粘性头部+流式布局

image.png

1.依赖

//    侧滑菜单、TabLayout
    implementation 'com.android.support:design:28.0.0'
    //粘性头部/悬浮头部
    implementation 'com.github.qdxxxx:StickyHeaderDecoration:1.0.1'

2.在 Project 的 build.gradle 文件里

allprojects {
        repositories {
            ...
            maven { url 'https://jitpack.io' }
        }
}

3.3、Activity 中

  private void initData() {
        mCars = new ArrayList<>();
        mCars.add(new Car("奥迪",  "A"));
        mCars.add(new Car("阿尔法罗密欧",  "A"));
        mCars.add(new Car("阿斯顿马丁",  "A"));
        mCars.add(new Car("ALPINA",  "A"));
        mCars.add(new Car("安凯客车",  "A"));


        mCars.add(new Car("本田", "B"));
        mCars.add(new Car("别克", "B"));
        mCars.add(new Car("奔驰",  "B"));
        mCars.add(new Car("宝马", "B"));
        mCars.add(new Car("保时捷",  "B"));
        mCars.add(new Car("比亚迪", "B"));
        mCars.add(new Car("北京", "B"));
        mCars.add(new Car("宾利",  "B"));
        mCars.add(new Car("巴博斯",  "B"));
        mCars.add(new Car("布加迪威龙", "B"));

        mCars.add(new Car("长安", "C"));
        mCars.add(new Car("长城",  "C"));

        mCars.add(new Car("大众", "D"));
        mCars.add(new Car("东南",  "D"));
        mCars.add(new Car("东风", "D"));
        mCars.add(new Car("DS", "D"));
        mCars.add(new Car("道奇", "D"));
        mCars.add(new Car("东风小康", "D"));

    }

    private void initView() {
        final LayoutInflater inflater = LayoutInflater.from(this);
        mRlv = (RecyclerView) findViewById(R.id.rlv);
        mRlv.setLayoutManager(new LinearLayoutManager(this));
        RlvAdapter rlvAdapter = new RlvAdapter(mCars);
        //返回头布局的内容
        final NormalDecoration decoration = new NormalDecoration() {
            @Override
            public String getHeaderName(int i) {
                return mCars.get(i).headerName;
            }
        };
        //自定义头布局,可不设置
        decoration.setOnDecorationHeadDraw(new NormalDecoration.OnDecorationHeadDraw() {
            @Override
            public View getHeaderView(final int i) {
                View inflate = inflater.inflate(R.layout.item_header, null);
                TextView tv = inflate.findViewById(R.id.tv);
                tv.setText(mCars.get(i).headerName);

                return inflate;
            }
        });
        mRlv.addItemDecoration(decoration);
        //头布局的点击事件
        decoration.setOnHeaderClickListener(new NormalDecoration.OnHeaderClickListener() {
            @Override
            public void headerClick(int i) {
                Toast.makeText(MainActivity.this, mCars.get(i).headerName, Toast.LENGTH_SHORT).show();
                startActivity(new Intent(MainActivity.this,FlowActivity.class));
            }
        });
        mRlv.setAdapter(rlvAdapter);
    }

4.粘性头部相当于是RecyclerView中两个条目之间的分割线，在数据如下情况下就可以使用粘性头部

import java.util.ArrayList;

public class NodeBean {
    String header;
    ArrayList<String> list;

    public NodeBean() {
    }

    public NodeBean(String header, ArrayList<String> list) {
        this.header = header;
        this.list = list;
    }

    public String getHeader() {

        return header;
    }

    public void setHeader(String header) {
        this.header = header;
    }

    public ArrayList<String> getList() {
        return list;
    }

    public void setList(ArrayList<String> list) {
        this.list = list;
    }
}

5.如果item条目中是简短的String类型的数据的时候还可以使用流式布局

image.png

流式布局里的内容就是每一个粘性头部下的数据放到了一起

1.FlowLayout（自定义View，直接复制就可以，在RecyclerView的item布局里引用就可以）

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

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

public class FlowLayout extends ViewGroup {

    private List<Line> mLines   = new ArrayList<Line>(); // 用来记录描述有多少行View
    private Line        mCurrrenLine;   // 用来记录当前已经添加到了哪一行
    private int         mHorizontalSpace    = 40;
    private int         mVerticalSpace      = mHorizontalSpace;
    private int mMaxLines = -1;

