设计一个音乐播放器，用List列表显示手机中所有音乐，支持播放、暂停、继续、上一首、下一首等功能。

package com.example.lenovo.musicplayer;

import android.Manifest;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.provider.MediaStore;
import android.view.KeyEvent;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
import android.support.v4.app.ActivityCompat;

import java.text.SimpleDateFormat;
import java.util.ArrayList;

public class MusicActivity extends Activity {

ArrayList<Music> musicList = new ArrayList<Music>(); //音乐列表
MediaPlayer mp=new MediaPlayer(); //音乐播放器
SeekBar seekBar;
TextView current_time, total_time; //显示当前音乐进度信息
ImageButton btn_play; //播放按钮
ImageButton btn_left;
ImageButton btn_right;

TextView playtitle;

int position1=0;
int count=0;

int duration=0; //获取时
4000
长(ms)
int current=0; //当前音乐播放位置
boolean isOver=false; //是否播放完毕
private Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
if ( msg.what == 0 ) {
if( ! isOver ) {
current = mp.getCurrentPosition();
seekBar.setProgress(current);
SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
String time=sdf.format(current);
current_time.setText(""+time); //""不要掉了
}
}
}
};
public ArrayList<Music> ScannerMusic() {
ArrayList<Music> list=new ArrayList<>();
//  查询媒体数据库
Cursor cursor = getContentResolver().query(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,
MediaStore.Audio.Media.TITLE); //按标题排序
// 遍历媒体数据库
if ( cursor.moveToFirst() ){ //遍历每一行
while ( !cursor.isAfterLast() ) { //遍历每一列
//歌曲ID：MediaStore.Audio.Media._ID
int id = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media._ID));
//歌曲的名称 ：MediaStore.Audio.Media.TITLE
String tilte =cursor.getString(
cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE));

//歌曲作者
String artist=cursor.getString(
cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.ARTIST));

//歌曲路径 ：MediaStore.Audio.Media.DATA
String url = cursor.getString(
cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DATA));
//歌曲时长 ：MediaStore.Audio.Media.DURATION
int duration = cursor.getInt(
cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION));
Music m = new Music(id, tilte,artist, url, duration);
list.add(m);
cursor.moveToNext();
} //end while
cursor.close();
} //end if
return list;
}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_music);
//初始化
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;
}
seekBar=(SeekBar)findViewById(R.id.musicSeekBar);
current_time=(TextView)findViewById(R.id.current_time);
total_time=(TextView)findViewById(R.id.total_time);
btn_play=(ImageButton)findViewById(R.id.btn_play);
btn_right=(ImageButton)findViewById(R.id.btn_right);
btn_left=(ImageButton)findViewById(R.id.btn_left);
playtitle=(TextView)findViewById(R.id.playtitle);
// 获取音乐列表
musicList=ScannerMusic();
// 使用MusicAdpater
MusicAdapter adapter = new MusicAdapter(
MusicActivity.this, R.layout.music_item, musicList );
ListView li=(ListView)findViewById(R.id.musicListView);
li.setAdapter(adapter);
count=li.getCount();
li.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
position1=position;

Music m=musicList.get(position);
playtitle.setText("正在播放："+m.getTitle());

String music_url=m.getUrl(); //获得音乐路径
isOver=false;
btn_play.setImageResource(R.drawable.play);
try{
mp.reset(); // 重置
mp.setDataSource(music_url);
mp.prepare(); // 准备
}catch (Exception e){
e.printStackTrace();
}
duration=mp.getDuration(); //获取音乐时长(ms)
SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
String time=sdf.format(duration);
total_time.setText(""+time);
seekBar.setMax(duration); //给SeekBar设置最大时长
mp.start(); //播放
btn_play.setImageResource(R.drawable.pause);
new Thread() {
@Override
public void run() {
while ( ! isOver ) {
try {
Thread.sleep(50); //每50ms执行一次mTimerTask任务
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0); //直接发送一个what=0的空消息
}
}
}.start();
} //end onItemClick
}); //end setOnItemClick
btn_play.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
isOver=false;
if( mp.isPlaying() ){
mp.pause();
btn_play.setImageResource(R.drawable.play);
}else{
mp.start();
btn_play.setImageResource(R.drawable.pause);
//后续，再次启动子线程
new Thread() {
@Override
public void run() {
while ( !isOver ) {
try {
Thread.sleep(50); //每50ms执行一次mTimerTask任务
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0); //直接发送一个what=0的空消息
}
}
}.start();
} //end else
} //end onClick
}); //end setOnClick
// 播放完毕
btn_right.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
position1+=1;
if(position1>=count)
{
position1=0;
}
Music m=musicList.get(position1);

