UIDynamic－iOS中的物理引擎

1. 創(chuàng)建一個物理仿真器 設(shè)置仿真范圍
2. 創(chuàng)建相應(yīng)的物理仿真行為 添加物理仿真元素
3. 將物理仿真行為添加到仿真器中開始仿真

懶加載方式 創(chuàng)建物理仿真器

-  (UIDynamicAnimator *) animator
{
if(!_animator) {
_animator = [[UIDynamicAnimator alloc] initWithReferenceView:self.view];
}
return _animator;
}

創(chuàng)建相應(yīng)的物理仿真行為

1. 模擬重力行為 UIGravityBehavior
   // 創(chuàng)建重力行為
   UIGravityBehavior *gravity = [[UIGravityBehavior alloc] init];
   // magnitude越大，速度增長越快
   gravity.magnitude = 100;
   // 添加元素 告訴仿真器哪些元素添加重力行為
   [gravity addItem:self.sxView];

   // 添加到仿真器中開始仿真
   [self.animator addBehavior:gravity];

2. 模擬碰撞行為 UICollisionBehavior
   // 1.創(chuàng)建重力行為
   UIGravityBehavior *gravity = [[UIGravityBehavior alloc] init];
   // magnitude越大，速度增長越快
   gravity.magnitude = 2;
   [gravity addItem:self.sxView];

   // 2.創(chuàng)建碰撞行為
   UICollisionBehavior *collision = [[UICollisionBehavior alloc] init];
   [collision addItem:self.sxView];
   [collision addItem:self.bigBlock];
   [collision addItem:self.smallBlock];
   // 設(shè)置碰撞的邊界
   collision.translatesReferenceBoundsIntoBoundary = YES;
   // 如果覺得屏幕作為邊界不好，可以自己設(shè)置一條邊可以是普通的邊
   // [collision addBoundaryWithIdentifier:@"line2" fromPoint:
   CGPointMake(self.view.frame.size.width, 0) toPoint:
   CGPointMake(self.view.frame.size.width, 400)];
   //也可以是個貝塞爾路徑
   UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:
   CGRectMake(0,150, self.view.frame.size.width, self.view.frame.size.width)];
   [collision addBoundaryWithIdentifier:@"circle" forPath:path];
   // 3.開始仿真
   [self.animator addBehavior:gravity];
   [self.animator addBehavior:collision];

3. 模擬捕捉行為 UISnapBehavior

   • (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
     {
     // 1.獲得手指對應(yīng)的觸摸對象
     UITouch *touch = [touches anyObject];

     // 2.獲得觸摸點
     CGPoint point = [touch locationInView:self.view];

     // 3.創(chuàng)建捕捉行為
     UISnapBehavior *snap = [[UISnapBehavior alloc] initWithItem:self.sxView snapToPoint:point];
     // 防震系數(shù)，damping越大，振幅越小
     snap.damping = 1;

     // 4.清空之前的并再次開始
     [self.animator removeAllBehaviors];
     [self.animator addBehavior:snap];
     }