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下面的范例代码实现两个View 动态切换。

- (IBAction)switchViews:(id)sender {

//开始准备动画
[UIView beginAnimations:@"View Flip" context:nil];

//设置动画持续时间
[UIView setAnimationDuration:1.25];

//设置动画曲线
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

if(self.yellowViewController.view.superview == nil){
if(self.yellowViewController == nil){
self.yellowViewController = [[BIDYellowViewController alloc]
initWithNibName:@”YellowView” bundle:nil];
}
//设置动画效果
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight
forView:self.view cache:YES];

[blueViewController.view removeFromSuperview];
[self.view insertSubview:self.yellowViewController.view atIndex:0];
}else {
if(self.blueViewController == nil){
self.blueViewController = [[BIDBlueViewController alloc]
initWithNibName:@”BlueView” bundle: nil];
}
//设置动画效果
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft
forView:self.view cache:YES];

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

//提交动画
[UIView commitAnimations];

}

这个是怎么样实现的呢? 原理解释:

这是由UIView类里面的beginAnimation:方法来现实的,就是这句

[UIView beginAnimations:@“View Flip” context:nil];

并且用setAnimationDuration:方法来制定动态的时间:(这里我们定义的是1.25秒钟,都是以秒为单位)

[UIView setAnimationDuration:1.25];

再用到setAnimationCurve:方法来设置动画的旋转曲度变化

[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];

然后，通过setAnimationTransition:方法可以定义在动画的类型。

在这个动画的结尾，需要用到commitAnimations:方法 [UIView commitAnimations]; 提交动画。

You need to #import the file, but you can do that in your implementation file (.m), and use the @class declaration in your header file.
@class does not (usually) remove the need to #import files, it just moves the requirement down closer to where the information is useful.

Three simple rules:
•    Only #import the super class in header files.
•    #import all classes you send messages to in implementation file.
•    Forward declarations for everything else.

英文链接

异常信息：

property view cannot be found in forward class object — 属性view 无法在前置class对象中找到

首先检查前置class对象（forward class object）的定义是否存在该属性view的定义。

In general,  a ViewController’s view outlet will connect to the view in the nib. The view outlet is inherited from the parent class, UIViewController, and gives the controller access to the view it controls. When we changed the underlying class of the file’s owner, the existing outlet connections were broken. So, we need to reestablish the connection from the controller to its view. Control-drag from the File’s Owner icon to the View icon, and select the view outlet to do that.

一般而言，一个ViewController的view outlet 将连接nib中View，view outlet是继承自父类 UIViewController，ViewController 就可以访问其控制的视图。当我们更改file‘s owner的底层类时，将会破坏现有的outlet连接。因此，我们需要重新建立从controller到对应View 之间的连接。按住Control 按钮，并拖拉 File’s Owner 图标到View 图标上，同时选中view outlet 来建立连接。