最近在学android开发，最近写了一个简易的音乐播放器，主要参考了《第一行代码》以及别人的博客。这里贴出代码，供大家交流分享，如有错误或疑问，欢迎批评或者交流探讨。本人使用的开发工具是android studio 2.1.2。
首先是MainActivity.java
package handsome.musicplayer;import android.database.Cursor;import android.graphics.Color;import android.media.MediaPlayer;import android.os.Handler;import android.os.Message;import android.provider.MediaStore;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.text.Layout;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.AdapterView;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ImageView;import android.widget.ListView;import android.widget.RelativeLayout;import android.widget.SeekBar;import android.widget.TextView;import android.widget.Toast;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {private ListView songView;private List<Song> songList;private MediaPlayer mediaPlayer;private Button mainPlay,mainNext;private SeekBar playTime;private TextView nowPlaying;private int playType;private static int ICON_PLAY=R.drawable.bfzn_004;private static int ICON_PAUSE=R.drawable.bfzn_003;private static final int UPDATE_PLAYTIME=1;private static final int PLAY_ORDER=0;private static final int PLAY_RANDOM=1;private static final int PLAY_SINGLE=2;private int previousSong,totalSong;private ImageView bgImage;private Handler handler=new Handler(){public void handleMessage(Message msg){switch (msg.what){case UPDATE_PLAYTIME:try {playTime.setProgress(mediaPlayer.getCurrentPosition());}catch(Exception e){}break;default:break;}}};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);/*musicList=new ArrayList<>();musicView=(ListView)findViewById(R.id.musicView);adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,musicList);musicView.setAdapter(adapter);*///初始化songList=new ArrayList<>();mediaPlayer=new MediaPlayer();totalSong=0;previousSong=-1;playType=PLAY_ORDER;//控件初始化songView=(ListView)findViewById(R.id.songView);mainPlay=(Button)findViewById(R.id.mainPlay);mainNext=(Button)findViewById(R.id.mainNext);playTime=(SeekBar)findViewById(R.id.playTime);nowPlaying=(TextView)findViewById(R.id.nowPlaying);bgImage=(ImageView)findViewById(R.id.bgImage);nowPlaying.setBackgroundColor(Color.WHITE);bgImage.setImageResource(R.drawable.setsuna);bgImage.setImageAlpha(0x77);Cursor cursor=getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null,null,null);while(cursor.moveToNext()){String title=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));//标题String artist=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));//艺术家String url=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));//文件路径int duration=cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.DURATION));//时长if(pareTo("<unknown>")==0)artist="";songList.add(new Song(title,artist,url,duration));totalSong++;}if(cursor!=null)cursor.close();final SongAdapter adapter=new SongAdapter(this,R.layout.song,songList);songView.setAdapter(adapter);songView.setOnItemClickListener(new AdapterView.OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {playSong(i);}});mainPlay.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {if(mediaPlayer.isPlaying()){mainPlay.setBackground(getResources().getDrawable(ICON_PLAY));mediaPlayer.pause();}else {mainPlay.setBackground(getResources().getDrawable(ICON_PAUSE));mediaPlayer.start();}}});mainNext.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {switch (playType){case PLAY_ORDER:if(previousSong==totalSong-1)previousSong=-1;playSong(previousSong+1);break;case PLAY_RANDOM:playSong((int)(Math.random()*songList.size()));break;case PLAY_SINGLE:playSong((int)(Math.random()*songList.size()));break;}}});playTime.