实现联系人功能，右侧A~Z滑动

先上效果图

1.需要字Build中引用

//将文字转化为汉语拼音
implementation 'com.belerweb:pinyin4j:2.5.1'
implementation 'com.android.support:recyclerview-v7:28.0.0'

2.创建 Cn2Spell 类

/**
 * 汉字转换位汉语拼音，英文字符不变
 */
public class Cn2Spell {

    public static StringBuffer sb = new StringBuffer();

    /**
     * 获取汉字字符串的首字母，英文字符不变
     * 例如：阿飞→af
     */
    public static String getPinYinHeadChar(String chines) {
        sb.setLength(0);
        char[] chars = chines.toCharArray();
        HanyuPinyinOutputFormat defaultFormat = new HanyuPinyinOutputFormat();
        defaultFormat.setCaseType(HanyuPinyinCaseType.LOWERCASE);
        defaultFormat.setToneType(HanyuPinyinToneType.WITHOUT_TONE);
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] > 128) {
                try {
                    sb.append(PinyinHelper.toHanyuPinyinStringArray(chars[i], defaultFormat)[0].charAt(0));
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                sb.append(chars[i]);
            }
        }
        return sb.toString();
    }

    /**
     * 获取汉字字符串的第一个字母
     */
    public static String getPinYinFirstLetter(String str) {
        sb.setLength(0);
        char c = str.charAt(0);
        String[] pinyinArray = PinyinHelper.toHanyuPinyinStringArray(c);
        if (pinyinArray != null) {
            sb.append(pinyinArray[0].charAt(0));
        } else {
            sb.append(c);
        }
        return sb.toString();
    }

    /**
     * 获取汉字字符串的汉语拼音，英文字符不变
     */
    public static String getPinYin(String chines) {
        sb.setLength(0);
        char[] nameChar = chines.toCharArray();
        HanyuPinyinOutputFormat defaultFormat = new HanyuPinyinOutputFormat();
        defaultFormat.setCaseType(HanyuPinyinCaseType.LOWERCASE);
        defaultFormat.setToneType(HanyuPinyinToneType.WITHOUT_TONE);
        for (int i = 0; i < nameChar.length; i++) {
            if (nameChar[i] > 128) {
                try {
                    sb.append(PinyinHelper.toHanyuPinyinStringArray(nameChar[i], defaultFormat)[0]);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                sb.append(nameChar[i]);
            }
        }
        return sb.toString();
    }

}

3.创建右侧  SideBar 类

public class SideBar extends TextView {
    private String[] letters = new String[]{"A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z", "#"};
    private Paint textPaint;
    private Paint bigTextPaint;
    private Paint scaleTextPaint;

    private Canvas canvas;
    private int itemH;
    private int w;
    private int h;
    /**
     * 普通情况下字体大小
     */
    float singleTextH;
    /**
     * 缩放离原始的宽度
     */
    private float scaleWidth;
    /**
     * 滑动的Y
     */
    private float eventY = 0;
    /**
     * 缩放的倍数
     */
    private int scaleSize = 1;
    /**
     * 缩放个数item，即开口大小
     */
    private int scaleItemCount = 6;
    private ISideBarSelectCallBack callBack;

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

    public SideBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public SideBar(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(attrs);
    }

    private void init(AttributeSet attrs) {
        if (attrs != null) {
            TypedArray ta = getContext().obtainStyledAttributes(attrs, R.styleable.SideBar);
            scaleSize = ta.getInteger(R.styleable.SideBar_scaleSize, 1);
            scaleItemCount = ta.getInteger(R.styleable.SideBar_scaleItemCount, 6);
            scaleWidth = ta.getDimensionPixelSize(R.styleable.SideBar_scaleWidth, dp(100));
            ta.recycle();
        }
        textPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        textPaint.setColor(getCurrentTextColor());
        textPaint.setTextSize(getTextSize());
        textPaint.setTextAlign(Paint.Align.CENTER);
        bigTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        bigTextPaint.setColor(getCurrentTextColor());
        bigTextPaint.setTextSize(getTextSize() * (scaleSize + 3));
        bigTextPaint.setTextAlign(Paint.Align.CENTER);
        scaleTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        scaleTextPaint.setColor(getCurrentTextColor());
        scaleTextPaint.setTextSize(getTextSize() * (scaleSize + 1));
        scaleTextPaint.setTextAlign(Paint.Align.CENTER);
    }

    public void setDataResource(String[] data) {
        letters = data;
        invalidate();
    }

    public void setOnStrSelectCallBack(ISideBarSelectCallBack callBack) {
        this.callBack = callBack;
    }

    /**
     * 设置字体缩放比例
     *
     * @param scale
     */
    public void setScaleSize(int scale) {
        scaleSize = scale;
        invalidate();
    }

    /**
     * 设置缩放字体的个数，即开口大小
     *
     * @param scaleItemCount
     */
    public void setScaleItemCount(int scaleItemCount) {
        this.scaleItemCount = scaleItemCount;
        invalidate();
    }

    private int dp(int px) {
        final float scale = getContext().getResources().getDisplayMetrics().density;
        return (int) (px * scale + 0.5f);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                if (event.getX() > (w - getPaddingRight() - singleTextH - 10)) {
                    eventY = event.getY();
                    invalidate();
                    return true;
                } else {
                    eventY = 0;
                    invalidate();
                    break;
                }
            case MotionEvent.ACTION_CANCEL:
                eventY = 0;
                invalidate();
                return true;
            case MotionEvent.ACTION_UP:
                if (event.getX() > (w - getPaddingRight() - singleTextH - 10)) {
                    eventY = 0;
                    invalidate();
                    return true;
                } else
                    break;
        }
        return super.onTouchEvent(event);
    }


    @Override
    protected void onDraw(Canvas canvas) {
        this.canvas = canvas;
        DrawView(eventY);
    }

    private void DrawView(float y) {
        int currentSelectIndex = -1;
        if (y != 0) {
            for (int i = 0; i < letters.length; i++) {
                float currentItemY = itemH * i;
                float nextItemY = itemH * (i + 1);
                if (y >= currentItemY && y < nextItemY) {
                    currentSelectIndex = i;
                    if (callBack != null) {
                        callBack.onSelectStr(currentSelectIndex, letters[i]);
                    }
                    //画大的字母
                    Paint.FontMetrics fontMetrics = bigTextPaint.getFontMetrics();
                    float bigTextSize = fontMetrics.descent - fontMetrics.ascent;
                    canvas.drawText(letters[i], w - getPaddingRight() - scaleWidth - bigTextSize, singleTextH + itemH * i, bigTextPaint);
                }
            }
        }
        drawLetters(y, currentSelectIndex);
    }

    private void drawLetters(float y, int index) {
        //第一次进来没有缩放情况，默认画原图
        if (index == -1) {
            w = getMeasuredWidth();
            h = getMeasuredHeight();
            itemH = h / letters.length;
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            singleTextH = fontMetrics.descent - fontMetrics.ascent;
            for (int i = 0; i < letters.length; i++) {
                canvas.drawText(letters[i], w - getPaddingRight(), singleTextH + itemH * i, textPaint);
            }
            //触摸的时候画缩放图
        } else {
            //遍历所有字母
            for (int i = 0; i < letters.length; i++) {
                //要画的字母的起始Y坐标
                float currentItemToDrawY = singleTextH + itemH * i;
                float centerItemToDrawY;
                if (index < i)
                    centerItemToDrawY = singleTextH + itemH * (index + scaleItemCount);
                else
                    centerItemToDrawY = singleTextH + itemH * (index - scaleItemCount);
                float delta = 1 - Math.abs((y - currentItemToDrawY) / (centerItemToDrawY - currentItemToDrawY));
                float maxRightX = w - getPaddingRight();
                //如果大于0，表明在y坐标上方
                scaleTextPaint.setTextSize(getTextSize() + getTextSize() * delta);
                float drawX = maxRightX - scaleWidth * delta;
                //超出边界直接花在边界上
                if (drawX > maxRightX)
                    canvas.drawText(letters[i], maxRightX, singleTextH + itemH * i, textPaint);
                else
                    canvas.drawText(letters[i], drawX, singleTextH + itemH * i, scaleTextPaint);
            }
        }
    }

    public interface ISideBarSelectCallBack {
        void onSelectStr(int index, String selectStr);
    }

}

或者LetterSideBar

public class LetterSideBar extends View {
    private Paint mPaint;
    private boolean isUp = false;


    // 定义26个字母
    public static String[] mLetters = {"A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z", "#"};

    // 当前触摸的位置字母
    private String mCurrentTouchLetter;
    private int currentPosition;

