开发中，我们都希望能通过属性动画对一些比较难做动画的布局做变化，而属性动画只对图层的可动画属性起作用，所以要改变一个不能动画的属性或者从当前界面移除，属性动画将不起作用。
为了解决上面的问题，才有了过渡动画，过渡动画不像属性动画那样很平滑的从一个值过渡到另一个值，而是先出现上一个图形的轮廓外观，然后在两者之间进行交换，替换。
要是用过渡动画就要使用CATransition，它有type和subType两个属性来控制变化的效果：
type的属性是一个NSString类型，有下面几个值：
kCATransitionFade kCATransitionMoveIn kCATransitionPush kCATransitionReveal
subType来控制滑入的方向：
kCATransitionFromRight kCATransitionFromLeft kCATransitionFromTop kCATransitionFromBottom
下面简单写了个Demo，先看效果图：
很明显两者的变化是有区别的。
// // ViewController.m // CATransition过渡 // // Created by 刘浩浩 on 16/6/27. // Copyright © 2016年 CodingFire. All rights reserved. // #import "ViewController.h" @interface ViewController () { UIImageView *imageView; NSArray *images; } @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. imageView=[[UIImageView alloc]initWithFrame:CGRectMake(80, 80, 150, 150)]; [self.view addSubview:imageView]; images = @[[UIImage imageNamed:@"1"], [UIImage imageNamed:@"2"], [UIImage imageNamed:@"3"], [UIImage imageNamed:@"4"]]; UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn.frame = CGRectMake(20, 568-100, 280, 40); [btn setTitle:@"Switch 突兀" forState:UIControlStateNormal]; btn.layer.cornerRadius=5; btn.layer.borderWidth=1; btn.layer.borderColor = [UIColor blackColor].CGColor; [btn addTarget:self action:@selector(switchImage) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:btn]; UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect]; btn1.frame = CGRectMake(20, 568-50, 280, 40); [btn1 setTitle:@"Switch 平滑" forState:UIControlStateNormal]; btn1.layer.cornerRadius=5; btn1.layer.borderWidth=1; btn1.layer.borderColor = [UIColor blackColor].CGColor; [btn1 addTarget:self action:@selector(switchImage1) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:btn1]; } -(void)switchImage { UIImage *currentImage = imageView.image; NSUInteger index = [images indexOfObject:currentImage]; index = (index + 1) % [images count]; imageView.image = images[index]; } - (void)switchImage1 { //set up crossfade transition CATransition *transition = [CATransition animation]; //切换模式 transition.type = kCATransitionFade; //apply transition to imageview backing layer [imageView.layer addAnimation:transition forKey:nil]; //cycle to next image UIImage *currentImage = imageView.image; NSUInteger index = [images indexOfObject:currentImage]; index = (index + 1) % [images count]; imageView.image = images[index]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end
Demo下载地址：https://github.com/codeliu6572/CATransition
