A service that prepares MediaPlayer instances and caches the most-requested ones for you

AudioLoaderService.java

package app

import android.content.Context;
import android.media.MediaPlayer;

import org.androidannotations.annotations.EBean;
import org.androidannotations.annotations.RootContext;

import java.io.IOException;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Map;

/**
 * Pre-loads audio files for quicker playback times
 */
@EBean
public class AudioLoaderService {

    public static final int DEFAULT_MAX_PLAYERS_ALLOWED = 2;

    private int maxPlayersAllowed;
    private Map<String, MediaPlayerWrapper> players;

    public AudioLoaderService() {
        players = new HashMap<>();
        this.maxPlayersAllowed = DEFAULT_MAX_PLAYERS_ALLOWED;
    }

    public void setMaxPlayersAllowed(int maxPlayersAllowed) {
        players = new HashMap<>();
        this.maxPlayersAllowed = maxPlayersAllowed;
    }

    public MediaPlayer getMediaPlayer(String audioFile) throws IOException {

        MediaPlayerWrapper wrapper;
        if (!players.containsKey(audioFile)) {
            ensurePlayerLimitIsRespected();

            MediaPlayer player = loadMediaPlayer(audioFile);
            wrapper = new MediaPlayerWrapper(audioFile, player);
            players.put(audioFile, wrapper);
        } else {
            wrapper = players.get(audioFile);
        }

        wrapper.getMediaPlayer().prepare();
        wrapper.bumpRequestCount();
        return wrapper.getMediaPlayer();
    }

    private void ensurePlayerLimitIsRespected() {

        if (players.size() == maxPlayersAllowed) {

            // evict a player
            String[] keys = (String[]) players.keySet().toArray(new String[] {});
            Arrays.sort(keys, new Comparator<String>() {
                @Override
                public int compare(String lhs, String rhs) {
                    return players.get(rhs).getRequestCount() -
                            players.get(lhs).getRequestCount();
                }
            });

            String keyToRemove = keys[0];
            MediaPlayerWrapper wrapper = players.remove(keyToRemove);
            wrapper.getMediaPlayer().release();
        }
    }

    private MediaPlayer loadMediaPlayer(String audioFile) throws IOException {

        MediaPlayer audioPlayer = new MediaPlayer();
        audioPlayer.setDataSource(audioFile);
        return audioPlayer;
    }

    // Release all media players
    public void release() {

        for (MediaPlayerWrapper wrapper : players.values()) {
            wrapper.getMediaPlayer().release();
        }

        players.clear();
    }

    private class MediaPlayerWrapper {

        private final String audioFile;
        private final MediaPlayer player;
        private int requestCount;

        public MediaPlayerWrapper(String audioFile, MediaPlayer player) {
            this.audioFile = audioFile;
            this.player = player;
            this.requestCount = 0;
        }

        public void bumpRequestCount() {
            requestCount++;
        }

        public int getRequestCount() {
            return requestCount;
        }

        public MediaPlayer getMediaPlayer() {
            return player;
        }

        @Override
        public String toString() {
            return String.format("(%s) - (%s)", requestCount, audioFile);
        }
    }
}