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UIDynamic是从iOS 7开始引入的一种新技术，隶属于UIKit框架 ,可以认为是一种物理引擎，能模拟和仿真现实生活中的物理现象 如：重力、弹性碰撞等现象
其实就是UIKit的一套动画和交互体系。我们现在进行UI动画基本都是使用CoreAnimation或者UIView animations。而UIKit动力学最大的特点是将现实世界动力驱动的动画引入了UIKit，比如重力，铰链连接，碰撞，悬挂等效果。总之就是，将2D物理引擎引入了人UIKit。需要注意，UIKit动力学的引入，并不是以替代CA或者UIView动画为目的的，在绝大多数情况下CA或者UIView动画仍然是最优方案，只有在需要引入逼真的交互设计的时候，才需要使用UIKit动力学它是作为现有交互设计和实现的一种补充而存在的。
UIDynamicAnimator；动画的播放者，动力行为（UIDynamicBehavior）的容器，添加到容器内的行为将发挥作用；
UIDynamicBehavior：动力行为的描述，用来指定UIDynamicItem应该如何运动，即定义适用的物理规则。一般我们使用这个类的子类对象来对一组UIDynamicItem应该遵守的行为规则进行描述；
UIDynamicItem：用来描述一个力学物体的状态，其实就是实现了UIDynamicItem委托的对象，或者抽象为有面积有旋转的质点；
ReferenceView：等同于力学参考系，如果你的初中物理不是语文老师教的话，我想你知道这是啥..只有当想要添加力学的UIView是ReferenceView的子view时，动力UI才发生作用。
(1)UIDynamicAnimator(仿真器)
它代表着实现仿真行为的上下文(为实行仿真行为提供的场所)
须知:它可以让物理仿真元素执行物理仿真行为
它是UIDynamicAnimator类型的对象
1>初始化和管理一个 Dynamic Animator
// 传入一个 Reference view创建一个 Dynamic Animator - (instancetype)initWithReferenceView:(UIView*)view; //view参数：是一个参照视图，表示物理仿真的范围 // 获取在 CGRect 内所有的动力项，这个 CGRect是基于 Reference view的二维坐标系统的 - (NSArray*)itemsInRect:(CGRect)rect; //添加1个物理仿真行为 - (void)addBehavior:(UIDynamicBehavior *)behavior; //移除1个物理仿真行为 - (void)removeBehavior:(UIDynamicBehavior *)behavior; //移除之前添加过的所有物理仿真行为 - (void)removeAllBehaviors;
2>获取 Dynamic Animator’s的状态
//是否正在进行物理仿真 @property (nonatomic, readonly, getter = isRunning) BOOL running; // 获取所有的 Behaviors @property (nonatomic, readonly, copy) NSArray* behaviors; //获取参照视图 @property (nonatomic, readonly) UIView* referenceView; //这个 delegate中有两个回调方法，一个是在 animator暂停的时候调用，一个是在将要恢复的时候调用 @property (nonatomic, assign) id <UIDynamicAnimatorDelegate> delegate; // 已经运行了多久的时间，是一个 NSTimeInterval - (NSTimeInterval)elapsedTime; //如果动力项不是通过 animator自动计算改变状态，比如，通过代码强制改变一个 item的 transfrom时，可以用这个方法通知 animator这个 item 的改变。如果不用这个方法，animator之后的动画会覆盖代码中对 item做的改变，相当于代码改变 transform变得没有意义。 - (void)updateItemUsingCurrentState:(id <UIDynamicItem>)item;
3>Collection View Additions
- (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout*)layout //传入一个 CollectionViewLayout创建一个 Dynamic Animator – layoutAttributesForCellAtIndexPath: – layoutAttributesForDecorationViewOfKind:atIndexPath: – layoutAttributesForSupplementaryViewOfKind:atIndexPath:
(2)UIDynamicBehavior(仿真行为)
1>主要的方法
//在将要进行动画时的 block回调 @property(nonatomic, copy) void (^action)(void) //添加到该动态行为中的子动态行为 @property(nonatomic, readonly, copy) NSArray *childBehaviors // 该动态行为相关联的dynamicAnimator @property(nonatomic, readonly) UIDynamicAnimator *dynamicAnimator
2>常用方法
//添加一个子动态行为 - (void)addChildBehavior:(UIDynamicBehavior *)behavior // 移除一个子动态行为 - (void)removeChildBehavior:(UIDynamicBehavior *)behavior // 当该动态行为将要被添加到一个UIDynamicAnimator中时，这个方法会被调用。 - (void)willMoveToAnimator:(UIDynamicAnimator *)dynamicAnimator
注意:
在开发中，大部分情况下使用 UIDynamicBehavior 的子类就足够了，因为UIKit 中已经有几个现成的模拟现实的 UIDynamicBehavior 类。
3>UIDynamicBehavior的子类,几种物理仿真行为
UIGravityBehavior：重力行为
UICollisionBehavior：碰撞行为
