自定义present、dismiss转场动画的步骤和自定义push、pop转场动画的步骤是一致的，相关内容请看《iOS自定义转场动画-push和pop》。
主要涉及的API
这里的内容是《iOS自定义转场动画-push和pop》的补充内容。
push和pop自定义转场动画通过导航控制器的UINavigationControllerDelegate配置，而present和dismiss自定义转场动画通过控制器的本身属性transitioningDelegate（UIViewControllerTransitioningDelegate）配置。
下面是要用到UIViewControllerTransitioningDelegate的几个方法：
//指定present动画
- (nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source;
//指定dismiss动画
- (nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed;
//指定交互式present动画的控制类
- (nullable id <UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id <UIViewControllerAnimatedTransitioning>)animator;
//指定交互式dismiss动画的控制类
- (nullable id <UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id <UIViewControllerAnimatedTransitioning>)animator;
present转场动画
1、准备工作：
ViewController类，要present到的下一级控制器SecondViewController类。
2、实现present动画：
这里演示的动画类似原生的push和pop动画，present时界面由右向左覆盖上一级界面，dismiss相反过程。
HSLeftPresentAnimation类定义：
@interface HSLeftPresentAnimation : NSObject <UIViewControllerAnimatedTransitioning>
@property (nonatomic, assign) BOOL isPresent;
@end
为了方便我们将present和dismiss动画写在一起，通过属性isPresent设置动画类型。
@implementation HSLeftPresentAnimation
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
return 1.f;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIView* toView = nil;
UIView* fromView = nil;
UIView* transView = nil;
if ([transitionContext respondsToSelector:@selector(viewForKey:)]) {
fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
toView = [transitionContext viewForKey:UITransitionContextToViewKey];
} else {
fromView = fromViewController.view;
toView = toViewController.view;
}
if (_isPresent) {
transView = toView;
[[transitionContext containerView] addSubview:toView];
}else {
transView = fromView;
[[transitionContext containerView] insertSubview:toView belowSubview:fromView];
}
CGFloat width = [UIScreen mainScreen].bounds.size.width;
CGFloat height = [UIScreen mainScreen].bounds.size.height;
transView.frame = CGRectMake(_isPresent ?width :0, 0, width, height);
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
transView.frame = CGRectMake(_isPresent ?0 :width, 0, width, height);
} completion:^(BOOL finished) {
[transitionContext completeTransition:!transitionContext.transitionWasCancelled];
}];
}
@end
3、指定present要使用的转场动画行为：present转场的动画行为是由UIViewControllerTransitioningDelegate协议指定，所以我们设置secondVC的transitioningDelegate属性：
SecondViewController * secondVC = [[SecondViewController alloc] init];
secondVC.transitioningDelegate = self;
[self presentViewController:secondVC animated:YES completion:nil];
实现以下协议，指定动画类：
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
HSLeftPresentAnimation* leftPresentAnimation = [[HSLeftPresentAnimation alloc] init];
leftPresentAnimation.isPresent = YES;
return leftPresentAnimation;
}
这样present转场动画就完成了，效果图如下：
dimiss转场动画
自定义dimiss转场动画和present动画步骤一样，在SecondViewController类里面指定transitioningDelegate，并实现协议方法即可。
- (void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
self.transitioningDelegate = self;
}
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed{
HSLeftPresentAnimation* leftPresentAnimation = [[HSLeftPresentAnimation alloc] init];
leftPresentAnimation.isPresent = NO;
return leftPresentAnimation;
}
dimiss转场动画效果图：
dismiss变为可交互转场动画
现在我们也希望通过向右拖拽界面将界面dismiss掉，上一篇文章有说到可交互转场通过实现UIViewControllerInteractiveTransitioning的协议的类控制，官方为我们提供了一个通过百分比控制交互转场动画的类UIPercentDrivenInteractiveTransition。那么我们就使用它将dismiss变为可交互转场动画。
1、在SecondViewController里面添加手势
//添加手势
UIPanGestureRecognizer * pan = [[UIPanGestureRecognizer alloc] init];
[pan addTarget:self action:@selector(panGestureRecognizerAction:)];
[self.view addGestureRecognizer:pan];
2、添加手势处理代码：
- (void)panGestureRecognizerAction:(UIPanGestureRecognizer *)pan{
//产生百分比
CGFloat process = [pan translationInView:self.view].x / ([UIScreen mainScreen].bounds.size.width);
process = MIN(1.0,(MAX(0.0, process)));
if (pan.state == UIGestureRecognizerStateBegan) {
self.interactiveTransition = [UIPercentDrivenInteractiveTransition new];
//触发dismiss转场动画
[self dismissViewControllerAnimated:YES completion:nil];
}else if (pan.state == UIGestureRecognizerStateChanged){
[self.interactiveTransition updateInteractiveTransition:process];
}else if (pan.state == UIGestureRecognizerStateEnded
|| pan.state == UIGestureRecognizerStateCancelled){
if (process > 0.5) {
[ self.interactiveTransition finishInteractiveTransition];
}else{
[ self.interactiveTransition cancelInteractiveTransition];
}
self.interactiveTransition = nil;
}
}
这里和pop手势处理一模一样只是更换了触发dismiss转场动画的代码。
3、通过UIViewControllerTransitioningDelegate指定交互动画的控制类
-(id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator{
return self.interactiveTransition;
}
现在基本完成了可交互的dismiss转场动画：
Demo地址：https://github.com/cnthinkcode/HSPresentTransitionDemo
