请问ios音频后台播放，如何实现（在线） ？

是ios保活的问题吗？可以申请background modes权限，选择audio

使用服务，即Service就可以满足你的要求。
给你我以前自己写的示例：

import java.util.List;

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.media.MediaPlayer.OnPreparedListener;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.util.Log;

import com.hs.leozheng.phonelinkhs.MusicListActivity;
import com.hs.leozheng.phonelinkhs.AudioMediaInfo;
import com.hs.leozheng.phonelinkhs.AppConstant;

/***
 * leo
 * 音乐播放服务
 */
@SuppressLint("NewApi")
public class PlayerService extends Service {
    private MediaPlayer mediaPlayer;    // 媒体播放器对象
    private String path;                // 音乐文件路径
    private int msg;
    private boolean isPause;            // 暂停状态
    private int current = 0;            // 记录当前正在播放的音乐
    private List<AudioMediaInfo> mp3Infos;      // 存放 AudioMediaInfo 对象的集合
    private int status = 3;             // 播放状态，默认为顺序播放
    private MyReceiver myReceiver;      // 自定义广播接收器
    private int currentTime;            // 当前播放进度
    private int duration;               // 播放长度

    /**
     * handler 用来接收消息，来发送广播更新播放时间
     */
    @SuppressLint("HandlerLeak")
    private Handler handler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            if (msg.what == 1) {
                if(mediaPlayer != null) {
                    currentTime = mediaPlayer.getCurrentPosition(); // 获取当前音乐播放的位置
                    duration = mediaPlayer.getDuration();

                    Intent intent = new Intent();
                    intent.setAction(AppConstant.AUDIO_SEND_CURRENT);
                    intent.putExtra("currentTime", currentTime);
                    intent.putExtra("totalTime", duration);
                    sendBroadcast(intent); // 给 PlayerActivity 发送广播
                    handler.sendEmptyMessageDelayed(1, 100);
                }
            }
        };
    };

    @Override
    public void onCreate() {
        super.onCreate();
        Log.i("service", "service created");
        mediaPlayer = new MediaPlayer();
        mp3Infos = MusicListActivity.getMp3Infos(PlayerService.this);

        myReceiver = new MyReceiver();
        IntentFilter filter = new IntentFilter();
        filter.addAction(AppConstant.AUDIO_CTRL_ACTION);
        registerReceiver(myReceiver, filter);

        /**
         * 设置音乐播放完成时的监听器
         */
        mediaPlayer.setOnCompletionListener(new OnCompletionListener() {

            @Override
            public void onCompletion(MediaPlayer mp) {
                if (1 == status) {          // 单曲循环
                    mediaPlayer.start();
                } else if (2 == status) {   // 全部循环
                    current++;
                    if(current > mp3Infos.size() - 1) { // 变为第一首的位置继续播放
                        current = 0;
                    }
                    path = mp3Infos.get(current).GetUrl();

                    Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
                    sendIntent.putExtra("current", current);
                    sendIntent.putExtra("url", path);
                    sendIntent.putExtra("total", mp3Infos.size());
                    // 发送广播，将被 Activity 组件中的 BroadcastReceiver 接收到
                    sendBroadcast(sendIntent);
                    play(0);
                } else if (3 == status) {   // 顺序播放
                    current++;              // 下一首位置
                    if (current <= mp3Infos.size() - 1) {
                        path = mp3Infos.get(current).GetUrl();
                        Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
                        sendIntent.putExtra("current", current);
                        sendIntent.putExtra("url", path);
                        sendIntent.putExtra("total", mp3Infos.size());

                        sendBroadcast(sendIntent);
                        play(0);
                    }else {
                        mediaPlayer.seekTo(0);
                        current = 0;
                        path = mp3Infos.get(current).GetUrl();
                        Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
                        sendIntent.putExtra("current", current);
                        sendIntent.putExtra("url", path);
                        sendIntent.putExtra("total", mp3Infos.size());

                        sendBroadcast(sendIntent);
                    }
                } else if (4 == status) {   // 随机播放
                    current = getRandomIndex(mp3Infos.size() - 1);
                    path = mp3Infos.get(current).GetUrl();
                    Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
                    sendIntent.putExtra("current", current);
                    sendIntent.putExtra("url", path);
                    sendIntent.putExtra("total", mp3Infos.size());

                    sendBroadcast(sendIntent);
                    play(0);
                }
            }
        });
    }

