iOS 在TabBarController视图切换的时候添加动画

iOS中TabBarController是很强大的控制器，使用起来也非常的方便，但是它点击tabbaritem切换视图时却不像navigation一样有种划入划出的效果，那么怎么在TabBarController控制器切换的时候添加动画呢？
在TabBarControllerDelegate中已经定义好了方法，我们可以在自己的TabBarController中实现这个协议中的方法，就可以在切换视图的时候加入动画效果。
TabBarControllerDelegate中有两个方法，这里先讲第一个
github地址：https://github.com/ColdChains/LAXTabBarControllerAnimation

一、创建一个类继承NSObject，实现协议UIViewControllerAnimatedTransitioning

#import "AnimationManager.h"@interface AnimationManager ()@end@implementation AnimationManagerstatic UIView *presentingView;- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {    return 1.0;}- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {    // 获取fromVc和toVc    UIViewController *fromVc = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];    UIViewController *toVc = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];    UIView *fromView = [[UIView alloc] init];;    UIView *toView = [[UIView alloc] init];    if ([transitionContext respondsToSelector:@selector(viewForKey:)]) {        // fromVc 的view        fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];        // toVc的view        toView = [transitionContext viewForKey:UITransitionContextToViewKey];    }else {        // fromVc 的view        fromView = fromVc.view;        // toVc的view        toView =toVc.view;    }    CGFloat x = [UIScreen mainScreen].bounds.size.width;    if ([toVc.title isEqualToString:@"B"]) {        x = -x;//根据title判断是从哪个控制器跳转到哪个控制器 设置动画的方向    }    // 转场环境    UIView *containView = [transitionContext containerView];    toView.frame = CGRectMake(-x, 0, containView.frame.size.width, containView.frame.size.height);    [containView addSubview:fromView];    [containView addSubview:toView];    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{        fromView.transform = CGAffineTransformTranslate(fromView.transform, x, 0);        toView.transform = CGAffineTransformTranslate(toView.transform, x, 0);    } completion:^(BOOL finished) {        [transitionContext completeTransition:YES];    }];}@end

创建TabBarController，设置代理，并实现UITabBarControllerDelegate的代理方法。
在animationControllerForTransitionFromViewController方法中返回刚才写的类的实例。

#import "DMMainViewController.h"#import "AnimationManager.h"@interface DMMainViewController ()<UITabBarControllerDelegate>@end@implementation DMMainViewController- (void)viewDidLoad {    [super viewDidLoad];    self.delegate = self;    [self setChildchildViewController:[[UITableViewController alloc] init] title:@"A"];    [self setChildchildViewController:[[UITableViewController alloc] init] title:@"B"];//    [self setChildchildViewController:[[UITableViewController alloc] init] title:@"C"];//    [self setChildchildViewController:[[UITableViewController alloc] init] title:@"D"];}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}- (void)setChildchildViewController:(UIViewController *)viewController title:(NSString *)title {    viewController.title = title;    UINavigationController *naviVc = [[UINavigationController alloc] initWithRootViewController:viewController];    [self addChildViewController:naviVc];}// 实现协议- (nullable id <UIViewControllerAnimatedTransitioning>)tabBarController:(UITabBarController *)tabBarController animationControllerForTransitionFromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC{    return [[AnimationManager alloc] init];}@end