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

    public LetterSideBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LetterSideBar(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        // 自定义属性，颜色  字体大小
        mPaint.setTextSize(sp2px(12));// 设置的是像素
        // 默认颜色
        mPaint.setColor(Color.BLUE);
    }

    // sp 转 px
    private float sp2px(int sp) {
        return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
                sp, getResources().getDisplayMetrics());
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        // 计算指定宽度 = 左右的padding + 字母的宽度(取决于你的画笔)
        int textWidth = (int) mPaint.measureText("A");// A字母的宽度
        int width = getPaddingLeft() + getPaddingRight() + textWidth;
        // 高度可以直接获取
        int height = MeasureSpec.getSize(heightMeasureSpec);
        setMeasuredDimension(width, height);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // 画26个字母

        int itemHeight = (getHeight() - getPaddingTop() - getPaddingBottom()) / mLetters.length;

        for (int i = 0; i < mLetters.length; i++) {
            // 知道每个字母的中心位置  1  字母的高度一半   2 字母高度一般+前面字符的高度
            int letterCenterY = i * itemHeight + itemHeight / 2 + getPaddingTop();
            // 基线，基于中心位置, 知道中心位置还不会基线，看一下之前的视频
            Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
            int dy = (int) ((fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom);
            int baseLine = letterCenterY + dy;
            // x 绘制在最中间 = 宽度/2 - 文字/2
            int textWidth = (int) mPaint.measureText(mLetters[i]);
            int x = getWidth() / 2 - textWidth / 2;
            if (!isUp){
                // 当前字母 高亮  用两个画笔(最好) 改变颜色
                if (mLetters[i].equals(mCurrentTouchLetter)) {
                    mPaint.setColor(Color.RED);
                    canvas.drawText(mLetters[i], x, baseLine, mPaint);
                } else {
                    mPaint.setColor(Color.BLUE);
                    canvas.drawText(mLetters[i], x, baseLine, mPaint);
                }
            }else {
                mPaint.setColor(Color.BLUE);
                canvas.drawText(mLetters[i], x, baseLine, mPaint);
            }

        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
          case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
                // 计算出当前触摸字母  获取当前的位置
                float currentMoveY = event.getY();
                // 位置 = currentMoveY / 字母高度 ， 通过位置获取字母  优化？
                int itemHeight = (getHeight() - getPaddingTop() - getPaddingBottom()) / mLetters.length;
                currentPosition = (int) (currentMoveY / itemHeight);

                if (currentPosition < 0)
                    currentPosition = 0;

                if (currentPosition > mLetters.length - 1)
                    currentPosition = mLetters.length - 1;

                // 要判断 ？

                mCurrentTouchLetter = mLetters[currentPosition];

                if (mListener != null) {
                    mListener.touch(mCurrentTouchLetter, true, currentPosition);
                }
                isUp = false;
                // 重新绘制
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                if (mListener != null) {
                    mListener.touch(mCurrentTouchLetter, false, currentPosition);
                }
                isUp = true;
                // 重新绘制
                invalidate();
                break;
        }
        return true;
    }

    private LetterTouchListener mListener;

    public void setOnLetterTouchListener(LetterTouchListener listener) {
        this.mListener = listener;
    }

    // 接口回掉其他View会不会使用？
    public interface LetterTouchListener {
        void touch(CharSequence letter, boolean isTouch, int currentPosition);
    }
}

4.创建实体类，进行排序等操作

public class User implements Comparable {

    private String name; // 姓名
    private String pinyin; // 姓名对应的拼音
    private String firstLetter; // 拼音的首字母

    public User() {
    }

    public User(String name) {
        this.name = name;
        pinyin = Cn2Spell.getPinYin(name); // 根据姓名获取拼音
        firstLetter = pinyin.substring(0, 1).toUpperCase(); // 获取拼音首字母并转成大写
        if (!firstLetter.matches("[A-Z]")) { // 如果不在A-Z中则默认为“#”
            firstLetter = "#";
        }
    }

    public String getName() {
        return name;
    }

    public String getPinyin() {
        return pinyin;
    }

    public String getFirstLetter() {
        return firstLetter;
    }


    @Override
    public int compareTo(User another) {
        if (firstLetter.equals("#") && !another.getFirstLetter().equals("#")) {
            return 1;
        } else if (!firstLetter.equals("#") && another.getFirstLetter().equals("#")){
            return -1;
        } else {
            return pinyin.compareToIgnoreCase(another.getPinyin());
        }
    }
}

