iOS -- Present/Dismiss之Animation简谈

需求:

需要在当前界面弹出一个视图框(这样的需求很多,采用的方式也比较多),因为弹出的视图控件和操作都比较多,避免当前视图控制器的代码冗余，所以不得寻求其他方法。多番思量还是觉得present当属首选

test：

1. 首先在当前视图控制器中需要做的事:
1.1初始化一个button添加present的点击跳转事件

- (void)presentAction{
    TestController * testVC = [[TestViewController alloc]init];
    //present模式设为自定义
    testVC.modalPresentationStyle = UIModalPresentationCustom;
    //遵循正在跳转协议
    testVC.transitioningDelegate = self;
     //跳转的animated必须为YES(ture)
    [self presentViewController:testVC animated:YES completion:nil];
}

1.2在跳转事件中,让self遵循testVC的跳转协议,也就是self遵循跳转动画协议
1.3 遵循协议实现两个协议方法:

//present动画协议
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
    return nil;
    //[PresentAnimation new];
}
//dismiss动画协议
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed{
    return nil;
    //[DismissAnimation new];
}

1.4 两个协议方法中需要我们返回”UIViewControllerAnimatedTransitioning”对象，这个对象就是跳转动画的具体实现内容。
2. 创建present动画;
添加UIKit框架，遵循协议。头文件如下

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface PresentAnimation : NSObject<UIViewControllerAnimatedTransitioning>

@end

在m文件中会提醒要实现两个协议方法：
1.返回执行动画的时间
2.具体实现内容

#import "PresentAnimation.h"

@implementation PresentAnimation

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
    return 1.0;
}


- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
    //1 从过渡上下文中取出目的View 用特有的key值获取哦 (也可以先获取目标视图控制器再取出它的view)
    UIView * toView = [transitionContext viewForKey:UITransitionContextToViewKey];

    //2 再得到过渡的容器View 用于在动画中呈现出toView
    UIView * containerView = [transitionContext containerView];
    //toView.alpha = 0;//将目标视图加入到转场容器中使其透明
    [containerView addSubview:toView];

    //3 接下来设置要呈现出来的View的大小等属性
    toView.layer.cornerRadius = 20.f;
    CGRect rect = toView.frame;
    //a 使其出来的时候是从上往下
    rect.origin.y = - rect.size.height;
    //b 使其从中心位置变大到指定位置
    // 实用与collectionCell中 暂时xxx
    toView.frame = rect;
    toView.layer.masksToBounds = YES;

    [UIView animateWithDuration:0.8 delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:2 options:UIViewAnimationOptionCurveEaseInOut animations:^{

        CATransform3D toViewTransform = toView.layer.transform;
        //通过之前设置的位置或大小 等在这里改变位置 大小等来显示动画效果
        toViewTransform = CATransform3DTranslate(toViewTransform, 0, rect.size.height, 0);
        //参数的具体解释看这里哦[参数解释](http://blog.sina.com.cn/s/blog_51a995b70101mz3q.html)
        toViewTransform = CATransform3DScale(toViewTransform, 0.8, 0.5, 1);

        toView.layer.transform = toViewTransform;
        //toView.alpha = 1;
    } completion:^(BOOL finished) {
        //动画结束 转场结束
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
}
@end

3. 创建dismiss动画;

#import "DismissAnimation.h"

@implementation DismissAnimation

- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
    return 1.0f;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
    UIViewController * fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIView *fromView = fromVC.view;
    //执行的dismiss动画
    [UIView animateWithDuration:1.1 delay:0 usingSpringWithDamping:1.0 initialSpringVelocity:5 options:UIViewAnimationOptionCurveEaseInOut animations:^{
     //如果在debug中打印如下结果，是因为：动画时间是1(具体原因不明，经多次调试只要动画时间不是1就OK)
      //stiffness must be greater than 0. 刚度必须大于0;
      //damping must be greater than or equal to 0. 阻尼必须大于或等于0;
        CATransform3D fromViewTransform = fromView.layer.transform;
        fromViewTransform = CATransform3DScale(fromViewTransform, 1.5, 1.5, 1);

        fromView.layer.transform = fromViewTransform;

        fromView .alpha = 0;

    } completion:^(BOOL finished) {
        //
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
}

4. 最后在TestVC的 .m文件中添加按钮dismiss点击事件，和一般的dismiss一样不做特殊处理,(当然也可以)

- (void)dismissAction{
    [self dismissViewControllerAnimated:YES completion:nil];
}
@end

模态跳转的动画就基本OK咯！见效果：
！！！如果有GIF的上传功能就……….