前言

美团的外卖商家，电商商品的特点说明，都由一组标签来说明，标签的要求是：1、不满一行不展示可展开图标；2、超过一行的默认展示一行，显示可展开图标，点击可以展开收起；3、在列表中需要保持之前展开或者折叠的状态

实现

Java代码如下：

public class GoodsTagGroupView extends LinearLayout {

    private LinearLayout ll_tags;
    private FlexboxLayout flexLayout;
    private ImageView iv_toggle;

    private boolean isExpand = false;
    public List<TagBean> tagBeanList;
    private ToggleListener listener;

    public GoodsTagGroupView(Context context) {
        super(context);
        initView(context);
    }

    public GoodsTagGroupView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initView(context);
    }

    private void initView(Context context) {
        View view = LayoutInflater.from(context).inflate(R.layout.goods_tag_group_view,this,true);
        ll_tags = view.findViewById(R.id.ll_tags);
        flexLayout = view.findViewById(R.id.flexLayout);
        iv_toggle = view.findViewById(R.id.iv_toggle);
    }

    public void setToggleListener(ToggleListener listener){
        this.listener = listener;
    }

    public void setIsExpand(boolean isExpand){
        this.isExpand = isExpand;
    }

    public void setData(List<TagBean> tagBeanList){
        this.tagBeanList = tagBeanList;
        flexLayout.removeAllViews();
        ((LinearLayout.LayoutParams)flexLayout.getLayoutParams()).height = LayoutParams.WRAP_CONTENT;
        for(int i=0;i<tagBeanList.size();i++){
            TextView tv = new TextView(getContext());
            tv.setIncludeFontPadding(false);
            tv.setGravity(Gravity.CENTER);
            tv.setTextSize(10);
            tv.setPadding(4,2,4,2);
            FlexboxLayout.LayoutParams flps = new FlexboxLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            flps.topMargin = DisplayUtil.dip2px(getContext(),5);
            flps.rightMargin = DisplayUtil.dip2px(getContext(),5);
            if(1==tagBeanList.get(i).style){
                tv.setTextColor(ContextCompat.getColor(getContext(),R.color.goods_tag_color));
                tv.setBackgroundResource(R.drawable.goods_label_tag);
            }else if(2==tagBeanList.get(i).style){
                tv.setTextColor(ContextCompat.getColor(getContext(),R.color.goods_fresh_tag_color));
                tv.setBackgroundResource(R.drawable.goods_green_tag);
            }else{
                tv.setTextColor(ContextCompat.getColor(getContext(),R.color.goods_tag_color));
                tv.setBackgroundResource(R.drawable.goods_red_bg_tag);
            }
            tv.setText(tagBeanList.get(i).name);
            flexLayout.addView(tv,flps);
        }
        /**
         * 展开折叠操作
         */
        flexLayout.post(new Runnable() {
            @Override
            public void run() {
                int measuredHeight = flexLayout.getMeasuredHeight();
                int itemHeight = flexLayout.getChildAt(0).getMeasuredHeight() + DisplayUtil.dip2px(getContext(),5);
                if (measuredHeight > itemHeight){//如果大于这个高度，则显示折叠
                    iv_toggle.setVisibility(View.VISIBLE);
                    showExpandView(isExpand,measuredHeight,itemHeight);
                    ll_tags.setOnClickListener(new OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            isExpand = !isExpand;
                            showExpandView(isExpand,measuredHeight,itemHeight);
                            if(listener!=null){
                                listener.onToggleClick(isExpand);//保持状态
                            }
                        }
                    });
                }else {//如果小于这个高度，则不显示折叠控件
                    iv_toggle.setVisibility(View.GONE);
                }
            }
        });
    }

    private void showExpandView(boolean isExpand,int measuredHeight,int itemHeight){
        ViewGroup.LayoutParams params = flexLayout.getLayoutParams();
        if(isExpand){
            params.height = measuredHeight;
            iv_toggle.setImageResource(R.mipmap.bq_shang);
        }else{
            params.height = itemHeight;
            iv_toggle.setImageResource(R.mipmap.bq_xia);
        }
        //调用requestLayout刷新布局
        flexLayout.requestLayout();
    }

    public interface ToggleListener{
        void onToggleClick(boolean isExpand);
    }
}

xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="@+id/ll_tags"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <com.google.android.flexbox.FlexboxLayout
        android:id="@+id/flexLayout"
        app:flexWrap="wrap"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content" />
    <ImageView
        android:id="@+id/iv_toggle"
        android:layout_width="23dp"
        android:layout_height="20dp"
        android:padding="8dp"
        android:visibility="gone"
        android:src="@mipmap/bq_xia"/>
</LinearLayout>

setData中先正常添加标签，添加完成，在view.post方法中去获取单个标签的高度（即单行的高度）和整个标签组的高度，二者比较来判断是否是多行，并且通过showExpandView来动态改变展开与收起。如果点击过收起展开，可以给一个接口回调在外层将对应位置以及对应位置item的标签组的展开/收起状态保存下来进行恢复。

但是这种写法有个问题，就是加载列表时有时候会让人感觉闪动了一下，因为先是挨个增加了标签，通过实际高度的判断之后再通过flexLayout.requestLayout();来重新布局的，多行标签时第一次加载会闪一下，暂时没有解决。