 1) % spanCount == 0) {//因为是从0可以所以要将ItemPosition先加1
                return true;
            }
        }
        return false;
    }

分配Item偏移量的时对position进行判断,符合则下部和右侧条件则将bottom和right设置偏移量。

  @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State
            state) {
        super.getItemOffsets(outRect, view, parent, state);

        if (isLastRow(parent.getChildLayoutPosition(view), parent))// 如果是最后一行,则不需要绘制底部
        {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        }

        if (isLastColum(parent.getChildLayoutPosition(view), parent))// 如果是最后一列,则不需要绘制右边
        {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
    原文作者:九宫格问题
    原文地址: https://blog.csdn.net/zane_xiao/article/details/81358369
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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