public class RecyclerViewDecoration extends RecyclerView.ItemDecoration {
private int horizontalSpace; // 整个RecyclerView与左右两侧的间距
private int verticalSpace; // 整个RecyclerView与上下的间距
private int leftMargin; // 每个item与左边的间距
private int topMargin; // 每个item与顶部的间距
private int rightMargin; // 每个item与右边的间距
private int bottomMargin; // 每个item与底部的间距
public RecyclerViewDecoration(int horizontalSpace, int verticalSpace) {
this(horizontalSpace, verticalSpace, 0, 0, 0, 0);
}
public RecyclerViewDecoration(int horizontalSpace, int verticalSpace, int margin) {
this(horizontalSpace, verticalSpace, margin, margin, margin, margin);
}
public RecyclerViewDecoration(int horizontalSpace, int verticalSpace, int leftMargin, int topMargin, int rightMargin, int bottomMargin) {
this.horizontalSpace = horizontalSpace;
this.verticalSpace = verticalSpace;
this.leftMargin = leftMargin;
this.topMargin = topMargin;
this.rightMargin = rightMargin;
this.bottomMargin = bottomMargin;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
super.getItemOffsets(outRect, view, parent, state);
// 得到当前Item在RecyclerView中的位置,从0开始
int position = parent.getChildAdapterPosition(view);
// 得到RecyclerView中Item的总个数
int count = parent.getAdapter().getItemCount();
if (parent.getLayoutManager() instanceof GridLayoutManager) { // 网格布局
GridLayoutManager gridLayoutManager = (GridLayoutManager) parent.getLayoutManager();
// 得到网格布局的列数
int spanCount = gridLayoutManager.getSpanCount();
// 判断该网格布局是水平还是垂直
if (LinearLayoutManager.VERTICAL == gridLayoutManager.getOrientation()) { // 垂直
if (spanCount == 1) { // 列数为1
verticalColumnOne(outRect, position, count);
} else { // 列数大于1
verticalColumnMulti(outRect, position, count, spanCount);
}
} else if (LinearLayoutManager.HORIZONTAL == gridLayoutManager.getOrientation()) { // 水平
if (spanCount == 1) { // 行数为1
horizontalColumnOne(outRect, position, count);
} else { // 行数大于1
horizontalColumnMulti(outRect, position, count, spanCount);
}
}
} else if (parent.getLayoutManager() instanceof LinearLayoutManager) { // 线性布局
LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
if (LinearLayoutManager.VERTICAL == layoutManager.getOrientation()) { // 垂直
verticalColumnOne(outRect, position, count);
} else if (LinearLayoutManager.HORIZONTAL == layoutManager.getOrientation()) { // 水平
horizontalColumnOne(outRect, position, count);
}
} else if (parent.getLayoutManager() instanceof StaggeredGridLayoutManager) { // 流布局
//TODO 瀑布流布局相关
}
}
/**
* 列表垂直且列数为1
*
* @param outRect 包括左上右下四个参数，分别控制view左上右下的margin
* @param position 当前view所处位置
* @param count RecyclerView中Item的总个数
*/
private void verticalColumnOne(Rect outRect, int position, int count) {
if (position == 0) { // 位置为0时(即第一个Item)，不设置底部间距
outRect.set(leftMargin, topMargin, rightMargin, 0);
} else if (position == count - 1) { // 最后一个Item
outRect.set(leftMargin, verticalSpace, rightMargin, bottomMargin);
} else { // 中间的Item，不设置底部间距
outRect.set(leftMargin, verticalSpace, rightMargin, 0);
}
}
/**
* 列表垂直且列数大于1
*
* @param outRect 包括左上右下四个参数，分别控制view左上右下的margin
* @param position 当前view所处位置
* @param count RecyclerView中Item的总个数
* @param spanCount 布局的列数
*/
private void verticalColumnMulti(Rect outRect, int position, int count, int spanCount) {
// 通过计算得出总行数
int totalRow = count / spanCount + ((count % spanCount) == 0 ? 0 : 1);
// 计算得出当前view所在的行
int row = position / spanCount;
// 通过对position加1对spanCount取余得到column
// 保证column等于1为第一列，等于0为最后一个，其它值为中间列
int column = (position + 1) % spanCount;
if (column == 1) {
outRect.set(leftMargin,
row == 0 ? topMargin : verticalSpace,
horizontalSpace / 2,
row == totalRow - 1 ? bottomMargin : 0);
} else if (column == 0) {
outRect.set(horizontalSpace / 2,
row == 0 ? topMargin : verticalSpace,
rightMargin,
row == totalRow - 1 ? bottomMargin : 0);
} else {
outRect.set(horizontalSpace / 2,
row == 0 ? topMargin : verticalSpace,
horizontalSpace / 2,
row == totalRow - 1 ? bottomMargin : 0);
}
}
/**
* 列表水平且行数为1
*
* @param outRect 包括左上右下四个参数，分别控制view左上右下的margin
* @param position 当前view所处位置
* @param count RecyclerView中Item的总个数
*/
private void horizontalColumnOne(Rect outRect, int position, int count) {
if (position == 0) { // 位置为0时(即第一个Item)
outRect.set(leftMargin, topMargin, horizontalSpace / 2, bottomMargin);
} else if (position == count - 1) { // 最后一个Item
outRect.set(horizontalSpace / 2, topMargin, rightMargin, bottomMargin);
} else { // 中间的Item
outRect.set(horizontalSpace / 2, topMargin, horizontalSpace / 2, bottomMargin);
}
}
/**
* 列表水平且行数大于1
*
* @param outRect 包括左上右下四个参数，分别控制view左上右下的margin
* @param position 当前view所处位置
* @param count RecyclerView中Item的总个数
* @param spanCount 布局的行数
*/
private void horizontalColumnMulti(Rect outRect, int position, int count, int spanCount) {
// 通过计算得出总列数
int totalColumn = count / spanCount + ((count % spanCount) == 0 ? 0 : 1);
// 计算得出当前view所在的列
int column = position / spanCount;
// 通过对position加1对spanCount取余得到row
// 保证row等于1为第一行，等于0为最后一个，其它值为中间行
int row = (position + 1) % spanCount;
if (row == 1) {
outRect.set(column == 0 ? leftMargin : horizontalSpace / 2,
topMargin,
column == totalColumn - 1 ? rightMargin : horizontalSpace / 2,
0);
} else if (row == 0) {
outRect.set(column == 0 ? leftMargin : horizontalSpace / 2,
verticalSpace,
column == totalColumn - 1 ? rightMargin : horizontalSpace / 2,
bottomMargin);
} else {
outRect.set(column == 0 ? leftMargin : horizontalSpace / 2,
verticalSpace,
column == totalColumn - 1 ? rightMargin : horizontalSpace / 2,
0);
}
}
}