UISnapBehavior：捕捉行为
UIPushBehavior：推动行为
UIAttachmentBehavior：附着行为
UIDynamicItemBehavior：动力元素行为
注意:上述所有物理仿真行为都继承自UIDynamicBehavior所有的UIDynamicBehavior都可以独立进行组合使用多种行为时，可以实现一些比较复杂的效果
要想使用UIDynamic来实现物理仿真效果，大致的步骤如下
（1）创建一个物理仿真器（顺便设置仿真范围）
（2）创建相应的物理仿真行为（顺便添加物理仿真元素)
（3）将物理仿真行为添加到物理仿真器中开始仿真
示例:
@interface DynamicItemBehavior ()
@property(nonatomic) UIDynamicAnimator * dynmicAnimation;
@property(nonatomic) UIImageView * imageView;
@end
@implementation DynamicItemBehavior
-(void)viewDidLoad{
[super viewDidLoad];
[self createUIDynmicAnimationObject];
[self createDynamicItemObject];
[self createUIDynamicBehaviorObject];
}
//第一步:创建UIDynamic Animation对象
-(void)createUIDynmicAnimationObject{
UIDynamicAnimator * dynmicAnimation = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
//参数:ReferenceView表示一个参照视图,表示物理仿真的范围
self.dynmicAnimation = dynmicAnimation;
}
//第二步:创建任何遵守了UIDynamicItem协议的对象 UIView默认已经遵守了UIDynamicItem协议，因此任何UI控件都能做物理仿真
-(void)createDynamicItemObject{
UIImageView * imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"image"]];
self.imageView = imageView;
imageView.frame = CGRectMake(0, 0, 50, 50);
imageView.center = self.view.center;
[self.view addSubview:imageView];
}
//第三步:创建UIDynamicBehavior对象
-(void)createUIDynamicBehaviorObject{
//UIDynamicBehavior的子类类型
UIGravityBehavior* gravityBeahvior = [[UIGravityBehavior alloc] initWithItems:@[_imageView]];
//将要实现的效果添加到仿真器中
[self.dynmicAnimation addBehavior:gravityBeahvior];
}
（1）谁要进行物理仿真？
物理仿真元素（Dynamic Item）
（2）执行怎样的物理仿真效果？怎样的动画效果？
物理仿真行为（Dynamic Behavior）
（3）让物理仿真元素执行具体的物理仿真行为
物理仿真器（Dynamic Animator）
(1)不是任何对象都能做物理仿真元素,不是任何对象都能进行物理仿真
(2)物理仿真元素要素：
任何遵守了UIDynamicItem协议的对象
UIView默认已经遵守了UIDynamicItem协议，因此任何UI控件都能做物理仿真
UICollectionViewLayoutAttributes类默认也遵守UIDynamicItem协议
(1)相关属性
// 添加到重力行为中的所有物理仿真元素 @property (nonatomic, readonly, copy) NSArray* items; //运动方向，默认是(0.0f, 1.0f)。dx为-1.0f时向左运动，dy为-1.0时向上运动，所以根据0.0~1.0可以定位所有的方向。 @property (readwrite, nonatomic) CGVector gravityDirection; // 重力方向（是一个角度，以x轴正方向为0°，顺时针正数，逆时针负数） @property (readwrite, nonatomic) CGFloat angle; // 量级（用来控制加速度，1.0代表加速度是1000 points /second²） @property (readwrite, nonatomic) CGFloat magnitude;
解释:
vector就是一个点，从坐标原点向这个点连线就是一个矢量，也就是重力的方向，默认是(0.0, 1.0)。这个属性的数据量很丰富，由这个点向X轴和Y轴分别做垂线构成了一个矩形，对角线与X轴夹角就是重力加速度的方向，即angle，对角线的长度就是重力加速度的值，即magnitude。也就是说我们完全可以用gravityDirection变量确定angle和magnitude的值，反之用angle和magnitude也可以确定gravityDirection的值。
(2)常用方法
//初始化方法 - (instancetype)initWithItems:(NSArray<id <UIDynamicItem>> *)items NS_DESIGNATED_INITIALIZER; //参数:items是实现UIDynamicItem委托协议的对象 - (void)addItem:(id <UIDynamicItem>)item; //添加一个物理仿真对象 - (void)removeItem:(id <UIDynamicItem>)item; //删除一个物理仿真对象 - (void)setAngle:(CGFloat)angle magnitude:(CGFloat)magnitude; //动态设置重力加速度方向和重力加速度的大小
(3)示例
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
UIGravityBehavior *gravity = [[UIGravityBehavior alloc] initWithItems:@[self.squareView]]; // 创建一个重力行为
gravity.gravityDirection = CGVectorMake(0, 1); // 在垂直向下方向 1000 点/平方秒 的速度
