添加ItemDecoration
/**
* 横条目数量
*/
private int mSpanCount;
/**
* 行间距
*/
private int mRowSpacing;
/**
* 列间距
*/
private int mColumnSpacing;
/**
* @param spanCount 列数
* @param rowSpacing 行间距
* @param columnSpacing 列间距
*/
public AlbumItemDecoration(int spanCount, int rowSpacing, int columnSpacing) {
this.mSpanCount = spanCount;
this.mRowSpacing = rowSpacing;
this.mColumnSpacing = columnSpacing;
}
@Override
public void getItemOffsets(@NonNull Rect outRect, @NonNull View view, @NonNull RecyclerView parent, @NonNull RecyclerView.State state) {
// 获取view 在adapter中的位置。
int position = parent.getChildAdapterPosition(view);
// view 所在的列
int column = position % mSpanCount;
// column * (列间距 * (1f / 列数))
outRect.left = column * mColumnSpacing / mSpanCount;
// 列间距 - (column + 1) * (列间距 * (1f /列数))
outRect.right = mColumnSpacing - (column + 1) * mColumnSpacing / mSpanCount;
// 如果position > 行数，说明不是在第一行，则不指定行高，其他行的上间距为 top=mRowSpacing
if (position >= mSpanCount) {
// item top
outRect.top = mRowSpacing;
}
}
image.png
类似于这样，两边紧贴屏幕，中间三个平均分配，三者间宽度一致
还有一种方式
此方法参考别的博主
package com.timestampcamera.map.gpscamera.pro.view.adapter;
import android.graphics.Rect;
import android.os.Build;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.View;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.chad.library.adapter.base.BaseSectionQuickAdapter;
import com.chad.library.adapter.base.entity.SectionEntity;
import com.chad.library.adapter.base.viewholder.BaseViewHolder;
import java.util.ArrayList;
import java.util.List;
/**
* 应用于RecyclerView的GridLayoutManager，水平方向上固定间距大小，从而使条目宽度自适应。<br>
* 配合Brvah的Section使用，不对Head生效，仅对每个Head的子Grid列表生效<br>
* Section Grid中Item的宽度应设为MATCH_PARAENT
*
* @author : renpeng
* @since : 2018/9/29
*/
public class GridSectionAverageGapItemDecoration extends RecyclerView.ItemDecoration {
private class Section {
public int startPos = 0;
public int endPos = 0;
public int getCount() {
return endPos - startPos + 1;
}
public boolean contains(int pos) {
return pos >= startPos && pos <= endPos;
}
@Override
public String toString() {
return "Section{" +
"startPos=" + startPos +
", endPos=" + endPos +
'}';
}
}
private float gapHorizontalDp;
private float gapVerticalDp;
private float sectionEdgeHPaddingDp;
private float sectionEdgeVPaddingDp;
private int gapHSizePx = -1;
private int gapVSizePx = -1;
private int sectionEdgeHPaddingPx;
private int eachItemHPaddingPx; //每个条目应该在水平方向上加的padding 总大小，即=paddingLeft+paddingRight
private int sectionEdgeVPaddingPx;
private List<Section> mSectionList = new ArrayList<>();
private BaseSectionQuickAdapter mAdapter;
private RecyclerView.AdapterDataObserver mDataObserver = new RecyclerView.AdapterDataObserver() {
@Override
public void onChanged() {
markSections();
}
@Override
public void onItemRangeChanged(int positionStart, int itemCount) {
markSections();
}
@Override
public void onItemRangeChanged(int positionStart, int itemCount, @Nullable Object payload) {
markSections();
}
@Override
public void onItemRangeInserted(int positionStart, int itemCount) {
markSections();
}
@Override
public void onItemRangeRemoved(int positionStart, int itemCount) {
markSections();
}
@Override
public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
markSections();
}
};
/**
* @param gapHorizontalDp item之间的水平间距
* @param gapVerticalDp item之间的垂直间距
* @param sectionEdgeHPaddingDp section左右两端的padding大小
* @param sectionEdgeVPaddingDp section上下两端的padding大小
*/
public GridSectionAverageGapItemDecoration(float gapHorizontalDp, float gapVerticalDp, float sectionEdgeHPaddingDp, float sectionEdgeVPaddingDp) {
this.gapHorizontalDp = gapHorizontalDp;
this.gapVerticalDp = gapVerticalDp;
this.sectionEdgeHPaddingDp = sectionEdgeHPaddingDp;
this.sectionEdgeVPaddingDp = sectionEdgeVPaddingDp;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (parent.getLayoutManager() instanceof GridLayoutManager && parent.getAdapter() instanceof BaseSectionQuickAdapter) {
GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
BaseSectionQuickAdapter<SectionEntity, BaseViewHolder> adapter = (BaseSectionQuickAdapter) parent.getAdapter();
if (mAdapter != adapter) {
setUpWithAdapter(adapter);
}
int spanCount = layoutManager.getSpanCount();
int position = parent.getChildAdapterPosition(view) - mAdapter.getHeaderLayoutCount();
if (position < 0) return;
SectionEntity entity = adapter.getItem(position);
if (entity == null || entity.isHeader()) {
//不处理header
outRect.set(0, 0, 0, 0);
// Log.w("GridAverageGapItem", "pos=" + position + "," + outRect.toShortString());
return;
}
Section section = findSectionLastItemPos(position);
if (gapHSizePx < 0 || gapVSizePx < 0) {
transformGapDefinition(parent, spanCount);
}
outRect.top = gapVSizePx;
outRect.bottom = 0;
//下面的visualPos为单个Section内的视觉Pos
int visualPos = position + 1 - section.startPos;
if (visualPos % spanCount == 1) {
//第一列
outRect.left = sectionEdgeHPaddingPx;
outRect.right = eachItemHPaddingPx - sectionEdgeHPaddingPx;
} else if (visualPos % spanCount == 0) {
//最后一列
outRect.left = eachItemHPaddingPx - sectionEdgeHPaddingPx;
outRect.right = sectionEdgeHPaddingPx;
} else {
outRect.left = gapHSizePx - (eachItemHPaddingPx - sectionEdgeHPaddingPx);
outRect.right = eachItemHPaddingPx - outRect.left;
}
if (visualPos - spanCount <= 0) {
//第一行
outRect.top = sectionEdgeVPaddingPx;
}
if (isLastRow(visualPos, spanCount, section.getCount())) {
//最后一行
outRect.bottom = sectionEdgeVPaddingPx;
// Log.w("GridAverageGapItem", "last row pos=" + position);
}
// Log.w("GridAverageGapItem", "pos=" + position + ",vPos=" + visualPos + "," + outRect.toShortString());
} else {
super.getItemOffsets(outRect, view, parent, state);
}
}
private void setUpWithAdapter(BaseSectionQuickAdapter<SectionEntity, BaseViewHolder> adapter) {
if (mAdapter != null) {
mAdapter.unregisterAdapterDataObserver(mDataObserver);
}
mAdapter = adapter;
mAdapter.registerAdapterDataObserver(mDataObserver);
markSections();
}
private void markSections() {
if (mAdapter != null) {
BaseSectionQuickAdapter<SectionEntity, BaseViewHolder> adapter = mAdapter;
mSectionList.clear();
SectionEntity sectionEntity = null;
Section section = new Section();
for (int i = 0, size = adapter.getItemCount(); i < size; i++) {
sectionEntity = adapter.getItem(i);
if (sectionEntity != null && sectionEntity.isHeader()) {
//找到新Section起点
if (section != null && i != 0) {
//已经有待添加的section
section.endPos = i - 1;
mSectionList.add(section);
}
section = new Section();
section.startPos = i + 1;
} else {
section.endPos = i;
}
}
//处理末尾情况
if (!mSectionList.contains(section)) {
mSectionList.add(section);
}
// Log.w("GridAverageGapItem", "section list=" + mSectionList);
}
}
private void transformGapDefinition(RecyclerView parent, int spanCount) {
DisplayMetrics displayMetrics = new DisplayMetrics();
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
parent.getDisplay().getMetrics(displayMetrics);
}
gapHSizePx = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, gapHorizontalDp, displayMetrics);
gapVSizePx = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, gapVerticalDp, displayMetrics);
sectionEdgeHPaddingPx = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, sectionEdgeHPaddingDp, displayMetrics);
sectionEdgeVPaddingPx = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, sectionEdgeVPaddingDp, displayMetrics);
eachItemHPaddingPx = (sectionEdgeHPaddingPx * 2 + gapHSizePx * (spanCount - 1)) / spanCount;
}
private Section findSectionLastItemPos(int curPos) {
for (Section section : mSectionList) {
if (section.contains(curPos)) {
return section;
}
}
return null;
}
private boolean isLastRow(int visualPos, int spanCount, int sectionItemCount) {
int lastRowCount = sectionItemCount % spanCount;
lastRowCount = lastRowCount == 0 ? spanCount : lastRowCount;
return visualPos > sectionItemCount - lastRowCount;
}
}
image.png
