Iphone 我的核心动画块不是'；我不能像我一样工作；我希望

我有一个名为

activityView

的

ui视图，它包含两个子视图
activityIndicator
和
取消操作按钮
。这些视图嵌入到XIB中，并连接到我的视图控制器

我有两种方法来处理激活（显示）和停用（隐藏）这两个子视图：

- (void) enableActivityIndicator {
    [activityIndicator startAnimating];
    [cancelOperationsButton setHidden:NO];
}

- (void) disableActivityIndicator {
    [activityIndicator stopAnimating];
    [cancelOperationsButton setHidden:YES];
}

就其本身而言，这两种方法效果很好

为了使其更加完善，我想添加一个动画，使这些子视图淡入淡出：

- (void) enableActivityIndicator {
    [activityIndicator startAnimating];
    [cancelOperationsButton setHidden:NO];

    [UIView beginAnimations:@"fadeIn" context:nil];
    [UIView setAnimationDelay:0.0f];
    [UIView setAnimationDuration:1.0f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
    activityView.alpha = 1.0f;
    [UIView commitAnimations];
}

- (void) disableActivityIndicator {
    [UIView beginAnimations:@"fadeOut" context:nil];
    [UIView setAnimationDelay:0.0f];
    [UIView setAnimationDuration:1.0f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
    activityView.alpha = 0.0f;
    [UIView commitAnimations];

    [activityIndicator stopAnimating];
    [cancelOperationsButton setHidden:YES];
}

但是动画不起作用-子视图只是显示或消失，而父视图的
alpha
属性对透明度没有影响

我应该如何编写这些方法来获得我想要的淡入淡出效果

编辑

这里有一个完美的安排：

- (void) enableActivityIndicator {
    activityView.alpha = 0.0f;
    [activityIndicator startAnimating];
    [cancelOperationsButton setHidden:NO];

    [UIView beginAnimations:@"fadeIn" context:nil];
    [UIView setAnimationDelay:0.0f];
    [UIView setAnimationDuration:0.2f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
    activityView.alpha = 1.0f;
    [UIView commitAnimations];
}

- (void) disableActivityIndicator {
    [UIView beginAnimations:@"fadeOut" context:nil];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(disableActivityIndicatorComplete)];
    [UIView setAnimationDelay:0.0f];
    [UIView setAnimationDuration:0.2f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
    activityView.alpha = 0.0f;
    [UIView commitAnimations];
}

- (void) disableActivityIndicatorComplete {
    [activityIndicator stopAnimating];
    [cancelOperationsButton setHidden:YES];
}

在“启用”中，将视图设置为“在设置为不透明动画之前清除”

- (void) enableActivityIndicator {
    ...
    activityView.alpha = 0.0f;
    [cancelOperationsButton setHidden:NO];
    ...

在“禁用”中，在动画完成之前不要隐藏视图

- (void) disableActivityIndicator {
    ...
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDidStopSelector:@selector(hideComplete)];
    ...

- (void) hideComplete {
    [activityIndicator stopAnimating];
    [cancelOperationsButton setHidden:YES];
}