Question

我正在学习iOS并通过一个例子 - 我最理解的。这是一些代码，我将跟进一个问题：

- (IBAction) switchViews:(id)sender{



[UIView beginAnimations:@"View Flip" context:nil];
[UIView setAnimationDuration:.5];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

if (self.yellowViewController.view.superview == nil) {
    if (self.yellowViewController == nil) {
        YellowViewController *yellowController = [[YellowViewController alloc] initWithNibName:@"YellowView" bundle:nil];
        self.yellowViewController = yellowController;
        [yellowController release];
    }
    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];

    [blueViewController viewWillAppear:YES];
    [yellowViewController viewWillDisappear:YES];


    [blueViewController.view removeFromSuperview];
    [self.view insertSubview:yellowViewController.view atIndex:0];

    [yellowViewController viewDidDisappear:YES];
    [blueViewController viewDidAppear:YES];

[UIView beginAnimations:@"View Flip" context:nil]; [UIView setAnimationDuration:.5]; [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut]; if (self.yellowViewController.view.superview == nil) { if (self.yellowViewController == nil) { YellowViewController *yellowController = [[YellowViewController alloc] initWithNibName:@"YellowView" bundle:nil]; self.yellowViewController = yellowController; [yellowController release]; } [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES]; [blueViewController viewWillAppear:YES]; [yellowViewController viewWillDisappear:YES]; [blueViewController.view removeFromSuperview]; [self.view insertSubview:yellowViewController.view atIndex:0]; [yellowViewController viewDidDisappear:YES]; [blueViewController viewDidAppear:YES]; 这是我的理解。动画很清晰。

我们正在检查是否显示了yellowViewController。如果没有，那么我们检查并查看它是否已实例化。如果没有，我们实例化它然后显示它，首先从SuperView中删除blueViewController。

到目前为止一切都很好。

这是我不明白的原因 - 为什么要做以下事情：


[blueViewController viewWillAppear:YES];

在我看来，我们应该消除blueViewController而不是黄色。

我真的很感激解释。感谢。

Answer 1

您不应该自己进行这些调用，它们是由iOS框架自动生成的。因此，您的所有viewWill…和viewDid…来电都是不必要的，可以删除。

当您显示View Controller时，为什么会消失它？向后看。

1 个答案: