为什么我的动画不起作用？

Question

我有一个蓝色的小圆圈，可以淡入和淡出两个不同的位置，直到用户触摸屏幕为止。 然后，我希望圆在其所处的位置逐渐消失。

- (void)fadePowerUpOut {

    [UIView animateWithDuration:.5 delay:2 options:UIViewAnimationOptionCurveLinear animations:^{//the power up will stay in its position until after 2 seconds it will fade out which is because of the delay
        self.powerUp.alpha=0;
    } completion:^(BOOL finished) {
        if (finished) {//I put if finished here because i don't want this method to be ran if the user touches the screen within the 2 second delay
            if (self.powerUp.frame.origin.x==self.rectPowerUp.origin.x) {//if its in the first location go to the second
                self.powerUp.frame=self.rectPowerUp2;

            }else{//if its in the second location go to the first 
                self.powerUp.frame=self.rectPowerUp;
            }
            [self fadePowerUpIn];
        }
    }];
}

- (void)fadePowerUpIn {
    [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{
        self.powerUp.alpha=1;
    } completion:^(BOOL finished) {
        if (finished) {
              [self FadePowerUpOut];
        }   
    }];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

     [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^(){ self.powerUp.alpha=0;} completion:^(BOOL completion){
  }];
}

发生的事情是，当用户触摸屏幕时，圆圈不会淡出，而只会在2秒钟后消失（我在fadePowerUpOut方法上设置了延迟）。

Answer 1

正如ACB所指出的，要做的第一件事就是将Delay设置为零。 为了能够开始延迟淡入淡出，我建议使用计时器。