近期产品提了有关流式布局的新需求，要求显示字数不定的标签，如果一行显示不完，就只显示一行的内容，而且还在一两个页面采取了多种样式，无语了

自己归类了一下，需求有以下几个区别

1：可选择添加标签与否
2：是否有具体数量限制（比如最多显示3个）
3：是否要靠右对齐
有需求，先找一波现有的工具，看是不是可以直接用

参考Android流式布局实现热门标签效果

FlowLayout原样式：

这个和我们的需求已经比较符合了，但是他并不能控制只显示单行内容

如果要实现这样的布局，官方也提供了Flexbox和FlexboxLayout，但查阅文档后发现他们都不支持设置单行，如果强行设置maxlines为1，所有子view都会被减少宽度来让第一行挤下所有的子view

希望的样式（第一行内能放下多少就放多少，第二行开始都不显示，也不占用高度）：

实际上：

可以看到这些view的宽度都被严重压缩了，即使设置了padding也是没有用的。正好项目本身使用了FlowLayout，就在他的基础上进行修改。

import android.content.Context;
import android.os.Build;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.RequiresApi;

import java.util.ArrayList;
import java.util.List;


public class SingleLineFlowLayout extends ViewGroup {
 private static final String TAG = "FlowLayout";
 public int position=-1;
 public boolean alignRight;
 public boolean countMore;
 private List<List<View>> mLineViews = new ArrayList<List<View>>();
 private List<Integer> mLineHeight = new ArrayList<Integer>();

 public SingleLineFlowLayout(Context context) {
 super(context);
 }

 public SingleLineFlowLayout(Context context, AttributeSet attrs) {
 super(context, attrs);
 }

 public SingleLineFlowLayout(Context context, AttributeSet attrs, int defStyleAttr) {
 super(context, attrs, defStyleAttr);
 }

 @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
 public SingleLineFlowLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
 super(context, attrs, defStyleAttr, defStyleRes);
 }

 /**
 * 测量所有子View大小,确定ViewGroup的宽高
 *
 * @param widthMeasureSpec
 * @param heightMeasureSpec
 */
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 super.onMeasure(widthMeasureSpec, heightMeasureSpec);

 //由于onMeasure会执行多次,避免重复的计算控件个数和高度,这里需要进行清空操作
 mLineViews.clear();
 mLineHeight.clear();
 //获取测量的模式和尺寸大小
 int widthMode = MeasureSpec.getMode(widthMeasureSpec);
 int widthSize = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
 int heightMode = MeasureSpec.getMode(heightMeasureSpec);
 int heightSize = MeasureSpec.getSize(heightMeasureSpec) + getPaddingTop() + getPaddingBottom();


 //记录ViewGroup真实的测量宽高
 int viewGroupWidth = widthSize;
 int viewGroupHeight = getPaddingTop() + getPaddingBottom();

 if (widthMode == MeasureSpec.EXACTLY && heightMode == MeasureSpec.EXACTLY) {
 viewGroupWidth = widthSize;
 viewGroupHeight = heightSize;
 } else {
 //当前所占的宽高
 int currentLineWidth = 0;
 int currentLineHeight = 0;
 int lastChildWidth=0;
 int doubleLastChildWidth=0;
 //用来存储每一行上的子View
 List<View> lineView = new ArrayList<View>();

 for (int i = 0; i < getChildCount(); i++) {

 View childView = getChildAt(i);
 //对子View进行测量
 measureChild(childView, widthMeasureSpec, heightMeasureSpec);
 MarginLayoutParams marginLayoutParams = (MarginLayoutParams) childView.getLayoutParams();
 int childViewWidth = childView.getMeasuredWidth() + marginLayoutParams.leftMargin + marginLayoutParams.rightMargin;
 int childViewHeight = childView.getMeasuredHeight() + marginLayoutParams.topMargin + marginLayoutParams.bottomMargin;
 if (currentLineWidth + childViewWidth > widthSize) {
  //从当前位置开始，删除view，保留最后一个moreView
  String tag=(String) childView.getTag();
  if (tag!=null&&tag.equals("More")){
  currentLineHeight = Math.max(currentLineHeight, childViewHeight);
  }else {
  removeViews(i,getChildCount()-1-i);
  childView = getChildAt(i);
  tag=(String) childView.getTag();
  if (tag==null||!tag.equals("More")){
  currentLineHeight = Math.max(currentLineHeight, childViewHeight);
  }else {
  //对子View进行测量
  measureChild(childView, widthMeasureSpec, heightMeasureSpec);
  marginLayoutParams = (MarginLayoutParams) childView.getLayoutParams();
  childViewWidth = childView.getMeasuredWidth() + marginLayoutParams.leftMargin + marginLayoutParams.rightMargin;
  childViewHeight = childView.getMeasuredHeight() + marginLayoutParams.topMargin + marginLayoutParams.bottomMargin;
  if (currentLineWidth + childViewWidth > widthSize) {
  //lineView.remove(i-1);
  lineView.remove(getChildAt(i-1));
  removeViewAt(i-1);
  currentLineWidth=currentLineWidth-lastChildWidth;
  }
  if (i-1>0&&currentLineWidth + childViewWidth > widthSize){
  currentLineWidth=currentLineWidth-doubleLastChildWidth-marginLayoutParams.leftMargin - marginLayoutParams.rightMargin;
  lineView.remove(getChildAt(i-2));
  removeViewAt(i-2);
  }
  currentLineWidth += childViewWidth;
  currentLineHeight = Math.max(currentLineHeight, childViewHeight);
  //添加行对象里的子View
  if (alignRight){
  int rightMargin=marginLayoutParams.rightMargin;
  marginLayoutParams.setMargins(marginLayoutParams.leftMargin,marginLayoutParams.topMargin,0,marginLayoutParams.bottomMargin);
  childView.setLayoutParams(marginLayoutParams);
  marginLayoutParams=(MarginLayoutParams) getChildAt(0).getLayoutParams();
  marginLayoutParams.setMargins(marginLayoutParams.leftMargin+widthSize-currentLineWidth+rightMargin,marginLayoutParams.topMargin,marginLayoutParams.rightMargin,marginLayoutParams.bottomMargin);
  getChildAt(0).setLayoutParams(marginLayoutParams);
  }else {
  marginLayoutParams.setMargins(widthSize-currentLineWidth,marginLayoutParams.topMargin,0,marginLayoutParams.bottomMargin);
  childView.setLayoutParams(marginLayoutParams);
  }
  lineView.add(childView);
  }
  }
 } else {
  //当前行宽+子View+左右外边距<=ViewGroup的宽度,不换行
  if (i>1){
  doubleLastChildWidth=lastChildWidth;
  }
  lastChildWidth=childViewWidth;
  currentLineWidth += childViewWidth;
  currentLineHeight = Math.max(currentLineHeight, childViewHeight);
  //添加行对象里的子View
  String tag=(String) childView.getTag();
  if (tag!=null&&tag.equals("More")){
  if (countMore){
  lineView.add(childView);
  }
  }else {
  lineView.add(childView);
  }
 }