[self.animator addBehavior:gravity];
}
运行项目可以看到效果：
@property (nonatomic, readonly, copy) NSArray<id <UIDynamicItem>> *items; //碰撞行为数组
@property (nonatomic, readwrite) UICollisionBehaviorMode collisionMode;//碰撞模式（分三种，
UICollisionBehaviorModeItems = 1 << 0,元素碰撞
UICollisionBehaviorModeBoundaries = 1 << 1,边界碰撞
UICollisionBehaviorModeEverything = NSUIntegerMax全体碰撞）
@property (nonatomic, readwrite) BOOL translatesReferenceBoundsIntoBoundary;//是否以参照视图的bounds为边界
@property (nullable, nonatomic, weak, readwrite) id <UICollisionBehaviorDelegate> collisionDelegate;//代理
@property (nullable, nonatomic, readonly, copy) NSArray<id <NSCopying>> *boundaryIdentifiers;//
(2)常用的方法
- (instancetype)initWithItems:(NSArray<id <UIDynamicItem>> *)items;//初始化方法 - (void)addItem:(id <UIDynamicItem>)item;//添加一个物理仿真对象 - (void)removeItem:(id <UIDynamicItem>)item;//移除一个物理仿真对象 - (void)removeAllBoundaries;//移除所有边界 - (void)removeBoundaryWithIdentifier:(id <NSCopying>)identifier; //移除ID对应的边界 - (UIBezierPath*)boundaryWithIdentifier:(id <NSCopying>)identifier; //通过ID找到边界路径 - (void)addBoundaryWithIdentifier:(id <NSCopying>)identifier forPath:(UIBezierPath *)bezierPath;//添加一个path作为碰撞边界 - (void)addBoundaryWithIdentifier:(id <NSCopying>)identifier fromPoint:(CGPoint)p1 toPoint:(CGPoint)p2;//通过添加两个点连成的线 作为边界 - (nullable UIBezierPath *)boundaryWithIdentifier:(id <NSCopying>)identifier;//添加一个贝塞尔曲线路径的边界 - (void)setTranslatesReferenceBoundsIntoBoundaryWithInsets:(UIEdgeInsets)insets;//
(3)代理方法
//两个元素相互碰撞 // item 与 item 之间开始碰撞 - (void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id <UIDynamicItem>)item1 withItem:(id <UIDynamicItem>)item2 atPoint:(CGPoint)p; // item 与 item 之间结束碰撞 - (void)collisionBehavior:(UICollisionBehavior *)behavior endedContactForItem:(id <UIDynamicItem>)item1 withItem:(id <UIDynamicItem>)item2; // item 和边界开始碰撞 - (void)collisionBehavior:(UICollisionBehavior*)behavior beganContactForItem:(id <UIDynamicItem>)item withBoundaryIdentifier:(nullable id <NSCopying>)identifier atPoint:(CGPoint)p; // item 和边界结束碰撞 - (void)collisionBehavior:(UICollisionBehavior*)behavior endedContactForItem:(id <UIDynamicItem>)item withBoundaryIdentifier:(nullable id <NSCopying>)identifier;
(3)示例
@interface CollisionBehavior ()<UICollisionBehaviorDelegate>
@property(nonatomic) UIDynamicAnimator * theAnimator;
@property(nonatomic) UIImageView * aimageView;
@end
@implementation CollisionBehavior
-(void)viewDidLoad{
[super viewDidLoad];
self.aimageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"1"]];
self.aimageView.frame = CGRectMake(100, 100, 100, 100);
[self.view addSubview:self.aimageView];
self.theAnimator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
}
-(void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
UIGravityBehavior * gravity = [[UIGravityBehavior alloc]initWithItems:@[self.aimageView]];
[self.theAnimator addBehavior:gravity];
UICollisionBehavior * collsion = [[UICollisionBehavior alloc]initWithItems:@[self.aimageView]];
