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1111111111111111111111111activity_main.xml
   
       
            
         
        
            
                 
                  
                  
              
             
                 
              
             
                 
                  
                  
              
         
    
   22222222222222222222AndroidManifest.xml  
       
   33333333333333MainActivity.javapackage com.example.musicmp3;import android.Manifest;import android.app.Activity;import android.content.pm.PackageManager;import android.media.MediaPlayer;import android.os.Build;import android.os.Bundle;import android.os.Environment;import android.os.Handler;import android.os.Message;import android.os.StrictMode;import android.view.View;import android.widget.AdapterView;import android.widget.ArrayAdapter;import android.widget.ImageButton;import android.widget.ListView;import android.widget.SeekBar;import android.widget.TextView;import android.widget.Toast;import androidx.core.app.ActivityCompat;import java.io.File;import java.io.IOException;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Date;import java.util.Timer;import java.util.TimerTask;public class MainActivity extends Activity {
       private static final int INTERNAL_TIME = 1000;    final MediaPlayer mp = new MediaPlayer();    String song_path = "";    private SeekBar seekBar;    private TextView currentTV;    private TextView totalTV;    boolean isStop = true;    private boolean isSeekBarChanging;//互斥变量，防止进度条与定时器冲突。    private int currentposition;//当前音乐播放的进度    private Timer timer;    private ArrayList
   
     list;    private File[] songFiles;    private Handler mHandler = new Handler(new Handler.Callback() {
           @Override        public boolean handleMessage(Message message) {
               // 展示给进度条和当前时间            int progress = mp.getCurrentPosition();            seekBar.setProgress(progress);            currentTV.setText(formatTime(progress));            // 继续定时发送数据            updateProgress();            return true;        }    });    //3、使用formatTime方法对时间格式化：    private String formatTime(int length) {
           Date date = new Date(length);        //时间格式化工具        SimpleDateFormat sdf = new SimpleDateFormat("mm:ss");        String totalTime = sdf.format(date);        return totalTime;    }    @Override    protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        totalTV = findViewById(R.id.music_total_time);        currentTV = findViewById(R.id.music_current_time);        seekBar = (SeekBar) findViewById(R.id.music_seekbar);        seekBar.setOnSeekBarChangeListener(new MySeekBar());        if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_EXTERNAL_STORAGE)                != PackageManager.PERMISSION_GRANTED) {
               ActivityCompat.requestPermissions(MainActivity.this,                    new String[]{
   Manifest.permission.READ_EXTERNAL_STORAGE}, 123);            return;        }        //判断是否是AndroidN以及更高的版本 N=24        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
               StrictMode.VmPolicy.Builder builder = new StrictMode.VmPolicy.Builder();            StrictMode.setVmPolicy(builder.build());        }        list = new ArrayList
    
     ();   //音乐列表        File sdpath = Environment.getExternalStorageDirectory(); //获得手机SD卡路径/sdcard/kgmusic/download        System.out.println("******"+Environment.getExternalStorageDirectory());        File path = new File(sdpath + "//kgmusic//download//");      //获得SD卡的mp3文件夹        //返回以.mp3结尾的文件 (自定义文件过滤)        songFiles = path.listFiles(new MyFilter(".mp3"));        for (File file : songFiles) {
               list.add(file.getAbsolutePath());   //获取文件的绝对路径        }        ArrayAdapter
     
