public struct JJPianoControlConfig {
    
    // 间距
    static var margin               : CGFloat           = 2.0
    
    // 图片内间距
    static var keyPadding           : CGFloat           = 2.0
    
    // 一页显示的最大钢琴键数
    static var numberOfKeysInPage   : Int               = 9
    
    // 钢琴键圆角度数
    static var keyCornerRadius      : CGFloat           = 7.5
    
    // 点击选中的最突出的钢琴键离顶部的距离
    static var pressKeyMaxTop       : CGFloat           = 8.0
    
    // 正常状态的钢琴键高度
    static var nomarlKeyHeight      : CGFloat           = 8.0
    
    // 动画持续时间
    static var animationDuration    : NSTimeInterval    = 0.6
    
    // 取消触屏时延迟时间执行动画
    static var cancelTouchAnimationAfterDelay: NSTimeInterval = 0.5
}

// config
JJPianoControlConfig.margin = 2.0

// setup UI
let frame   = CGRectMake(0, UIScreen.mainScreen().bounds.height - 54, UIScreen.mainScreen().bounds.width, 54)
let layout  : JJPianoBarFlowLayout  = JJPianoBarFlowLayout()
let bar     : JJPianoBarView        = JJPianoBarView(frame: frame, collectionViewLayout: layout)
bar.registerClass(JJPianoBarCell.self, forCellWithReuseIdentifier: "Cell")
bar.delegate            = self
bar.dataSource          = self
bar.pianoDelegate       = self
bar.autoresizingMask    = [.FlexibleTopMargin]
self.paino              = bar
self.view.addSubview(bar)
bar.scrollTo(0)

// MARK: - JJPianoBarView Delegate
   
func playPiano(from: NSIndexPath, to: NSIndexPath) {
    print("play from:\(from.row) to:\(to.row)")
}

// mark: - UIColletionView Delegate

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell : JJPianoBarCell! = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! JJPianoBarCell
    cell.iconUrl = self.avatars[indexPath.row % avatars.count]
    return cell
}