上一篇写了播放器的总体实现思路，http://blog.csdn.net/huweigoodboy/article/details/39855653，如今来总结下载入歌曲列表。
代码地址：https://github.com/huweigoodboy/SweetMusicPlayer
比較好的实现思路就是。自己维护一个SQLite数据库，然后音乐信息都从sd卡上扫描，优点有非常多，可是这样做的话代码量会比較大，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，可能自己的文件夹太多，太深。眼下还没想到一个比較好的算法去高速扫描sd卡。
楼主比較偷懒，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，假设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，作为一个程序猿。这样的态度可不好。
我眼下能想到的是。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。
一，从数据库载入歌曲信息
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。我们仅仅须要获得一个ContextResolver对象去获得歌曲信息。
基本的方法
Cursor android.content.ContentResolver.query(Uri
uri, String[] projection,String
selection,String[] selectionArgs,String
sortOrder)
然后把首字母同样的列表项排在一起。在显示的仅显示第一个。
上面參数的主要意思是：
uri通用资源訪问符。在这里MediaStore.Audio.Media.EXTERNAL_CONTENT_URI
projection返回信息的行，用一个数组去设置要返回哪些行的信息
selection筛选条件
selectionArgs筛选条件的參数
sortOrder排序的顺序 这个用默认的就好了MediaStore.Audio.Media.DEFAULT_SORT_ORDER
关键代码
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));
//增加song到MusicManager
MusicManager.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; //id
private 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 ,匹配大写和小写字母
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时载入歌曲信息。
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));
//增加song到MusicManager
MusicManager.getInstance().addSong(song);
cursor.moveToNext();
}
//关闭游标
cursor.close();
} 存放歌曲信息的类
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; //id
private 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 ,匹配大写和小写字母
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时载入歌曲信息。
二，A-Z检索功能：
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，首字母的获取能够依据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。依据byte数组的长度，所以非常easy推断第一个字符是英文还是中文。
1。英文
能够直接获取ansi值
2，中文
相应的拼音会相应一个值，比方
"a", "ai", "an", "ang"分别相应-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？依据gb2312编码，汉字由区码（高字节）+位码（低字节）表示。
1）区码：high
01-09区为特殊符号。
16-55区为一级汉字。按拼音排序。
56-87区为二级汉字，按部首/笔画排序。
10-15区及88-94区则未有编码。
0xA1-0xF7(把01-87区的区号加上0xA0)
2）位码：low
就是该分区的第几个汉字
0xA1-0xFE(把01-94加上 0xA0)
比方汉字“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。
详细解析代码：
//单个汉字转成ansi
public 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 block
e.printStackTrace();
}
return asc;
}详细解析的CharacterParser.javapackage 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ansi
public 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 block
e.printStackTrace();
}
return asc;
}
//首字符是否是字母
//大写return 1 小写return -1 非retrun 0
public 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，大写和小写均可
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;
}
}
然后把首字母同样的列表项排在一起。在显示的仅显示第一个。
见下图
比方七号公园。七里香。七夕。。。仅仅显示七号公园中的catalog。其它两个隐藏。
列表项布局文件song_listitem.xml
详细控件代码解释能够參考： http://blog.csdn.net/xiaanming/article/details/12684155
<?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 -->
<TextView
android:id="@+id/catalog"
style="@style/catalog"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="catalog"
android:visibility="gone" />
<RelativeLayout
android: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" >
<TextView
android: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" />
<TextView
android: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" />
<TextView
android: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" />
<View
android: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>详细控件代码解释能够參考： http://blog.csdn.net/xiaanming/article/details/12684155
三，选中歌曲特效
如今的问题是，当我点击“七号公园”，焦点却在整个listitem上，字母q和七号公园是一个总体，我们必需要屏蔽Listitem的焦点，而让焦点在song_item这个相对布局上。
我们须要在最外层布局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仅仅有当其子类控件不须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非一个背景，最開始我也想用一个背景来实现，后来參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。
最開始是这样写的，比方要显示紫色方块。就在onSelecte()后，立即设置为控件的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。由于再把歌曲滑下来，会去调用listView的adapter的getView(),所以setVisibility()就不起作用了。建议写出以下这样。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