collsion.translatesReferenceBoundsIntoBoundary = YES;
collsion.collisionDelegate = self;
[self.theAnimator addBehavior:collsion];
}
#pragma --mark Delegate
-(void)collisionBehavior:(UICollisionBehavior *)behavior beganContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier atPoint:(CGPoint)p{
self.aimageView.image = [UIImage imageNamed:@"3"];
}
-(void)collisionBehavior:(UICollisionBehavior *)behavior endedContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier{
self.aimageView.image = [UIImage imageNamed:@"4"];
}现在运行项目将会看到如下效果：
@property (readonly, nonatomic) UIAttachmentBehaviorType attachedBehaviorType;// 吸附行为的类型
typedef NS_ENUM(NSInteger, UIAttachmentBehaviorType) {
UIAttachmentBehaviorTypeItems:表示连接两个item的吸附行为
UIAttachmentBehaviorTypeAnchor:表示连接一个item与锚点的吸附行为
} NS_ENUM_AVAILABLE_IOS(7_0);
@property (readwrite, nonatomic) CGPoint anchorPoint;//锚点
@property (readwrite, nonatomic) CGFloat length;// 吸附行为中的两个吸附点之间的距离，通常用这个属性来调整吸附的长度，可以创建吸附行为之后调用。系统基于你创建吸附行为的方法来自动初始化这个长度
@property (readwrite, nonatomic) CGFloat damping; // // 描述吸附行为减弱的阻力大小，经测试，这个值越大，可以减震
@property (readwrite, nonatomic) CGFloat frequency; //// 吸附行为震荡的频率 , 该值越大，物理仿真元素运动越剧烈
@property (readwrite, nonatomic) CGFloat frictionTorque NS_AVAILABLE_IOS(9_0);// 反抗旋转的程度
@property (readwrite, nonatomic) UIFloatRange attachmentRange NS_AVAILABLE_IOS(9_0);
(2)常用方法
initWithItem:attachedToAnchor: 初始化连接动力item的中心和锚点的吸附行为 - (instancetype)initWithItem:(id<UIDynamicItem>)item attachedToAnchor:(CGPoint)point 参数：item是你要应用吸附行为的动力项，point是吸附行为的锚点，与跟行为相关的动态动画所在在系统坐标有关。 返回：初始化的attachment behavior,如果初始化过程出错将会返回nil。 该初始化方法的吸附行为的类型是 UIAttachmentBehaviorTypeAnchor initWithItem:attachedToItem: 初始化 连接两个动力项中心的 吸附行为 - (instancetype)initWithItem:(id<UIDynamicItem>)item1 attachedToItem:(id<UIDynamicItem>)item2 参数：item1第一个被吸附行为连接的动力项，item2第二个被吸附行为连接的动力项 返回：初始化的attachment behavior,如果初始化过程出错将会返回nil。 该初始化方法的吸附行为的类型是UIAttachmentBehaviorTypeItems initWithItem:offsetFromCenter:attachedToAnchor: 初始化 连接动力项中某一点和锚点的 吸附行为 - (instancetype)initWithItem:(id<UIDynamicItem>)item offsetFromCenter:(UIOffset)p1 attachedToAnchor:(CGPoint)point 参数：item要应用吸附行为的动力项，p1相对于item中心的偏移，point 是吸附行为的锚点，与跟行为相关的动力动画所在在系统坐标有关。 返回： 初始化的 attachment behavior,如果初始化过程出错将会返回nil。 该初始化方法的吸附行为的类型是UIAttachmentBehaviorTypeAnchor initWithItem:offsetFromCenter:attachedToItem:offsetFromCenter: 初始化连接一个动力item中某一点和另一个动力item中某一点的吸附行为 - (instancetype)initWithItem:(id<UIDynamicItem>)item1 offsetFromCenter:(UIOffset)p1 attachedToItem:(id<UIDynamicItem>)item2 offsetFromCenter:(UIOffset)p2 参数：item1第一个被吸附行为连接的动力项，p1相对于item1中心的偏移，item2第二个被吸附行为连接的动力项，p2相对于item2中心的偏移 返回：返回：初始化的attachment behavior,如果初始化过程出错将会返回nil。 这是为UIAttachmentBehavior类指定的初始化程序。
(3)示例:
#import "AttachmentBehavior.h"
@interface AttachmentBehavior ()
@property(nonatomic) UIDynamicAnimator * animator;
@property(nonatomic) UIImageView * imageView;
@property(nonatomic) UIAttachmentBehavior * attachmentBehave;
