[libgdx游戏开发教程]使用Libgdx进行游戏开发(10)-音乐和音效

本章音效文件都来自于公共许可： http://files.cnblogs.com/mignet/sounds.zip

在游戏中，播放背景音乐和音效是基本的功能。

Libgdx提供了跨平台的声音播放功能，支持的文件格式有:
•wav (RIFF WAVE)
•mp3 (MPEG-2 Audio Layer III)
•ogg (Ogg Vorbis)

Libgdx有2个接口来管理音乐和音效：Music和Sound.

Music通常要花更多的CPU周期，因为它在播放到声卡之前需要解析。Sound就不用了，因为Sound在加载的时候都已经解析过了。

常规用法：Sound sound = Gdx.audio.newSound(Gdx.files.internal("sound.wav"));同时记得sound.dispose(); // free allocated memory

除了Music和Sound，Libgdx还提供了底层的接口AudioDevice、AudioRecorder用来访问声卡以记录和播放原始的声音样本。

AudioDevice接口允许您直接发送PCM编码音频样本到音频设备。例如：

AudioDevice audioDevice = Gdx.audio.newAudioDevice(44100, false);//44.1 kHz

audioDevice.dispose(); // free allocated memory

发送到声卡的声音数据可以是一组浮点数或者是一组16位带符号短整形数.

void writeSamples(float[] samples, int offset, int numSamples);//offset (start),numSamples (length)
void writeSamples(short[] samples, int offset, int numSamples);

立体声意味着需要采集的样本是双倍的，因为立体声就是左声道和右声道交叉合成的。就是说44.1 kHz的采样率需要44100的单声道样本和88200的立体声样本。

AudioRecorder audioRecordedr = Gdx.audio.newAudioRecorder(44100, false);

audioRecorder.dispose(); // free allocated memory

同样的：void read(short[] samples, int offset, int numSamples);

现在，我们拥有足够的知识来生成自己的声音了，自己合成并保存，播放合成的声音测试效果，都可以实行了。

但是这样做对于很多经验丰富的程序员来讲都太高端了，哈哈。我们这里不讨论。

一个可行的解决方案来获得一些不错的音响效果是使用一个现有的*的和开放源码的声音生成器。

程序员自己的音效生成工具->声音生成器：

sfxr

这个生成器最初是由托马斯“DrPetter“佩特森在2007年开发的，后来慢慢的又出现了几个sfxr变体版本，像bfxr, cfxr, as3sfxr

首先来看sfxr：

sfxr之所以可以很快流行并被全球的程序员们使用，是因为只需要简单的按下这个软件上面的“RANDOMIZE”按钮，就可以生成声音。

而且还提供了很多基本的音效像PICKUP/COIN, LASER/SHOOT, EXPLOSION, POWERUP, HIT/HURT, JUMP, BLIP/SELECT

生成想要的声音之后，导出.wav文件就可以用了。

官方源码：https://code.google.com/p/sfxr/

cfxr是Cocoa sfxr的缩写，是Mac OS下原生的Cocoa应用程序，专门为Cocoa写的实现版本。

官方源码：https://github.com/nevyn/cfxr/

bfxr：这个功能很丰富，可以创建更复杂的音效，有兴趣可以自己摸索。

官方源码：https://github.com/increpare/bfxr/

现在开始在我们的游戏中使用音乐和音效。先把文件添加到assert（背景音乐没有提供下载因为太大了，你可以随便用什么音乐文件代替）：

和前面的资源管理提到的一样，我们使用内部类来统一管理各种资源。在Asserts中添加：

    public AssetSounds sounds;
    public AssetMusic music;

    public class AssetSounds {
        public final Sound jump;
        public final Sound jumpWithFeather;
        public final Sound pickupCoin;
        public final Sound pickupFeather;
        public final Sound liveLost;

        public AssetSounds(AssetManager am) {
            jump = am.get("sounds/jump.wav", Sound.class);
            jumpWithFeather = am.get("sounds/jump_with_feather.wav",
                    Sound.class);
            pickupCoin = am.get("sounds/pickup_coin.wav", Sound.class);
            pickupFeather = am.get("sounds/pickup_feather.wav", Sound.class);
            liveLost = am.get("sounds/live_lost.wav", Sound.class);
        }
    }

    public class AssetMusic {
        public final Music song01;

        public AssetMusic(AssetManager am) {
            song01 = am.get("music/keith303_-_brand_new_highscore.mp3",
                    Music.class);
        }
    }

然后在init里添加：

public void init(AssetManager assetManager) {
        this.assetManager = assetManager;
        // set asset manager error handler
        assetManager.setErrorListener(this);
        // load texture atlas
        assetManager.load(Constants.TEXTURE_ATLAS_OBJECTS, TextureAtlas.class);
        // load sounds
        assetManager.load("sounds/jump.wav", Sound.class);
        assetManager.load("sounds/jump_with_feather.wav", Sound.class);
        assetManager.load("sounds/pickup_coin.wav", Sound.class);
        assetManager.load("sounds/pickup_feather.wav", Sound.class);
        assetManager.load("sounds/live_lost.wav", Sound.class);
        // load music
        assetManager.load("music/keith303_-_brand_new_highscore.mp3",
                Music.class);
        // start loading assets and wait until finished
        assetManager.finishLoading();
        Gdx.app.debug(TAG,
                "# of assets loaded: " + assetManager.getAssetNames().size);
        for (String a : assetManager.getAssetNames())
            Gdx.app.debug(TAG, "asset: " + a);
        TextureAtlas atlas = assetManager.get(Constants.TEXTURE_ATLAS_OBJECTS);
        // enable texture filtering for pixel smoothing
        for (Texture t : atlas.getTextures())
            t.setFilter(TextureFilter.Linear, TextureFilter.Linear);
        // create game resource objects
        fonts = new AssetFonts();
        bunny = new AssetBunny(atlas);
        rock = new AssetRock(atlas);
        goldCoin = new AssetGoldCoin(atlas);
        feather = new AssetFeather(atlas);
        levelDecoration = new AssetLevelDecoration(atlas);
        sounds = new AssetSounds(assetManager);
        music = new AssetMusic(assetManager);
    }