    public int getMaxLines() {
        return mMaxLines;
    }

    public void setMaxLines(int maxLines) {
        mMaxLines = maxLines;
    }

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

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

    public void setSpace(int horizontalSpace, int verticalSpace) {
        this.mHorizontalSpace = horizontalSpace;
        this.mVerticalSpace = verticalSpace;
    }

    public void clearAll(){
        mLines.clear();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // 清空
        mLines.clear();
        mCurrrenLine = null;

        int layoutWidth = MeasureSpec.getSize(widthMeasureSpec);

        // 获取行最大的宽度
        int maxLineWidth = layoutWidth - getPaddingLeft() - getPaddingRight();

        // 测量孩子
        int count = getChildCount();
        for (int i = 0; i < count; i++)
        {
            View view = getChildAt(i);

            // 如果孩子不可见
            if (view.getVisibility() == View.GONE)
            {
                continue;
            }

            // 测量孩子
            measureChild(view, widthMeasureSpec, heightMeasureSpec);

            // 往lines添加孩子
            if (mCurrrenLine == null)
            {
                // 说明还没有开始添加孩子
                mCurrrenLine = new Line(maxLineWidth, mHorizontalSpace);

                // 添加到 Lines中
                mLines.add(mCurrrenLine);

                // 行中一个孩子都没有
                mCurrrenLine.addView(view);
            }
            else
            {
                // 行不为空,行中有孩子了
                boolean canAdd = mCurrrenLine.canAdd(view);
                if (canAdd) {
                    // 可以添加
                    mCurrrenLine.addView(view);
                }
                else {
                    // 不可以添加,装不下去
                    // 换行
                    if (mMaxLines >0){
                        if (mLines.size()<mMaxLines){
                            // 新建行
                            mCurrrenLine = new Line(maxLineWidth, mHorizontalSpace);
                            // 添加到lines中
                            mLines.add(mCurrrenLine);
                            // 将view添加到line
                            mCurrrenLine.addView(view);
                        }
                    }else {
                        // 新建行
                        mCurrrenLine = new Line(maxLineWidth, mHorizontalSpace);
                        // 添加到lines中
                        mLines.add(mCurrrenLine);
                        // 将view添加到line
                        mCurrrenLine.addView(view);
                    }
                }
            }
        }

        // 设置自己的宽度和高度
        int measuredWidth = layoutWidth;
        // paddingTop + paddingBottom + 所有的行间距 + 所有的行的高度

        float allHeight = 0;
        for (int i = 0; i < mLines.size(); i++)
        {
            float mHeigth = mLines.get(i).mHeigth;

            // 加行高
            allHeight += mHeigth;
            // 加间距
            if (i != 0)
            {
                allHeight += mVerticalSpace;
            }
        }

        int measuredHeight = (int) (allHeight + getPaddingTop() + getPaddingBottom() + 0.5f);
        setMeasuredDimension(measuredWidth, measuredHeight);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        // 给Child 布局---> 给Line布局

        int paddingLeft = getPaddingLeft();
        int offsetTop = getPaddingTop();
        for (int i = 0; i < mLines.size(); i++)
        {
            Line line = mLines.get(i);

            // 给行布局
            line.layout(paddingLeft, offsetTop);

            offsetTop += line.mHeigth + mVerticalSpace;
        }
    }

    class Line
    {
        // 属性
        private List<View>  mViews  = new ArrayList<View>();    // 用来记录每一行有几个View
        private float       mMaxWidth;                          // 行最大的宽度
        private float       mUsedWidth;                     // 已经使用了多少宽度
        private float       mHeigth;                            // 行的高度
        private float       mMarginLeft;
        private float       mMarginRight;
        private float       mMarginTop;
        private float       mMarginBottom;
        private float       mHorizontalSpace;                   // View和view之间的水平间距

        // 构造
        public Line(int maxWidth, int horizontalSpace) {
            this.mMaxWidth = maxWidth;
            this.mHorizontalSpace = horizontalSpace;
        }