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {@Overridepublic void onProgressChanged(SeekBar seekBar, int i, boolean b) {}@Overridepublic void onStartTrackingTouch(SeekBar seekBar) {}@Overridepublic void onStopTrackingTouch(SeekBar seekBar) {mediaPlayer.seekTo(playTime.getProgress());}});mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {@Overridepublic void onCompletion(MediaPlayer mediaPlayer) {switch (playType){case PLAY_ORDER:if(previousSong==totalSong-1)previousSong=-1;playSong(previousSong+1);break;case PLAY_RANDOM:playSong((int)(Math.random()*songList.size()));break;case PLAY_SINGLE:mediaPlayer.start();break;}}});}@Overrideprotected void onDestroy(){super.onDestroy();if(mediaPlayer!=null) {mediaPlayer.stop();mediaPlayer.release();}}void playSong(int i){Song song=songList.get(i);try {Log.e("url",song.getUrl());mediaPlayer.reset();mediaPlayer.setDataSource(song.getUrl());mediaPlayer.prepare();mediaPlayer.start();mainPlay.setBackground(getResources().getDrawable(ICON_PAUSE));previousSong=i;playTime.setMax(song.getDuration());nowPlaying.setText("正在播放："+song.getTitle());new Thread(new Runnable() {@Overridepublic void run() {Message message=new Message();message.what=UPDATE_PLAYTIME;handler.sendMessage(message);handler.postDelayed(this,1000);}}).start();}catch (Exception e){String errorInformation="Play failed!";Toast.makeText(MainActivity.this,errorInformation,Toast.LENGTH_SHORT).show();}}public boolean onCreateOptionsMenu(Menu menu){getMenuInflater().inflate(R.menu.main_menu,menu);return true;}public boolean onOptionsItemSelected(MenuItem item){switch (item.getItemId()){case R.id.playOrder:playType=PLAY_ORDER;break;case R.id.playRandom:playType=PLAY_RANDOM;break;case R.id.playSingle:playType=PLAY_SINGLE;break;default:break;}return true;}}
然后是Song.java
package handsome.musicplayer;/*** Created by Administrator on /7/17.*/public class Song {private String title;private String artist;private String url;private int duration;public Song(String title,String artist,String url,int duration){this.title=title;this.artist=artist;this.url=url;this.duration=duration;}public String getTitle(){return title;}public String getArtist(){return artist;}public String getUrl(){return url;}public int getDuration(){return duration;}}
最后是SongAdapter.java
package handsome.musicplayer;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ArrayAdapter;import android.widget.TextView;import java.util.List;/*** Created by Administrator on /7/17.*/public class SongAdapter extends ArrayAdapter<Song> {private int resourceId;public SongAdapter(Context context,int textViewResourceId,List<Song> objects){super(context,textViewResourceId,objects);resourceId=textViewResourceId;}@Overridepublic View getView(int position, View convertView, ViewGroup parent){Song song=getItem(position);View view= LayoutInflater.from(getContext()).inflate(resourceId,null);TextView title=(TextView)view.findViewById(R.id.title);TextView artist=(TextView)view.findViewById(R.id.artist);title.setText(song.getTitle());artist.setText(song.getArtist());return view;}}
这里简要分析一下，界面部分：首先调用 Cursor cursor=getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null,null,null)函数提取出手机当中所有的音频文件（这里由于个人水平原因，处理得比较粗暴。而且我这里每次程序启动都会这样做一遍，其实我们可以利用数据库技术来存储这个列表，把这个操作改成手动的，这个就留给读者自己去完善了。）读取的同时，将它们用Song类型（存储了音乐名，作曲家，音乐时间长短和音乐存储位置）保存在songList内，通过songAdapter让它在songView这个控件上显示。几个layout就不贴出了，我已将源码上传至百度云盘，可供大家下载。
音乐播放部分：
首先是如何播放音乐，这个非常容易。我这里实现的功能是点击songView上的对应项就可以播放对应的音乐，这个只要在songView.setOnItemClickListener里调用一下playSong这个函数就可以了，playSong的函数里主要是通过点击的序号在songList里找到对应的对象，这样可以得到它的存储路径，通过mediaPlayer.setDataSource(song.getUrl());可以设置播放路径，然后播放即可。
最后我想说一下滚动条部分。这里我们必须要用到多线程来实时获得歌曲播放信息，但子线程是不支持UI修改的，所以我们通过handler.sendMessage，主线程通过handleMessage接收这个方法来对SeekBar的位置进行修改。具体大家可以参考我是怎么写的，更详细的可以看《第一行代码》第九章内容。
其他还实现了下一曲，循环播放，随机播放，单曲循环等功能，这些都不难，大家自己研究一下就可以了。
时间关系，就写到这里，附上源码：/s/1ge8Iv8f
