android音乐播放器开发SweetMusicPlayer载入歌曲列表 _音乐播放器

大道之行，天下为公。这篇文章主要讲述android音乐播放器开发SweetMusicPlayer载入歌曲列表相关的知识，希望能为你提供帮助。
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。
【android音乐播放器开发SweetMusicPlayer载入歌曲列表】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)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_URIprojection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 = https://www.songbingjia.com/android/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：high01-09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.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 = https://www.songbingjia.com/android/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

< ?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

文章图片

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); }