UIDynamic 详细用法

什么是UIDynamic?

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
重力、弹性碰撞等现象

UIDynamic使用步骤

• 创建一个物理仿真器（顺便设置仿真范围）
• 创建相应的物理仿真行为（顺便添加物理仿真元素）
• 将物理仿真行为添加到物理仿真器中，开始仿真

物理仿真元素

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

哪些对象才能做物理仿真元素？

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

物理仿真行为

• UIDynamic提供了以下几种物理仿真行为
• 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

物理仿真器

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
UIDynamicAnimator的初始化

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

view参数：是一个参照视图，表示物理仿真的范围

UIDynamicAnimator的常见方法

//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;

UIDynamicAnimator的常见属性

//参照视图

@property (nonatomic, readonly) UIView* referenceView;

//添加到物理仿真器中的所有物理仿真行为

@property (nonatomic, readonly, copy) NSArray* behaviors;

//是否正在进行物理仿真
@property (nonatomic, readonly, getter = isRunning) BOOL running;

//代理对象（能监听物理仿真器的仿真过程，比如开始和结束）
@property (nonatomic, assign) id <UIDynamicAnimatorDelegate> delegate;

直接上代码

#import "ViewController.h"

@interface ViewController ()
@property (nonatomic,strong) UIDynamicAnimator *animator;
@property (weak, nonatomic) IBOutlet UISegmentedControl *segmented;
@property (weak, nonatomic) IBOutlet UIView *blueView;
@property (weak, nonatomic) IBOutlet UIView *redView;
@property (weak, nonatomic) IBOutlet UIView *orangeView;
@end

@implementation ViewController

-(void)viewDidLoad {
    [super viewDidLoad];
    self.blueView.transform =   CGAffineTransformMakeRotation(M_PI_4);
    self.segmented.transform = CGAffineTransformMakeRotation(-M_PI / 8);
 }

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:  (UIEvent *)event {

    //创建重力行为
    UIGravityBehavior *gravityBehavior = [[UIGravityBehavior alloc]init];
    [gravityBehavior addItem:self.blueView];
    [gravityBehavior addItem:self.orangeView];
    //加速度
    gravityBehavior.magnitude = 3;
    //创建碰撞行为
    UICollisionBehavior *collisionBehavior = [[UICollisionBehavior alloc]init];
    //碰撞类型为元素和边界
    collisionBehavior.collisionMode = UICollisionBehaviorModeEverything;

    CGFloat Y = self.view.frame.size.height - CGRectGetHeight(self.redView.frame);
    CGFloat X = self.view.frame.size.width;
    CGFloat height = self.view.frame.size.height;

    //设置红色的View为底边界,左边框跟右边框作为边界
    [collisionBehavior addBoundaryWithIdentifier:@"collision1" fromPoint:CGPointMake(0,Y) toPoint:CGPointMake(X, Y)];
    [collisionBehavior addBoundaryWithIdentifier:@"collision2" fromPoint:CGPointMake(0, 0) toPoint:CGPointMake(0, height)];
    [collisionBehavior addBoundaryWithIdentifier:@"collision3" fromPoint:CGPointMake(X,0) toPoint:CGPointMake(X, height)];

    [collisionBehavior addItem:self.blueView];
    [collisionBehavior addItem:self.segmented];
    [collisionBehavior addItem:self.orangeView];
    [self.animator addBehavior:collisionBehavior];
    [self.animator addBehavior:gravityBehavior];
}

- (UIDynamicAnimator *)animator{
    if (_animator == nil) {
        _animator = [[UIDynamicAnimator alloc]init];
    }
    return _animator;
}
@end

效果