5.适配器

public class SortAdapter extends BaseAdapter{

    private List list = null;
    private Context mContext;

    public SortAdapter(Context mContext, List list) {
        this.mContext = mContext;
        this.list = list;
    }

    public int getCount() {
        return this.list.size();
    }

    public Object getItem(int position) {
        return list.get(position);
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(final int position, View view, ViewGroup arg2) {
        ViewHolder viewHolder;
        final User user = list.get(position);
        if (view == null) {
            viewHolder = new ViewHolder();
            view = LayoutInflater.from(mContext).inflate(R.layout.item, null);
            viewHolder.name = (TextView) view.findViewById(R.id.name);
            viewHolder.catalog = (TextView) view.findViewById(R.id.catalog);
            view.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) view.getTag();
        }

        //根据position获取首字母作为目录catalog
        String catalog = list.get(position).getFirstLetter();

        //如果当前位置等于该分类首字母的Char的位置 ，则认为是第一次出现
        if(position == getPositionForSection(catalog)){
            viewHolder.catalog.setVisibility(View.VISIBLE);
            viewHolder.catalog.setText(user.getFirstLetter().toUpperCase());
        }else{
            viewHolder.catalog.setVisibility(View.GONE);
        }

        viewHolder.name.setText(this.list.get(position).getName());

        return view;

    }

    final static class ViewHolder {
        TextView catalog;
        TextView name;
    }

    /**
     * 获取catalog首次出现位置
     */
    public int getPositionForSection(String catalog) {
        for (int i = 0; i < getCount(); i++) {
            String sortStr = list.get(i).getFirstLetter();
            if (catalog.equalsIgnoreCase(sortStr)) {
                return i;
            }
        }
        return -1;
    }

}

6.适配器的XML

7.主Activity

public class MainActivity extends AppCompatActivity {

    private ListView listView;
    private SideBar sideBar;
    private ArrayList list;

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

    private void initView() {
        listView = (ListView) findViewById(R.id.listView);
        sideBar = (SideBar) findViewById(R.id.side_bar);
        sideBar.setOnStrSelectCallBack(new SideBar.ISideBarSelectCallBack() {
            @Override
            public void onSelectStr(int index, String selectStr) {
                for (int i = 0; i < list.size(); i++) {
                    if (selectStr.equalsIgnoreCase(list.get(i).getFirstLetter())) {
                        listView.setSelection(i); // 选择到首字母出现的位置
                        return;
                    }
                }
            }
        });
    }

    private void initData() {
        list = new ArrayList<>();
        list.add(new User("张琪"));
        list.add(new User("柯南"));
        list.add(new User("罗峰"));
        list.add(new User("林动"));
        list.add(new User("武侠"));
        list.add(new User("鸣人"));
        list.add(new User("佐助"));
        list.add(new User("我爱罗"));
        list.add(new User("卡卡西"));
        list.add(new User("如来"));
        list.add(new User("沸羊羊"));
        list.add(new User("暖羊羊"));
        list.add(new User("慢羊羊"));
        list.add(new User("灰太狼"));
        list.add(new User("红太狼"));
        list.add(new User("孙悟空"));
        list.add(new User("玉帝"));
        list.add(new User("舒克"));
        list.add(new User("贝塔"));
        list.add(new User("海尔"));
        list.add(new User("阿凡提"));
        list.add(new User("邋遢大王"));
        list.add(new User("哪吒"));
        list.add(new User("没头脑"));
        list.add(new User("不高兴"));
        list.add(new User("蓝皮鼠"));
        list.add(new User("大脸猫"));
        list.add(new User("大头儿子"));
        list.add(new User("小头爸爸"));
        list.add(new User("蓝猫"));
        list.add(new User("淘气"));
        list.add(new User("叶峰"));
        list.add(new User("楚天歌"));
        list.add(new User("江流儿"));
        list.add(new User("Tom"));
        list.add(new User("Jerry"));
        list.add(new User("12345"));
        list.add(new User("54321"));
        list.add(new User("_(:з」∠)_"));
        list.add(new User("……%￥#￥%#"));
        Collections.sort(list); // 对list进行排序，需要让User实现Comparable接口重写compareTo方法
        SortAdapter adapter = new SortAdapter(this, list);
        listView.setAdapter(adapter);
    }
}

Demo下载地址：https://download.csdn.net/download/yyxhzdm/15383959