总结---present／dismiss

modal presentation style

这个枚举在iphone上常用的只有三个：fullScreen， overFullScreen，custom。
下面说明这三个的区别：
先点一下，在转场过程中，系统会加入一个过渡控制器：UIPresentationController。
在自定义转场的过程中，presentingView presentedView 会被add到过渡控制器的view上。
然而，一个view只能有一个父视图，当他被add到过渡控制器上，前父视图自然不再持有它，这也就导致了会有返回产生黑屏的情况。

fullScreen：推出的视图会占满屏幕。动画结束后，过渡控制器会移除add到自身的presentingView。
overFullScreen：推出的视图不是占满屏幕，而且在presentedView的下方可以响应操作。动画结束后，过渡控制器会不会移除add到自身的presentingView。与上方相反。
custom：完全自定义。需要自定义实现过渡控制器（协议中的最后一个方法），一般继承自系统的UIPresentationController即可。同样不会移除presentingView

UIViewControllerTransitioningDelegate

vc.transitioningDelegate = self;
vc.modalPresentationStyle = @"枚举";

- (nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source;

- (nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed;

- (nullable id <UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id <UIViewControllerAnimatedTransitioning>)animator;

- (nullable id <UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id <UIViewControllerAnimatedTransitioning>)animator;

- (nullable UIPresentationController *)presentationControllerForPresentedViewController:(UIViewController *)presented presentingViewController:(nullable UIViewController *)presenting sourceViewController:(UIViewController *)source

自动驱动

前两个方法需要返回遵守UIViewControllerAnimatedTransitioning的对象，继承自NSObject即可，下方是实现

- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext{
    return 0.5;
}
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{
    UIView *view = [transitionContext containerView];
    __block UIView *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view;
    __block UIView *toView = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;
    [view addSubview:fromView];
    [view addSubview:toView];
    //根据需求操作两个view即可。
    //[UIView animate....]  + view的位置只能是通过设置transForm来决定。
}

其中有个上下文变量 transitionContext 下方是key 。

UIKIT_EXTERN UITransitionContextViewControllerKey const UITransitionContextFromViewControllerKey 
UIKIT_EXTERN UITransitionContextViewControllerKey const UITransitionContextToViewControllerKey 

UIKIT_EXTERN UITransitionContextViewKey const UITransitionContextFromViewKey 
UIKIT_EXTERN UITransitionContextViewKey const UITransitionContextToViewKey

手势驱动器

中间两个是需要返回遵守UIViewControllerInteractiveTransitioning的对象，继承自UIPercentDrivenInteractiveTransition即可
在需要手势驱动的控制器上加上手势，在手势的selector中根据手势的状态调用下方的方法即可。
第一个方法中的百分比：根据手势拖拽的距离／屏幕的宽度

- (void)updateInteractiveTransition:(CGFloat)percentComplete;
- (void)cancelInteractiveTransition;
- (void)finishInteractiveTransition;

自定义过渡控制器

继承自UIPresentationController，有六个方法需要重写
初始化方法、过渡器进入时、进入完成、消失时、消失完毕以及presentedView呈现的frame
过渡器是特殊的控制器，自身并没有view。
dimmingView是加在过渡器上的view，再加个手势备用。如果用户能够点击这个view，可以给予响应回馈。

- (instancetype)initWithPresentedViewController:(UIViewController *)presentedViewController presentingViewController:(UIViewController *)presentingViewController
{
    if ((self = [super initWithPresentedViewController:presentedViewController presentingViewController:presentingViewController])) {
        _dimmingView = [[UIView alloc] init];
        _dimmingView.backgroundColor = [UIColor clearColor];
        _dimmingView.alpha = 1;
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]bk_initWithHandler:^(UIGestureRecognizer *sender, UIGestureRecognizerState state, CGPoint location) {
            if (self.touchDimmingView) {
                self.touchDimmingView();
            }
        }];
        [_dimmingView addGestureRecognizer:tap];
    }
    return self;
}
- (void)presentationTransitionWillBegin
{
    _dimmingView.frame = self.containerView.bounds;
    [self.containerView addSubview:_dimmingView];
    [self.containerView addSubview:self.presentedView];
}
- (void)presentationTransitionDidEnd:(BOOL)completed
{
    if (!completed) {
        [_dimmingView removeFromSuperview];
    }
}
- (void)dismissalTransitionWillBegin
{
    [UIView animateWithDuration:0.3 animations:^{
        _dimmingView.alpha = 0;
    }];
}
- (void)dismissalTransitionDidEnd:(BOOL)completed
{
    if (completed) {
        [_dimmingView removeFromSuperview];
    }
}
-(CGRect)frameOfPresentedViewInContainerView
{
    return self.presentContnetSize;
}

总结--push／pop

第一个是手势驱动器，第二个是动画。
实现：代理方法的实现与上方提到的基本一致。按需实现即可。

- (nullable id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
                         interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>) animationController;

- (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                  animationControllerForOperation:(UINavigationControllerOperation)operation
                                               fromViewController:(UIViewController *)fromVC
                                                 toViewController:(UIViewController *)toVC;

转场动画