@end
@implementation AttachmentBehavior
-(void)viewDidLoad{
[super viewDidLoad];
[self createGeture];
[self addGravity];
}
-(void)createGeture{
UIPanGestureRecognizer * panGesture = [[UIPanGestureRecognizer alloc]
initWithTarget:self
action:@selector(handleAttachmentGesture:)];
[self.view addGestureRecognizer:panGesture];
}
-(UIImageView *)imageView{
if (!_imageView) {
_imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"1"]];
_imageView.frame =CGRectMake(100, 100, 50, 50);
[self.view addSubview:_imageView];
}
return _imageView;
}
-(void)addGravity{
self.animator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
UICollisionBehavior * collsionBehaviour = [[UICollisionBehavior alloc]initWithItems:@[self.imageView]];
collsionBehaviour.translatesReferenceBoundsIntoBoundary = YES;
[self.animator addBehavior:collsionBehaviour];
UIGravityBehavior * gravityBehaviour = [[UIGravityBehavior alloc]initWithItems:@[self.imageView]];
[self.animator addBehavior:gravityBehaviour];
}
-(void)handleAttachmentGesture:(UIPanGestureRecognizer *)panGesture{
if (panGesture.state ==UIGestureRecognizerStateBegan) {
CGPoint imageViewCenterPoint =CGPointMake(self.imageView.center.x, self.imageView.center.y-100);
UIAttachmentBehavior * attachmentBehave = [[UIAttachmentBehavior alloc]initWithItem:self.imageView attachedToAnchor:imageViewCenterPoint ];
[self.animator addBehavior:attachmentBehave];
self.attachmentBehave = attachmentBehave;
}else if(panGesture.state ==UIGestureRecognizerStateChanged){
[self.attachmentBehave setAnchorPoint:[panGesture locationInView:self.view]];
}else if(panGesture.state ==UIGestureRecognizerStateEnded){
[self.animator removeBehavior:self.attachmentBehave];
}
}
@end
效果:
(1)相关属性
@property (nonatomic, readonly, copy) NSArray<id <UIDynamicItem>> *items;
@property (nonatomic, readonly) UIPushBehaviorMode mode;// 推力模式
{
UIPushBehaviorModeContinuous,//持续的力
UIPushBehaviorModeInstantaneous //一次性的力
}
@property (nonatomic, readwrite) BOOL active;//默认值是YES，将其设置为NO，可以将行为停止。在激活状态下，物体才会受到推力效果
@property (readwrite, nonatomic) CGFloat angle;//角度
@property (readwrite, nonatomic) CGFloat magnitude;//加速度
@property (readwrite, nonatomic) CGVector pushDirection;//运动方向
(2)常见方法
- (instancetype)initWithItems:(NSArray<id <UIDynamicItem>> *)items mode:(UIPushBehaviorMode)mode; - (void)addItem:(id <UIDynamicItem>)item; - (void)removeItem:(id <UIDynamicItem>)item; - (UIOffset)targetOffsetFromCenterForItem:(id <UIDynamicItem>)item;// - (void)setTargetOffsetFromCenter:(UIOffset)o forItem:(id <UIDynamicItem>)item;//方法是说推力作用点的偏移量，默认是center。 - (void)setAngle:(CGFloat)angle magnitude:(CGFloat)magnitude;//
(3)示例
#import "PushBehavior.h"
@interface PushBehavior ()
@property(nonatomic) UIDynamicAnimator * animator;
@property(nonatomic) UIImageView * imageView;
@end
@implementation PushBehavior
-(void)viewDidLoad{
[super viewDidLoad];
[self imageView];
[self createGesture];
}
-(void)createGesture{
