1.8推行为UIPushBehavior

(一)碰撞行为UIPushBehavior作用

(二)常用属性和方法

// 根据指定的模型初始化一个推行为
- (instancetype)initWithItems:(NSArray<id <UIDynamicItem>> *)items mode:(UIPushBehaviorMode)mode;

// 添加一个动力学元素给推行为
- (void)addItem:(id <UIDynamicItem>)item;
// 移除一个动力学元素从推行为
- (void)removeItem:(id <UIDynamicItem>)item;
// 推行为包含的所有的动力学元素
@property (nonatomic, readonly, copy) NSArray<id <UIDynamicItem>> *items;
// 推行为的模型 持续推力还是瞬时推力
@property (nonatomic, readonly) UIPushBehaviorMode mode;
// 设置推行为的活跃状态 YES:活跃 NO:不活跃
@property (nonatomic, readwrite) BOOL active;
// 推力方向(弧度)
@property (readwrite, nonatomic) CGFloat angle;
// 推力大小
@property (readwrite, nonatomic) CGFloat magnitude;
// 推力方向(向量)
@property (readwrite, nonatomic) CGVector pushDirection;
// 同时设置方向和推力大小
- (void)setAngle:(CGFloat)angle magnitude:(CGFloat)magnitude;

示例代码:

@interface ViewController ()
@property (nonatomic, weak) UIView *redView;
@property (nonatomic, strong) UIDynamicAnimator *animator;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    UIView *redView = [[UIView  alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
    redView.backgroundColor = [UIColor redColor];
    [self.view addSubview:redView];
    self.redView = redView;
    
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    // 获取触摸对象
    UITouch *t = touches.anyObject;
    // 获取手指的坐标点
    CGPoint p = [t locationInView:t.view];
    
    // 1.创建动画者对象
    self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
    
    // 2.创建行为
    //     UIPushBehaviorModeContinuous 持续推理(越来越快)
    //     UIPushBehaviorModeInstantaneous (瞬时推理)(越来越慢)
    UIPushBehavior *push = [[UIPushBehavior alloc] initWithItems:@[self.redView] mode:UIPushBehaviorModeContinuous];
    push.magnitude = 1;
    // 计算手指到redView中心点的偏移量
    CGFloat offsetX = p.x - self.redView.center.x;
    CGFloat offsetY = p.y - self.redView.center.y;
    // 设置手指到redView中心偏移量为推行为的向量方向
    push.pushDirection = CGVectorMake(-offsetX, -offsetY);
    // 设置推行为的活跃状态 YES:活跃 NO:不活跃
    push.active = NO;
    
    // 3.添加行为到动画者对象
    
    [self.animator addBehavior:push];
    
    // 添加一个碰撞
    UICollisionBehavior  *collision = [[UICollisionBehavior alloc] initWithItems:@[self.redView]];
    collision.translatesReferenceBoundsIntoBoundary = YES;
    [self.animator addBehavior:collision];
}

@end