ANDROID_MARS学习笔记_S01原始版_023_MP3PLAYER004_同步显示歌词

一、流程分析

1.点击播放按钮，会根据lrc名调用LrcProcessor的process()分析歌词文件，得到时间队列和歌词队列

2.new一个hander,把时间队列和歌词队列传给自定义的线程类UpdateTimeCallback，调用handler.postDelayed(updateTimeCallback, 5);启动线程

3.UpdateTimeCallback会在线程执行时用当前时间减去成员变量begin，则可知歌曲播放了多久，再根据此时间与时间队列的时间比较，就是知道此时要显示什么歌词，从而把歌词队列的一个message设置给lrcTextView以显示

4.UpdateTimeCallback最后会自己调用handler.postDelayed(updateTimeCallback, 100);，所以线程会每0.1秒判断一次歌词的显示

PS:此代码有一个不足之处，即使app后台播放，更新歌词的线程仍会执行，浪费资源，一个版本会通过broastreciever来解决此问题

二、简介

在linux用apk处理歌词

三、代码
1.xml

2.java
(1)PlayerActivity.java

 package tony.mp3player;

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.InputStream;
 import java.util.List;
 import java.util.Queue;

 import tony.model.Mp3Info;
 import tony.mp3player.service.PlayerService;
 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.os.Environment;
 import android.os.Handler;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.ImageButton;
 import android.widget.TextView;

 public class PlayerActivity extends Activity {

     private ImageButton beginBtn = null;
     private ImageButton pauseBtn = null;
     private ImageButton stopBtn = null;

     private List<Queue> queues = null;
     private TextView lrcTextView = null;
     private Mp3Info info = null;
     private Handler handler = new Handler();
     private UpdateTimeCallback updateTimeCallback = null;
     private long begin = 0;
     private long nextTimeMill = 0;
     private long currentTimeMill = 0;
     private String msg = null;
     private long pauseTimeMills = 0;
     private boolean isPlaying = false;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.player);
         Intent intent = getIntent();
         info = (Mp3Info) intent.getSerializableExtra("mp3Info");
         beginBtn = (ImageButton) findViewById(R.id.begin);
         pauseBtn = (ImageButton) findViewById(R.id.pause);
         stopBtn = (ImageButton) findViewById(R.id.stop);
         lrcTextView = (TextView) findViewById(R.id.lrcText);

         beginBtn.setOnClickListener(new BeginListener());
         pauseBtn.setOnClickListener(new PauseListener());
         stopBtn.setOnClickListener(new StopListener());
     }

     /**
      * 根据歌词文件的名字，来读取歌词文件当中的信息
      * @param lrcName
      */
     private void prepareLrc(String lrcName) {
         try {
             InputStream inputStream;
             inputStream = new FileInputStream(Environment.getExternalStorageDirectory().getAbsolutePath() +
                     File.separator + "mp3" + File.separator + info.getLrcName());
             LrcProcessor lrcProcessor = new LrcProcessor();
             queues = lrcProcessor.process(inputStream);
             updateTimeCallback = new UpdateTimeCallback(queues);
             begin = 0;
             currentTimeMill = 0;
             nextTimeMill = 0;
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     class BeginListener implements OnClickListener {
         @Override
         public void onClick(View v) {
             if(!isPlaying) {
                 //创建一个Intent对象，用于通知Service开始播放MP3
                 Intent intent = new Intent();
                 intent.putExtra("mp3Info", info);
                 intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG);
                 intent.setClass(PlayerActivity.this, PlayerService.class);
                 //读取LRC文件,放于startservice前,是为了防止歌曲已播放，但歌词没读完，造成不同步
                 prepareLrc(info.getLrcName());
                 startService(intent);
                 begin = System.currentTimeMillis();
                 handler = new Handler();
                 handler.postDelayed(updateTimeCallback, 5);//5毫秒是试验得出的
                 isPlaying = true;
             }
         }
     }

