func handleGesture(recognizer: UIPanGestureRecognizer) {    let translation = recognizer.translationInView(recognizer.view!.superview!)    // (isOpening ? 1.0 : -1.0) isOpening為BOOL值,表示打開或者關閉    var progress = translation.x / menuWidth * (isOpening ? 1.0 : -1.0)    // 保證在0~1之間    progress = min(max(progress, 0), 1.0)    switch recognizer.state {    case .Began:      let isOpen = mainVC.view.frame.origin.x/menuWidth      isOpening = isOpen == 1.0 ? false:true      // 為layer的效果添加一個緩存,作用是避免旋轉的時候產生鋸齒      sideMenuVC.view.layer.shouldRasterize = true;      // 設置渲染的范圍      sideMenuVC.view.layer.rasterizationScale = UIScreen.mainScreen().scale    case .Changed:      // 核心代碼:調整容器中視圖的位置 3D效果 以及透明度 以及左上角按鈕的翻轉效果      setToPercent(isOpening ? progress: (1.0 - progress))    case .Ended: fallthrough    case .Cancelled: fallthrough    case .Failed:      // 分頁效果      var targetProgress: CGFloat      if (isOpening) {        targetProgress = progress < 0.5 ? 0.0 : 1.0      }else {        targetProgress = progress < 0.5 ? 1.0 : 0.0      }      // 設置failed狀態下的sideMenuVC的view的效果      UIView.animateWithDuration(animationTime, animations: { () -> Void in        self.setToPercent(targetProgress)        }, completion: { (_) -> Void in        // 記得關閉layer的緩存渲染        self.sideMenuVC.view.layer.shouldRasterize = false      })    default: break    }  }

  func setToPercent(percent: CGFloat) {    // 調整mainVC.view的位置    mainVC.view.frame.origin.x = menuWidth * CGFloat(percent)    // 設置3D效果及透明度    sideMenuVC.view.layer.transform = menuTransformForPercent(percent)    sideMenuVC.view.alpha = CGFloat(max(0.2, percent))    // 左上角按鈕的翻轉設置    let mainVc = (mainVC as! UINavigationController).viewControllers.first as? MainViewController    if let menuButton = mainVc?.menuButton {      menuButton.imageView.layer.transform = buttonTransformForPercent(percent)    }  }

  // 根據百分比添加一個3D特效  func menuTransformForPercent(percent: CGFloat) -> CATransform3D {    var identify = CATransform3DIdentity    // m34負責z軸方向的translation（移動），m34= -1/D, 默認值是0, D越小透視效果越明顯,這邊的1000視情況調整的    identify.m34 = -1.0/1000    let remainingPercent = 1.0 - percent    let angle = remainingPercent * CGFloat(-M_PI_2)    // 后面3個數為 x y z    let rotationTransform = CATransform3DRotate(identify, angle, 0.0, 1.0, 0.0)    // 將值轉換成一個矩陣    let translationTransform =    CATransform3DMakeTranslation(menuWidth * percent, 0, 0)    // 將上面兩者結合起來    return CATransform3DConcat(rotationTransform,      translationTransform)  }  // 為按鈕添加一個3D效果  func buttonTransformForPercent(percent: CGFloat) -> CATransform3D {    var identity = CATransform3DIdentity    identity.m34 = -1.0/1000    let angle = percent * CGFloat(-M_PI)    let rotationTransform = CATransform3DRotate(identity, angle, 1.0, 1.0, 0.0)    return rotationTransform  }