适配RecycleView的 ItemDecoration 的封

作者: kai_w | 来源:发表于2017-11-10 13:36 被阅读0次

适配RecycleView的 ItemDecoration 的封
AndroidQ强制黑暗(ForceDark)模式适配补充
Recycleview.Itemdecoration
RecycleView.ItemDecoration
自定义View之实战篇(一) 实现时光轴
硬件加速开启的情况下，RecycleView绘制ItemDeco
RecycleView的ItemDecoration的基本操作
RecycleView ItemDecoration介绍(一)
RecycleView ItemDecoration介绍(二)头
RecycleView自定义ItemDecoration

1. ItemDecoration类的定义

ItemDecoration-->RecycleView的item系统间距以及系统item绘制封装类

/**
 * ItemDecoration允许程序对适配器的数据源中的特殊的条目      
 * view 添加一些特别的图形和布局的偏移，这被用于在条目之      
 * 间画间隔线，高亮显示，视觉分组界限和更多。
 * 所有的ItemDecorations
 * <p>所有的ItemDecorations都是按照它们添加的顺序绘制的, 
 * 在所有的条目view绘制之前
*  (in {@link ItemDecoration#onDraw(Canvas, RecyclerView, RecyclerView.State) onDraw()}
 * 在所有的条目view绘制之后 (in {@link ItemDecoration#onDrawOver(Canvas, RecyclerView,
 * RecyclerView.State)}.</p>
 */
public abstract static class ItemDecoration {
   ...
   ...
}

2. ItemDecoration的方法分析

此类下的六个方法有三个为过时方法，只需要复写另外三个未过时的方法即可，谷歌对这三个方法的定义如下：

在提供给RecyclerView的Canvas中绘制任何适当的装饰。此方法绘制的任何内容将在绘制项目视图之前绘制，因此将被视图覆盖.

  public void onDraw(Canvas c, RecyclerView parent, State state{
      onDraw(c, parent);
  }

在提供给RecyclerView的Canvas中绘制任何适当的装饰。此方法绘制的任何内容将在绘制项目视图之后绘制，因此将覆盖视图

  public void onDrawOver(Canvas c, RecyclerView parent, State state) {
        onDrawOver(c, parent);
  }

检索给定条目的所有偏移量， outRect 的每个字段指定条目视图应该被插入的像素大小，类似于填充或边距。默认实现将outRect的边界设置为0并返回。

  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {
        getItemOffsets(outRect, ((LayoutParams)view.getLayoutParams()).getViewLayoutPosition(), parent);
  }

注：onDraw 和 onDrawOver的区别在于，若未规定条目视图的左上右下的偏移量，在条目视图的基础上，使用canvas 所做的任何装饰，前者会被条目视图所覆盖，而后者方法则会在条目视图的基础上作画。

3. 封装 getItemOffsets

通过构造函数传入左上右下的间距

private int   mSpaceHorizontal;
private int   mSpaceVertical;
private Paint mPaint;

DividerDecoration(Activity activity, int spaceHorizontal, int spaceVertical) {
    mSpaceHorizontal = spaceHorizontal;
    mSpaceVertical = spaceVertical;
    mPaint = new Paint();
    mPaint.setStyle(Paint.Style.FILL);
    mPaint.setAntiAlias(true);
    mPaint.setColor(ContextCompat.getColor(activity, android.R.color.transparent));
}

DividerDecoration(Activity activity, int color, int spaceHorizontal, int spaceVertical) {
    mSpaceHorizontal = spaceHorizontal;
    mSpaceVertical = spaceVertical;
    mPaint = new Paint();
    mPaint.setStyle(Paint.Style.FILL);
    mPaint.setAntiAlias(true);
    mPaint.setColor(ContextCompat.getColor(activity, color));
}

