swift - 如何在swift中实现无限滚动背景

Question

我正在尝试在游戏中无限滚动背景。当我尝试这样做时，我的应用程序崩溃了:

@IBAction func levelClicked(sender: AnyObject) {
  let screenSize: CGRect = UIScreen.mainScreen().bounds
  let screenHeight = screenSize.height
  let imageName = "levelBackground"
  let image = UIImage(named: imageName)
  imageView = UIImageView(image: image!)

  imageView.frame = CGRect (x: 0, y: 0, width: 5500, height: screenHeight)
  view.addSubview(imageView)

  timer = NSTimer.scheduledTimerWithTimeInterval(0.5, 
                                         target: self, 
                                       selector: Selector("moveBackground"), 
                                       userInfo: nil, 
                                        repeats: true)
}

func moveBackground() {
    imageView.frame = CGRect(x: imageView.frame.origin.x - 5,
                             y: imageView.origin.y,
                         width: 5500, 
                        height: UIScreen.mainScreen().bounds.height)
}

这是我的崩溃日志:

2015-01-03 15:57:56.579 zombieSurvival[3395:708290] -[zombieSurvival.firstBuildingViewController moveBackground]: unrecognized selector sent to instance 0x15e7e150

2015-01-03 15:57:56.585 zombieSurvival[3395:708290] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[zombieSurvival.firstBuildingViewController moveBackground]: unrecognized selector sent to instance 0x15e7e150'

*** First throw call stack:

(0x29dad5f7 0x374e7c77 0x29db2abd 0x29db0999 0x29ce1b88 0x2aac1a45 0x29d73f07 0x29d73a89 0x29d71cf3 0x29cbeb31 0x29cbe943 0x31077051 0x2d2b46f1 0xccc04 0xccc40 0x37a83aaf)

libc++abi.dylib: terminating with uncaught exception of type NSException

Answer 1

我不是 swift 方面的专家，但似乎这行不通:

您将 moveBackground 声明为 levelClicked 内的函数，但在计时器上您将 self 引用为目标。该类本身没有方法moveBackground。它仅在您的函数 levelClicked 内可见。

尝试将整个 moveBackground 移出 levelClicked。

为了使 moveBackground 工作，我想你必须给 imageView 一个属性。

@IBAction func levelClicked(sender: AnyObject) {
  let screenSize: CGRect = UIScreen.mainScreen().bounds
  let screenHeight = screenSize.height
  let imageName = "levelBackground"
  let image = UIImage(named: imageName)
  self.imageView = UIImageView(image: image!)

  self.imageView.frame = CGRect (x: 0, y: 0, width: 5500, height: screenHeight)
  view.addSubview(self.imageView)

  timer = NSTimer.scheduledTimerWithTimeInterval(0.5, 
                                         target: self, 
                                       selector: Selector("moveBackground"), 
                                       userInfo: nil, 
                                        repeats: true)
}

func moveBackground() {
    self.imageView.frame = CGRect(x: self.imageView.frame.origin.x - 5,
                                  y: self.imageView.origin.y,
                              width: 5500, 
                             height: UIScreen.mainScreen().bounds.height)
}