private void drawHorizontal(Canvas c, RecyclerView parent, State state) {
 int childCount = parent.getChildCount() - 1;
 int left = 0;
 int top = parent.getPaddingTop();
 int right = 0;
 int bottom = parent.getHeight() - parent.getPaddingBottom();
 for (int i = 0; i < childCount; i++) {
 View view = parent.getChildAt(i);
 RecyclerView.LayoutParams params = (LayoutParams) view.getLayoutParams(); //考慮，padding
 left = view.getRight();
 right = left + divider.getIntrinsicHeight(); //我們在自定義drawable的是是，寫死了高度，所以只能用高度
 divider.setBounds(left, top, right, bottom);
 divider.draw(c);
 }
}

/**
 * 思路：就是獲取每個item，計算divider的left,top,right,bottom
 */
private void drawVertical(Canvas c, RecyclerView parent, State state) {

 int childCount = parent.getChildCount() - 1;
 int left = parent.getPaddingLeft();
 int top = 0;
 int right = parent.getWidth() - parent.getPaddingRight(); //考慮右邊的padding
 int bottom = 0;
 for (int i = 0; i < childCount; i++) { //不繪制最后一個條目的分割線
 View view = parent.getChildAt(i);
 RecyclerView.LayoutParams params = (LayoutParams) view.getLayoutParams(); //考慮，padding
 top = view.getBottom() + params.topMargin; //就是當前view底部到頂部的距離
 bottom = top + divider.getIntrinsicHeight() - params.bottomMargin; //就是top+divider高度
 divider.setBounds(left, top, right, bottom);
 divider.draw(c);
 }
}

@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {
 int childAdapterPosition = parent.getChildAdapterPosition(view);

 int lastCount = parent.getAdapter().getItemCount() - 1;

 //如果當前條目與是最后一個條目，就不設置divider padding
 if (childAdapterPosition == lastCount) {
 outRect.set(0, 0, 0, 0);
 return;
 }

 Log.d("TAG", childAdapterPosition + "," + lastCount);
 if (orientation == LinearLayoutCompat.HORIZONTAL) {
 outRect.set(0, 0, divider.getIntrinsicHeight(), 0); //0,0,30,0，設置寬度
 } else {
 outRect.set(0, 0, 0, divider.getIntrinsicHeight()); //0,0,0,30，設置高度
 }

}