SKAction 方法fadeInWithDuration 不工作

Question

我正在制作一个 Ball Node，我添加了 alpha 设置为 0.01 的 Ball Node，并且在文档中，fadeInWithDuration 应该使 alpha 为 1.0。我放了一个断点，该方法正在被调用，但它没有使球节点出现。

-(void)addBallToFrame {
    _ballNode = [SKSpriteNode spriteNodeWithImageNamed:@"Ball"];
    SKAction *ballPosition = [SKAction runBlock:^(void) {
        _ballNode.position = CGPointMake(CGRectGetMidX(self.frame), 295*ratio);
        [_ballNode setZPosition:10];
        [_ballNode setAlpha:0.01];
        [self addChild:_ballNode];
    }];
    SKAction *timeForBallToAppear = [SKAction waitForDuration:1.5];
    SKAction *changeAlpha = [SKAction fadeInWithDuration:0.5];
    SKAction *ballAppearSequence = [SKAction sequence:@[timeForBallToAppear, ballPosition, changeAlpha]];   
    [self runAction:ballAppearSequence];
    _ballNode.zPosition = 10;
    [_ballNode setPhysicsBody:[SKPhysicsBody bodyWithCircleOfRadius:_ballNode.frame.size.height / 2.0]];
    _ballNode.physicsBody.categoryBitMask = BALL_CATEGORY;
    _ballNode.physicsBody.collisionBitMask = WALL_CATEGORY | PLAYER_ONE_CATEGORY | PLAYER_TWO_CATEGORY | GOAL_POST_CATEGORY;
    _ballNode.physicsBody.contactTestBitMask = GOAL_ONE_CATEGORY |GOAL_TWO_CATEGORY;
    _ballNode.physicsBody.friction = 0.0;
    _ballNode.physicsBody.linearDamping = 0.0;
}
-(void)removeBallFromFrame {
    _ballNode.position = CGPointMake(-100, -100);
    [self.ballNode removeFromParent];
}

Answer 1

这是因为您对 self 运行 changeAlpha 操作，而不是 _ballNode。尝试改变

 [self runAction:ballAppearSequence];

到

 [_ballNode runAction:ballAppearSequence];