筛选RecycleView的布局管理器，对应做单独处理

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
      super.getItemOffsets(outRect, view, parent, state);
      RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
      if (layoutManager instanceof GridLayoutManager) {
          layoutGridItem(outRect, view, parent, (GridLayoutManager) layoutManager);
      } else if (layoutManager instanceof LinearLayoutManager) {
          layoutLinearItem(outRect, view, parent, (LinearLayoutManager) layoutManager);
      } else if (layoutManager instanceof StaggeredGridLayoutManager) {
          layoutStaggeredItem(outRect, view, parent, (StaggeredGridLayoutManager) layoutManager);
      }
  }

LinearLayoutManager 的布局偏移封装

private void layoutLinearItemSpace(Rect outRect, View view, RecyclerView parent, LinearLayoutManager linearManager) {
    int viewPosition = parent.getChildAdapterPosition(view);

    if (linearManager.getOrientation() == LinearLayoutManager.VERTICAL) {
        outRect.left = mSpaceHorizontal;
        outRect.right = mSpaceHorizontal;
        if (viewPosition == 0) {
            outRect.top = mSpaceVertical;
            outRect.bottom = mSpaceVertical / 2;
        } else if (viewPosition == linearManager.getItemCount() - 1) {
            outRect.top = mSpaceVertical / 2;
            outRect.bottom = mSpaceVertical;
        } else {
            outRect.top = mSpaceVertical / 2;
            outRect.bottom = mSpaceVertical / 2;
        }
    } else {
        outRect.top = mSpaceVertical;
        outRect.bottom = mSpaceVertical;

        if (viewPosition == 0) {
            outRect.left = mSpaceHorizontal;
            outRect.right = mSpaceHorizontal / 2;
        } else if (viewPosition == linearManager.getItemCount() - 1) {
            outRect.left = mSpaceHorizontal / 2;
            outRect.right = mSpaceHorizontal;
        } else {
            outRect.left = mSpaceHorizontal / 2;
            outRect.right = mSpaceHorizontal / 2;
        }
    }
}

GridLayoutManager 的布局偏移封装

private void layoutGridItemSpace(Rect outRect, View view, RecyclerView parent, GridLayoutManager gridManager) {
    int viewPosition = parent.getChildAdapterPosition(view);
    int spanCount = gridManager.getSpanCount();
    int index = viewPosition % spanCount;


    if (viewPosition < spanCount) {//第一行
        outRect.top = mSpaceVertical;
        outRect.bottom = mSpaceVertical / 2;
    } else if (viewPosition / spanCount == (gridManager.getItemCount() - 1) / spanCount) {//多宫格如何判断最后一行？
        outRect.top = mSpaceVertical / 2;
        outRect.bottom = mSpaceVertical;
    } else {
        outRect.top = mSpaceVertical / 2;
        outRect.bottom = mSpaceVertical / 2;
    }


    if (index == 0) {//第一列
        outRect.left = mSpaceHorizontal;
        outRect.right = mSpaceHorizontal / 2;

    } else if (index == spanCount - 1) {//最后一列
        outRect.left = mSpaceHorizontal / 2;
        outRect.right = mSpaceHorizontal;

    } else {
        outRect.left = mSpaceHorizontal / 2;
        outRect.right = mSpaceHorizontal / 2;
    }

}

StaggeredGridLayoutManager的布局偏移封装

private void layoutStaggeredItemSpace(Rect outRect, View view, RecyclerView parent, StaggeredGridLayoutManager staggeredManager) {

}

LinearLayoutManager 的布局偏移颜色封装

private void drawLinearItemSpace(Canvas c, RecyclerView parent, LinearLayoutManager linearManager) {

    if (linearManager.getOrientation() == LinearLayoutManager.VERTICAL) {
        for (int viewPosition = 0; viewPosition < linearManager.getItemCount(); viewPosition++) {
            View childView = parent.getChildAt(viewPosition);

            if (childView == null) {
                continue;
            }

            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) childView.getLayoutParams();

