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已更新至 Xcode8.2、Swift3
在第一次打开App或者App更新后通常用引导页来展示产品特性
我们用NSUserDefaults类来判断程序是不是第一次启动或是否更新，在 AppDelegate.swift中加入以下代码：
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// 得到当前应用的版本号
let infoDictionary = Bundle.main.infoDictionary
let currentAppVersion = infoDictionary!["CFBundleShortVersionString"] as! String
// 取出之前保存的版本号
let userDefaults = UserDefaults.standard
let appVersion = userDefaults.string(forKey: "appVersion")
let storyboard = UIStoryboard(name: "Main", bundle: nil)
// 如果 appVersion 为 nil 说明是第一次启动；如果 appVersion 不等于 currentAppVersion 说明是更新了
if appVersion == nil || appVersion != currentAppVersion {
// 保存最新的版本号
userDefaults.setValue(currentAppVersion, forKey: "appVersion")
let guideViewController = storyboard.instantiateViewController(withIdentifier: "GuideViewController") as! GuideViewController
self.window?.rootViewController = guideViewController
}
return true
}
在GuideViewController中，我们用UIScrollView来装载我们的引导页:
class GuideViewController: UIViewController {
@IBOutlet weak var pageControl: UIPageControl!
@IBOutlet weak var startButton: UIButton!
fileprivate var scrollView: UIScrollView!
fileprivate let numOfPages = 3
override func viewDidLoad() {
super.viewDidLoad()
let frame = self.view.bounds
scrollView = UIScrollView(frame: frame)
scrollView.isPagingEnabled = true
scrollView.showsHorizontalScrollIndicator = false
scrollView.showsVerticalScrollIndicator = false
scrollView.scrollsToTop = false
scrollView.bounces = false
scrollView.contentOffset = CGPoint.zero
// 将 scrollView 的 contentSize 设为屏幕宽度的3倍(根据实际情况改变)
scrollView.contentSize = CGSize(width: frame.size.width * CGFloat(numOfPages), height: frame.size.height)
scrollView.delegate = self
for index in 0..<numOfPages {
let imageView = UIImageView(image: UIImage(named: "GuideImage\(index + 1)"))
imageView.frame = CGRect(x: frame.size.width * CGFloat(index), y: 0, width: frame.size.width, height: frame.size.height)
scrollView.addSubview(imageView)
}
self.view.insertSubview(scrollView, at: 0)
// 给开始按钮设置圆角
startButton.layer.cornerRadius = 15.0
// 隐藏开始按钮
startButton.alpha = 0.0
}
// 隐藏状态栏
override var prefersStatusBarHidden : Bool {
return true
}
}
最后我们让GuideViewController遵循UIScrollViewDelegate协议，在这里判断是否滑动到最后一张以显示进入按钮：
// MARK: - UIScrollViewDelegate
extension GuideViewController: UIScrollViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offset = scrollView.contentOffset
// 随着滑动改变pageControl的状态
pageControl.currentPage = Int(offset.x / view.bounds.width)
// 因为currentPage是从0开始，所以numOfPages减1
if pageControl.currentPage == numOfPages - 1 {
UIView.animate(withDuration: 0.5, animations: {
self.startButton.alpha = 1.0
})
} else {
UIView.animate(withDuration: 0.2, animations: {
self.startButton.alpha = 0.0
})
}
}
}
在上面的代码中，为了显得自然我们给进入按钮加入了一点动画 :]
最终效果如下：
GuideScreenshot.gif