 if (i >= getChildCount() - 1) {
  //最后一个子View的时候
  //添加行对象
  if (alignRight){
  int rightMargin=marginLayoutParams.rightMargin;
  marginLayoutParams.setMargins(marginLayoutParams.leftMargin,marginLayoutParams.topMargin,0,marginLayoutParams.bottomMargin);
  childView.setLayoutParams(marginLayoutParams);
  marginLayoutParams=(MarginLayoutParams) getChildAt(0).getLayoutParams();
  marginLayoutParams.setMargins(marginLayoutParams.leftMargin+widthSize-currentLineWidth+rightMargin,marginLayoutParams.topMargin,marginLayoutParams.rightMargin,marginLayoutParams.bottomMargin);
  getChildAt(0).setLayoutParams(marginLayoutParams);
  }
  mLineViews.add(lineView);
  viewGroupWidth = Math.max(childViewWidth, widthSize);
  viewGroupHeight = viewGroupHeight+currentLineHeight;
  //添加行高
  mLineHeight.add(currentLineHeight);

 }


 }

 }

 setMeasuredDimension(viewGroupWidth, viewGroupHeight);

 }

 /**
 * 设置ViewGroup里子View的具体位置
 *
 * @param changed
 * @param l
 * @param t
 * @param r
 * @param b
 */
 @Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {

 int left = getPaddingLeft();
 int top = getPaddingTop();
 //一共有几行
 int lines = mLineViews.size();
 for (int i = 0; i < lines; i++) {
 //每行行高
 int lineHeight = mLineHeight.get(i);
 //行内有几个子View
 List<View> viewList = mLineViews.get(i);
 int views = viewList.size();
 for (int j = 0; j < views; j++) {
 View view = viewList.get(j);
 MarginLayoutParams marginLayoutParams = (MarginLayoutParams) view.getLayoutParams();
 int vl = left + (j == 0 ? 0 : marginLayoutParams.leftMargin);
 if (alignRight){
  vl = left + marginLayoutParams.leftMargin;
 }
 int vt = top + marginLayoutParams.topMargin;
 int vr = vl + view.getMeasuredWidth();
 int vb = vt + view.getMeasuredHeight();
 view.layout(vl, vt, vr, vb);
 if (alignRight){
  left += view.getMeasuredWidth() + marginLayoutParams.leftMargin + marginLayoutParams.rightMargin;
 }else {
  left += view.getMeasuredWidth() + (j == 0 ? 0 : marginLayoutParams.leftMargin) + marginLayoutParams.rightMargin;
 }
 }
 left = getPaddingLeft();
 top += lineHeight;

 }


 }

 /**
 * 指定ViewGroup的LayoutParams
 *
 * @param attrs
 * @return
 */
 @Override
 public LayoutParams generateLayoutParams(AttributeSet attrs) {
 return new MarginLayoutParams(getContext(), attrs);
 }

}

使用方法：

1：使用addView()将所有的标签都添加到布局中
2：如果需要显示代表更多的标签，在添加完所有标签后，再添加对应的view，并且设置view.setTag("More")即可（该View会自动靠右对齐，并且会检测是否能放得下该标签，如果放不下的话会依次尝试两次从后往前删除子view后能否放得下，如果遇到特殊情况需要删除更多的子view的话，可以自己修改代码）
3：如果需要所有的view都右对齐，要在addView()前设置布局的alignRight=true
4:如果需要超过某个数量后，即使可以单行显示，也要添加更多标签的话，要在addView()前设置布局的countMore=true，使用addView()时自己控制添加的数量，并在超过数量的时候添加对应的view，并且设置view.setTag("More")

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