Android Studio【シンプル音楽プレーヤーコード】

MusicActivity.

package com.example.a55205.myapplication;

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.support.v4.app.ActivityCompat;
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 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 MusicActivity 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;//    ，           。
    private int currentposition;//         
    private Timer timer;
    private ArrayList list;
    private File[] songFiles;

    private Handler mHandler = new Handler(new Handler.Callback() {
        @Override
        public boolean handleMessage(Message message) {
            //            
            int progress = mp.getCurrentPosition();
            seekBar.setProgress(progress);
            currentTV.setText(formatTime(progress));
            //         
            updateProgress();
            return true;
        }
    });

    //3、  formatTime        ：
    private String formatTime(int length) {
        Date date = new Date(length);
        //       
        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_music);
        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(MusicActivity.this, Manifest.permission.READ_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MusicActivity.this,
                    new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, 123);
            return;
        }

        //     AndroidN        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();   //    
        File sdpath = Environment.getExternalStorageDirectory(); //    SD   
        File path = new File(sdpath + "//mp3//");      //  SD  mp3   
        //   .mp3      (       )
        songFiles = path.listFiles(new MyFilter(".mp3"));
        for (File file : songFiles) {
            list.add(file.getAbsolutePath());   //         
        }

        ArrayAdapter adapter = new ArrayAdapter(MusicActivity.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();    //  
                    mp.setDataSource(song_path);
                    mp.prepare();     //  
                    mp.start(); //  
                    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) {
                }
            }

        });

        //     
        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(), "        ", Toast.LENGTH_SHORT).show();
                if (mp.isPlaying()) {
                    mp.pause();  //  
                    isStop = true;
                    btnpause.setImageResource(android.R.drawable.ic_media_play);
                } else if (!song_path.isEmpty()) {
                    mp.start();   //    
                    isStop = false;
                    btnpause.setImageResource(android.R.drawable.ic_media_pause);
                }
            }
        });
        //       
        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 {
            //        ，        
            mp.reset();
            //      
            mp.setDataSource(song_path);
            //           ，       ，      
            mp.prepare();

            //     
            mp.start();
        } catch (IOException e) {
            e.printStackTrace();
        }
        seekBar.setProgress(0);//       
        seekBar.setMax(mp.getDuration());//              
        totalTV.setText(formatTime(mp.getDuration()));//       

        updateProgress();//     
    }

    private void updateProgress() {
        //   Handler   1s       ，       
        Message msg = Message.obtain();//          
        //   MediaPlayer                
        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) {
        }

        /*   ,         */
        public void onStartTrackingTouch(SeekBar seekBar) {
            isSeekBarChanging = true;
        }

        /*     ，     */
        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(), "   ", Toast.LENGTH_SHORT).show();
    }
}

activity_music

 

MyFilter（     ）

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);
    }
}