xcode – SKSpriteNode不会使用序列精灵套件中的SKAction来淡入淡入淡出

我按顺序运行3个SKActions,前两个运行正常,但fadeInWithDuration不会在节点中淡入,当视图加载时,节点会立即添加.我是否必须将节点的初始Alpha通道设置为0？有人可以解决问题吗？

- (void)setUpButtonStart
{
    SKSpriteNode *buttonStart = [SKSpriteNode spriteNodeWithImagenamed:@"start"];
    buttonStart.name = @"buttonStart";
    buttonStart.position = CGPointMake(900,50);
    [self addChild:buttonStart];

    SKAction *wait = [SKAction waitForDuration:2.5];
    SKAction *readIntro = [SKAction playSoundFilenamed:@"intro.mp3" waitForCompletion:NO];
    SKAction *fadeIn = [SKAction fadeInWithDuration:1.0];

    SKAction *sequence = [SKAction sequence:@[wait,readIntro,fadeIn]];

    [buttonStart runAction: sequence];
}