iOS 实现自带 “信息” APP 的导航栏动态变化功能

在看到一网友提的问题 iOS 自带 “信息” APP 的导航栏动态变化功能？, 自己好奇去了解下。
PS ： 在 5s 和 5 的模拟器上看不出效果，得 6 以上的模拟器才可以。

导航栏高度的变化

注意仔细看上面导航栏的高度的变化，不注意还真不知道。

一、最简单粗暴的实现

//  注意实现 
- (IBAction)goTestVC:(id)sender {
    TestViewController *testVC = [[TestViewController alloc] init];
    self.navigationController.delegate = self;
    [self.navigationController pushViewController:testVC animated:YES];
}

- (nullable id )navigationController:(UINavigationController *)navigationController
                                            animationControllerForOperation:(UINavigationControllerOperation)operation
                                                         fromViewController:(UIViewController *)fromVC
                                                           toViewController:(UIViewController *)toVC  {
    
    if (operation == UINavigationControllerOperationPush) {
        [UIView animateWithDuration:0.5 animations:^{
            CGRect rect = CGRectMake(toVC.navigationController.navigationBar.frame.origin.x, toVC.navigationController.navigationBar.frame.origin.y, toVC.navigationController.navigationBar.frame.size.width, 64);
            toVC.navigationController.navigationBar.frame = rect;
        } completion:^(BOOL finished) {}];

    }
    else if (operation == UINavigationControllerOperationPop) {
        [UIView animateWithDuration:0.5 animations:^{
            CGRect rect = CGRectMake(fromVC.navigationController.navigationBar.frame.origin.x, fromVC.navigationController.navigationBar.frame.origin.y, fromVC.navigationController.navigationBar.frame.size.width, 44);
            fromVC.navigationController.navigationBar.frame = rect;
        } completion:^(BOOL finished) {}];
    }
    return nil;
}

上述实现，可以直接变换其高度，但是有点生硬，而且没有了向右滑动取消的效果。

二、稍微改良下的实现，加上手势

UIPercentDrivenInteractiveTransition 的运用

@property (nonatomic, strong) UIPercentDrivenInteractiveTransition* interactionController;

经典的添加手势

- (void)addPanGesture {
    UIPanGestureRecognizer* panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    [self.navigationController.view addGestureRecognizer:panRecognizer];
}

- (void)pan:(UIPanGestureRecognizer*)recognizer {
    UIView* view = self.navigationController.view;
    switch (recognizer.state) {
        case UIGestureRecognizerStateBegan:
        {
            CGPoint location = [recognizer locationInView:view];
            if (location.x <  CGRectGetMidX(view.bounds) && self.navigationController.viewControllers.count > 1) {
                self.interactionController = [UIPercentDrivenInteractiveTransition new];
                [self.navigationController popViewControllerAnimated:YES];
            }
        }
            break;
        case UIGestureRecognizerStateChanged:
        {
            CGPoint translation = [recognizer translationInView:view];
            CGFloat d = fabs(translation.x / CGRectGetWidth(view.bounds));
            [self.interactionController updateInteractiveTransition:d];
        }
            break;
        case UIGestureRecognizerStateEnded:
        {
            if ([recognizer velocityInView:view].x > 0) {
                [self.interactionController finishInteractiveTransition];
            } else {
                [self.interactionController cancelInteractiveTransition];
            }
            self.interactionController = nil;
        }
            break;
        default:
            break;
    }
}

代理的实现

- (id)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id)animationController {
    return self.interactionController;
}

但是目前仍然有一个问题，右边滑动时，太快，没有信息的那个慢慢滑动效果。

三、发现一个很奇怪的问题

自定义 UIViewControllerAnimatedTransitioning 居然出现卡顿

- (nullable id )navigationController:(UINavigationController *)navigationController
                                            animationControllerForOperation:(UINavigationControllerOperation)operation
                                                         fromViewController:(UIViewController *)fromVC
                                                           toViewController:(UIViewController *)toVC  {
    
    if (operation == UINavigationControllerOperationPush || operation == UINavigationControllerOperationPop) {
        self.animator.operation = operation;
        return self.animator;
    }
    return nil;
}

#import 

@interface TestAnimator : NSObject 

@property (nonatomic, assign) UINavigationControllerOperation operation;

@end

#import "TestAnimator.h"

@implementation TestAnimator

- (NSTimeInterval)transitionDuration:(id )transitionContext {
    return 0.5;
}

- (void)animateTransition:(id)transitionContext {
    UIViewController* toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController* fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    [[transitionContext containerView] addSubview:toVC.view];
    [[transitionContext containerView]bringSubviewToFront:fromVC.view];
    
    switch (self.operation) {
        case UINavigationControllerOperationPush:
        {
            [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
                CGRect rect = CGRectMake(toVC.navigationController.navigationBar.frame.origin.x, toVC.navigationController.navigationBar.frame.origin.y, toVC.navigationController.navigationBar.frame.size.width, 64);
                toVC.navigationController.navigationBar.frame = rect;
            } completion:^(BOOL finished) {
                [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
            }];
        }
            break;
        case UINavigationControllerOperationPop:
        {
            [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
                CGRect rect = CGRectMake(fromVC.navigationController.navigationBar.frame.origin.x, fromVC.navigationController.navigationBar.frame.origin.y, fromVC.navigationController.navigationBar.frame.size.width, 44);
                fromVC.navigationController.navigationBar.frame = rect;
            } completion:^(BOOL finished) {
                [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
            }];
        }
            break;
            
        default:
            break;
    }
}

说白了就是高度出现卡顿的。

高度变化时出现卡顿，右边滑动可以慢

高度变化没有卡段，右边滑动太快

• 用自定义时： 高度变化出现卡段，不符合要求；右边滑动缓慢，符合要求。
• 直接在代理写时： 高度有个缓慢动态变化，符合要求；右边滑动太快，不符合要求。

此时就在想既能高度木有卡段，右边滑动又可以慢下来呢？

暂时一下子不知道如何将 POP 的动画 和 最后完成的结合起来：

• 采取方法一，我需要找一个结合点

[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
    CGRect rect = CGRectMake(fromVC.navigationController.navigationBar.frame.origin.x, fromVC.navigationController.navigationBar.frame.origin.y, fromVC.navigationController.navigationBar.frame.size.width, 44);
    fromVC.navigationController.navigationBar.frame = rect;
} completion:^(BOOL finished) {
    // 这个地方需要处理
}];

• 采取方法二，那个过渡动画不知道再哪

暂时先采取方法一，毕竟只缺少一个慢慢滑动的效果缺陷，总体来说还能接受。
当然有朋友有方法解决这个问题，非常欢迎告知。