Android(安卓)首字母索引

Aandroid 首字母索引在一般具有选择联系和城市列表的功能的App中都是非常常见，并且实用性很高。由于之前做的应用真的没有用到过首字母索引的功能，并且android没有提供对应的组件，也就没向这方面考虑过。但是现在的项目要求要有这项功能，并且在网上一搜会有很多，都挺好的，并且大致思想都差不多，所以我也研究了一下，自己实现了一个，并且把自己的实现实例记录了下来。希望能对需要的小伙伴提供帮助。
效果图：

实现字母索引导航条：
从界面上就可以看出要实现的主要功能为两部分：
第一，绘制字母，因为android 没有提供对应的组件所以只能通过自定view去绘制26英文字母和#号，这里就应该想到自定控件的三个常用方法，onMeasure ,onLayout,onDraw ,现在我要实现的就是一个绘制工作，并且没有子view ，所以onMeasure 和onLayout 就不需要重写。只需要实现onDraw就行啦，因为绘制的是文字索引就应该使用到drawText ,同时还要计算出26个字母和#的平均高度，这样才能均匀分布。
第二就是实现对应字母的触摸事件，onTouchEvent方法，由当前触碰的位置获取到当前位子上的字母。
代码实现：

public class SideBar extends View {    private String initials[] = {"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 mPaint;    private int initialHeight;    private int touchItem = -1;    private SideBarItemSelectedListener listener;    public SideBar(Context context) {        this(context, null);    }    public SideBar(Context context, @Nullable AttributeSet attrs) {        this(context, attrs, 0);    }    public SideBar(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initView();    }    private void initView() {        mPaint = new Paint();    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        int height = getHeight();//获取控件高度        int width = getWidth();//获取控件宽度        initialHeight = height / initials.length;//计算出要分陪给每个字母的高度        //进行绘制        for (int i = 0; i < initials.length; i++) {            mPaint.setColor(i == touchItem ? Color.GREEN : Color.BLUE);//如果当前字母被选中字体颜色就为绿色            mPaint.setAntiAlias(true);            mPaint.setTextSize(30);            float pionx = (width / 2 - mPaint.measureText(initials[i]) / 2);//字体的x轴上的位置            canvas.drawText(initials[i], pionx, (initialHeight * i) + initialHeight, mPaint);            mPaint.reset();        }    }    @Override    public boolean onTouchEvent(MotionEvent event) {        switch (event.getAction()) {            case MotionEvent.ACTION_MOVE:            case MotionEvent.ACTION_DOWN:                float point = event.getY();                int index = (int) (point / getHeight() * initials.length);// 通过获取触摸的y轴的位置，计算出是第几个字母                if (listener != null) {                    touchItem = index;                    listener.itemSelected(initials[index]);                }                return true;            case MotionEvent.ACTION_UP:                break;        }        invalidate();        return super.onTouchEvent(event);    }    public void setItemSelectedListener(SideBarItemSelectedListener listener) {        this.listener = listener;    }    public interface SideBarItemSelectedListener {//触摸事件的监听接口        void itemSelected(String str);    }}

首字母索引还要解决一个问题，就是把汉字转换为拼音，看到网上有两种方法，一种是利用汉语转拼音的框架，另外一种就是通过汉字的ASCII码，我用的是网上的ASCII方法。

