IOS 自定义转场动画

    // 自定义过场动画
    func performAnimationBack(firstVCView: UIView, secondVCView: UIView, viewCon: UIViewController) {
        // Assign the source and destination views to local variables.
        
        // Get the screen width and height.
        let screenWidth = UIScreen.mainScreen().bounds.size.width
        let screenHeight = UIScreen.mainScreen().bounds.size.height
        
        // Specify the initial position of the destination view.
        secondVCView.frame = CGRectMake(-screenWidth, 0.0, screenWidth, screenHeight)
        
        // Access the app‘s key window and insert the destination view above the current (source) one.
        let window = UIApplication.sharedApplication().keyWindow
        window?.insertSubview(secondVCView, aboveSubview: firstVCView)
        
        // Animate the transition.
        UIView.animateWithDuration(0.4, animations: { () -> Void in
            firstVCView.frame = CGRectOffset(firstVCView.frame, screenWidth, 0.0)
            secondVCView.frame = CGRectOffset(secondVCView.frame, screenWidth, 0.0)
            }) { (Finished) -> Void in
//                self.dismissViewControllerAnimated(true, completion: nil)
                self.presentViewController(viewCon,
                    animated: false,
                    completion: nil)
        } 
    }