一、需求：請實現下圖所示的動畫(物理碰撞)

 

 

二、上面引入過UIDynamic 可以實現碰撞的物理效果動畫，how to start ?

在工程中導入UIKit，從Headers 找一些UIDynamic，發現了UIDynamicAnimator.h,UIDynamicBehavior,UIDynamicItemBehavior

既然是要動畫效果 那就應該是UIDynamicAnimator.h

到UIDynamicAnimator.h 頭文件去查看注釋

// 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.

- (instancetype)initWithReferenceView:(UIView *)view NS_DESIGNATED_INITIALIZER;

大概意思是使用這個初始化方法的時候，需要為你的試圖關聯behaviors

what’s the behaviors ? jump into defination 然而還不是很懂，UIDynamicBehavior,那就查看API (注意文檔中的如下描述)。

This parent class, UIDynamicBehavior, is inherited by the primitive dynamic behavior classes UIAttachmentBehavior, UICollisionBehavior, UIGravityBehavior, UIDynamicItemBehavior, UIPushBehavior, and UISnapBehavior.

文檔中提到UIDynamicBehavior的父類，那麼UIDynamicBehavior父類(Dynamic 行為相關類)描述什麼行為呢?

UIAttachmentBehavior：附著行為

UICollisionBehavior：碰撞行為

UIGravityBehavior：重力行為

UIDynamicItemBehavior：動態元素行為

UIPushBehavior：推行為

UISnapBehavior：吸附行為

上述的各種行為可單獨使用，也可以組合使用更復雜的動畫效果。

解決方案的思路就引導到這邊，也就可以實現上述需求。Dynamic 行為相關類的屬性可自行研究。

三、解決方案。

上述需求的解決方案(我這邊用的是6sP的模擬器奧，因為在設置floor的y坐標是600)

既然是球落地效果，必然有兩個模擬對象：floor，basketBall

1.創建UIDynamicAnimator 對象

self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

2.剛剛在API 看到了初始化UIDynamicAnimator需要關聯一個或者多個行為

NSArray *animatorObjects = @[self.imageV1];

// 剛剛在API 看到了初始化UIDynamicAnimator需要關聯一個或者多個行為

self.gravityBehav = [[UIGravityBehavior alloc] initWithItems:animatorObjects];

self.colision = [[UICollisionBehavior alloc] initWithItems:animatorObjects];

3.如果你想監聽碰撞的狀態，可以設置一下代理

self.colision.collisionDelegate = self;

4.設置碰撞邊界

[self.colision addBoundaryWithIdentifier:@"boundaryLine" fromPoint:CGPointMake(0, 600) toPoint:CGPointMake(SCREENWITH, 600)];

5.設置動態行為參數

// 設置動態行為參數

UIDynamicItemBehavior *itemBehavior = [[UIDynamicItemBehavior alloc] initWithItems:animatorObjects];

// 設置彈性

[itemBehavior setElasticity:0.5];

6.行為創建了，別忘了給animator添加上

[self.animator addBehavior:self.gravityBehav];

[self.animator addBehavior:self.colision];

[self.animator addBehavior:itemBehavior];

三、下面代碼只能說功能實現

PS：以下代碼不符合代碼書寫規范

//

// ViewController.m

// DynamicAnimation

//

// Created by JeversonJee on 16/5/27.

// Copyright © 2016年 JeversonJee. All rights reserved.

//

#import "ViewController.h"

#define SCREENWITH [UIScreen mainScreen].bounds.size.width

#define SCREENHEIGHT [UIScreen mainScreen].bounds.size.height

@interface ViewController ()

@property (nonatomic, strong) UIDynamicAnimator *animator;

@property (nonatomic, strong) UIGravityBehavior *gravityBehav;

@property (nonatomic, strong) UICollisionBehavior *colision;

@property (nonatomic, strong) UIImageView *imageV1;

@property (nonatomic, strong) UIImageView *imageV2;

@end

@implementation ViewController

- (void)viewDidLoad {

[super viewDidLoad];

// Do any additional setup after loading the view, typically from a nib.

[self jjCollisionBehav];

}

- (void)jjCollisionBehav {

// 創建碰撞需要的對象

[self jjCreateBall];

[self jjCreateFloor];

// 創建UIDynamicAnimator 對象

self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];

NSArray *animatorObjects = @[self.imageV1];

// 剛剛在API 看到了初始化UIDynamicAnimator需要關聯一個或者多個行為

self.gravityBehav = [[UIGravityBehavior alloc] initWithItems:animatorObjects];

self.colision = [[UICollisionBehavior alloc] initWithItems:animatorObjects];

// 這裡設置代理是為了監聽碰撞狀態的，可以去了解一下代理方法

self.colision.collisionDelegate = self;

// 設置碰撞邊界

[self.colision addBoundaryWithIdentifier:@"boundaryLine" fromPoint:CGPointMake(0, 600) toPoint:CGPointMake(SCREENWITH, 600)];

// 設置動態行為參數

UIDynamicItemBehavior *itemBehavior = [[UIDynamicItemBehavior alloc] initWithItems:animatorObjects];

// 設置彈性

[itemBehavior setElasticity:0.5];

// 創建了行為需要animator添加

[self.animator addBehavior:self.gravityBehav];

[self.animator addBehavior:self.colision];

[self.animator addBehavior:itemBehavior];

}

-(void)collisionBehavior:(UICollisionBehavior *)behavior endedContactForItem:(id)item withBoundaryIdentifier:(id)identifier {

NSLog(@"collisionBehavior=%@", item);

NSString *identifierStr = [NSString stringWithFormat:@"%@", identifier];

NSLog(@"s=%@", identifier);

if ( [identifierStr isEqualToString:@"boundaryLine"] ) {

[self.imageV2 setBackgroundColor:[UIColor grayColor]];

[UIView animateWithDuration:2 animations:^(void){

[self.imageV2 setBackgroundColor:[UIColor grayColor]];

}];

}

}

-(void)jjCreateBall {

_imageV1 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"basketBall"]];

_imageV1.frame = CGRectMake(100, 100, 60, 60);

[self.view addSubview:_imageV1];

}

- (void)jjCreateFloor {

_imageV2 = [[UIImageView alloc] init];

[_imageV2 setBackgroundColor:[UIColor grayColor]];

_imageV2.frame = CGRectMake(0, 600, SCREENWITH, SCREENHEIGHT - 400);

[self.view addSubview:_imageV2];

}

-(void)didReceiveMemoryWarning {

[super didReceiveMemoryWarning];

// Dispose of any resources that can be recreated.

}

@end