        // 方法
        /**
         * 添加view，记录属性的变化
         * 
         * @param view
         */
        public void addView(View view)
        {
            // 加载View的方法

            int size = mViews.size();
            int viewWidth = view.getMeasuredWidth();
            int viewHeight = view.getMeasuredHeight();
            // 计算宽和高
            if (size == 0)
            {
                // 说还没有添加View
                if (viewWidth > mMaxWidth)
                {
                    mUsedWidth = mMaxWidth;
                }
                else
                {
                    mUsedWidth = viewWidth;
                }
                mHeigth = viewHeight;
            }
            else
            {
                // 多个view的情况
                mUsedWidth += viewWidth + mHorizontalSpace;
                mHeigth = mHeigth < viewHeight ? viewHeight : mHeigth;
            }

            // 将View记录到集合中
            mViews.add(view);
        }

        /**
         * 用来判断是否可以将View添加到line中
         * 
         * @param view
         * @return
         */
        public boolean canAdd(View view)
        {
            // 判断是否能添加View

            int size = mViews.size();

            if (size == 0) { return true; }

            int viewWidth = view.getMeasuredWidth();

            // 预计使用的宽度
            float planWidth = mUsedWidth + mHorizontalSpace + viewWidth;

            if (planWidth > mMaxWidth)
            {
                // 加不进去
                return false;
            }

            return true;
        }

        /**
         * 给孩子布局
         * 
         * @param offsetLeft
         * @param offsetTop
         */
        public void layout(int offsetLeft, int offsetTop)
        {
            // 给孩子布局

            int currentLeft = offsetLeft;

            int size = mViews.size();
            // 判断已经使用的宽度是否小于最大的宽度
            float extra = 0;
            float widthAvg = 0;
            if (mMaxWidth > mUsedWidth)
            {
                extra = mMaxWidth - mUsedWidth;
                widthAvg = extra / size;
            }

            for (int i = 0; i < size; i++)
            {
                View view = mViews.get(i);
                int viewWidth = view.getMeasuredWidth();
                int viewHeight = view.getMeasuredHeight();

                // 判断是否有富余
                if (widthAvg != 0)
                {
                    // 改变宽度,变为不改变,避免最后一行因label不足,单个label变宽
                    //int newWidth = (int) (viewWidth + widthAvg + 0.5f);
                    int newWidth = viewWidth;
                    int widthMeasureSpec = MeasureSpec.makeMeasureSpec(newWidth, MeasureSpec.EXACTLY);
                    int heightMeasureSpec = MeasureSpec.makeMeasureSpec(viewHeight, MeasureSpec.EXACTLY);
                    view.measure(widthMeasureSpec, heightMeasureSpec);

                    viewWidth = view.getMeasuredWidth();
                    viewHeight = view.getMeasuredHeight();
                }

                // 布局
                int left = currentLeft;
                int top = (int) (offsetTop + (mHeigth - viewHeight) / 2 +
                            0.5f);
                // int top = offsetTop;
                int right = left + viewWidth;
                int bottom = top + viewHeight;
                view.layout(left, top, right, bottom);

                currentLeft += viewWidth + mHorizontalSpace;
            }
        }
    }

}

2.RecyclerView的item布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.example.lenovo.day04.widget.FlowLayout
        android:id="@+id/fl"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </com.example.lenovo.day04.widget.FlowLayout>

</LinearLayout>

3.在RecyclerView的适配器的onBindViewHolder()方法里

NodeBean 就是上面提到的数据的 bean 类

@Override
  public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {

      NodeBean nodeBean = recyclerviewList.get(i);

      ArrayList<String> list = nodeBean.getList();
      // 清空 fl 里的数据，不然会把其他集合里的数据添加进来
      viewHolder.fl.removeAllViews();
      for (int j = 0; j < list.size(); j++) {
          //获取视图,视图可以自定义,可以添加自己想要的效果
          TextView label = (TextView) View.inflate(context, R.layout.item_label, null);
          //获取数据
          final String data = list.get(j);
          //绑定数据
          label.setText(data);
          
          // 监听方法
          label.setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  
              }
          });

          //加到容器中,parent是FlowLayout
          viewHolder.fl.addView(label);
      }

  }