拖拽函数快速生成问题

Question

我正在用Swift构建一个应用程序。我编写了一个UIGravityBehavior，一个拖放函数，以及3个按钮和地板UIImageView之间的碰撞检测，但是当按下其中一个按钮时，该按钮的UIGravityBehavior就不再存在了。帮个忙就好了。

import UIKit

class ViewController: UIViewController {

var location = CGPoint(x: 0, y: 0)
var animator:  UIDynamicAnimator?
var gravity: UIGravityBehavior?
var isRotating = false
var collision: UICollisionBehavior!
@IBOutlet var Ball1: UIButton!

@IBOutlet var Ball2: UIButton!

@IBOutlet var Ball3: UIButton!

@IBOutlet var Floor: UIImageView!

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
    let touch = touches.first as UITouch!

    location = touch.locationInView(self.view)

    Ball1.center = location
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
    let touch = touches.first as UITouch!
    location = touch.locationInView(self.view)

    Ball1.center = location
}

override func viewDidLoad() {
    super.viewDidLoad()

    self.animator = UIDynamicAnimator(referenceView: self.view)

    let gravity = UIGravityBehavior (items: [self.Ball1!, self.Ball2!, self.Ball3!])
    let direction = CGVectorMake(0.0, 1.0)
    gravity.gravityDirection = direction
    self.animator?.addBehavior(gravity)

    collision = UICollisionBehavior(items: [ Ball1!, Ball2!, Ball3!])
    collision.translatesReferenceBoundsIntoBoundary = true
     collision.addBoundaryWithIdentifier("Floor", fromPoint: CGPointMake(self.view.frame.origin.x, -7), toPoint: CGPointMake(self.view.frame.origin.x + self.view.frame.width, -7))
    animator!.addBehavior(collision)
}

Answer 1

您应该添加一个附件属性，就像处理其他行为一样。例如：

var attachment: UIAttachmentBehavior?

在touchesBegan中，将Ball1.center = location替换为

if CGRectContainsPoint(Ball1.frame,location)
{
    attachment = UIAttachmentBehavior(item: Ball1, attachedToAnchor: location)
    animator!.addBehavior(attachment!)
}
if CGRectContainsPoint(Ball2.frame,location)
{
    attachment = UIAttachmentBehavior(item: Ball2, attachedToAnchor: location)
    animator!.addBehavior(attachment!)
}
if CGRectContainsPoint(Ball3.frame,location)
{
    attachment = UIAttachmentBehavior(item: Ball3, attachedToAnchor: location)
    animator!.addBehavior(attachment!)
}

然后在touchesMoved中将Ball1.center = location替换为

if attachment != nil
{
    attachment!.anchorPoint = location
}

然后实现touchesEnded

if animator != nil && attachment != nil
{
    animator.removeBehavior(self.attachment!)
    self.attachment = nil
}

我将添加您编写的代码，这将始终使Ball1遵循用户的触摸。不知道你是不是打算这么做。