iOS push动画改为淡入动画

上一篇中写了rootViewController更改时的淡入动画,如果我们push界面也用上一篇中的方法.那么就会发现淡入动画和push自己本身的动画会同时进行.达不到预期的效果

            [UIView transitionWithView:[[UIApplication sharedApplication] delegate].window duration:1 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{
                BOOL oldState = [UIView areAnimationsEnabled];
                [UIView setAnimationsEnabled:NO];
                [self.navigationController pushViewController:controller animated:YES]
                [UIView setAnimationsEnabled:oldState];
            } completion:nil];

要想实现只有淡入效果动画我们需要创建一个类,重写push动画
创建PushTransitionUtil类
PushTransitionUtil.h

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface PushTransitionUtil : NSObject<UIViewControllerAnimatedTransitioning>

@end

PushTransitionUtil.m

#import "PushTransitionUtil.h"
@interface PushTransitionUtil()<CAAnimationDelegate>

@property (nonatomic, strong)id<UIViewControllerContextTransitioning> transitionContext;

@end
@implementation PushTransitionUtil
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
    return 0.7;
}
// 转场动画的具体内容
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{
    self.transitionContext = transitionContext;
    // 获取动画的源控制器和目标控制器
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView * container = transitionContext.containerView;
    
    // 设置目标控制器的位置，并把透明度设为0，在后面的动画中慢慢显示出来变为1
    toVC.view.frame = [transitionContext finalFrameForViewController:toVC];
    toVC.view.alpha = 0;
    
    // 都添加到container中。注意顺序
    [container addSubview:toVC.view];
    
    // 执行动画
    [UIView animateKeyframesWithDuration:[self transitionDuration:transitionContext] delay:0 options:UIViewKeyframeAnimationOptionCalculationModeLinear animations:^{
        //        snapshotView.frame = toVC.avatarImageView.frame;
        toVC.view.alpha = 1;
    } completion:^(BOOL finished) {
        //一定要记得动画完成后执行此方法，让系统管理 navigation
        [transitionContext completeTransition:YES];
    }];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{
    
    //告诉 iOS 这个 transition 完成
    [self.transitionContext completeTransition:YES];
    [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view.layer.mask = nil;
    [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view.layer.mask = nil;
    
}

在接下来就是要自定义一个UINavigationController

#import "BaseNavigationViewController.h"
#import "PushTransitionUtil.h"
@interface BaseNavigationViewController ()<UINavigationControllerDelegate>

@end

@implementation BaseNavigationViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.delegate = self;
}



- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC{
    
        // 就是在这里判断是哪种动画类型
        // 也可以判断是哪一个viewcongroller
        if (operation == UINavigationControllerOperationPush){ 
            return [PushTransitionUtil new]; // 返回push动画的类
        }else{
            return nil;
        } 
    
}
@end