    /**
     * 获取随机位置
     */
    protected int getRandomIndex(int end) {
        int index = (int) (Math.random() * end);
        return index;
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

    @SuppressWarnings("deprecation")
    @Override
    public void onStart(Intent intent, int startId) {
        path = intent.getStringExtra("url");                // 歌曲路径
        current = intent.getIntExtra("listPosition", -1);   // 当前播放歌曲的在 mp3Infos 的位置
        Log.i("Play Service", "onStart current is: " + Integer.toString(current));
        msg = intent.getIntExtra("MSG", 0);                 // 播放信息
        AppConstant.PlayerMsg msgEnum = AppConstant.PlayerMsg.values()[msg];
        if (AppConstant.PlayerMsg.PLAY_MSG == msgEnum) {    // 直接播放音乐
            Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
            sendIntent.putExtra("current", current);
            sendIntent.putExtra("url", path);
            sendIntent.putExtra("total", mp3Infos.size());
            // 发送广播，将被 Activity 组件中的 BroadcastReceiver 接收到
            sendBroadcast(sendIntent);

            play(0);
        }
        else if (AppConstant.PlayerMsg.PAUSE_MSG == msgEnum) {          // 暂停
            pause();
        }
        else if (AppConstant.PlayerMsg.STOP_MSG == msgEnum) {           // 停止
            stop();
        }
        else if (AppConstant.PlayerMsg.CONTINUE_MSG == msgEnum) {       // 继续播放
            resume();
        }
        else if (AppConstant.PlayerMsg.PRIVIOUS_MSG == msgEnum) {       // 上一首
            previous();
        }
        else if (AppConstant.PlayerMsg.NEXT_MSG == msgEnum) {           // 下一首
            next();
        }
        else if (AppConstant.PlayerMsg.PROGRESS_CHANGE == msgEnum) {    // 进度更新
            currentTime = intent.getIntExtra("progress", -1);
            play(currentTime);
        }
        else if (AppConstant.PlayerMsg.PLAYING_MSG == msgEnum) {
            handler.sendEmptyMessage(1);
        }

        super.onStart(intent, startId);
    }

    /**
     * 播放音乐
     *
     * @param position
     */
    private void play(int currentTime) {
        try {
            mediaPlayer.reset();                // 把各项参数恢复到初始状态
            mediaPlayer.setDataSource(path);

            Intent commonCtrl_intent = new Intent();
            commonCtrl_intent.setAction(AppConstant.COMMON_UI_MSG);
            commonCtrl_intent.putExtra("ACTION", "UIPlayingFilename");
            // 对 URL 进行处理: 保显示文件名,不显示目录
            int find = path.lastIndexOf('/') + 1;
            String strFilename = null;
            if(-1 != find)
            {
                strFilename = path.substring(find);
                commonCtrl_intent.putExtra("filename", strFilename);
                sendBroadcast(commonCtrl_intent);
            }

            mediaPlayer.prepare();              // 进行缓冲
            mediaPlayer.setOnPreparedListener(new PreparedListener(currentTime));   // 注册一个监听器
            handler.sendEmptyMessage(1);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 暂停音乐
     */
    private void pause() {
        if (mediaPlayer != null && mediaPlayer.isPlaying()) {
            mediaPlayer.pause();
            isPause = true;

            Intent commonCtrl_intent = new Intent();
            commonCtrl_intent.setAction(AppConstant.COMMON_UI_MSG);
            commonCtrl_intent.putExtra("ACTION", "UIPlayingStatus");
            commonCtrl_intent.putExtra("playingStatus", 2);
            sendBroadcast(commonCtrl_intent);
        }
    }

    private void resume() {
        if (isPause) {
            mediaPlayer.start();
            isPause = false;

            Intent commonCtrl_intent = new Intent();
            commonCtrl_intent.setAction(AppConstant.COMMON_UI_MSG);
            commonCtrl_intent.putExtra("ACTION", "UIPlayingStatus");
            commonCtrl_intent.putExtra("playingStatus", 1);
            sendBroadcast(commonCtrl_intent);
        }
    }

    /**
     * 上一首
     */
    private void previous() {
        int size = mp3Infos.size();
        if((current - 1) >= 0) {
            current--;
        }
        else {
            current = size - 1;
        }
        path = mp3Infos.get(current).GetUrl();

        Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
        sendIntent.putExtra("current", current);
        sendIntent.putExtra("url", path);
        sendIntent.putExtra("total", size);
        // 发送广播，将被 Activity 组件中的 BroadcastReceiver 接收到
        sendBroadcast(sendIntent);
        play(0);
    }

    /**
     * 下一首
     */
    private void next() {
        int size = mp3Infos.size();
        if((current + 1) <= (size - 1)) {
            current++;
        }
        else {
            current = 0;
        }
        path = mp3Infos.get(current).GetUrl();

        Intent sendIntent = new Intent(AppConstant.AUDIO_SEND_UPDATE);
        sendIntent.putExtra("current", current);
        sendIntent.putExtra("url", path);
        sendIntent.putExtra("total", size);
        // 发送广播，将被 Activity 组件中的 BroadcastReceiver 接收到
        sendBroadcast(sendIntent);
        play(0);
    }

    /**
     * 停止音乐
     */
    private void stop() {
        if (mediaPlayer != null) {
            mediaPlayer.stop();
            try {
                mediaPlayer.prepare(); // 在调用 stop 后如果需要再次通过 start 进行播放,需要之前调用 prepare 函数
            } catch (Exception e) {
                e.printStackTrace();
            }

            Intent commonCtrl_intent = new Intent();
            commonCtrl_intent.setAction(AppConstant.COMMON_UI_MSG);
            commonCtrl_intent.putExtra("ACTION", "UIPlayingStatus");
            commonCtrl_intent.putExtra("playingStatus", 3);
            sendBroadcast(commonCtrl_intent);
        }
    }

    @Override
    public void onDestroy() {
        if (mediaPlayer != null) {
            mediaPlayer.stop();
            mediaPlayer.release();
            mediaPlayer = null;
        }
    }

    /**
     *
     * 实现一个 OnPrepareLister 接口,当音乐准备好的时候开始播放
     *
     */
    private final class PreparedListener implements OnPreparedListener {
        private int currentTime;

        public PreparedListener(int currentTime) {
            this.currentTime = currentTime;
        }

        @Override
        public void onPrepared(MediaPlayer mp) {
            mediaPlayer.start();    // 开始播放
            if (currentTime > 0) {  // 如果音乐不是从头播放
                mediaPlayer.seekTo(currentTime);
            }
            Intent intent = new Intent();
            intent.setAction(AppConstant.AUDIO_SEND_DURATION);
            duration = mediaPlayer.getDuration();
            intent.putExtra("duration", duration);  // 通过 Intent 来传递歌曲的总长度
            sendBroadcast(intent);
        }
    }

    public class MyReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            AppConstant.PlayerMsg msgEnum = AppConstant.PlayerMsg.APP_CONSTANT_MAX;
            String action = intent.getAction();
            int msg = intent.getIntExtra("MSG", -1);
            int mode = intent.getIntExtra("mode", 3);
            if(msg > 0) {
                msgEnum = AppConstant.PlayerMsg.values()[msg];
            }
            if(action.equals(AppConstant.AUDIO_CTRL_ACTION)) {
                Log.v("Play Service", "Control: " + Integer.toString(msg));
                if(msgEnum == AppConstant.PlayerMsg.PRIVIOUS_MSG)
                {
                    Log.v("Play Service", "Control.Prev");
                    previous();
                }
                else if(msgEnum == AppConstant.PlayerMsg.NEXT_MSG)
                {
                    Log.v("Play Service", "Control.Next");
                    next();
                }
                else if(msgEnum == AppConstant.PlayerMsg.PLAY_MODE)
                {
                    Log.v("Play Service", "Control.Mode: " + Integer.toString(mode));
                }
                else if(msgEnum == AppConstant.PlayerMsg.CONTINUE_MSG)
                {
                    Log.v("Play Service", "Control.Continue");
                    resume();
                }
                else if(msgEnum == AppConstant.PlayerMsg.PAUSE_MSG)
                {
                    Log.v("Play Service", "Control.Pause");
                    pause();
                }
            }
        }
    }

}

调用 方式：

Intent intent = new Intent();
intent.putExtra("url", audioMediaInfo.GetUrl());   // 参数可要、可不要
intent.putExtra("listPosition", positionSelected/*getPlayingIndex(audioMediaInfo.GetUrl())*/);
intent.putExtra("MSG", AppConstant.PlayerMsg.PLAY_MSG.ordinal());
intent.setClass(MusicListActivity.this, PlayerService.class);
startService(intent);