UIPanGestureRecognizer * leftPanGesture = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(handlePanGesture:)];
[self.view addGestureRecognizer:leftPanGesture];
}
#pragma mark --lasyLoad
-(UIDynamicAnimator *)animator{
if (!_animator) {
_animator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
}
return _animator;
}
-(UIImageView *)imageView{
if (!_imageView) {
_imageView = [[UIImageView alloc]initWithImage:[UIImage imageNamed:@"1"]];
_imageView.frame = CGRectMake(0, 0, 50,50);
_imageView.center = CGPointMake(self.view.bounds.size.width/2-100, self.view.bounds.size.height/2);
[self.view addSubview:_imageView];
}
return _imageView;
}
#pragma mark --gesture触发方法
-(void)handlePanGesture:(UIPanGestureRecognizer *)panGesture{
if (panGesture.state==UIGestureRecognizerStateEnded) {
if ([self gestureHitsBarView:panGesture]) {
UIPushBehavior * pushBehavior = [[UIPushBehavior alloc]initWithItems:@[self.imageView] mode:UIPushBehaviorModeInstantaneous];
[pushBehavior setPushDirection:CGVectorMake([panGesture velocityInView:self.view].x /5000.f, 0)];
[self.animator removeAllBehaviors];
[self.animator addBehavior:pushBehavior];
}
}
}
-(BOOL)gestureHitsBarView:(UIPanGestureRecognizer *)panGesture{
CGPoint locationInView =[panGesture locationInView:self.view];
return self.imageView.frame.origin.x <=locationInView.x &&locationInView.y<=self.imageView.frame.origin.y +self.imageView.frame.size.height;
}
@end
效果图:
将一个物体钉在某一点。它只有一个初始化方法和一个属性。
(1)相关属性
@property (nonatomic, assign) CGPoint snapPoint; @property (nonatomic, assign) CGFloat damping;//用于减幅、减震（取值范围是0.0 ~ 1.0，值越大，震动幅度越小）
(2)常见方法
- (instancetype)initWithItem:(id <UIDynamicItem>)item snapToPoint:(CGPoint)point;//初始化, 根据 item 和 point 来确定一个 item 要被定到哪个点上。
(3)示例
#import "ViewController.h"
@interface ViewController ()
@property(nonatomic) UIView * blueView;
@property(nonatomic) UIDynamicAnimator * animator;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIView * View =({
UIView * blueView = [[UIView alloc]initWithFrame:CGRectMake(100, 100, 100, 100)];
blueView.backgroundColor = [UIColor blueColor];
[self.view addSubview:blueView];
blueView;
});
self.blueView = View;
}
-(UIDynamicAnimator *)animator{
if (!_animator) {
_animator = [[UIDynamicAnimator alloc]initWithReferenceView:self.view];
}
return _animator;
}
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
//获取一个触摸点
UITouch * touch = [touches anyObject];
CGPoint point = [touch locationInView:self.view];
UISnapBehavior * snap =[[UISnapBehavior alloc]initWithItem:self.blueView snapToPoint:point];
snap.damping = arc4random_uniform(10)/10.0;
[self.animator removeAllBehaviors];
[self.animator addBehavior:snap];
}
效果图:
(1)相关属性
