比较好的实现思路就是，自己维护一个SQLite数据库，然后音乐信息都从sd卡上扫描，好处有很多，但是这样做的话代码量会比较大，写了一段扫描sd卡的代码，然后发现扫描音乐的速度简直慢的惊人，可能自己的目录太多，太深，目前还没想到一个比较好的算法去快速扫描sd卡。

  楼主比较偷懒，android自己本身有一个关于媒体信息的数据库，直接用这个就够了，你可能又要吐槽了，如果我要制作一个能在线播放音乐的播放器，下载歌曲后，这个自带的数据库不刷新歌曲怎么办。哈哈，我这是个本地播放器，我就不考虑这些事了。不，作为一个程序员，这种态度可不好。我目前能想到的是，每次下完一首歌让android系统自己去扫描一下。

     ok，还是进入正题吧。

已经存在这个数据库，我们就直接从里面获取呗，android系统通过ContextProvider把这个暴露出来，我们只需要获得一个ContextResolver对象去获得歌曲信息。

主要的方法

         Cursor android.content.ContentResolver.query(Uri uri, String[] projection,String selection,String[] selectionArgs,String sortOrder)

           public void loadSongFromSQL(){Cursor cursor=  getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, MusicManager.media_info, null, null, MediaStore.Audio.Media.DEFAULT_SORT_ORDER);cursor.moveToFirst();//游标遍历数据库for(int i=0;i<cursor.getCount();i++){Song song=new Song();song.setTitle(cursor.getString(0));song.setArtist(cursor.getString(2));song.setDuration(Integer.parseInt(cursor.getString(1)));song.setId(cursor.getInt(3));song.setPath(cursor.getString(5));//加入song到MusicManagerMusicManager.getInstance().addSong(song);cursor.moveToNext();}//关闭游标cursor.close();} 

存放歌曲信息的类

Song.java

package com.huwei.sweetmusicplayer.models;import java.io.Serializable;import com.huwei.sweetmusicplayer.util.CharacterParser;
import com.huwei.sweetmusicplayer.util.TimeUtil;public class Song implements Serializable{private String title; //歌曲名private int duration;  //时长private String artist;      //艺术家private int id;    //idprivate String display_name;private String data;private String date_added;private String path;      //歌曲路径private String sortLetters;       //检索的首字母public int getId() {return id;}public void setId(int id) {this.id = id;}public String getDisplay_name() {return display_name;}public void setDisplay_name(String display_name) {this.display_name = display_name;}public String getData() {return data;}public void setData(String data) {this.data = data;}public String getDate_added() {return date_added;}public void setDate_added(String date_added) {this.date_added = date_added;}public Song(){}public Song(String title){super();this.title=title;if(title.equals("安居客")) {System.out.println();}String firstLetter=CharacterParser.getFirstLetter(title);//正则匹配 ,匹配大小写字母if(firstLetter.matches("^[a-zA-Z]$")){this.sortLetters=firstLetter.toUpperCase();}else{this.sortLetters="#";}}public Song(String title, String sortLetters) {super();this.title = title;this.sortLetters = sortLetters;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getSortLetters() {return CharacterParser.getFirstUpperLetter(title);}public void setSortLetters(String sortLetters) {this.sortLetters = sortLetters;}public String getDurationTime(){return TimeUtil.toTime(duration);}public int getDuration() {return duration;}public void setDuration(int duration) {this.duration = duration;}public String getArtist() {return artist;}public void setArtist(String artist) {this.artist = artist;}public String getPath() {return path;}public void setPath(String path) {this.path = path;}} 

在Splash界面从数据库读入歌曲信息，然后在创建SongsFragment时加载歌曲信息。

至于SongsFragment的a-z检索功能，先来讲讲思路，每次得到歌曲名，去获取它的首字母，首字母的获取可以根据ansi编码。

提取第一个字母，得到它的gb2312编码的byte数组，英文占一个字节，中文占两个字节，根据byte数组的长度，所以很容易判断第一个字符是英文还是中文。

1，英文

可以直接获取ansi值

2，中文

相应的拼音会对应一个值，比如

"a", "ai", "an", "ang"分别对应-20319, -20317, -20304, -20295，容我解释一下，a发音的字符是-20319到-20318，而ai的发音是-20317到-20303。

这些奇怪的负数代表什么呢？根据gb2312编码，汉字由区码（高字节）+位码（低字节）表示，

1）区码：high

2）位码：low

就是该分区的第几个汉字

0xA1-0xFE(把01-94加上 0xA0)

 

比如汉字“啊”，按拼音排序的话，属于16区的第一个字，区码是0xB0(16进制的表示),位码是0xA1,所以区码加位码表示0xB0A1

所以表示该汉字为256*high+low

而上面-20319就是 （256*high+low）-256*256,为什么负数表示呢？我猜想是避免不必要的冲突吧。

具体解析代码：

//单个汉字转成ansipublic static int getChsAscii(String chs){int asc=0;try {byte[] bytes=chs.getBytes("gb2312");if(bytes==null||bytes.length==0){throw new RuntimeException("illegal resource string");}if(bytes.length==1){   //英文字符asc=bytes[0];}if(bytes.length==2){ //中文字符int highByte=256+bytes[0];int lowByte=256+bytes[1];asc=(256*highByte+lowByte)-256*256;  }} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();}return asc;}

