Question

我不确定我在这里做错了什么。我把它带到了你可以从列表中随机播放一首歌但可以随机播放整个列表的地方。我能得到的任何帮助将不胜感激。我的代码是：

import java.util.ArrayList;
import java.util.Random;

/**
 * A class to hold details of audio tracks.
 * Individual tracks may be played.
 * 
 * @author William Gambill
 * @version July 10, 2013
 */
public class MusicOrganizer
{
    // An ArrayList for storing music tracks.
    private ArrayList<Track> tracks;
    // A player for the music tracks.
    private MusicPlayer player;
    // A reader that can read music files and load them as tracks.
    private TrackReader reader;
    // Used to initialize the random feature.
    private Random randomtrack;

    /**
     * Create a MusicOrganizer
     */
    public MusicOrganizer()
    {
        tracks = new ArrayList<Track>();
        player = new MusicPlayer();
        reader = new TrackReader();
        randomtrack = new Random();
        readLibrary("audio");
        System.out.println("Music library loaded. " + getNumberOfTracks() + " tracks.");
        System.out.println();
    }

    /**
     * Add a track file to the collection.
     * @param filename The file name of the track to be added.
     */
    public void addFile(String filename)
    {
        tracks.add(new Track(filename));
    }

    /**
     * Add a track to the collection.
     * @param track The track to be added.
     */
    public void addTrack(Track track)
    {
        tracks.add(track);
    }

    /**
     * Play a track in the collection.
     * @param index The index of the track to be played.
     */
    public void playTrack(int index)
    {
        if(indexValid(index)) {
            Track track = tracks.get(index);
            player.startPlaying(track.getFilename());
            System.out.println("Now playing: " + track.getArtist() + " - " + track.getTitle());
        }
    }

    /**
     * Play a track in the collection at random.
     * @param index The index of the track to begin the randomizer.
     */
    public void randomTrack(int index)
    {
        int trackNumber = getNumberOfTracks();
        int rindex = randomtrack.nextInt(trackNumber);
        if(indexValid(index)) {
            Track track = tracks.get(rindex);
            player.startPlaying(track.getFilename());
            System.out.println("Now playing: " + track.getArtist() + " - " + track.getTitle());
        }
    }

    /**
     * Play all tracks in the collection at random.
     * @param index The index of the track to begin the randomizer.
     */
    public void randomAllTracks(int index)
    {
        int trackNumber = getNumberOfTracks();
        int rindex = randomtrack.nextInt(trackNumber);
        if(indexValid(index)) 
        {
            for(Track track : tracks)    
            {
            player.startPlaying(track.getFilename());
            System.out.println("Now playing: " + track.getArtist() + " - " +   track.getTitle());
            System.out.println();
            }


        }
    }

    /**
     * Return the number of tracks in the collection.
     * @return The number of tracks in the collection.
     */
    public int getNumberOfTracks()
    {
        return tracks.size();
    }

    /**
     * List a track from the collection.
     * @param index The index of the track to be listed.
     */
    public void listTrack(int index)
    {
        System.out.print("Track " + index + ": ");
        Track track = tracks.get(index);
        System.out.println(track.getDetails());
    }

    /**
     * Show a list of all the tracks in the collection.
     */
    public void listAllTracks()
    {
        System.out.println("Track listing: ");

        for(Track track : tracks) {
        System.out.println(track.getDetails());
        }
        System.out.println();
    }

    /**
     * List all tracks by the given artist.
     * @param artist The artist's name.
     */
    public void listByArtist(String artist)
    {
        for(Track track : tracks) {
            if(track.getArtist().contains(artist)) {
                System.out.println(track.getDetails());
            }
        }
    }

    /**
     * Remove a track from the collection.
     * @param index The index of the track to be removed.
     */
    public void removeTrack(int index)
    {
        if(indexValid(index)) {
            tracks.remove(index);
        }
    }

    /**
     * Play the first track in the collection, if there is one.
     */
    public void playFirst()
    {
        if(tracks.size() > 0) {
            player.startPlaying(tracks.get(0).getFilename());
        }
    }

    /**
     * Stop the player.
     */
    public void stopPlaying()
    {
        player.stop();
    }

    /**
     * Determine whether the given index is valid for the collection.
     * Print an error message if it is not.
     * @param index The index to be checked.
     * @return true if the index is valid, false otherwise.
     */
    private boolean indexValid(int index)
    {
        // The return value.
        // Set according to whether the index is valid or not.
        boolean valid;

        if(index < 0) {
            System.out.println("Index cannot be negative: " + index);
            valid = false;
        }
        else if(index >= tracks.size()) {
            System.out.println("Index is too large: " + index);
            valid = false;
        }
        else {
            valid = true;
        }
        return valid;
    }

    private void readLibrary(String folderName)
    {
        ArrayList<Track> tempTracks = reader.readTracks(folderName, ".mp3");

        // Put all thetracks into the organizer.
        for(Track track : tempTracks) {
            addTrack(track);
        }
    }
}

Answer 1

您可以在代码中使用Collections.shuffle()吗？根据文档：

使用默认的随机源随机置换指定的列表。 所有排列的可能性大致相等。

您可以随机播放List并每次从洗牌List获取第一个元素。

Answer 2

你需要做的是，不是每次播放一首歌时都选择一个随机数，而是生成所有歌曲的列表，然后将整个列表随机播放，使其按随机顺序播放，然后播放每个歌曲。时间。

Answer 3

@ The New Idiot和@SharkofMirkWood的答案组合是正确的。像这样的东西

public void randomAllTracks() {
    List<Track> randomList = buildRandomList();
    playList(randomList);
}

private List<Track> buildRandomList() {
    List<Track> randomList = new ArrayList<Track>(this.tracks);
    Collections.shuffle(randomList);

    return randomList;
}

public void playList(List<Track> playList) {
    if(playList.size() > 0) {
        for(Track track : playList) {
            player.startPlaying(track.getName());
        }
    }
}

编写一种方法，以随机顺序播放曲目列表中的每个曲目

3 个答案: