一.设置setImageParams方式

mAdapter = new DiamondRingZoneAdapter(R.layout.item_diamondringzone_item, list);
            mAdapter.setImageParams(Util.getImageParams(mContext, 3, 0.9, 8));
            mRecyclerView.setAdapter(mAdapter);

    /**
     * 获取Image图片的宽高
     *
     * @param context
     * @param count
     * @param scale
     * @param left
     * @return
     */
    public static RelativeLayout.LayoutParams getImageParams(Context context,
                                                             int count, double scale, int left) {
        //获取当前显示的界面大小
        DisplayMetrics dm = context.getResources().getDisplayMetrics();
        int w = dm.widthPixels; //获取当前界面的宽度
        int imageWidth = w / count;//得到屏幕宽度的一半
        int imageHeight = (int) (imageWidth * scale);
 //       int imageHeight = w / count;

        //定义好控件的属性即把屏幕宽度的一半设置成imageview的宽高。LinearLayout表示 iv_hot_item 外层布局
//        LinearLayout.LayoutParams imageParams = new LinearLayout.LayoutParams(imageWidth, imageHeight);
        RelativeLayout.LayoutParams imageParams = new RelativeLayout.LayoutParams(imageWidth, imageHeight);
        imageParams.setMargins(DensityUtil.dp2px(context, left), 0, 0, 0);
        imageParams.addRule(RelativeLayout.CENTER_HORIZONTAL);//添加水平居中
        return imageParams;
    }

在Adapter中设置ImageView的params

public void setImageParams(RelativeLayout.LayoutParams imageParams) {
        this.mImageParams = imageParams;
}

if (null != mImageParams) {
            imgView.setLayoutParams(mImageParams);
}

整体左右边距在RecyclerView布局中设置

<android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"    
        android:paddingLeft="4dp"
        android:paddingRight="4dp" />

二.设置RecyclerView addItemDecoration方式

mRecyclerView.setLayoutManager(new GridLayoutManager(mContext, 2));
//重点
mRecyclerView.addItemDecoration(new RecyclerItemDecoration(dp2px(30), dp2px(30),2));
if (null == mAdapter) {
   mAdapter = new GuessYouLikeAdapter(R.layout.item_guessyoulike, youLikeList,mContext);
   mRecyclerView.setAdapter(mAdapter);
}

public class RecyclerItemDecoration extends RecyclerView.ItemDecoration {

    private int itemSpaceLeft;
    private int itemSpaceCenter;
    private int itemNum;

    public RecyclerItemDecoration(int itemSpaceLeft, int itemSpaceCenter, int itemNum) {
        this.itemSpaceLeft = itemSpaceLeft;
        this.itemSpaceCenter = itemSpaceCenter;
        this.itemNum = itemNum;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildAdapterPosition(view);
        if (parent.getChildCount() > 0) {
            if (position % itemNum == 0) {                  //最左边Item
                outRect.left = itemSpaceLeft;
                outRect.right = itemSpaceCenter / 2;
            } else if (position % itemNum == itemNum - 1) { //最右边Item
                outRect.left = itemSpaceCenter / 2;
                outRect.right = itemSpaceLeft;
            } else {                                        //中间Item
                outRect.left = itemSpaceCenter / 2;
                outRect.right = itemSpaceCenter / 2;
            }
        }
    }

}