当程序被打开时,在创建KeyWindow的RootViewController时判断是否是首次登陆,这里的逻辑是如果用户是首次打开应用的话显示引导页,当点击引导页最后一页的立即体验时直接进入主页
在AppDelegate.swift中加入以下代码:这里我使用的是第一种方法，这里没有贴出效果图，大家只要把代码粘贴到项目中，并且替换图片，即可运行：

第一种方法：

    private func buildKeyWindow() {
        window = UIWindow(frame: ScreenBounds)
        window!.makeKeyAndVisible()
        let isFristOpen = NSUserDefaults.standardUserDefaults().objectForKey("isFristOpenApp")
        if isFristOpen == nil {
            window?.rootViewController = GuideViewController()
            NSUserDefaults.standardUserDefaults().setObject("isFristOpenApp", forKey: "isFristOpenApp")
        } else {
             window!.rootViewController = ViewController()
        }
    }

第二种方法：

    //MARK: - 引导页设置
    private func showLeadpage() -> UIViewController{
        
        let versionStr = "CFBundleShortVersionString"
        let cureentVersion = NSBundle.mainBundle().infoDictionary![versionStr] as! String
        let oldVersion = (NSUserDefaults.standardUserDefaults().objectForKey(versionStr) as? String) ?? ""
        if cureentVersion.compare(oldVersion) == NSComparisonResult.OrderedAscending {
            NSUserDefaults.standardUserDefaults().setObject(cureentVersion, forKey: versionStr)
            NSUserDefaults.standardUserDefaults().synchronize()
                 return GuideViewController()
        }
        return ViewController()
    }

在GuideViewController中，我们使用UICollectionView来转载我们的引导页：

import UIKit

public let ScreenWidth: CGFloat = UIScreen.mainScreen().bounds.size.width
public let ScreenHeight: CGFloat = UIScreen.mainScreen().bounds.size.height
public let ScreenBounds: CGRect = UIScreen.mainScreen().bounds

class GuideViewController: UIViewController {

    private var collectView: UICollectionView?
    private var imageNames = ["guide_40_1", "guide_40_2", "guide_40_3", "guide_40_4"]
    private let cellIdentifier = "GuideCell"
    private var isHiddenNextButton = true
    private var pageController = UIPageControl(frame: CGRectMake(0, ScreenHeight - 50, ScreenWidth, 20))
    
    override func viewDidLoad() {
        super.viewDidLoad()
        buildCollectionView()
        buildPageController()
    }
    
    // MARK: - Build UI
    private func buildCollectionView() {
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        layout.itemSize = ScreenBounds.size
        layout.scrollDirection = .Horizontal

        collectView = UICollectionView(frame: ScreenBounds, collectionViewLayout: layout)
        collectView?.delegate = self
        collectView?.dataSource = self
        collectView?.showsVerticalScrollIndicator = false
        collectView?.showsHorizontalScrollIndicator = false
        collectView?.pagingEnabled = true
        collectView?.bounces = false
        collectView?.registerClass(GuideCell.self, forCellWithReuseIdentifier: cellIdentifier)
        view.addSubview(collectView!)
    }
    
    func buildPageController() {
        pageController.numberOfPages = imageNames.count
        pageController.currentPage = 0
        view.addSubview(pageController)
    }

}

extension GuideViewController: UICollectionViewDelegate, UICollectionViewDataSource {
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return imageNames.count
    }
    
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(cellIdentifier, forIndexPath: indexPath) as! GuideCell
        cell.newImage = UIImage(named: imageNames[indexPath.row])
        if indexPath.row != imageNames.count - 1 { // 3
            cell.setNextButtonHidden(true) // 如果不是第三张就隐藏button
        }
        return cell
    }
    
    func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
        if scrollView.contentOffset.x == ScreenWidth * CGFloat(imageNames.count - 1) {
            let cell = collectView!.cellForItemAtIndexPath(NSIndexPath(forRow: imageNames.count - 1, inSection: 0)) as! GuideCell
            cell.setNextButtonHidden(false)
            isHiddenNextButton = false
        }
    }
    
    func scrollViewDidScroll(scrollView: UIScrollView) {
        if scrollView.contentOffset.x != ScreenWidth * CGFloat(imageNames.count - 1) && !isHiddenNextButton && scrollView.contentOffset.x > ScreenWidth * CGFloat(imageNames.count - 2) {
            let cell = collectView!.cellForItemAtIndexPath(NSIndexPath(forRow: imageNames.count - 1, inSection: 0)) as! GuideCell
            cell.setNextButtonHidden(true)
            isHiddenNextButton = true
        }
        pageController.currentPage = Int(scrollView.contentOffset.x / ScreenWidth + 0.5)
    }
}

在GuideCell中的代码：

import UIKit

// 点击Guide页的button
public let GuideViewControllerDidFinish = "GuideViewControllerDidFinish"

class GuideCell: UICollectionViewCell {
    private let newImageView = UIImageView(frame: ScreenBounds)
    private let nextButton = UIButton(frame: CGRectMake((ScreenWidth - 100) * 0.5, ScreenHeight - 110, 100, 33))
    
    var newImage: UIImage? {
        didSet {
            newImageView.image = newImage
        }
    }
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        newImageView.contentMode = .ScaleAspectFill
        contentView.addSubview(newImageView)

        nextButton.setBackgroundImage(UIImage(named: "icon_next"), forState: UIControlState.Normal)
        nextButton.addTarget(self, action: #selector(GuideCell.nextButtonClick), forControlEvents: UIControlEvents.TouchUpInside)
        nextButton.hidden = true
        contentView.addSubview(nextButton)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func setNextButtonHidden(hidden: Bool) {
        nextButton.hidden = hidden
    }
    
    // GuideViewControllerDidFinish 还有一处在app.delegate中 进入到主界面中使用的
    func nextButtonClick() {
        NSNotificationCenter.defaultCenter().postNotificationName(GuideViewControllerDidFinish, object: nil)
    }
}