playtitle.setText("正在播放："+m.getTitle());
String music_url=m.getUrl(); //获得音乐路径
isOver=false;
btn_play.setImageResource(R.drawable.pause);
try{
mp.reset(); // 重置
mp.setDataSource(music_url);
mp.prepare(); // 准备
}catch (Exception e){
e.printStackTrace();
}
duration=mp.getDuration(); //获取音乐时长(ms)
SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
String time=sdf.format(duration);
total_time.setText(""+time);
seekBar.setMax(duration); //给SeekBar设置最大时长
mp.start(); //播放
new Thread() {
@Override
public void run() {
while ( !isOver ) {
try {
Thread.sleep(50); //每50ms执行一次mTimerTask任务
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0); //直接发送一个what=0的空消息
}
}
}.start();
}
});
btn_left.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view){
position1-=1;
if(position1<=0)
{
position1=count-1;
}
Music m=musicList.get(position1);

playtitle.setText("正在播放："+m.getTitle());
String music_url=m.getUrl(); //获得音乐路径
isOver=false;
btn_play.setImageResource(R.drawable.pause);
try{
mp.reset(); // 重置
mp.setDataSource(music_url);
mp.prepare(); // 准备
}catch (Exception e){
e.printStackTrace();
}
duration=mp.getDuration(); //获取音乐时长(ms)
SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
String time=sdf.format(duration);
total_time.setText(""+time);
seekBar.setMax(duration); //给SeekBar设置最大时长
mp.start(); //播放
new Thread() {
@Override
public void run() {
while ( !isOver ) {
try {
Thread.sleep(50); //每50ms执行一次mTimerTask任务
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0); //直接发送一个what=0的空消息
}
}
}.start();

}
});

mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
@Override
public void onCompletion(MediaPlayer mp) {
position1+=1;
if(position1>=count)
{
position1=0;
}
Music m=musicList.get(position1);
playtitle.setText("正在播放："+m.getTitle());
String music_url=m.getUrl(); //获得音乐路径
isOver=false;
btn_play.setImageResource(R.drawable.pause);
try{
mp.reset(); // 重置
mp.setDataSource(music_url);
mp.prepare(); // 准备
}catch (Exception e){
e.printStackTrace();
}
duration=mp.getDuration(); //获取音乐时长(ms)
SimpleDateFormat sdf=new SimpleDateFormat("mm:ss");
String time=sdf.format(duration);
total_time.setText(""+time);
seekBar.setMax(duration); //给SeekBar设置最大时长
mp.start(); //播放
new Thread() {
@Override
public void run() {
while ( !isOver ) {
try {
Thread.sleep(50); //每50ms执行一次mTimerTask任务
} catch (InterruptedException e) {
e.printStackTrace();
}
mHandler.sendEmptyMessage(0); //直接发送一个what=0的空消息
}
}
}.start();
}
});
seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
//此处无代码
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
//此处无代码
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
current=seekBar.getProgress();
current_time.setText(""+current);
mp.seekTo(current);
}
}); //end setOnSeekBar
} // end onCreate
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if( keyCode==event.KEYCODE_BACK ){
new AlertDialog.Builder(MusicActivity.this)
.setIcon(R.drawable.login)
.setTitle("提示")
.setMessage("确定退出吗？")
.setPositiveButton("确定",new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
})
.setNegativeButton("取消", null)
.show();
}
return false;
}
@Override
protected void onDestroy() {
super.onDestroy();
isOver=true;
if( mp!=null ){
mp.stop();
mp.release();
}
Toast.makeText(getApplicationContext(), "退出啦", Toast.LENGTH_SHORT).show();
}
} // end activity（完）