       adapter = new ArrayAdapter
      
       (MainActivity.this,                android.R.layout.simple_list_item_single_choice,                list);        ListView li = (ListView) findViewById(R.id.listView1);        li.setAdapter(adapter);        li.setChoiceMode(ListView.CHOICE_MODE_SINGLE);        li.setOnItemClickListener(new AdapterView.OnItemClickListener() {
               @Override            public void onItemClick(AdapterView
        parent, View view, int position, long id) {
                   song_path = ((TextView) view).getText().toString();                currentposition = position;                changeMusic(currentposition);                try {
                       mp.reset();    //重置                    mp.setDataSource(song_path);                    mp.prepare();     //准备                    mp.start(); //播放                    seekBar.setMax(mp.getDuration());                    isStop = false;                    timer = new Timer();                    timer.schedule(new TimerTask() {
                           @Override                        public void run() {
                               if (!isSeekBarChanging) {
                                   seekBar.setProgress(mp.getCurrentPosition());                            }                        }                    }, 0, 50);                } catch (Exception e) {
                   }            }        });        //暂停和播放        final ImageButton btnpause = (ImageButton) findViewById(R.id.btn_pause);        btnpause.setOnClickListener(new View.OnClickListener() {
               @Override            public void onClick(View v) {
                   if (song_path.isEmpty())                    Toast.makeText(getApplicationContext(), "先选收歌曲先听听", Toast.LENGTH_SHORT).show();                if (mp.isPlaying()) {
                       mp.pause();  //暂停                    isStop = true;                    btnpause.setImageResource(android.R.drawable.ic_media_play);                } else if (!song_path.isEmpty()) {
                       mp.start();   //继续播放                    isStop = false;                    btnpause.setImageResource(android.R.drawable.ic_media_pause);                }            }        });        //上一曲和下一曲        final ImageButton previous = (ImageButton) findViewById(R.id.previous);        previous.setOnClickListener(new View.OnClickListener() {
               @Override            public void onClick(View v) {
                   changeMusic(--currentposition);            }        });        final ImageButton next = (ImageButton) findViewById(R.id.next);        next.setOnClickListener(new View.OnClickListener() {
               @Override            public void onClick(View v) {
                   changeMusic(++currentposition);            }        });    }    private void changeMusic(int position) {
           if (position < 0) {
               currentposition = position = list.size() - 1;        } else if (position > list.size() - 1) {
               currentposition = position = 0;        }        song_path = songFiles[position].getAbsolutePath();        try {
               // 切歌之前先重置，释放掉之前的资源            mp.reset();            // 设置播放源            mp.setDataSource(song_path);            // 开始播放前的准备工作，加载多媒体资源，获取相关信息            mp.prepare();            // 开始播放            mp.start();        } catch (IOException e) {
               e.printStackTrace();        }        seekBar.setProgress(0);//将进度条初始化        seekBar.setMax(mp.getDuration());//设置进度条最大值为歌曲总时间        totalTV.setText(formatTime(mp.getDuration()));//显示歌曲总时长        updateProgress();//更新进度条    }    private void updateProgress() {
           // 使用Handler每间隔1s发送一次空消息，通知进度条更新        Message msg = Message.obtain();// 获取一个现成的消息        // 使用MediaPlayer获取当前播放时间除以总时间的进度        int progress = mp.getCurrentPosition();        msg.arg1 = progress;        mHandler.sendMessageDelayed(msg, INTERNAL_TIME);    }    public class MySeekBar implements SeekBar.OnSeekBarChangeListener {
           public void onProgressChanged(SeekBar seekBar, int progress,                                      boolean fromUser) {
           }        /*滚动时,应当暂停后台定时器*/        public void onStartTrackingTouch(SeekBar seekBar) {
               isSeekBarChanging = true;        }        /*滑动结束后，重新设置值*/        public void onStopTrackingTouch(SeekBar seekBar) {
               isSeekBarChanging = false;            mp.seekTo(seekBar.getProgress());        }    }    protected void onDestroy() {
           super.onDestroy();        if (mp != null) {
               mp.stop();            mp.release();        }        Toast.makeText(getApplicationContext(), "退出啦", Toast.LENGTH_SHORT).show();    }}4444444MyFilter.javapackage com.example.musicmp3;import java.io.File;import java.io.FilenameFilter;class MyFilter implements FilenameFilter {
       private String type;    public MyFilter(String type) {
           this.type = type;    }    @Override    public boolean accept(File dir, String name) {
           return name.endsWith(type);    }}
      
     
    
   

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