     class PauseListener implements OnClickListener {
         @Override
         public void onClick(View v) {
             //通知Service暂停播放MP3
             Intent intent = new Intent();
             intent.putExtra("MSG", AppConstant.PlayerMsg.PAUSE_MSG);
             intent.setClass(PlayerActivity.this, PlayerService.class);
             startService(intent);
             if(isPlaying) {
                 //不再更新歌词
                 handler.removeCallbacks(updateTimeCallback);
                 //用来下面代码计算暂停了多久
                 pauseTimeMills = System.currentTimeMillis();
             } else {
                 handler.postDelayed(updateTimeCallback, 5);
                 //因为下面的时间偏移是这样计算的offset = System.currentTimeMillis() - begin;
                 //所以要把暂停的时间加到begin里去,
                 begin = System.currentTimeMillis() - pauseTimeMills + begin;
             }
             isPlaying = !isPlaying;
         }
     }

     class StopListener implements OnClickListener {
         @Override
         public void onClick(View v) {
             //通知Service停止播放MP3文件
             Intent intent = new Intent();
             intent.putExtra("MSG", AppConstant.PlayerMsg.STOP_MSG);
             intent.setClass(PlayerActivity.this, PlayerService.class);
             startService(intent);
             //从Handler当中移除updateTimeCallback
             handler.removeCallbacks(updateTimeCallback);
             isPlaying = false;
         }
     }

     class UpdateTimeCallback implements Runnable{
         Queue<Long> times = null;
         Queue<String> msgs = null;

         public UpdateTimeCallback(List<Queue> queues) {
             this.times = queues.get(0);
             this.msgs = queues.get(1);
         }

         @Override
         public void run() {
             //计算偏移量，也就是说从开始播放MP3到现在为止，共消耗了多少时间，以毫秒为单位
             long offset = System.currentTimeMillis() - begin;
             if(currentTimeMill == 0) {//刚开始播放时，调用prepareLrc()，在其中设置currentTimeMill=0
                 nextTimeMill = times.poll();
                 msg = msgs.poll();
             }
             //歌词的显示是如下：例如
             //[00:01.00]Look
             //[00:03.00]Up
             //[00:06.00]Down
             //则在第1~3秒间是显示“look”,在第3~6秒间是显示"Up",在第6秒到下一个时间点显示"Down"
             if(offset >= nextTimeMill) {
                 lrcTextView.setText(msg);
                 msg = msgs.poll();
                 nextTimeMill = times.poll();
             }
             currentTimeMill = currentTimeMill + 100;
             //在run方法里调用postDelayed，则会形成循环，每0.01秒执行一次线程
             handler.postDelayed(updateTimeCallback, 100);
         }
     }
 }

(2)PlayService.java

 package tony.mp3player.service;

 import java.io.File;

 import tony.model.Mp3Info;
 import tony.mp3player.AppConstant;
 import android.app.Service;
 import android.content.Intent;
 import android.media.MediaPlayer;
 import android.net.Uri;
 import android.os.Environment;
 import android.os.IBinder;

 public class PlayerService extends Service {

     private boolean isPlaying = false;
     private boolean isPause = false;
     private boolean isReleased = false;
     private MediaPlayer mediaPlayer = null;

     @Override
     public IBinder onBind(Intent intent) {
         return null;
     }

     @Override
     public int onStartCommand(Intent intent, int flags, int startId) {
         Mp3Info info = (Mp3Info) intent.getSerializableExtra("mp3Info");
         int MSG = intent.getIntExtra("MSG", 0);
         if(info != null) {
             if(MSG == AppConstant.PlayerMsg.PLAY_MSG) {
                 play(info);
             }
         } else {
             if(MSG == AppConstant.PlayerMsg.PAUSE_MSG) {
                 pause();
             }
             else if(MSG == AppConstant.PlayerMsg.STOP_MSG) {
                 stop();
             }
         }
         return super.onStartCommand(intent, flags, startId);
     }