public class CharacterParser {    private static int[] pyvalue = new int[] { -20319, -20317, -20304, -20295,            -20292, -20283, -20265, -20257, -20242, -20230, -20051, -20036,            -20032, -20026, -20002, -19990, -19986, -19982, -19976, -19805,            -19784, -19775, -19774, -19763, -19756, -19751, -19746, -19741,            -19739, -19728, -19725, -19715, -19540, -19531, -19525, -19515,            -19500, -19484, -19479, -19467, -19289, -19288, -19281, -19275,            -19270, -19263, -19261, -19249, -19243, -19242, -19238, -19235,            -19227, -19224, -19218, -19212, -19038, -19023, -19018, -19006,            -19003, -18996, -18977, -18961, -18952, -18783, -18774, -18773,            -18763, -18756, -18741, -18735, -18731, -18722, -18710, -18697,            -18696, -18526, -18518, -18501, -18490, -18478, -18463, -18448,            -18447, -18446, -18239, -18237, -18231, -18220, -18211, -18201,            -18184, -18183, -18181, -18012, -17997, -17988, -17970, -17964,            -17961, -17950, -17947, -17931, -17928, -17922, -17759, -17752,            -17733, -17730, -17721, -17703, -17701, -17697, -17692, -17683,            -17676, -17496, -17487, -17482, -17468, -17454, -17433, -17427,            -17417, -17202, -17185, -16983, -16970, -16942, -16915, -16733,            -16708, -16706, -16689, -16664, -16657, -16647, -16474, -16470,            -16465, -16459, -16452, -16448, -16433, -16429, -16427, -16423,            -16419, -16412, -16407, -16403, -16401, -16393, -16220, -16216,            -16212, -16205, -16202, -16187, -16180, -16171, -16169, -16158,            -16155, -15959, -15958, -15944, -15933, -15920, -15915, -15903,            -15889, -15878, -15707, -15701, -15681, -15667, -15661, -15659,            -15652, -15640, -15631, -15625, -15454, -15448, -15436, -15435,            -15419, -15416, -15408, -15394, -15385, -15377, -15375, -15369,            -15363, -15362, -15183, -15180, -15165, -15158, -15153, -15150,            -15149, -15144, -15143, -15141, -15140, -15139, -15128, -15121,            -15119, -15117, -15110, -15109, -14941, -14937, -14933, -14930,            -14929, -14928, -14926, -14922, -14921, -14914, -14908, -14902,            -14894, -14889, -14882, -14873, -14871, -14857, -14678, -14674,            -14670, -14668, -14663, -14654, -14645, -14630, -14594, -14429,            -14407, -14399, -14384, -14379, -14368, -14355, -14353, -14345,            -14170, -14159, -14151, -14149, -14145, -14140, -14137, -14135,            -14125, -14123, -14122, -14112, -14109, -14099, -14097, -14094,            -14092, -14090, -14087, -14083, -13917, -13914, -13910, -13907,            -13906, -13905, -13896, -13894, -13878, -13870, -13859, -13847,            -13831, -13658, -13611, -13601, -13406, -13404, -13400, -13398,            -13395, -13391, -13387, -13383, -13367, -13359, -13356, -13343,            -13340, -13329, -13326, -13318, -13147, -13138, -13120, -13107,            -13096, -13095, -13091, -13076, -13068, -13063, -13060, -12888,            -12875, -12871, -12860, -12858, -12852, -12849, -12838, -12831,            -12829, -12812, -12802, -12607, -12597, -12594, -12585, -12556,            -12359, -12346, -12320, -12300, -12120, -12099, -12089, -12074,            -12067, -12058, -12039, -11867, -11861, -11847, -11831, -11798,            -11781, -11604, -11589, -11536, -11358, -11340, -11339, -11324,            -11303, -11097, -11077, -11067, -11055, -11052, -11045, -11041,            -11038, -11024, -11020, -11019, -11018, -11014, -10838, -10832,            -10815, -10800, -10790, -10780, -10764, -10587, -10544, -10533,            -10519, -10331, -10329, -10328, -10322, -10315, -10309, -10307,            -10296, -10281, -10274, -10270, -10262, -10260, -10256, -10254                                             };    public static String[] pystr = new String[] { "a", "ai", "an", "ang", "ao",            "ba", "bai", "ban", "bang", "bao", "bei", "ben", "beng", "bi",            "bian", "biao", "bie", "bin", "bing", "bo", "bu", "ca", "cai",            "can", "cang", "cao", "ce", "ceng", "cha", "chai", "chan", "chang",            "chao", "che", "chen", "cheng", "chi", "chong", "chou", "chu",            "chuai", "chuan", "chuang", "chui", "chun", "chuo", "ci", "cong",            "cou", "cu", "cuan", "cui", "cun", "cuo", "da", "dai", "dan",            "dang", "dao", "de", "deng", "di", "dian", "diao", "die", "ding",            "diu", "dong", "dou", "du", "duan", "dui", "dun", "duo", "e", "en",            "er", "fa", "fan", "fang", "fei", "fen", "feng", "fo", "fou", "fu",            "ga", "gai", "gan", "gang", "gao", "ge", "gei", "gen", "geng",            "gong", "gou", "gu", "gua", "guai", "guan", "guang", "gui", "gun",            "guo", "ha", "hai", "han", "hang", "hao", "he", "hei", "hen",            "heng", "hong", "hou", "hu", "hua", "huai", "huan", "huang", "hui",            "hun", "huo", "ji", "jia", "jian", "jiang", "jiao", "jie", "jin",            "jing", "jiong", "jiu", "ju", "juan", "jue", "jun", "ka", "kai",            "kan", "kang", "kao", "ke", "ken", "keng", "kong", "kou", "ku",            "kua", "kuai", "kuan", "kuang", "kui", "kun", "kuo", "la", "lai",            "lan", "lang", "lao", "le", "lei", "leng", "li", "lia", "lian",            "liang", "liao", "lie", "lin", "ling", "liu", "long", "lou", "lu",            "lv", "luan", "lue", "lun", "luo", "ma", "mai", "man", "mang",            "mao", "me", "mei", "men", "meng", "mi", "mian", "miao", "mie",            "min", "ming", "miu", "mo", "mou", "mu", "na", "nai", "nan",            "nang", "nao", "ne", "nei", "nen", "neng", "ni", "nian", "niang",            "niao", "nie", "nin", "ning", "niu", "nong", "nu", "nv", "nuan",            "nue", "nuo", "o", "ou", "pa", "pai", "pan", "pang", "pao", "pei",            "pen", "peng", "pi", "pian", "piao", "pie", "pin", "ping", "po",            "pu", "qi", "qia", "qian", "qiang", "qiao", "qie", "qin", "qing",            "qiong", "qiu", "qu", "quan", "que", "qun", "ran", "rang", "rao",            "re", "ren", "reng", "ri", "rong", "rou", "ru", "ruan", "rui",            "run", "ruo", "sa", "sai", "san", "sang", "sao", "se", "sen",            "seng", "sha", "shai", "shan", "shang", "shao", "she", "shen",            "sheng", "shi", "shou", "shu", "shua", "shuai", "shuan", "shuang",            "shui", "shun", "shuo", "si", "song", "sou", "su", "suan", "sui",            "sun", "suo", "ta", "tai", "tan", "tang", "tao", "te", "teng",            "ti", "tian", "tiao", "tie", "ting", "tong", "tou", "tu", "tuan",            "tui", "tun", "tuo", "wa", "wai", "wan", "wang", "wei", "wen",            "weng", "wo", "wu", "xi", "xia", "xian", "xiang", "xiao", "xie",            "xin", "xing", "xiong", "xiu", "xu", "xuan", "xue", "xun", "ya",            "yan", "yang", "yao", "ye", "yi", "yin", "ying", "yo", "yong",            "you", "yu", "yuan", "yue", "yun", "za", "zai", "zan", "zang",            "zao", "ze", "zei", "zen", "zeng", "zha", "zhai", "zhan", "zhang",            "zhao", "zhe", "zhen", "zheng", "zhi", "zhong", "zhou", "zhu",            "zhua", "zhuai", "zhuan", "zhuang", "zhui", "zhun", "zhuo", "zi",            "zong", "zou", "zu", "zuan", "zui", "zun", "zuo"                                                };    private StringBuilder buffer;    private String resource;    private static CharacterParser characterParser = new CharacterParser();    public static CharacterParser getInstance() {        return characterParser;    }    public String getResource() {        return resource;    }    public void setResource(String resource) {        this.resource = resource;    }    /** * 汉字转成ASCII码 * * @param chs * @return */    private int getChsAscii(String chs) {        int asc = 0;        try {            byte[] bytes = chs.getBytes("gb2312");            if (bytes == null || bytes.length > 2 || bytes.length <= 0) {                throw new RuntimeException("illegal resource string");            }            if (bytes.length == 1) {                asc = bytes[0];            }            if (bytes.length == 2) {                int hightByte = 256 + bytes[0];                int lowByte = 256 + bytes[1];                asc = (256 * hightByte + lowByte) - 256 * 256;            }        } catch (Exception e) {            System.out            .println("ERROR:ChineseSpelling.class-getChsAscii(String chs)"                     + e);        }        return asc;    }    /** * 单字解析 * * @param str * @return */    public String convert(String str) {        String result = null;        int ascii = getChsAscii(str);        if (ascii > 0 && ascii < 160) {            result = String.valueOf((char) ascii);        } else {            for (int i = (pyvalue.length - 1); i >= 0; i--) {                if (pyvalue[i] <= ascii) {                    result = pystr[i];                    break;                }            }        }        return result;    }    /** * 词组解析 * * @param chs * @return */    public String getSelling(String chs) {        if (chs == null) {            return null;        }        String key, value;        buffer = new StringBuilder();        for (int i = 0; i < chs.length(); i++) {            key = chs.substring(i, i + 1);            if (key.getBytes().length >= 2) {                value = (String) convert(key);                if (value == null) {                    value = "unknown";                }            } else {                value = key;            }            buffer.append(value);        }        return buffer.toString();    }    public String getSpelling() {        return this.getSelling(this.getResource());    }}

测试demo
布局文件：我这里的列表控件使用的是RecyclerView ，其实不管是ListView 还是RecyclerView都一样看个人使用习惯。

<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context=".MainActivity">    <android.support.v7.widget.RecyclerView        android:id="@+id/recycelview"        android:layout_width="match_parent"        android:layout_height="match_parent"        />    <demo.song.com.sidebar.SideBar        android:id="@+id/sidebar"        android:layout_width="30dp"        android:layout_height="match_parent"        android:layout_gravity="center|right"        android:padding="10dp"        />FrameLayout>

MainActivity 代码

public class MainActivity extends AppCompatActivity {    private final String TAG = MainActivity.class.getSimpleName();    private SideBar mSideBar;    private List citys;    private RecyclerView mRecyclerView;    private CityAdapter mCityAdapter;    private static Toast makeText;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        mSideBar = findViewById(R.id.sidebar);        mRecyclerView = findViewById(R.id.recycelview);        mSideBar.setItemSelectedListener(new SideBar.SideBarItemSelectedListener() {            @Override            public void itemSelected(String str) {                int index = mCityAdapter.getIndex(str);                showToast(str);                if (index != -1) {                    mRecyclerView.scrollToPosition(index);                }            }        });        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);        mRecyclerView.setLayoutManager(linearLayoutManager);        mCityAdapter = new CityAdapter();        mRecyclerView.addItemDecoration(new DividerItemDecoration(this, DividerItemDecoration.VERTICAL));        mRecyclerView.setAdapter(mCityAdapter);    }    private void showToast(String str) {        if (makeText == null) {            makeText = Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT);            makeText.setGravity(Gravity.CENTER, 0, 0);        } else {            makeText.setText(str);            makeText.setDuration(Toast.LENGTH_SHORT);        }        makeText.show();    }    private void initData() {        citys = new ArrayList<>();        citys.add(new CityInfo("北京", 1));        citys.add(new CityInfo("上海", 2));        citys.add(new CityInfo("天津", 3));        citys.add(new CityInfo("重庆", 4));        citys.add(new CityInfo("山东", 5));        citys.add(new CityInfo("山西", 6));        citys.add(new CityInfo("河南", 7));        citys.add(new CityInfo("河北", 8));        citys.add(new CityInfo("广东", 9));        citys.add(new CityInfo("广西", 10));        citys.add(new CityInfo("安徽", 11));        citys.add(new CityInfo("江苏", 12));        citys.add(new CityInfo("福建", 13));        citys.add(new CityInfo("湖南", 14));        citys.add(new CityInfo("湖北", 15));        citys.add(new CityInfo("浙江", 16));        citys.add(new CityInfo("四川", 17));        citys.add(new CityInfo("云南", 18));        citys.add(new CityInfo("台湾", 19));        citys.add(new CityInfo("辽宁", 20));        citys.add(new CityInfo("吉林", 21));        citys.add(new CityInfo("黑龙江", 22));        citys.add(new CityInfo("西藏", 23));        citys.add(new CityInfo("青海", 24));        citys.add(new CityInfo("新疆", 25));        citys.add(new CityInfo("宁夏", 26));        citys.add(new CityInfo("#东京", 27));        citys.add(new CityInfo("@伦敦", 28));        for (CityInfo city : citys) {            String pinyin = CharacterParser.getInstance().getSelling(city.getName());            String letter = pinyin.substring(0, 1);            if (letter.matches("\\w")) {// 匹配拼音第一个位置是否为a-zA-Z                city.setLetter(letter.toUpperCase());            } else {                city.setLetter("#");            }        }        Collections.sort(citys, new PinyinComparable());    }    public class PinyinComparable implements Comparator<CityInfo> {        @Override        public int compare(CityInfo cityInfo, CityInfo t1) {            if (cityInfo.getLetter().equals("@") || t1.getLetter().equals("#")) {                return -1;            } else if (cityInfo.getLetter().equals("#") || t1.getLetter().equals("@")) {                return 1;            }            return cityInfo.getLetter().compareTo(t1.getLetter());        }    }    private class CityAdapter extends RecyclerView.Adapter<CityHolder> {        @NonNull        @Override        public CityHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {            View view = android.view.LayoutInflater.from(MainActivity.this).inflate(R.layout.layout_item, viewGroup, false);            CityHolder holder = new CityHolder(view);            return holder;        }        @Override        public void onBindViewHolder(@NonNull CityHolder cityHolder, int i) {            cityHolder.cityname.setText(citys.get(i).getName());        }        @Override        public int getItemCount() {            return citys.size();        }        public int getIndex(String letter) {            for (CityInfo cityInfo : citys) {                if (cityInfo.getLetter().equals(letter)) {                    return citys.indexOf(cityInfo);                }            }            return -1;        }    }    private class CityHolder extends RecyclerView.ViewHolder {        private android.widget.TextView cityname;        public CityHolder(@NonNull View itemView) {            super(itemView);            cityname = itemView.findViewById(R.id.tv_city);        }    }}

到这里一个完整的首字母索引的demo 已经完成了，里面没有复杂的逻辑，应该是android自定view比较简单的了。如果有需要优化和改进的地方，希望大家指正，源码地址 https://github.com/songdaren123/SideBar

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