如何在cocos2d中交叉淡化音乐？

Question

很简单......我在我的游戏中播放了一首背景歌曲,我想交叉淡化一首曲目,而不是硬停.

//Prep Background Music
        if (![[SimpleAudioEngine sharedEngine]isBackgroundMusicPlaying]) {
             [[SimpleAudioEngine sharedEngine] preloadBackgroundMusic:@"song.mp3"];
        }
        [[SimpleAudioEngine sharedEngine] setBackgroundMusicVolume:1.0]; 

        //Play Background Music
         if (![[SimpleAudioEngine sharedEngine]isBackgroundMusicPlaying]) {
             [[SimpleAudioEngine sharedEngine] playBackgroundMusic:@"song.mp3" loop:YES];
         }

Answer 1

我用这个简单的方法来取代当前的背景音乐:

-(void)replaceBackgroundMusic:(NSString *)filePath volume:(float)volume
{
    // no music's playing right now
    if (![[SimpleAudioEngine sharedEngine] isBackgroundMusicPlaying])
        return [self playBackgroundMusic:filePath volume:volume];

    // already playing requested track
    if ([filePath isEqualToString:[[[CDAudioManager sharedManager] backgroundMusic] audioSourceFilePath]])
        return;

    // replace current track with fade out effect
    float currentVolume = [SimpleAudioEngine sharedEngine].backgroundMusicVolume;
    id fadeOut = [CCActionTween actionWithDuration:1 key:@"backgroundMusicVolume" from:currentVolume to:0.0f];
    id playNew =
    [CCCallBlock actionWithBlock:^
     {
         [[SimpleAudioEngine sharedEngine] setBackgroundMusicVolume:volume];
         [[SimpleAudioEngine sharedEngine] playBackgroundMusic:filePath];
     }];

    [[[CCDirector sharedDirector] actionManager] addAction:[CCSequence actions:fadeOut, playNew, nil] target:[SimpleAudioEngine sharedEngine] paused:NO];
}

希望有所帮助!

Answer 2

你不能使用 来做到这一点SimpleAudioEngine。我是这样做的：

1. 创建一个扩展类CDAudioManager

2. 在您调用开始播放新背景音乐的方法中，首先检查 ivar backgroundMusic（继承自CDAudioManager）是否不为零并且正在播放。如果是，则使用 淡出它CDLongAudioSourceFader。

3. 将新的背景音乐加载到backgroundMusic（它是CDLongAudioSource- 查找它的一个实例）。使用中淡化它CDLongAudioSourceFader。

这是第 2 步中方法的片段（抱歉无法向您展示其余部分，因为它是我自己的专有库的一部分）

- (void)audioBackgroundPlay:(NSString *)bgmfile crossfade:(float)fade {
    CDLongAudioSource *audioSource = [self audioBackgroundLoad:bgmfile];
    if (audioSource != backgroundMusic) {
        if (backgroundMusic) {
            [self audioBackgroundControl:AUDIOCTRL_STOP fade:fade];
            backgroundMusic.audioSourcePlayer.meteringEnabled = NO;
            [backgroundMusic release];
        }
        backgroundMusic = [audioSource retain];
        if (meteringEnabled_) {
            backgroundMusic.audioSourcePlayer.meteringEnabled = YES;
        }
    }
    if (![backgroundMusic isPlaying]) {
        [self audioBackgroundControl:AUDIOCTRL_PLAY fade:fade];
    }
}