UIDynamicAnimator

//
//  UIDynamicAnimator.h
//  UIKit
//
//  Copyright (c) 2012-2015 Apple Inc. All rights reserved.
//

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

NS_ASSUME_NONNULL_BEGIN

@class UIDynamicBehavior;   // 动态行为
@class UIDynamicAnimator;   // 动态动画管理者


// 动画管理者的代理协议
@protocol UIDynamicAnimatorDelegate <NSObject>

@optional

// 动画将要启动
- (void)dynamicAnimatorWillResume:(UIDynamicAnimator *)animator;

// 动画已经暂停
- (void)dynamicAnimatorDidPause:(UIDynamicAnimator *)animator;

@end

// 动画管理者
NS_CLASS_AVAILABLE_IOS(7_0) @interface UIDynamicAnimator: NSObject

// When you initialize a dynamic animator with this method, you should only associates views with your behaviors.
// the behaviors (and their dynamic items) that you add to the animator employ the reference view’s coordinate system.
// 通过传递引用视图的方式来创建动画管理者
// 引用视图只是给动画执行者提供坐标体系
- (instancetype)initWithReferenceView:(UIView *)view NS_DESIGNATED_INITIALIZER;

// 添加动画行为
- (void)addBehavior:(UIDynamicBehavior *)behavior;
// 移除动画行为
- (void)removeBehavior:(UIDynamicBehavior *)behavior;
// 移除所有动画行为
- (void)removeAllBehaviors;


// 动画执行者引用的 View 
@property (nullable, nonatomic, readonly) UIView *referenceView;

// 获取所有的动画行为
@property (nonatomic, readonly, copy) NSArray<__kindof UIDynamicBehavior*> *behaviors;

// Returns the dynamic items associated with the animator’s behaviors that intersect a specified rectangle
// 获取某个范围内的 item 
- (NSArray<id<UIDynamicItem>> *)itemsInRect:(CGRect)rect;

// Update the item state in the animator if an external change was made to this item 
// 更新项目状态的动画师如果外部改变了这个项目
- (void)updateItemUsingCurrentState:(id <UIDynamicItem>)item;

// 是否正在运行
@property (nonatomic, readonly, getter = isRunning) BOOL running;

// 获取已经执行的时间
#if UIKIT_DEFINE_AS_PROPERTIES
@property (nonatomic, readonly) NSTimeInterval elapsedTime;
#else
// elapsed : 过去的，已经消失的。
- (NSTimeInterval)elapsedTime;
#endif

// 动画管理者代理
@property (nullable, nonatomic, weak) id <UIDynamicAnimatorDelegate> delegate;

@end






// collectionView 附加的方法
@interface UIDynamicAnimator (UICollectionViewAdditions)

// When you initialize a dynamic animator with this method, you should only associate collection view layout attributes with your behaviors.
// The animator will employ thecollection view layout’s content size coordinate system.
// 通过传递布局对象的方式来创建动画管理对象
// 主要是用来提供一个坐标体系
- (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout *)layout;

// The three convenience methods returning layout attributes (if associated to behaviors in the animator) if the animator was configured with collection view layout
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForCellAtIndexPath:(NSIndexPath *)indexPath;
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForSupplementaryViewOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath;
- (nullable UICollectionViewLayoutAttributes *)layoutAttributesForDecorationViewOfKind:(NSString *)decorationViewKind atIndexPath:(NSIndexPath *)indexPath;

@end

NS_ASSUME_NONNULL_END