Android recyclerview字母索引

implementation 'com.github.SilenceDut:jpinyin:v1.0'

public class FastIndexView extends View {

    private static final String INDEX_NAME = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private OnLetterUpdateListener listener;
    private Paint mPaint;
    private float cellHeight, viewWidth;
    private int touchIndex = -1, selectedColor;

    public FastIndexView(Context context) {
        this(context, null);
    }

    public FastIndexView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public FastIndexView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setTextSize(AppUtils.dp2px(14));
        mPaint.setAntiAlias(true);
        //获取文字被选中的颜色
//        selectedColor = ContextCompat.getColor(context, );
        selectedColor = Color.parseColor("#999DA1");
    }

    @Override
    protected void onDraw(Canvas canvas) {
        for (int i = 0; i < INDEX_NAME.length(); i++) {
            String text = INDEX_NAME.substring(i, i + 1);
            //计算绘制字符的X方向起点
            int x = (int) (viewWidth / 2.0f - mPaint.measureText(text) / 2.0f);
            Rect bounds = new Rect();
            mPaint.getTextBounds(text, 0, text.length(), bounds);
            int textHeight = bounds.height();
            //计算绘制字符的Y方向起点
            int y = (int) (cellHeight / 2.0f + textHeight / 2.0f + i
                    * cellHeight);
            mPaint.setColor(/*touchIndex == i ? Color.WHITE : */selectedColor);
            canvas.drawText(text, x, y, mPaint);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        int index;
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                //计算当前触摸的字符索引
                index = (int) (event.getY() / cellHeight);
                if (index >= 0 && index < INDEX_NAME.length()) {
                    if (listener != null) {
                        listener.onLetterUpdate(INDEX_NAME.substring(index, index + 1));
                    }
                    touchIndex = index;
                }
                break;
            case MotionEvent.ACTION_MOVE:
                //计算当前触摸的字符索引
                index = (int) (event.getY() / cellHeight);
                if (index >= 0 && index < INDEX_NAME.length()) {
                    if (index != touchIndex) {
                        if (listener != null) {
                            listener.onLetterUpdate(INDEX_NAME.substring(index, index + 1));
                        }
                        touchIndex = index;
                    }
                }
                break;
        }
        invalidate();
        return true;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        //得到当前控件的宽度
        viewWidth = getMeasuredWidth();
        int mHeight = getMeasuredHeight();
        //获取单个字符能够拥有的高度
        cellHeight = mHeight * 1.0f / INDEX_NAME.length();
    }

    public interface OnLetterUpdateListener {
        void onLetterUpdate(String letter);
    }

    public void setListener(OnLetterUpdateListener listener) {
        this.listener = listener;
    }

}

public class AppUtils {

    private static float density;

    /**
     * 根据手机的分辨率从 dp 的单位 转成为 px(像素)
     */
    public static int dp2px(float dpValue) {
        if (density == 0)
            density = Resources.getSystem().getDisplayMetrics().density;
        return (int) (0.5f + dpValue * Resources.getSystem().getDisplayMetrics().density);
    }


}

public class CityAdapter extends RecyclerView.Adapter<CityAdapter.BaseViewHolder> {

    private List<CityInfoModel> mDatas;
    private Context mContext;



    public CityAdapter(Context context, List<CityInfoModel> data) {
        this.mDatas = data;
        this.mContext = context;
    }

    @Override
    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //创建不同的 ViewHolder
        View view = null;
        //根据viewtype来创建条目
        view = LayoutInflater.from(mContext).inflate(R.layout.item_layout_normal, parent, false);
        return new NormalHolder(view);

    }

    @Override
    public void onBindViewHolder(BaseViewHolder holder, final int position) {
        CityInfoModel cityInfoModel = mDatas.get(position);
        NormalHolder realHolder = (NormalHolder) holder;
        realHolder.tvContent.setText(cityInfoModel.getCityName());
        realHolder.tvContent.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
    }

    static class BaseViewHolder extends RecyclerView.ViewHolder {
        BaseViewHolder(View itemView) {
            super(itemView);
        }
    }

    @Override
    public int getItemCount() {
        if (mDatas != null) {
            return mDatas.size();
        }
        return 0;
    }


    private class NormalHolder extends BaseViewHolder {
        TextView tvContent;

        public NormalHolder(View itemView) {
            super(itemView);
            tvContent = itemView.findViewById(R.id.tv_city);
        }
    }

}

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.recy_list)
    RecyclerView recyList;
    @BindView(R.id.fastIndexView)
    FastIndexView fastIndexView;
    //主要用于展示数据的list
    private List<CityInfoModel> list;
    //第一次加载之后缓存的数据
    private List<CityInfoModel> cacheList;

