首先，支持并感谢@wazrx 的 http://www.jianshu.com/p/45434f73019e和@onevcat 的https://onevcat.com/2013/10/vc-transition-in-ios7/ 对于转场动画的讲解和实现，非常详细，本人也是看过他们的文章后受的启发，快速实现了基于本项目需求的转场动画效果。

效果如下：（gif是我们的美术大师帮忙做的演示动效，实际的效果要比这个好，可通过文章最后链接下载我们的app：柠檬跑步，查看效果）

地图切换.gif

我的需求是两个页面push、pop之间的切换，所以自定义了push的转场动画，首先需要个遵循<UIViewControllerAnimatedTransitioning>协议的管理对象，并实现其两个方法：
XWCircleSpreadTransition.h

#import <UIKit/UIKit.h>typedef NS_ENUM(NSUInteger, XWCircleSpreadTransitionType) {         XWCircleSpreadTransitionTypePush = 0,         XWCircleSpreadTransitionTypePop };@interface XWCircleSpreadTransition : NSObject<UIViewControllerAnimatedTransitioning>@property (nonatomic, assign) XWCircleSpreadTransitionType type;  + (instancetype)transitionWithTransitionType:(XWCircleSpreadTransitionType)type; - (instancetype)initWithTransitionType:(XWCircleSpreadTransitionType)type;@end

XWCircleSpreadTransition.m

#import "XWCircleSpreadTransition.h"@implementation XWCircleSpreadTransition+ (instancetype)transitionWithTransitionType:(XWCircleSpreadTransitionType)type{        return [[self alloc] initWithTransitionType:type]; }  - (instancetype)initWithTransitionType:(XWCircleSpreadTransitionType)type{        self = [super init];        if (self) {                 _type = type;         }        return self; }  - (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{        return 0.7; }  - (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{        switch (_type) {                case XWCircleSpreadTransitionTypePush:                         [self presentAnimation:transitionContext];                        break;                case XWCircleSpreadTransitionTypePop:                         [self dismissAnimation:transitionContext];                        break;          } }  - (void)dismissAnimation:(id<UIViewControllerContextTransitioning>)transitionContext{        UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];        UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];        UIView *containerView = [transitionContext containerView];         [containerView insertSubview:toVC.view atIndex:0];    //画两个圆路径         CGFloat radius = sqrtf(containerView.frame.size.height * containerView.frame.size.height + containerView.frame.size.width * containerView.frame.size.width) / 2;    UIBezierPath *startCycle = [UIBezierPath bezierPathWithArcCenter:containerView.center radius:radius startAngle:0 endAngle:M_PI * 2 clockwise:YES];//    UIBezierPath *endCycle =  [UIBezierPath bezierPathWithOvalInRect:temp.mapBtnFrame];         UIBezierPath *endCycle =  [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 0, 0)];    //创建CAShapeLayer进行遮盖         CAShapeLayer *maskLayer = [CAShapeLayer layer];         maskLayer.fillColor = [UIColor greenColor].CGColor;         maskLayer.path = endCycle.CGPath;         fromVC.view.layer.mask = maskLayer;    //创建路径动画         CABasicAnimation *maskLayerAnimation = [CABasicAnimation animationWithKeyPath:@"path"];         maskLayerAnimation.delegate = self;         maskLayerAnimation.fromValue = http://www.mamicode.com/(__bridge id)(startCycle.CGPath);     "transitionContext"];         [maskLayer addAnimation:maskLayerAnimation forKey:@"path"]; }  - (void)presentAnimation:(id<UIViewControllerContextTransitioning>)transitionContext{    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];    UIView *containerView = [transitionContext containerView];         [containerView addSubview:toVC.view];    //画两个圆路径//    UIBezierPath *startCycle =  [UIBezierPath bezierPathWithOvalInRect:fromVC.mapBtnFrame];         UIBezierPath *startCycle =  [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 0, 0)];    CGFloat x = MAX(100, containerView.frame.size.width - 100);    CGFloat y = MAX(100, containerView.frame.size.height - 100);    CGFloat radius = sqrtf(pow(x, 2) + pow(y, 2));    UIBezierPath *endCycle = [UIBezierPath bezierPathWithArcCenter:containerView.center radius:radius startAngle:0 endAngle:M_PI * 2 clockwise:YES];    //创建CAShapeLayer进行遮盖         CAShapeLayer *maskLayer = [CAShapeLayer layer];         maskLayer.path = endCycle.CGPath;    //将maskLayer作为toVC.View的遮盖         toVC.view.layer.mask = maskLayer;    //创建路径动画         CABasicAnimation *maskLayerAnimation = [CABasicAnimation animationWithKeyPath:@"path"];         maskLayerAnimation.delegate = self;    //动画是加到layer上的，所以必须为CGPath，再将CGPath桥接为OC对象         maskLayerAnimation.fromValue = http://www.mamicode.com/(__bridge id)(startCycle.CGPath);     "transitionContext"];         [maskLayer addAnimation:maskLayerAnimation forKey:@"path"]; }  - (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{        switch (_type) {                case XWCircleSpreadTransitionTypePush:{                        id<UIViewControllerContextTransitioning> transitionContext = [anim valueForKey:@"transitionContext"];             [transitionContext completeTransition:YES];                        UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];                         toView.layer.mask = nil;                        UIViewController *vc = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];             vc.view.layer.mask = nil;         }                        break;                case XWCircleSpreadTransitionTypePop:{                        id<UIViewControllerContextTransitioning> transitionContext = [anim valueForKey:@"transitionContext"];                         [transitionContext completeTransition:YES];                        UIViewController *vc = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];                         vc.view.layer.mask = nil;         }                        break;         } }@end

剩下的就是在ViewControllerA中实现代理<UINavigationControllerDelegate>中的animationControllerForOperation：

#pragma mark -#pragma mark - UINavigation Delegate-(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC {        if (fromVC == self) {                return [XWCircleSpreadTransition transitionWithTransitionType:XWCircleSpreadTransitionTypePush];         }        if (toVC == self) {                return [XWCircleSpreadTransition transitionWithTransitionType:XWCircleSpreadTransitionTypePop];         }        return nil; }

到此，这个简单的转场动画已经实现完毕，而且动画效果可以自定义成自己想要的展现形式。

类似nike+、香蕉打卡的转场动画效果-b