iOS 自定义转场切换动画

在开发中，我们经常会遇到系统转场动画不适用自己项目的时候，所以需要自定义转场动画来满足我们的需求。一般自定义专场动画是以下三种情况：

• Push
• Modal
• Segue

Push Modal 都是采用的Transition的方式

Push

步骤

1. 创建一个继承NSObject并遵守UIViewControllerAnimatedTransitioning协议的类
2. 1创建的类必须实现以下两个方法：
   -(NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext; //转场动画时间
   -(void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext; //动画效果
3. 在需要调用动画的ViewController必须遵守UINavigationControllerDelegate协议，并实现方法 :
   -(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC; 在此方法返回第1步创建的类的实例。

示例

(做一个简单的把push从右往左滑入动画改为类似modal默认的从下往上滑入动画效果)

第一步，创建遵守UIViewControllerAnimatedTransitioning协议的类，一个push的，一个pop的。

Push动画部分

• TDTransitionVerticalPush.h 文件

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface TDTransitionVerticalPush : NSObject <UIViewControllerAnimatedTransitioning>

@end

• TDTransitionVerticalPush.m 文件

#import "TDTransitionVerticalPush.h"
@implementation TDTransitionVerticalPush

//转场时间
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext{
    return 0.5;
}
// This method can only  be a nop if the transition is interactive and not a percentDriven interactive transition.
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{
    // 起始VC
//    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    // 目的VC
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    // 转场视图容器
    UIView *containerView = [transitionContext containerView];

    //动画
    toVC.view.frame = CGRectMake(0, Main_Screen_Height, toVC.view.frame.size.width, toVC.view.frame.size.height);
    [containerView addSubview:toVC.view];

    [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        toVC.view.frame = CGRectMake(0, 0, toVC.view.frame.size.width, toVC.view.frame.size.height);
    } completion:^(BOOL finished) {
        BOOL cancelled = transitionContext.transitionWasCancelled;
        // 声明过渡结束
        [transitionContext completeTransition:!cancelled];
    }];
}

Pop动画部分

• TDTransitionVerticalPop.h 文件

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface TDTransitionVerticalPop : NSObject <UIViewControllerAnimatedTransitioning>

@end

• TDTransitionVerticalPop.m 文件

#import "TDTransitionVerticalPop.h"
@implementation TDTransitionVerticalPush

//转场时间
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext{
    return 0.5;
}
// This method can only  be a nop if the transition is interactive and not a percentDriven interactive transition.
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{
    // 起始VC
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    // 目的VC
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    // 转场视图容器
    UIView *containerView = [transitionContext containerView];

    //下降动画
    fromVC.view.frame = CGRectMake(0, 0, fromVC.view.frame.size.width, fromVC.view.frame.size.height);
    [containerView addSubview:toVC.view];
    [containerView addSubview:fromVC.view];

    [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        fromVC.view.frame = CGRectMake(0, Main_Screen_Height, fromVC.view.frame.size.width, fromVC.view.frame.size.height);
    } completion:^(BOOL finished) {
        BOOL cancelled = transitionContext.transitionWasCancelled;
        // 声明过渡结束
        [transitionContext completeTransition:!cancelled];
    }];
}

第二步，调用动画代理方法实现
（例如有FirstViewController和SecondViewController两个ViewController。现在要从FirstViewController push跳转到SecondViewController。所以在FirstVeiwController中处理代理方法）

• FirstViewController.h文件

#import <UIKit/UIKit.h>
#import "SecondViewController.h"
#import "TDTransitionVerticalPush.h"
#import "TDTransitionVerticalPop.h"

@interface FirstViewController : UIViewController <UINavigationControllerDelegate>

@end

• FirstViewController.m文件

#import "FirstViewController.h"

@interface FirstViewController () 

@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // 指定navigationController代理
    self.navigationController.delegate = self;
}
//实现代理方法，此方法返回nil为默认效果，返回自定义对象则为自定义动画效果
-(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC{

    //指定特殊ViewController之间的跳转动画
    if (operation == UINavigationControllerOperationPush && [toVC isKindOfClass:[SecondViewController class]]) {
        return [[TDTransitionVerticalPush alloc]init];
    }else if(operation == UINavigationControllerOperationPop && [fromVC isKindOfClass:[SecondViewController class]]){
        return [[TDTransitionVerticalPop alloc]init];
    }else{
        return nil;
    }
}
//跳转到SecondViewController
- (IBAction)toSecond:(id)sender {
    SecondViewController *vc = [[SecondViewController alloc]init];
    [self.navigationController pushViewController:vc animated:YES];
}

自定义push动画完成啦

Modal

modal的转场动画自定义步骤跟Push的类似，只是在实现动画时不同。

1. 先创建两个遵守UIViewControllerAnimatedTransitioning协议的类，一个用于present，一个用于dismiss。实现协议的两个基础方法：
   -(NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;和-(void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;，自定义动画效果。
2. 在需要调用动画的ViewController必须遵守UIViewControllerTransitioningDelegate协议。实现
   -(id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source;和
   -(id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed;方法。
3. 在第一个ViewController的跳转方法中指定第二个ViewController的transitioningDelegate属性值为self.

第三步的代码示例：

• ThirdViewController.m文件

#import <UIKit/UIKit.h>
#import "FourthViewController.h"
#import "TDTransitionHorzontalPresent.h"
#import "TDTransitionHorizontalDismiss.h"

@interface ThridViewController : UIViewController <UIViewControllerTransitioningDelegate>

@end

• ThirdViewController.m文件

#import "ThridViewController.h"

@interface ThridViewController ()

@end

@implementation ThridViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.transitioningDelegate = self;
}
//present动画实现
-(id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
    if ([presented isKindOfClass:[FourthViewController class]]) {
        return [[TDTransitionHorzontalPresent alloc]init];
    }
    return nil;
}
//dismiss动画实现
-(id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed{
    if ([dismissed isKindOfClass:[FourthViewController class]]) {
        return [[TDTransitionHorizontalDismiss alloc]init];
    }
    return nil;
}
//storyboard button实现
- (IBAction)modalToFourthVC:(id)sender {
    FourthViewController *vc = [[FourthViewController alloc] init];
    vc.transitioningDelegate = self;
    [self presentViewController: vc animated:YES completion:^{

    }];
}

---

Segue

StoryBoard有它的优势，以后用的越来越多，而且有些逻辑简单的viewcontroller之间 跳转直接连线即可，非常方便。自定义转场动画时，可以选择自定义UIStoryboardSegue子类，或者继续使用跟Push的transition。

先讲在前面，用自定义UIStoryboardSegue子类的式不适用于Push跳转，因为这样会导致NavigationBar消失。自定义UIStoryboardSegue子类推荐用于Modal跳转方式。

自定义UIStoryboard子类的方式这里就不讲了，我讲讲继续使用Transition的这种方式，在Storyboard中使用了Push跳转继续使用这种方式可以完美自定义动画效果，不会出现使用自定义UIStoryboardSegue后navigationbar消失的情况。

1. 创建两个继承NSObject并遵守UIViewControllerAnimatedTransitioning协议的类，一个用于Push，一个用于Pop。实现协议的两个基础方法自定义动画效果；
   -(NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;和
   -(void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;
2. 创建一个继承NSObject并遵守UINavigationControllerDelegate协议的类。实现协议的方法：
   -(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC;。
3. 在Storyboard文件中的NavigationController添加Object，然后指定此Object的Class为第二步建立的类。 ，并设置delegate

完整的demo在我的Github。