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 + "
";//防止msg为null时抛nullpoint
                } else {
                    result = result + temp + "
";
                    //比如歌词如下：则上面的if会得到result = a + "
",
                    //而else里会使result = a + "
" + b + "
" + c + "
"
                    //[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/";
    }
}