@property (nonatomic, readonly, copy) NSArray<id <UIDynamicItem>> *items; @property (readwrite, nonatomic) CGFloat elasticity; // Usually between 0 (inelastic) and 1 (collide elastically) //（弹性系数）决定了碰撞的弹性程度，比如碰撞时物体的弹性 @property (readwrite, nonatomic) CGFloat friction; // 0 being no friction between objects slide along each other.//（摩擦系数）决定了沿接触面滑动时的摩擦力大小 @property (readwrite, nonatomic) CGFloat density; // 1 by default//(密度） 跟size结合使用，计算物体的总质量。质量越大，物体加速或减速就越困难 @property (readwrite, nonatomic) CGFloat resistance; // 0: no velocity damping //（阻力）：决定线性移动的阻力大小，与摩擦系数不同，摩擦系数只作用于滑动运动 @property (readwrite, nonatomic) CGFloat angularResistance; // 0: no angular velocity damping //（角阻力） ：决定旋转运动时的阻力大小 @property (readwrite, nonatomic) CGFloat charge NS_AVAILABLE_IOS(9_0); @property (nonatomic, getter = isAnchored) BOOL anchored NS_AVAILABLE_IOS(9_0); @property (readwrite, nonatomic) BOOL allowsRotation; // force an item to never rotate ////（允许旋转）：这个属性很有意思，它在真实的物理世界没有对应的模型。设置这个属性为 NO 物体就完全不会转动，而无论施加多大的转动力
(2)常见方法
- (instancetype)initWithItems:(NSArray<id <UIDynamicItem>> *)items NS_DESIGNATED_INITIALIZER; - (void)addItem:(id <UIDynamicItem>)item; - (void)removeItem:(id <UIDynamicItem>)item; - (void)addLinearVelocity:(CGPoint)velocity forItem:(id <UIDynamicItem>)item; - (CGPoint)linearVelocityForItem:(id <UIDynamicItem>)item; - (void)addAngularVelocity:(CGFloat)velocity forItem:(id <UIDynamicItem>)item; - (CGFloat)angularVelocityForItem:(id <UIDynamicItem>)item;
(3)示例:
#import "PushBehavior.h"
@interface PushBehavior ()
@property(nonatomic) UIDynamicAnimator * animator;
@end
@implementation PushBehavior
-(void)viewDidLoad{
[super viewDidLoad];
}
- (UIView *) newViewWithCenter:(CGPoint)paramCenter backgroundColor:(UIColor *)paramBackgroundColor{
UIView *newView = [[UIView alloc] initWithFrame: CGRectMake(0.0f, 0.0f, 50.0f, 50.0f)];
newView.backgroundColor = paramBackgroundColor;
newView.center = paramCenter;
return newView;
}
- (void)viewDidAppear:(BOOL)animated{
[super viewDidAppear:animated];
UIView *topView = [self newViewWithCenter:CGPointMake(100.0f, 0.0f)
backgroundColor:[UIColor greenColor]];
UIView *bottomView = [self newViewWithCenter:CGPointMake(100.0f, 50.0f)
backgroundColor:[UIColor redColor]];
[self.view addSubview:topView];
[self.view addSubview:bottomView];
//构造动画
self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
//gravity
UIGravityBehavior *gravity = [[UIGravityBehavior alloc]
initWithItems:@[topView, bottomView]];
[self.animator addBehavior:gravity];
//collision
UICollisionBehavior *collision = [[UICollisionBehavior alloc]
initWithItems:@[topView, bottomView]];
collision.translatesReferenceBoundsIntoBoundary = YES;
[self.animator addBehavior:collision];
//指派不同特性值 弹性bounce
UIDynamicItemBehavior *moreElasticItem = [[UIDynamicItemBehavior alloc]
initWithItems:@[bottomView]];
moreElasticItem.elasticity = 1.0f;
UIDynamicItemBehavior *lessElasticItem = [[UIDynamicItemBehavior alloc]
initWithItems:@[topView]];
lessElasticItem.elasticity = 0.5f;
[self.animator addBehavior:moreElasticItem];
[self.animator addBehavior:lessElasticItem];
}
@end效果图:
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原文地址：http://blog.csdn.net/lxl_815520/article/details/51912242
