可以滑动流式布局

网上很多流式布局不支持滑动，由于我们的需求要求多的时候必须能滑动，于是我就想到了recyclerview，改造他们manager

public class FlowLayoutManagerextends RecyclerView.LayoutManager {

private static final StringTAG = FlowLayoutManager.class.getSimpleName();

final FlowLayoutManagerself =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 Rowrow =new Row();

private ListlineRows =new ArrayList<>();

//保存所有的Item的上下左右的偏移量信息

private SparseArrayallItemFrames =new SparseArray<>();

public FlowLayoutManager() {

//设置主动测量规则,适应recyclerView高度为wrap_content

setAutoMeasureEnabled(true);

}

//每个item的定义

public class Item {

int useHeight;

Viewview;

public void setRect(Rect rect) {

this.rect = rect;

}

Rectrect;

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item

Listviews =new ArrayList<>();

public void addViews(Item view) {

views.add(view);

}

@Override

public RecyclerView.LayoutParamsgenerateDefaultLayoutParams() {

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

@Override

public 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

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 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 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 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

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

@Override

public boolean canScrollVertically() {

return true;

}

//监听竖直方向滑动的偏移量

@Override

public 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+travel

verticalScrollOffset += travel;

// 平移容器内的item

offsetChildrenVertical(-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();

}

就这么一个类搞定，接下来的用法和recyclerview的用法一样了