源码
首先定义一个类就叫 GridItemDecoration吧，接下来就是该类的具体代码：
public class GridItemDecoration extends RecyclerView.ItemDecoration {
private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
private Drawable mVerticalDivider;
private Drawable mHorizontalDivider;
private Rect mBounds = new Rect();
private boolean hasBorder = false;
public GridItemDecoration(Context context) {
this(context, false);
}
public GridItemDecoration(Context context, boolean hasBorder) {
this.hasBorder = hasBorder;
final TypedArray a = context.obtainStyledAttributes(ATTRS);
mVerticalDivider = a.getDrawable(0);
mHorizontalDivider = a.getDrawable(0);
a.recycle();
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (mVerticalDivider == null && mHorizontalDivider == null) {
outRect.set(0, 0, 0, 0);
return;
}
//列表中item个数
int itemCount = parent.getAdapter().getItemCount();
//列表中位置
int position = parent.getChildAdapterPosition(view);
//列数
int spanCount = getSpanCount(parent);
//左右偏移
//行中位置
int indexHorizontal = position % spanCount;
//纵向分割线宽度
int dividerWidth = mVerticalDivider.getIntrinsicWidth();
//有边界 itemWidth = ( 列数 + 1 ) * 分割线宽度 / 列数
//无边界 itemWidth = ( 列数 - 1 ) * 分割线宽度 / 列数
//每个item内分割线占用的宽度,
// 无边框：每个item内分割线占的宽度 = ( item个数 - 1 ) * 分割线宽度 / item个数
// 有边框：每个item内分割线占的宽度 = ( item个数 + 1 ) * 分割线宽度 / item个数
int itemDividerWidth = (spanCount + (hasBorder ? 1 : -1)) * dividerWidth / spanCount;
int left;
int right;
if (hasBorder) {
//有边框
// left = ( 行中位置 + 1 ) * 分割线宽度 - 行中位置 * 每个item内分割线占用的宽度
left = (indexHorizontal + 1) * dividerWidth - indexHorizontal * itemDividerWidth;
//right = 每个item内分割线占用的宽度 - left
right = itemDividerWidth - left;
} else {
//无边框
//left = 行中位置 * ( 分割线宽度 - 每个item内分割线占用的宽度 )
left = indexHorizontal * (dividerWidth - itemDividerWidth);
//right = 每个item内分割线占用的宽度 - left
right = itemDividerWidth - left;
}
//上下偏移
//横向分割线高度
int dividerHeight = mHorizontalDivider.getIntrinsicHeight();
int top;
int bottom;
if (hasBorder) {
//有边框，最上面偏移分割线高度，最下面偏移分割线高度，其他都上下各偏移分割线一半的高度
top = isFirstRow(position, spanCount) ? dividerHeight : (dividerHeight / 2);
bottom = isLastRow(position, itemCount, spanCount) ? dividerHeight : (dividerHeight / 2);
} else {
//无边框，最上面高度偏移0，最下面高度偏移0，其他上下各偏移分割线一半高度
top = isFirstRow(position, spanCount) ? 0 : (dividerHeight / 2);
bottom = isLastRow(position, itemCount, spanCount) ? 0 : (dividerHeight / 2);
}
outRect.set(left, top, right, bottom);
}
/**
* 获取列数
*/
private int getSpanCount(RecyclerView parent) {
int spanCount = -1;
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
if (layoutManager instanceof GridLayoutManager) {
spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
}
return spanCount;
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
drawVertical(c, parent);
drawHorizontal(c, parent);
}
/**
* 绘制水平分割线
*/
private void drawHorizontal(Canvas canvas, RecyclerView parent) {
canvas.save();
//总item数
int itemCount = parent.getAdapter().getItemCount();
//列数
int spanCount = getSpanCount(parent);
//每个item宽度
int itemWidth = (parent.getWidth() - parent.getPaddingLeft() - parent.getPaddingRight()) / spanCount;
//分割线高度
int dividerHeight = mVerticalDivider.getIntrinsicHeight();
int left;
int right;
int bottom;
int top;
int position;
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
View childView = parent.getChildAt(i);
position = parent.getChildAdapterPosition(childView);
parent.getDecoratedBoundsWithMargins(childView, mBounds);
//分割线左右坐标
left = mBounds.left;
right = left + itemWidth;
//每个item下边分割线上边沿（getItemOffsets时每个item多空了一个分割线高度的一半）
top = mBounds.bottom;
if (isLastRow(position, itemCount, spanCount)) {
//最后一行，有边界需要完整分割线高度，没边界减掉
top += hasBorder ? -dividerHeight : 0;
}else{
top -= dividerHeight / 2;
}
if (position >= itemCount - spanCount && !hasBorder) {
//最后几个，且没有边框
bottom = top;
} else {
