RecyclerView添加分割线

在使用ListView 的时候可以通过java 代码或者在xml 中设置分割线，但是到了RecyclerView 发现并没有可以直接设置分割线的方法了。xml 中也没有设置的属性，查看源码，我们可以通过recyclerview.addItemDecoration() 添加自定义的分割线，该方法的参数是ItemDecoration抽象类，google并没有提供现成的实现类，所以我们要自己写一个类实现分割线方法。
下面看一个实现类

public class RecyclerViewItemDecoration extends RecyclerView.ItemDecoration {

    private Context context;
    private Drawable divider;
    private int orientation;
    private static  final  int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
    private static final int VERTICAL_LIST= LinearLayoutManager.VERTICAL;

    public RecyclerViewItemDecoration(Context context , int orientation,int drawableId){
        this.orientation=orientation;
        this.context=context;
        divider=context.getResources().getDrawable(drawableId);
        setOrientation(orientation);
    }

    private void setOrientation(int orientation){
        if (orientation!=HORIZONTAL_LIST&&orientation!=VERTICAL_LIST){
            throw  new IllegalArgumentException("没有初始化 列表方向");
        }
    }

    /**
     * 画竖线
     * @param c
     * @param parent
     * @param state
     */

    private void   drawVerticalLine(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int top = parent.getPaddingTop();
        int bottom = parent.getHeight() - parent.getPaddingBottom();
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight()+ params.leftMargin;
            final int right =left + divider.getIntrinsicHeight();
            divider.setBounds(left, top, right, bottom);
            divider.draw(c);
        }
    }

    /**
     * 画竖线
     * @param c
     * @param parent
     * @param state
     */
    private void drawHorizontalLine(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int left= parent.getPaddingLeft();
        int right =parent.getWidth()-parent.getPaddingRight();
        for (int i=0;i<parent.getChildCount();i++){
            final  View child =parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final  int top =child.getBottom() +params.bottomMargin;
            final  int bottom =top+divider.getIntrinsicHeight();
            divider.setBounds(left,top,right,bottom);
            divider.draw(c);
        }
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {

        if (orientation==HORIZONTAL_LIST){
            drawVerticalLine(c,parent,state);
        }else {

            drawHorizontalLine(c,parent,state);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            if (orientation ==HORIZONTAL_LIST){
                outRect.set(0,0,0,divider.getIntrinsicHeight());
            }else {
                outRect.set(0,0,divider.getIntrinsicWidth(),0);
            }
    }
}