     private void stop() {
         if(mediaPlayer != null) {
             if(isPlaying) {
                 if(!isReleased) {
                     mediaPlayer.stop();
                     mediaPlayer.release();
                     isReleased = true;
                     isPlaying = false;
                 }
             }
         }
     }

     private void pause() {
         if(mediaPlayer != null) {
             if(!isReleased){
                 if(!isPause) {
                     mediaPlayer.pause();
                     isPause = true;
                 } else {
                     mediaPlayer.start();
                     isPause = false;
                 }
             }
         }
     }

     private void play(Mp3Info info) {
         if(!isPlaying) {
             String path = getMp3Path(info);
             mediaPlayer = MediaPlayer.create(this, Uri.parse("file://" + path));
             mediaPlayer.setLooping(false);
             mediaPlayer.start();
             isPlaying = true;
             isReleased = false;
         }
     }

     private String getMp3Path(Mp3Info mp3Info) {
         String SDCardRoot = Environment.getExternalStorageDirectory()
                 .getAbsolutePath();
         String path = SDCardRoot + File.separator + "mp3" + File.separator
                 + mp3Info.getMp3Name();
         return path;
     }
 }

3.LrcProcessor.java

 package tony.mp3player;

 import java.io.BufferedReader;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.Queue;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;

 public class LrcProcessor {

     public ArrayList<Queue> process(InputStream inputStream) {
         Queue<Long> timeMills = new LinkedList<Long>();
         Queue<String> messages = new LinkedList<String>();
         ArrayList<Queue> queues = new ArrayList<Queue>();
         try {
             InputStreamReader inputReader = new InputStreamReader(inputStream);
             BufferedReader bufferReader = new BufferedReader(inputReader);
             //创建一个正则表达式对象，寻找两边都带中括号的文本
             Pattern p = Pattern.compile("\\[([^\\]]+)\\]");
             String temp = null;
             String result = null;
             while((temp = bufferReader.readLine()) != null) {
                 Matcher m = p.matcher(temp);
                 if(m.find()) {
                     if(result != null) {//正则第一次到时是，此时result还没值，到下一次循环时，就会把第一次计算出的result加到队列里
                         messages.add(result);
                     }
                     String timeStr = m.group();
                     Long timeMill = time2Long(timeStr.substring(1, timeStr.length() - 1));
                     timeMills.offer(timeMill);//和add相比，offer不会抛异常
                     //取出时间串后面的歌词，如[00:02.31]Lose Yourself，得到“Lose Yourself”
                     String msg = temp.substring(timeStr.length());
                     result = "" + msg + "\n";//防止msg为null时抛nullpoint
                 } else {
                     result = result + temp + "\n";
                     //比如歌词如下：则上面的if会得到result = a + "\n",
                     //而else里会使result = a + "\n" + b + "\n" + c + "\n"
                     //[00:32.42]a
                     //b
                     //c
                 }
             }
             messages.add(result);//把最后一次循环的result加到quenue里
             queues.add(timeMills);//把时间队列和歌词队列都加到list里
             queues.add(messages);
         } catch (Exception e) {
             e.printStackTrace();
         }
         return queues;
     }

     private Long time2Long(String timeStr) {
         //eg : 00:02.31
         String [] s = timeStr.split(":");
         int min = Integer.parseInt(s[0]);
         String ss[] = s[1].split("\\.");
         int sec = Integer.parseInt(ss[0]);
         int mill = Integer.parseInt(ss[1]);
         return min * 60 * 1000 + sec * 1000 + mill * 10L;
     }

 }

4.AppConstant.java

 package tony.mp3player;

 public interface AppConstant {

     public class PlayerMsg {
         public static final int PLAY_MSG = 1;
         public static final int PAUSE_MSG = 2;
         public static final int STOP_MSG =3;
     }
     public class URL {
         public static final String BASE_URL = "http://192.168.1.104:8080/mp3/";
     }
 }