好久不写安卓相关的文章了，最近项目需要就做了一个recylerview和顶部导航栏联动，并且导航栏要有折叠效果，楼层效果，大体效果如下（手机录屏，分辨率不是很高）

1528945837537.gif

下面来讲解具体实现

一，先看布局文件

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <android.support.v7.widget.RecyclerView        android:id="@+id/rv_list"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_marginTop="50dp"/>    <com.example.qcl.demo.floorview.FloorView        android:id="@+id/widget_show_all_tabs"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:background="@color/colorWhite"        android:visibility="visible"/></RelativeLayout>

布局文件里用到了FloorView这个自定义控件。

二，来看自定义控件FloorView

package com.example.qcl.demo.floorview;import android.content.Context;import android.support.annotation.Nullable;import android.support.v7.widget.LinearSmoothScroller;import android.support.v7.widget.RecyclerView;import android.util.AttributeSet;import android.util.DisplayMetrics;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.TextView;import com.alibaba.android.vlayout.VirtualLayoutManager;import com.example.qcl.demo.R;import com.google.android.flexbox.FlexboxLayoutManager;import java.util.ArrayList;import java.util.List;public class FloorView extends LinearLayout {    private Context context;    private View widgetView;    private RecyclerView recyclerView;    MyAdapter myAdapter;    private boolean isArrowDown;    private ImageView ivArrow;    VirtualLayoutManager vLayoutManager;    private int selectNum = 0;    private List<String> listAll;    private List<String> listFirstLine;    public FloorView(Context context) {        this(context, null);    }    public FloorView(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, -1);    }    public FloorView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        this.context = context;        widgetView = inflate(context, R.layout.widget_indicator_floor_view, this);        initRecylerView();        initArrow();    }    private void initArrow() {        ivArrow = widgetView.findViewById(R.id.iv_arrow);        ivArrow.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                if (isArrowDown) {                } else {                }                isArrowDown = !isArrowDown;                setArrow(isArrowDown);            }        });    }    private void initRecylerView() {        recyclerView = widgetView.findViewById(R.id.rv_list);        //设置flexbox        FlexboxLayoutManager layoutManager = new FlexboxLayoutManager(context);        //        layoutManager.setFlexDirection(FlexDirection.ROW);        //        layoutManager.setJustifyContent(JustifyContent.FLEX_END);        recyclerView.setLayoutManager(layoutManager);        myAdapter = new MyAdapter();        recyclerView.setAdapter(myAdapter);    }    public void addDisplayItem(ArrayList<String> lists, int num) {        if (lists == null) {            return;        }        listAll = lists;        myAdapter.setSelectPosition(num);        if (lists.size() > 4) {            listFirstLine = lists.subList(0, 4);            ivArrow.setVisibility(View.VISIBLE);            setArrow(true);            myAdapter.setListData(listFirstLine);            myAdapter.notifyDataSetChanged();        } else {            ivArrow.setVisibility(View.GONE);            myAdapter.setListData(listAll);            myAdapter.notifyDataSetChanged();        }    }    //展开或者折叠的箭头    public void setArrow(boolean isDown) {        if (isDown) {            ivArrow.setImageResource(R.drawable.arrow_down);            myAdapter.setListData(listAll);            myAdapter.notifyDataSetChanged();        } else {            ivArrow.setImageResource(R.drawable.arrow_up);            myAdapter.setListData(listFirstLine);            myAdapter.notifyDataSetChanged();        }    }    public void setRecyclerView(RecyclerView outRecyclerView, VirtualLayoutManager            vLayoutManager2) {        this.vLayoutManager = vLayoutManager2;        outRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {            @Override            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {                super.onScrollStateChanged(recyclerView, newState);                int firstVisibleItemPosition = vLayoutManager.findFirstVisibleItemPosition();                myAdapter.setSelectPosition((firstVisibleItemPosition / 5) % 8);            }            @Override            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {                super.onScrolled(recyclerView, dx, dy);            }        });    }    public void selectPosition(int position) {        if (vLayoutManager == null) {            return;        }        LinearSmoothScroller smoothScroller = new LinearSmoothScroller                (context) {            @Override            protected int getVerticalSnapPreference() {                return LinearSmoothScroller.SNAP_TO_START;            }            //设置滑动1px所需时间            @Override            protected float calculateSpeedPerPixel            (DisplayMetrics displayMetrics) {                //缩短每px的滑动时间                float MILLISECONDS_PER_INCH = getResources().getDisplayMetrics()                        .density * 0.03f;                return MILLISECONDS_PER_INCH / displayMetrics.density;                //返回滑动一个pixel需要多少毫秒            }        };        smoothScroller.setTargetPosition(position * 5);        vLayoutManager.startSmoothScroll(smoothScroller);        myAdapter.setSelectPosition(position);    }    /**     * 用内部类来写adapter     */    public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {        private List<String> contents;        public void setListData(List<String> lists) {            this.contents = lists;        }        public void setSelectPosition(int num) {            selectNum = num;            notifyDataSetChanged();        }        //创建新View，被LayoutManager所调用        @Override        public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {            View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.item_floor, viewGroup, false);            ViewHolder vh = new ViewHolder(view);            return vh;        }        //将数据与界面进行绑定的操作        @Override        public void onBindViewHolder(ViewHolder viewHolder, final int position) {            viewHolder.mTextView.setText(contents.get(position));            if (selectNum == position) {                viewHolder.mTextView.setBackgroundResource(R.drawable.shape_show_all_indicator_rectangle_active);                viewHolder.mTextView.setTextColor(0xff12CFC9);            } else {                viewHolder.mTextView.setBackgroundResource(R.drawable.shape_show_all_indicator_rectangle);                viewHolder.mTextView.setTextColor(0xff666666);            }            viewHolder.mTextView.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    setSelectPosition(position);                    selectPosition(position);                }            });        }        //获取数据的数量        @Override        public int getItemCount() {            return contents.size();        }        //自定义的ViewHolder，持有每个Item的的所有界面元素        class ViewHolder extends RecyclerView.ViewHolder {            TextView mTextView;            ViewHolder(View view) {                super(view);                mTextView = view.findViewById(R.id.tv);            }        }    }}