    //页面recyclerview的适配器
    private CityAdapter mainAdapter;
    //布局管理器
    private LinearLayoutManager layoutManager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        initAdapter();

        initListener();
    }

    private void initAdapter() {
        list = new ArrayList<>();
        cacheList = new ArrayList<>();
        list.add(new CityInfoModel("安徽省"));
        list.add(new CityInfoModel("北京市"));
        list.add(new CityInfoModel("上海市"));
        list.add(new CityInfoModel("广州市"));
        list.add(new CityInfoModel("深圳市"));
        list.add(new CityInfoModel("天津市"));
        list.add(new CityInfoModel("南京市"));
        list.add(new CityInfoModel("杭州市"));
        list.add(new CityInfoModel("重庆市"));
        list.add(new CityInfoModel("成都市"));
        list.add(new CityInfoModel("石家庄市"));
        list.add(new CityInfoModel("自贡市"));
        list.add(new CityInfoModel("攀枝花市"));
        list.add(new CityInfoModel("泸州市"));
        list.add(new CityInfoModel("德阳市"));
        list.add(new CityInfoModel("绵阳市"));
        list.add(new CityInfoModel("广元市"));
        list.add(new CityInfoModel("遂宁市"));
        List<CityInfoModel> cityInfoModels = bindData(list);
        layoutManager = new LinearLayoutManager(this);
        recyList.setLayoutManager(layoutManager);
        recyList.addItemDecoration(new CustomItemDecoration(this, new CustomItemDecoration.TitleDecorationCallback() {
            @Override
            public String getGroupId(int position) {
                //这个是用来比较是否是同一组数据的
                return list.get(position).getSortId();
            }

            @Override
            public String getGroupName(int position) {
                CityInfoModel cityInfoModel = list.get(position);
                //拼音都是小写的
                return cityInfoModel.getSortId().toUpperCase();
            }
        }));
        mainAdapter = new CityAdapter(this, cityInfoModels);
        recyList.setAdapter(mainAdapter);
    }

    private void initListener() {
        fastIndexView.setListener(new FastIndexView.OnLetterUpdateListener() {
            @Override
            public void onLetterUpdate(String letter) {
                moveToLetterPosition(letter);
            }
        });
    }

    //滚动recyclerview
    private void moveToLetterPosition(String letter) {
        //这里主要是为了跳转到最顶端
        if ("#".equals(letter)) {
            letter = "*";
        }
        for (int i = 0; i < list.size(); i++) {
            CityInfoModel cityInfoModel = list.get(i);
            if (cityInfoModel.getSortId().toUpperCase().equals(letter)) {
                layoutManager.scrollToPositionWithOffset(i, 0);
                return;
            }
        }
    }

    /**
     * 给View绑定数据
     *
     * @param allCity 所有城市列表
     */
    public List<CityInfoModel> bindData(List<CityInfoModel> allCity) {
        if (allCity != null) {
            for (CityInfoModel cityModel : allCity) {
                try {
                    String pingYin = PinyinHelper.convertToPinyinString(cityModel.getCityName(), " ", PinyinFormat.WITHOUT_TONE);
                    cacheList.add(new CityInfoModel(cityModel.getCityName(), pingYin.substring(0, 1), pingYin));
                } catch (PinyinException e) {
                    e.printStackTrace();
                }
            }
            //排序
            Collections.sort(cacheList, new Comparator<CityInfoModel>() {
                @Override
                public int compare(CityInfoModel o1, CityInfoModel o2) {
                    return o1.getSortName().compareTo(o2.getSortName());
                }
            });
            this.list.clear();
            this.list.addAll(cacheList);
        }
        return list;
    }

}

public class CityInfoModel {

    private String cityName;//用于显示的城市的名字
    private String sortId;//用于排序的id 在这里是城市拼音的首字母
    private String sortName;//用于排序的全拼音 这个是用于后面的排序以及搜索

    public CityInfoModel(String cityName) {
        this.cityName = cityName;
    }

    public CityInfoModel(String cityName, String sortId, String sortName) {
        this.cityName = cityName;
        this.sortId = sortId;
        this.sortName = sortName;
    }

    public String getCityName() {
        return cityName;
    }

    public void setCityName(String cityName) {
        this.cityName = cityName;
    }

    public String getSortId() {
        return sortId;
    }

    public void setSortId(String sortId) {
        this.sortId = sortId;
    }

    public String getSortName() {
        return sortName;
    }

    public void setSortName(String sortName) {
        this.sortName = sortName;
    }
}

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

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recy_list"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1" />

    <com.simin.indexrecyclerview.FastIndexView
        android:id="@+id/fastIndexView"
        android:layout_width="25dp"
        android:layout_height="match_parent"
        app:layout_constraintHeight_percent="0.7" />
</LinearLayout>