RV LayoutManager 流式布局
目录
RV 流式布局 LayoutManager
使用
.setLayoutManager(new FlowLayoutManager());
测试代码
public static List<TemplateTag> getTemplateTagList() {
List<TemplateTag> list = new ArrayList<>();
int colors[] = new int[10];
for (int i = 0, j = colors.length; i < j; i++) {
colors[i] = 0xFF000000 + new Random().nextInt(0xFFFFFF);
//注意，Integer.MAX_VALUE= 0x7fffffff，超过这个值就是负数了，所以通过随机数获取int值时，传入的值要小于0x7fffffff
}
list.add(new TemplateTag("白乾涛", colors[0]));
list.add(new TemplateTag("tag", colors[1]));
list.add(new TemplateTag("标签 tag", colors[2]));
list.add(new TemplateTag("1", colors[3]));
list.add(new TemplateTag("颜色 " + colors[4], colors[4]));
list.add(new TemplateTag("包青天", colors[5]));
list.add(new TemplateTag("包青天包青天", colors[6]));
list.add(new TemplateTag("包青天包青天包青天包青天包青天包青天包青天", colors[7]));
list.add(new TemplateTag("包青天天包青天", colors[8]));
list.add(new TemplateTag("包青天123456789123456789123456789123456789123456789", colors[9]));
return list;
}
根据颜色设置背景
tvContent.setBackground(getDrawable(mTemplateTag.color));
private GradientDrawable getDrawable(int bgColor) {
GradientDrawable gradientDrawable = new GradientDrawable();
gradientDrawable.setColor(bgColor);
gradientDrawable.setCornerRadius(DisplayUtil.dip2px(ApplicationContext.getContext(), 4));
return gradientDrawable;
}
FlowLayoutManager
/**
* 描述：一种流式布局的LayoutManager<p>
* 添加时间：2017/12/26 <p>
* 开发者：<a href="http://www.cnblogs.com/baiqiantao">白乾涛</a><p>
*/
public class FlowLayoutManager extends RecyclerView.LayoutManager {
private static final String TAG = FlowLayoutManager.class.getSimpleName();
final FlowLayoutManager self = this;
private 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
private 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_content
setAutoMeasureEnabled(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item
List<Item> views = new ArrayList<>();
public void addViews(Item view) {
views.add(view);
}
}
@Override
public 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
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
Log.d(TAG, "onLayoutChildren");
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;
}
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();
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());
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()) { // 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
*/
@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();
}
}
2017-12-27
本文来自博客园，作者：白乾涛，转载请注明原文链接：https://www.cnblogs.com/baiqiantao/p/8124560.html
