Android通过Recyclerview实现流式布局自适应列数及高度

调用 FlowAdapter 跟普通recyclerview一样使用

RecyclerView rvLayout = holder.getView(R.id.spe_tag_layout);
FlowAdapter rvAdapter = new FlowAdapter();
FlowLayoutManager flowLayoutManager = new FlowLayoutManager();
rvLayout.setLayoutManager(flowLayoutManager);
rvLayout.setAdapter(rvAdapter);

/*** date:2024/1/10* author:wsm* describe:一种流式布局的LayoutManager*/
public class FlowLayoutManager extends RecyclerView.LayoutManager {private static final String TAG = FlowLayoutManager.class.getSimpleName();final FlowLayoutManager self = this;protected int width, height;private int left, top, right;//最大容器的宽度private int usedMaxWidth;//竖直方向上的偏移量private int verticalScrollOffset = 0;public int getTotalHeight() {return totalHeight;}//计算显示的内容的高度protected int totalHeight = 0;private Row row = new Row();private List<Row> lineRows = new ArrayList<>();//保存所有的Item的上下左右的偏移量信息private SparseArray<Rect> allItemFrames = new SparseArray<>();public FlowLayoutManager() {//设置主动测量规则,适应recyclerView高度为wrap_contentsetAutoMeasureEnabled(true);}//每个item的定义public class Item {int useHeight;View view;public void setRect(Rect rect) {this.rect = rect;}Rect rect;public Item(int useHeight, View view, Rect rect) {this.useHeight = useHeight;this.view = view;this.rect = rect;}}//行信息的定义public class Row {public void setCuTop(float cuTop) {this.cuTop = cuTop;}public void setMaxHeight(float maxHeight) {this.maxHeight = maxHeight;}//每一行的头部坐标float cuTop;//每一行需要占据的最大高度float maxHeight;//每一行存储的itemList<Item> views = new ArrayList<>();public void addViews(Item view) {views.add(view);}}@Overridepublic RecyclerView.LayoutParams generateDefaultLayoutParams() {return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);}//该方法主要用来获取每一个item在屏幕上占据的位置@Overridepublic void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {Log.d(TAG, "onLayoutChildren");totalHeight = 0;int cuLineTop = top;//当前行使用的宽度int cuLineWidth = 0;int itemLeft;int itemTop;int maxHeightItem = 0;row = new Row();lineRows.clear();allItemFrames.clear();removeAllViews();if (getItemCount() == 0) {detachAndScrapAttachedViews(recycler);verticalScrollOffset = 0;return;}if (getChildCount() == 0 && state.isPreLayout()) {return;}//onLayoutChildren方法在RecyclerView 初始化时 会执行两遍detachAndScrapAttachedViews(recycler);if (getChildCount() == 0) {width = getWidth();height = getHeight();left = getPaddingLeft();right = getPaddingRight();top = getPaddingTop();usedMaxWidth = width - left - right;}for (int i = 0; i < getItemCount(); i++) {Log.d(TAG, "index:" + i);View childAt = recycler.getViewForPosition(i);if (View.GONE == childAt.getVisibility()) {continue;}measureChildWithMargins(childAt, 0, 0);int childWidth = getDecoratedMeasuredWidth(childAt);int childHeight = getDecoratedMeasuredHeight(childAt);int childUseWidth = childWidth;int childUseHeight = childHeight;//如果加上当前的item还小于最大的宽度的话if (cuLineWidth + childUseWidth <= usedMaxWidth) {itemLeft = left + cuLineWidth;itemTop = cuLineTop;Rect frame = allItemFrames.get(i);if (frame == null) {frame = new Rect();}frame.set(itemLeft, itemTop, itemLeft + childWidth, itemTop + childHeight);allItemFrames.put(i, frame);cuLineWidth += childUseWidth;maxHeightItem = Math.max(maxHeightItem, childUseHeight);row.addViews(new Item(childUseHeight, childAt, frame));row.setCuTop(cuLineTop);row.setMaxHeight(maxHeightItem);} else {//换行formatAboveRow();cuLineTop += maxHeightItem;totalHeight += maxHeightItem;itemTop = cuLineTop;itemLeft = left;Rect frame = allItemFrames.get(i);if (frame == null) {frame = new Rect();}frame.set(itemLeft, itemTop, itemLeft + childWidth, itemTop + childHeight);allItemFrames.put(i, frame);cuLineWidth = childUseWidth;maxHeightItem = childUseHeight;row.addViews(new Item(childUseHeight, childAt, frame));row.setCuTop(cuLineTop);row.setMaxHeight(maxHeightItem);}//不要忘了最后一行进行刷新下布局if (i == getItemCount() - 1) {formatAboveRow();totalHeight += maxHeightItem;}}totalHeight = Math.max(totalHeight, getVerticalSpace());Log.d(TAG, "onLayoutChildren totalHeight:" + totalHeight);fillLayout(recycler, state);}//对出现在屏幕上的item进行展示，超出屏幕的item回收到缓存中private void fillLayout(RecyclerView.Recycler recycler, RecyclerView.State state) {if (state.isPreLayout() || getItemCount() == 0) { // 跳过preLayout，preLayout主要用于支持动画return;}// 当前scroll offset状态下的显示区域Rect displayFrame = new Rect(getPaddingLeft(), getPaddingTop() + verticalScrollOffset,getWidth() - getPaddingRight(), verticalScrollOffset + (getHeight() - getPaddingBottom()));//对所有的行信息进行遍历for (int j = 0; j < lineRows.size(); j++) {Row row = lineRows.get(j);float lineTop = row.cuTop;float lineBottom = lineTop + row.maxHeight;//如果该行在屏幕中，进行放置item
//            if (lineTop < displayFrame.bottom && displayFrame.top < lineBottom) {List<Item> views = row.views;for (int i = 0; i < views.size(); i++) {View scrap = views.get(i).view;measureChildWithMargins(scrap, 0, 0);addView(scrap);Rect frame = views.get(i).rect;//将这个item布局出来layoutDecoratedWithMargins(scrap,frame.left,frame.top - verticalScrollOffset,frame.right,frame.bottom - verticalScrollOffset);}
//            } else {
//                //将不在屏幕中的item放到缓存中
//                List<Item> views = row.views;
//                for (int i = 0; i < views.size(); i++) {
//                    View scrap = views.get(i).view;
//                    removeAndRecycleView(scrap, recycler);
//                }
//            }}}/*** 计算每一行没有居中的viewgroup，让居中显示*/private void formatAboveRow() {List<Item> views = row.views;for (int i = 0; i < views.size(); i++) {Item item = views.get(i);View view = item.view;int position = getPosition(view);//如果该item的位置不在该行中间位置的话，进行重新放置if (allItemFrames.get(position).top < row.cuTop + (row.maxHeight - views.get(i).useHeight) / 2) {Rect frame = allItemFrames.get(position);if (frame == null) {frame = new Rect();}frame.set(allItemFrames.get(position).left, (int) (row.cuTop + (row.maxHeight - views.get(i).useHeight) / 2),allItemFrames.get(position).right, (int) (row.cuTop + (row.maxHeight - views.get(i).useHeight) / 2 + getDecoratedMeasuredHeight(view)));allItemFrames.put(position, frame);item.setRect(frame);views.set(i, item);}}row.views = views;lineRows.add(row);row = new Row();}/*** 竖直方向需要滑动的条件** @return*/@Overridepublic boolean canScrollVertically() {return true;}//监听竖直方向滑动的偏移量@Overridepublic int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler,RecyclerView.State state) {Log.d("TAG", "totalHeight:" + totalHeight);//实际要滑动的距离int travel = dy;//如果滑动到最顶部if (verticalScrollOffset + dy < 0) {//限制滑动到顶部之后，不让继续向上滑动了travel = -verticalScrollOffset;//verticalScrollOffset=0} else if (verticalScrollOffset + dy > totalHeight - getVerticalSpace()) {//如果滑动到最底部travel = totalHeight - getVerticalSpace() - verticalScrollOffset;//verticalScrollOffset=totalHeight - getVerticalSpace()}//将竖直方向的偏移量+travelverticalScrollOffset += travel;// 平移容器内的itemoffsetChildrenVertical(-travel);fillLayout(recycler, state);return travel;}private int getVerticalSpace() {return self.getHeight() - self.getPaddingBottom() - self.getPaddingTop();}public int getHorizontalSpace() {return self.getWidth() - self.getPaddingLeft() - self.getPaddingRight();}
}