            int left;
            int top;
            int right;
            int bottom;
            left = childView.getLeft() - params.leftMargin;
            right = childView.getRight() + params.rightMargin;
            top = childView.getBottom() + params.bottomMargin;
            bottom = top + mSpaceVertical;
            c.drawRect(left, top, right, bottom, mPaint);
            if (viewPosition == 0) {
                top = childView.getTop() - params.topMargin - mSpaceVertical;
                bottom = top + mSpaceVertical;
                c.drawRect(left, top, right, bottom, mPaint);
            }
        }
    } else {


        for (int viewPosition = 0; viewPosition < linearManager.getItemCount(); viewPosition++) {
            View childView = parent.getChildAt(viewPosition);

            if (childView == null) {
                continue;
            }

            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) childView.getLayoutParams();

            int left;
            int top;
            int right;
            int bottom;


            left = childView.getRight() + params.rightMargin;
            top = childView.getTop() - params.topMargin;
            right = left + mSpaceHorizontal;
            bottom = childView.getBottom() + params.bottomMargin;
            c.drawRect(left, top, right, bottom, mPaint);

            if(viewPosition == 0) {
                left = childView.getLeft() - params.leftMargin - mSpaceHorizontal;
                top = childView.getTop() - params.topMargin;
                right = left + mSpaceHorizontal;
                bottom = childView.getBottom() + params.bottomMargin;
                c.drawRect(left, top, right, bottom, mPaint);
            }
        }
    }
}

GridLayoutManager 的布局颜色填充封装

private void drawGridItemSpace(Canvas c, RecyclerView parent, GridLayoutManager gridManager) {
    for (int viewPosition = 0; viewPosition < gridManager.getItemCount(); viewPosition++) {
        View childView = parent.getChildAt(viewPosition);

        if (childView == null) {
            continue;
        }

        final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) childView.getLayoutParams();

        int spanCount = gridManager.getSpanCount();
        int index = viewPosition % spanCount;

        int left;
        int top;
        int right;
        int bottom;

        left = childView.getLeft() - params.leftMargin;
        right = childView.getRight() + params.rightMargin + mSpaceHorizontal;
        if (viewPosition < spanCount) {//第一行
            top = childView.getTop() - params.topMargin - mSpaceVertical;
            bottom = top + mSpaceVertical;
            c.drawRect(left, top, right, bottom, mPaint);

            top = childView.getBottom() + params.bottomMargin;
            bottom = top + mSpaceVertical;
            c.drawRect(left, top, right, bottom, mPaint);
        } else {
            top = childView.getBottom() + params.bottomMargin;
            bottom = top + mSpaceVertical;
            c.drawRect(left, top, right, bottom, mPaint);
        }


        if (index == 0) {//第一列
            top = childView.getTop() - params.topMargin;
            bottom = childView.getBottom() + params.bottomMargin + mSpaceVertical;
            left = childView.getLeft() - params.leftMargin - mSpaceHorizontal;
            right = left + mSpaceHorizontal;
            c.drawRect(left, top, right, bottom, mPaint);

            top = childView.getTop() - params.topMargin;
            bottom = childView.getBottom() + params.bottomMargin;
            left = childView.getRight() + params.rightMargin;
            right = left + mSpaceHorizontal;
            c.drawRect(left, top, right, bottom, mPaint);

            if (viewPosition == 0) {
                top = childView.getTop() - params.topMargin - mSpaceVertical;
                bottom = top + mSpaceVertical;
                left = childView.getLeft() - params.leftMargin - mSpaceHorizontal;
                right = left + mSpaceHorizontal;
                c.drawRect(left, top, right, bottom, mPaint);
            }

        } else {
            top = childView.getTop() - params.topMargin;
            bottom = childView.getBottom() + params.bottomMargin;
            left = childView.getRight() + params.rightMargin;
            right = left + mSpaceHorizontal;
            c.drawRect(left, top, right, bottom, mPaint);
        }
    }
}

StaggeredGridLayoutManager的布局偏移颜色填充封装

StaggeredGridLayoutManager 相关的目前正在研究，后面会补充完善

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