还记得我们在Options菜单中让用户来设置音乐音效吗，现在派上用场了。

创建新类AudioManager来管理播放和停止:

package com.packtpub.libgdx.canyonbunny.util;

import com.badlogic.gdx.audio.Music;
import com.badlogic.gdx.audio.Sound;

public class AudioManager {
    public static final AudioManager instance = new AudioManager();
    private Music playingMusic;

    // singleton: prevent instantiation from other classes
    private AudioManager() {
    }

    public void play(Sound sound) {
        play(sound, 1);
    }

    public void play(Music music) {
        stopMusic();
        playingMusic = music;
        if (GamePreferences.instance.music) {
            music.setLooping(true);
            music.setVolume(GamePreferences.instance.volMusic);
            music.play();
        }
    }

    public void stopMusic() {
        if (playingMusic != null)
            playingMusic.stop();
    }

    public void onSettingsUpdated() {
        if (playingMusic == null)
            return;
        playingMusic.setVolume(GamePreferences.instance.volMusic);
        if (GamePreferences.instance.music) {
            if (!playingMusic.isPlaying())
                playingMusic.play();
        } else {
            playingMusic.pause();
        }
    }

    public void play(Sound sound, float volume) {
        play(sound, volume, 1);
    }

    public void play(Sound sound, float volume, float pitch) {
        play(sound, volume, pitch, 0);
    }

    public void play(Sound sound, float volume, float pitch, float pan) {
        if (!GamePreferences.instance.sound)
            return;
        sound.play(GamePreferences.instance.volSound * volume, pitch, pan);
    }
}

修改MenuScreen：

    private void onSaveClicked() {
        saveSettings();
        onCancelClicked();
        AudioManager.instance.onSettingsUpdated();
    }

    private void onCancelClicked() {
        btnMenuPlay.setVisible(true);
        btnMenuOptions.setVisible(true);
        winOptions.setVisible(false);
        AudioManager.instance.onSettingsUpdated();
    }

修改CanyonBunnyMain的create方法：

@Override
    public void create() {
        // Set Libgdx log level
        Gdx.app.setLogLevel(Application.LOG_DEBUG);
        // Load assets
        Assets.instance.init(new AssetManager());
        // Load preferences for audio settings and start playing music
        GamePreferences.instance.load();
        AudioManager.instance.play(Assets.instance.music.song01);
        // Start game at menu screen
        ScreenTransition transition = ScreenTransitionSlice.init(2,
                ScreenTransitionSlice.UP_DOWN, 10, Interpolation.pow5Out);
        setScreen(new MenuScreen(this), transition);
    }

Libgdx自动处理在游戏暂停和返回时的音乐播放问题，所以这里不需要额外的代码修改。

继续修改WorldController：

..
public void update(float deltaTime) {
..
if (!isGameOver() && isPlayerInWater()) {
AudioManager.instance.play(Assets.instance.sounds.liveLost);
..
}
private void onCollisionBunnyWithGoldCoin(GoldCoin goldcoin) {
        goldcoin.collected = true;
        AudioManager.instance.play(Assets.instance.sounds.pickupCoin);
        score += goldcoin.getScore();
        Gdx.app.log(TAG, "Gold coin collected");
    }

    private void onCollisionBunnyWithFeather(Feather feather) {
        feather.collected = true;
        AudioManager.instance.play(Assets.instance.sounds.pickupFeather);
        score += feather.getScore();
        level.bunnyHead.setFeatherPowerup(true);
        Gdx.app.log(TAG, "Feather collected");
    }

修改BunnyHead：

public void setJumping(boolean jumpKeyPressed) {
        switch (jumpState) {
        case GROUNDED: // Character is standing on a platform
            if (jumpKeyPressed) {
                AudioManager.instance.play(Assets.instance.sounds.jump);
                // Start counting jump time from the beginning
                timeJumping = 0;
                jumpState = JUMP_STATE.JUMP_RISING;
            }
            break;
        case JUMP_RISING: // Rising in the air
            if (!jumpKeyPressed) {
                jumpState = JUMP_STATE.JUMP_FALLING;
            }
            break;
        case FALLING:// Falling down
        case JUMP_FALLING: // Falling down after jump
            if (jumpKeyPressed && hasFeatherPowerup) {
                AudioManager.instance.play(
                        Assets.instance.sounds.jumpWithFeather, 1,
                        MathUtils.random(1.0f, 1.1f));
                timeJumping = JUMP_TIME_OFFSET_FLYING;
                jumpState = JUMP_STATE.JUMP_RISING;
            }
            break;
        }
    }

ok，运行起来看看。游戏从无声世界进入了有声世界里。从此，程序员也可以自己玩音乐了。