具体解析的CharacterParser.java

package com.huwei.sweetmusicplayer.util;import java.io.UnsupportedEncodingException;/** java汉字转拼音*/
public class CharacterParser {//private static LinkedHashMap<String, Integer> spellMap;;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 static CharacterParser instance;private StringBuilder resource;//单例模式public CharacterParser getInstance(){if(instance==null) {instance=new CharacterParser();}return instance;}public StringBuilder getResource() {return resource;}public void setResource(StringBuilder resource) {this.resource = resource;}//单个汉字转成ansipublic static int getChsAscii(String chs){int asc=0;try {byte[] bytes=chs.getBytes("gb2312");if(bytes==null||bytes.length==0){throw new RuntimeException("illegal resource string");}if(bytes.length==1){    //英文字符asc=bytes[0];}if(bytes.length==2){ //中文字符int highByte=256+bytes[0];int lowByte=256+bytes[1];asc=(256*highByte+lowByte)-256*256;  }} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();}return asc;}//首字符是否是字母//大写return 1 小写return -1 非retrun 0public static int firstIsLetter(String name){int asc=getChsAscii(name.substring(0,1));if( asc>='A'&&asc<='Z'){//单字符return 1;}else if(asc>='a'&&asc<='z'){return -1;}else{return 0;}}//提取首字母，大小写均可public static String getSpellByAscii(int asc){String res=null;if(asc>0&&asc<160){//单字符res=String.valueOf((char)asc);}else if (asc< -20319 || asc > -10247) { //未知字符return null;}  else {for(int i=pyvalue.length-1;i>=0;i--){if(asc>=pyvalue[i]){res=pystr[i];break;}}}//提取首字母res=res.substring(0,1);return res;}//获取首字母的大写字母public static String getFirstUpperLetter(String cn){return getFirstLetter(cn).toUpperCase();}//获取首字母public static String getFirstLetter(String cn){return getSpellByAscii(getChsAscii(cn.substring(0, 1)));}//获取全拼public static String getFullSpell(String cn){String resString=null;for(int i=0;i<cn.length();i++){String string=cn.substring(i, i+1);resString+=getSpellByAscii(getChsAscii(string));}return resString;}}

然后把首字母相同的列表项排在一起，在显示的仅显示第一个。

见下图

比如七号公园，七里香，七夕。。。只显示七号公园中的catalog，其他两个隐藏。

列表项布局文件song_listitem.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="fill_parent"android:descendantFocusability="afterDescendants"android:orientation="vertical" ><!-- 显示字母项 --><TextViewandroid:id="@+id/catalog"style="@style/catalog"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="catalog"android:visibility="gone" /><RelativeLayoutandroid:id="@+id/song_item"android:layout_width="match_parent"android:layout_height="60dp"android:background="@drawable/effect_list_item_bg"android:clickable="true"android:focusable="true" ><TextViewandroid:id="@+id/song_title"style="@style/song_title"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentLeft="true"android:layout_alignParentTop="true"android:maxEms="20"android:text="song_text"android:textSize="@dimen/text_size_medium" /><TextViewandroid:id="@+id/duration_tv"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentRight="true"android:layout_centerVertical="true"android:layout_marginRight="14dp"android:text="00:00"android:textColor="@color/darkgray" /><TextViewandroid:id="@+id/artist_tv"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_alignParentLeft="true"android:layout_margin="10dp"android:text="artist_tv"android:textAppearance="?android:attr/textAppearanceSmall"android:textColor="@color/darkgray" /><Viewandroid:id="@+id/selected_view"android:layout_width="8dp"android:layout_height="match_parent"android:layout_alignParentLeft="true"android:layout_centerVertical="true"android:background="@color/darkorchid"android:visibility="invisible" /></RelativeLayout></LinearLayout>

具体控件代码解释可以参考： http://blog.csdn.net/xiaanming/article/details/12684155

三，选中歌曲特效

现在的问题是，当我点击“七号公园”，焦点却在整个listitem上，字母q和七号公园是一个整体，我们必须要屏蔽Listitem的焦点，而让焦点在song_item这个相对布局上。

 

我们需要在最外层布局LinearLayout加上一个属性， android:descendantFocusability="afterDescendants"，以致子控件优于viewgroup获取焦点。

android:descendantFocusability属性的值有三种：

beforeDescendants：viewgroup会优先其子类控件而获取到焦点

afterDescendants：viewgroup只有当其子类控件不需要获取焦点时才获取焦点

blocksDescendants：viewgroup会覆盖子类控件而直接获得焦点

然后这个紫色的小方块并不是一个背景，最开始我也想用一个背景来实现，后来参考了字母的实现方案，在选中时显示这个方块，未选中时隐藏这个方块就好了。

楼主在实现的过程中，遇到一个小问题，特此记录一下。

最开始是这样写的，比如要显示紫色方块，就在onSelecte()后，马上设置为控件的setVisibility(),后来发现把这个歌曲滑到看不见位置，然后又滑下来，发现设置的效果不起作用了。后来思考了下，因为再把歌曲滑下来，会去调用listView的adapter的getView(),所以setVisibility()就不起作用了。建议写出下面这样，用一个selectedpos去标记选中的位置，然后在getView（）设置属性。  所以选中后，刷新一下listView就好了。

                //设置正在播放的音乐的视图（紫色小方块）int selectedpos=MusicManager.getInstance().getNowplaying_index();if(position==selectedpos){mViewHolder.selected_view.setVisibility(View.VISIBLE);}else{mViewHolder.selected_view.setVisibility(View.INVISIBLE);}

下一篇总结播放本地音乐： http://blog.csdn.net/huweigoodboy/article/details/39861539