bottom = top + dividerHeight;
}
mVerticalDivider.setBounds(left, top, right, bottom);
mVerticalDivider.draw(canvas);
if (isFirstRow(position, spanCount) && hasBorder) {
//第一行且有边界，需要最上面一条
top = mBounds.top;
bottom = top + dividerHeight;
mVerticalDivider.setBounds(left, top, right, bottom);
mVerticalDivider.draw(canvas);
}
}
canvas.restore();
}
/**
* 绘制垂直分割线
*/
private void drawVertical(Canvas canvas, RecyclerView parent) {
canvas.save();
//总item数
int itemCount = parent.getAdapter().getItemCount();
//列数
int spanCount = getSpanCount(parent);
//每个item宽度
int itemWidth = (parent.getWidth() - parent.getPaddingLeft() - parent.getPaddingRight()) / spanCount;
//分割线宽度
int dividerWidth = mHorizontalDivider.getIntrinsicWidth();
//每个item中分割线占的宽度
int itemDividerWidth = (spanCount + (hasBorder ? 1 : -1)) * dividerWidth / spanCount;
int top;
int bottom;
int right;
int left;
int position;
int childCount = parent.getChildCount();
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
parent.getLayoutManager().getDecoratedBoundsWithMargins(child, mBounds);
position = parent.getChildAdapterPosition(child);
//分割线上下坐标
top = mBounds.top;
bottom = mBounds.bottom;
if (!hasBorder) {
//没有边界时
if (position + spanCount == itemCount) {
//最后一个item上面那个
bottom += mVerticalDivider.getIntrinsicHeight() / 2;
} else if ((itemCount % spanCount != 0) && (itemCount % spanCount < position % spanCount) && (position > itemCount - spanCount)) {
//item不是整行数时，倒数第二行最后几个的下边界线需要减去
bottom -= mVerticalDivider.getIntrinsicHeight() / 2;
}
}
//行中位置
int indexHorizontal = position % spanCount;
if (hasBorder) {
//有边界
left = mBounds.left - (itemDividerWidth - dividerWidth) * indexHorizontal;
right = left + dividerWidth;
} else {
left = mBounds.left - (dividerWidth - indexHorizontal * (dividerWidth - itemDividerWidth));
//无边界且是第一列不绘制
right = left + (indexHorizontal == 0 ? 0 : dividerWidth);
}
//画左边纵向分割线
mVerticalDivider.setBounds(left, top, right, bottom);
mVerticalDivider.draw(canvas);
if (hasBorder && isLastColumn(position, spanCount, itemCount)) {
//最后一列
if ((indexHorizontal + 1) % spanCount == 0) {
//每行满格最后一个
left = parent.getWidth() - parent.getPaddingRight() - dividerWidth;
} else {
//不满格的最后一个
left = left + itemWidth - (itemDividerWidth - dividerWidth);
}
right = left + dividerWidth;
mVerticalDivider.setBounds(left, top, right, bottom);
mVerticalDivider.draw(canvas);
}
}
canvas.restore();
}
/**
* 第一行
*/
private boolean isFirstRow(int position, int spanCount) {
return position < spanCount;
}
/**
* 最后一行
*/
private boolean isLastRow(int position, int itemCount, int spanCount) {
//当前个数小于总个数
//并且
//item个数正好排成N行spanCount，且当前位置>=总item-每行个数
//或
//item个数多了一部分((item+1)%spanCount)，且当前位置在多出来部分
return position < itemCount
&& ((itemCount % spanCount == 0 && position >= itemCount - spanCount)
|| (itemCount % spanCount >= itemCount - position));
}
/**
* 最后一列
*/
private boolean isLastColumn(int position, int spanCount, int itemCount) {
//每行最后一个或总item最后一个
return ((position + 1) % spanCount == 0) || (position + 1 == itemCount);
}
public void setVerticalDivider(Drawable verticalDivider) {
this.mVerticalDivider = verticalDivider;
}
public void setHorizontalDivider(Drawable horizontalDivider) {
this.mHorizontalDivider = horizontalDivider;
}
public void setHasBorder(boolean hasBorder) {
this.hasBorder = hasBorder;
}
}使用
首先定义好drawable文件 divider_s10，代码如下：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<size
android:width="10dp"
android:height="10dp" />
</shape>然后使用：
GridItemDecoration divider = new GridItemDecoration(getContext());
divider.setHorizontalDivider(getResources().getDrawable(R.drawable.divider_s10));
divider.setVerticalDivider(getResources().getDrawable(R.drawable.divider_s15));
recyclerView.addItemDecoration(divider);这样就给RecyclerView添加了横向纵向都为10dp的网格分割线
