view source print ?
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
if (self.firstViewController.view.superview == nil) {
self.firstViewController = nil;
} else {
self.secondViewController = nil;
}
}
11、打开FirstView.xib文件，选择左边的File's Owner，然后在Identity Inspector中选择Class为FirstViewController；然后按住Control键从File's Owner图标拖到View，在弹出的菜单选择view。为SecondView.xib进行同样的操作，不过Class选择为SecondViewController。
12、打开FirstView.xib文件，选择View，打开Attribute Inspector，进行如下设置：
对SecondView.xib进行同样设置，不过背景颜色设成红色。
13、此时运行程序，你会看见刚启动的时候，程序显示的绿色背景，轻触Switch Views按钮后，背景变成了红色。不断轻触按钮，背景不断变换。
14、添加切换背景的动画效果：
打开RootViewController.m，修改其中的switchViews方法如下：
view source print ?
- (IBAction)switchViews:(id)sender {
[UIView beginAnimations:@"View Flip" context:nil];
[UIView setAnimationDuration:1.25];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
if (self.secondViewController.view.superview == nil) {
if (self.secondViewController == nil) {
self.secondViewController = [[SecondViewController alloc] initWithNibName:@"SecondView" bundle:nil];
}
[UIView setAnimationTransition: UIViewAnimationTransitionFlipFromRight forView:self.view cache:YES];
[self.firstViewController.view removeFromSuperview];
[self.view insertSubview:self.secondViewController.view atIndex:0];
} else {
if (self.firstViewController == nil) {
self.firstViewController = [[FirstViewController alloc] initWithNibName:@"FirstView" bundle:nil];
}
[UIView setAnimationTransition: UIViewAnimationTransitionCurlUp forView:self.view cache:YES];
[self.secondViewController.view removeFromSuperview];
[self.view insertSubview:self.firstViewController.view atIndex:0];
}
[UIView commitAnimations];
}
注意四个表示切换效果的常量：
view source print ?
UIViewAnimationTransitionFlipFromLeft
UIViewAnimationTransitionFlipFromRight
UIViewAnimationTransitionCurlDown
UIViewAnimationTransitionCurlUp
分别表示从左翻转、从右翻转、向下卷、向上卷。
运行后翻页效果如下：
