1.源码地址
https://github.com/youlookwhat/ByRecyclerView/blob/master/ByRecyclerview/src/main/java/me/jingbin/library/decoration/GridSpaceItemDecoration.java
2.修改参考地址
https://github.com/airbnb/epoxy/blob/master/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyItemSpacingDecorator.java
package cc.abase.demo.widget.decoration;
import android.graphics.Rect;
import android.view.View;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;
/**
* 给 GridLayoutManager or StaggeredGridLayoutManager 设置间距，可设置去除首尾间距个数
*
* @author jingbin
* 原文地址：https://github.com/youlookwhat/ByRecyclerView
*
* 修改By CASE 2020年11月21日17:52:11(注意拖拽"上"+"下"会有1/2的间距)
* 是否处于第一行和最后一行参考：https://github.com/airbnb/epoxy/blob/master/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyItemSpacingDecorator.java
*/
public class GridSpaceItemDecoration extends RecyclerView.ItemDecoration {
/**
* 每行个数
*/
private int mSpanCount;
/**
* 间距
*/
private int mSpacing;
/**
* 距屏幕周围是否也有间距
*/
private boolean mIncludeEdge;
/**
* 头部 不显示间距的item个数
*/
private int mStartFromSize;
/**
* 尾部 不显示间距的item个数 默认不处理最后一个item的间距
*/
private int mEndFromSize = 0;//CASE修改为默认0
/**
* 瀑布流 头部第一个整行的position
*/
private int fullPosition = -1;
public GridSpaceItemDecoration(int spacing) {
this(spacing, true);
}
/**
* @param spacing item 间距
* @param includeEdge item 距屏幕周围是否也有间距
*/
public GridSpaceItemDecoration(int spacing, boolean includeEdge) {
this.mSpacing = spacing;
this.mIncludeEdge = includeEdge;
}
/**
* 已不需要手动设置spanCount
*/
@Deprecated
public GridSpaceItemDecoration(int spanCount, int spacing) {
this(spanCount, spacing, true);
}
/**
* 已不需要手动设置spanCount
*/
@Deprecated
public GridSpaceItemDecoration(int spanCount, int spacing, boolean includeEdge) {
this.mSpanCount = spanCount;
this.mSpacing = spacing;
this.mIncludeEdge = includeEdge;
}
@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent,
@NonNull RecyclerView.State state) {
//
outRect.setEmpty();
int position = parent.getChildAdapterPosition(view);
if (position == RecyclerView.NO_POSITION) {
// View is not shown
return;
}
RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
calculatePositionDetails(parent, position, layoutManager);
//
int lastPosition = state.getItemCount() - 1;
if (mStartFromSize <= position && position <= lastPosition - mEndFromSize) {
// 行
int spanGroupIndex = -1;
// 列
int column = 0;
// 瀑布流是否占满一行
boolean fullSpan = false;
if (layoutManager instanceof GridLayoutManager) {
GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();
int spanCount = gridLayoutManager.getSpanCount();
// 当前position的spanSize
int spanSize = spanSizeLookup.getSpanSize(position);
// 一行几个
mSpanCount = spanCount / spanSize;
// =0 表示是最左边 0 2 4
int spanIndex = spanSizeLookup.getSpanIndex(position, spanCount);
// 列
column = spanIndex / spanSize;
// 行 减去mStartFromSize,得到从0开始的行
spanGroupIndex = spanSizeLookup.getSpanGroupIndex(position, spanCount) - mStartFromSize;
} else if (layoutManager instanceof StaggeredGridLayoutManager) {
// 瀑布流获取列方式不一样
StaggeredGridLayoutManager.LayoutParams params = (StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams();
// 列
column = params.getSpanIndex();
// 是否是全一行
fullSpan = params.isFullSpan();
mSpanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
}
// 减掉不设置间距的position,得到从0开始的position
position = position - mStartFromSize;
if (mIncludeEdge || isIncludeStartEnd) {//CASE添加的代码2"||isIncludeStartEnd"
/*
*示例：
* spacing = 10 ；spanCount = 3
* ---------10--------
* 10 3+7 6+4 10
* ---------10--------
* 10 3+7 6+4 10
* ---------10--------
*/
if (fullSpan) {
outRect.left = 0;
outRect.right = 0;
} else {
outRect.left = mSpacing - column * mSpacing / mSpanCount;
outRect.right = (column + 1) * mSpacing / mSpanCount;
}
if (spanGroupIndex > -1) {
// grid 显示规则
if (spanGroupIndex < 1 && position < mSpanCount) {
// 第一行才有上间距
outRect.top = mSpacing;
}
} else {
if (fullPosition == -1 && position < mSpanCount && fullSpan) {
// 找到头部第一个整行的position，后面的上间距都不显示
fullPosition = position;
}
// Stagger显示规则 头部没有整行或者头部体验整行但是在之前的position显示上间距
