RecycleView打造悬浮 吸顶效果

先上效果

导入依赖

implementation 'com.android.support:recyclerview-v7:28.0.0'
implementation 'com.gavin.com.library:stickyDecoration:1.1.0'

这是一个bean 类

public class City {
    private String name;    //城市名
    private String province;    //所属省份
    private int icon;    //所属省份

    public City(String name, String province, int icon) {
        this.name = name;
        this.province = province;
        this.icon = icon;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public int getIcon() {
        return icon;
    }

    public void setIcon(int icon) {
        this.icon = icon;
    }
}

这是一个方法 用来得到要展示的数据

public class CityUtil {
    /**
     * 获取城市名
     *
     * @return
     */
    public static List getCityList() {
        List dataList = new ArrayList<>();
        final String FU_JIAN = "福建省";
        final int FU_JIAN_ICON = 1;
        dataList.add(new City("福州", FU_JIAN, FU_JIAN_ICON));
        dataList.add(new City("厦门", FU_JIAN, FU_JIAN_ICON));
        dataList.add(new City("泉州", FU_JIAN, FU_JIAN_ICON));
        dataList.add(new City("宁德", FU_JIAN, FU_JIAN_ICON));
        dataList.add(new City("漳州", FU_JIAN, FU_JIAN_ICON));
        final String AN_HUI = "安徽省";
        final int AN_HUI_ICON = 2;
        dataList.add(new City("合肥", AN_HUI, AN_HUI_ICON));
        dataList.add(new City("芜湖", AN_HUI, AN_HUI_ICON));
        dataList.add(new City("蚌埠", AN_HUI, AN_HUI_ICON));
        final String ZHE_JIANG = "浙江省";
        final int ZHE_JIANG_ICON = 3;
        dataList.add(new City("杭州", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("宁波", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("温州", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("嘉兴", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("绍兴", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("金华", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("湖州", ZHE_JIANG, ZHE_JIANG_ICON));
        dataList.add(new City("舟山", ZHE_JIANG, ZHE_JIANG_ICON));
        final String JIANG_SU = "江苏省";
        final int JIANG_SU_ICOM = 4;
        dataList.add(new City("南京", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("苏州", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("徐州", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("南通", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("无锡", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("盐城", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("淮安", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("泰州", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("常州", JIANG_SU, JIANG_SU_ICOM));
        dataList.add(new City("连云港", JIANG_SU, JIANG_SU_ICOM));
        return dataList;
    }
}

这是一个DensityUtil 类

public class DensityUtil {
    /**
     * 获得屏幕宽度
     *
     * @param context
     * @return
     */
    public static int getScreenWidth(Context context) {
        WindowManager wm = (WindowManager) context
                .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(outMetrics);
        return outMetrics.widthPixels;
    }

    /**
     * 获得屏幕宽度
     *
     * @param context
     * @return
     */
    public static int getScreenHeight(Context context) {
        WindowManager wm = (WindowManager) context
                .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(outMetrics);
        return outMetrics.heightPixels;
    }

    /**
     * 根据手机的分辨率从 dp 的单位 转成为 px(像素)
     */
    public static int dip2px(Context context, float dpValue) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }

    /**
     * 根据手机的分辨率从 px(像素) 的单位 转成为 dp
     */
    public static int px2dip(Context context, float pxValue) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (pxValue / scale + 0.5f);
    }

    // 将px值转换为sp值，保证文字大小不变
    public static int px2sp(Context context, float pxValue) {
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (pxValue / fontScale + 0.5f);
    }

    // 将sp值转换为px值，保证文字大小不变
    public static int sp2px(Context context, float spValue) {
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (spValue * fontScale + 0.5f);
    }
}

这是MainActivity的代码

public class MainActivity extends AppCompatActivity {

    RecyclerView.Adapter mAdapter;
    List dataList = new ArrayList<>();
    private RecyclerView mRecyclerView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }

    private void initView() {
        mRecyclerView = (RecyclerView) findViewById(R.id.rv);
        //模拟数据
        dataList.addAll(CityUtil.getCityList());
        dataList.addAll(CityUtil.getCityList());

        LinearLayoutManager manager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        mRecyclerView.setLayoutManager(manager);
        //使用StickyDecoration
        StickyDecoration decoration = StickyDecoration.Builder
                .init(new GroupListener() {
                    @Override
                    public String getGroupName(int position) {
                        //组名回调
                        if (dataList.size() > position) {
                            //获取城市对应的省份
                            return dataList.get(position).getProvince();
                        }
                        return null;
                    }
                })
                .setGroupBackground(Color.parseColor("#48BDFF"))    //背景色
                .setGroupHeight(DensityUtil.dip2px(this, 35))       //高度
                .setDivideColor(Color.parseColor("#CCCCCC"))        //分割线颜色
                .setDivideHeight(DensityUtil.dip2px(this, 1))       //分割线高度 (默认没有分割线)
                .setGroupTextColor(Color.WHITE)                     //字体颜色
                .setGroupTextSize(DensityUtil.sp2px(this, 15))      //字体大小
                .setTextSideMargin(DensityUtil.dip2px(this, 10))    // 边距   靠左时为左边距  靠右时为右边距
                .isAlignLeft(false)                                 //靠右显示  （默认靠左）
                .build();
        mRecyclerView.addItemDecoration(decoration);

        mAdapter = new RecyclerView.Adapter() {
            @Override
            public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_recycler_view, parent, false);
                return new Holder(view);
            }

            @Override
            public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
                Holder holder = (Holder) viewHolder;
                holder.mTextView.setText(dataList.get(position).getName());
            }

            @Override
            public int getItemCount() {
                return dataList.size();
            }
        };
        mRecyclerView.setAdapter(mAdapter);
    }

    static class Holder extends RecyclerView.ViewHolder {
        TextView mTextView;

        public Holder(View itemView) {
            super(itemView);
            mTextView =itemView.findViewById(R.id.tv);
        }
    }
}

mainactivity 的布局

item_recycle_view的布局