是不是感觉代码挺多的，其实原理很简单

• 1，FlexboxLayoutManager+ RecyclerView实现流式布局
• 2，RecyclerView的MyAdapter来实现折叠或者展开效果

//展开或者折叠的箭头    public void setArrow(boolean isDown) {        if (isDown) {            ivArrow.setImageResource(R.drawable.arrow_down);            myAdapter.setListData(listAll);            myAdapter.notifyDataSetChanged();        } else {            ivArrow.setImageResource(R.drawable.arrow_up);            myAdapter.setListData(listFirstLine);            myAdapter.notifyDataSetChanged();        }    }

通过往myAdapter里传入第一行4个数据，或者传入全部数据来实现折叠和展开。

三，列表和导航栏联动

 outRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {            @Override            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {                super.onScrollStateChanged(recyclerView, newState);                int firstVisibleItemPosition = vLayoutManager.findFirstVisibleItemPosition();                myAdapter.setSelectPosition((firstVisibleItemPosition / 5) % 8);            }            @Override            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {                super.onScrolled(recyclerView, dx, dy);            }        });

主要通过监听RecyclerView的第一个可见条目的位置来实现导航栏的跟随选中

四，点击导航栏实现列表锚点

LinearSmoothScroller smoothScroller = new LinearSmoothScroller                (context) {            @Override            protected int getVerticalSnapPreference() {                return LinearSmoothScroller.SNAP_TO_START;            }            //设置滑动1px所需时间            @Override            protected float calculateSpeedPerPixel            (DisplayMetrics displayMetrics) {                //缩短每px的滑动时间                float MILLISECONDS_PER_INCH = getResources().getDisplayMetrics()                        .density * 0.03f;                return MILLISECONDS_PER_INCH / displayMetrics.density;                //返回滑动一个pixel需要多少毫秒            }        };        smoothScroller.setTargetPosition(position * 5);

源码地址：https://github.com/qiushi123/demo3
我的demo项目里是一个合集

demo合集.png

原著是一个有趣的人,若有侵权,请通知删除