boolean isFirstLineStagger = (fullPosition == -1 || position < fullPosition) && (position < mSpanCount);
if (isFirstLineStagger) {
// 第一行才有上间距
outRect.top = mSpacing;
}
}
outRect.bottom = mSpacing;
} else {
/*
*示例：
* spacing = 10 ；spanCount = 3
* --------0--------
* 0 3+7 6+4 0
* -------10--------
* 0 3+7 6+4 0
* --------0--------
*/
if (fullSpan) {
outRect.left = 0;
outRect.right = 0;
} else {
outRect.left = column * mSpacing / mSpanCount;
outRect.right = mSpacing - (column + 1) * mSpacing / mSpanCount;
}
if (spanGroupIndex > -1) {
if (spanGroupIndex >= 1) {
// 超过第0行都显示上间距
outRect.top = mSpacing;
}
} else {
if (fullPosition == -1 && position < mSpanCount && fullSpan) {
// 找到头部第一个整行的position
fullPosition = position;
}
// Stagger上间距显示规则
boolean isStaggerShowTop =
position >= mSpanCount || (fullSpan && position != 0) || (fullPosition != -1 && position != 0);
if (isStaggerShowTop) {
// 超过第0行都显示上间距
outRect.top = mSpacing;
}
}
}
}
//
if (layoutManager instanceof GridLayoutManager) {//只处理上下间距，左右交给原本处理即可
if (isDragGrid) {
outRect.top = mSpacing / 2;
outRect.bottom = mSpacing / 2;
} else {
outRect.top = isInFirstRow ? (isIncludeTop ? mSpacing : 0) : mSpacing / 2;
outRect.bottom = isInLastRow ? (isIncludeBottom ? mSpacing : 0) : mSpacing / 2;
}
}
//
}
/**
* 设置从哪个位置 开始设置间距
*
* @param startFromSize 一般为HeaderView的个数 + 刷新布局(不一定设置)
*/
public GridSpaceItemDecoration setStartFrom(int startFromSize) {
this.mStartFromSize = startFromSize;
return this;
}
/**
* 设置从哪个位置 结束设置间距。默认为1，默认用户设置了上拉加载
*
* @param endFromSize 一般为FooterView的个数 + 加载更多布局(不一定设置)
*/
public GridSpaceItemDecoration setEndFromSize(int endFromSize) {
this.mEndFromSize = endFromSize;
return this;
}
/**
* 设置从哪个位置 结束设置间距
*
* @param startFromSize 一般为HeaderView的个数 + 刷新布局(不一定设置)
* @param endFromSize 默认为1，一般为FooterView的个数 + 加载更多布局(不一定设置)
*/
public GridSpaceItemDecoration setNoShowSpace(int startFromSize, int endFromSize) {
this.mStartFromSize = startFromSize;
this.mEndFromSize = endFromSize;
return this;
}
//
private boolean isInFirstRow;//是否在第一行
private boolean isInLastRow;//是否在最后一行，如果只有一行isInFirstRow和isInLastRow都为true
private boolean isIncludeStartEnd;//是否包含最前面和最后面
private boolean isIncludeTop;//是否包含最上面
private boolean isIncludeBottom;//是否包含最下面
private boolean isDragGrid;//是否是可拖动的grid模式，如果为true则最顶部和最底部默认也是有间距的
public GridSpaceItemDecoration setDragGridEdge(boolean includeStartEnd) {
this.isDragGrid = true;
this.isIncludeStartEnd = includeStartEnd;
this.mIncludeEdge = includeStartEnd;
this.isIncludeTop = false;
this.isIncludeBottom = false;
mEndFromSize = 0;
return this;
}
public GridSpaceItemDecoration setNoDragGridEdge(boolean includeStartEnd, boolean includeTop, boolean includeBottom) {
this.isDragGrid = false;
this.isIncludeStartEnd = includeStartEnd;
this.mIncludeEdge = includeStartEnd;
this.isIncludeTop = includeTop;
this.isIncludeBottom = includeBottom;
mEndFromSize = 0;
return this;
}
private void calculatePositionDetails(RecyclerView parent, int position, RecyclerView.LayoutManager layout) {
if (layout instanceof GridLayoutManager) {
int itemCount = parent.getAdapter() == null ? 0 : parent.getAdapter().getItemCount();
GridLayoutManager grid = (GridLayoutManager) layout;
final GridLayoutManager.SpanSizeLookup spanSizeLookup = grid.getSpanSizeLookup();
int spanCount = grid.getSpanCount();
isInFirstRow = isInFirstRow(position, spanSizeLookup, spanCount);
isInLastRow = isInLastRow(position, itemCount, spanSizeLookup, spanCount);
}
}
private boolean isInFirstRow(int position, GridLayoutManager.SpanSizeLookup spanSizeLookup, int spanCount) {
int totalSpan = 0;
for (int i = 0; i <= position; i++) {
totalSpan += spanSizeLookup.getSpanSize(i);
if (totalSpan > spanCount) {
return false;
}
}
return true;
}
private boolean isInLastRow(int position, int itemCount, GridLayoutManager.SpanSizeLookup spanSizeLookup, int spanCount) {
int totalSpan = 0;
for (int i = itemCount - 1; i >= position; i--) {
totalSpan += spanSizeLookup.getSpanSize(i);
if (totalSpan > spanCount) {
return false;
}
}
return true;
}
//
}