最近在学习swift，就用swift实现轮播图来练习一下
轮播图的创建有两种方式：
1>可以用scrollview创建3个view，自己实现循环利用
2>利用collectionView由系统来处理item的循环利用问题
显然使用collectionView实现的方式比较简单。
轮播图由两部分组成，collectionView和一个pageControl。自定义一个CarouselView，懒加载创建collectionView和pageControl：
fileprivate lazy var carouselCollectionView : UICollectionView = { [unowned self] in
let layout = UICollectionViewFlowLayout()
layout.scrollDirection = UICollectionViewScrollDirection.horizontal//横向滚动
layout.itemSize = CGSize(width: kViewWidth, height: kViewHeight)
layout.minimumLineSpacing = 0//行间距为0
let carouselCollectionView:UICollectionView = UICollectionView(frame: self.bounds, collectionViewLayout: layout)
carouselCollectionView.showsHorizontalScrollIndicator = false
carouselCollectionView.isPagingEnabled = true//按页滚动
carouselCollectionView.backgroundColor = UIColor.white
carouselCollectionView.register(CarouselCollectionViewCell.self, forCellWithReuseIdentifier: CellIdentifier)//注册自定义cell
//添加代理
carouselCollectionView.dataSource = self
carouselCollectionView.delegate = self
return carouselCollectionView
}()
fileprivate lazy var pageControl : UIPageControl = {
let pageControl:UIPageControl = UIPageControl()
pageControl.translatesAutoresizingMaskIntoConstraints = false//用代码为pageControl添加NSLayoutConstraint的时候,需要设置
pageControl.numberOfPages = 1
return pageControl
}()
重写自定义视图的初始化方法
init(Y: CGFloat,H:CGFloat) {
kViewHeight = H
super.init(frame: CGRect(x: 0, y: Y, width: kViewWidth, height: kViewHeight))
setupUI()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
使用extension为CarouselView添加一个布局方法
//MARK:- setup UI
extension CarouselView {
func setupUI() {
self.addSubview(carouselCollectionView)
self.addSubview(pageControl)
//将pageControl添加到自定义视图后，给pageControl添加约束
let rightConstraint:NSLayoutConstraint = NSLayoutConstraint(item: pageControl, attribute: .right, relatedBy: .equal, toItem: self, attribute: .right, multiplier: 1.0, constant: -10)
let bottomConstraint:NSLayoutConstraint = NSLayoutConstraint(item: pageControl, attribute: .bottom, relatedBy: .equal, toItem: self, attribute: .bottom, multiplier: 1.0, constant: -5)
let heightConstraint:NSLayoutConstraint = NSLayoutConstraint(item: pageControl, attribute: .height, relatedBy: .equal, toItem: nil, attribute: .notAnAttribute, multiplier: 1.0, constant: 20)
pageControl.superview?.addConstraint(rightConstraint)
pageControl.superview?.addConstraint(bottomConstraint)
pageControl.superview?.addConstraint(heightConstraint)
}
}
创建一个数组用来存储自定义CarouselModel
var carouselModelArr : [CarouselModel]? {
didSet {
//数组发生变化时刷新collectionView
self.carouselCollectionView.reloadData()
pageControl.numberOfPages = carouselModelArr?.count ?? 0
//初识时，让collectionView滚动到中间某个位置，使用户可以向前翻页
let index = (carouselModelArr?.count ?? 0)*10
self.carouselCollectionView.scrollToItem(at: IndexPath(item: index, section: 0), at: .left, animated: false)
//添加计时器
removeTimer()
addTimer()
}
}
自定义一个CarouselModel用来接收数据
class CarouselModel: NSObject {
var title:String = ""
var pic_url:String = ""
init(dic:[String:NSObject]) {
super.init()
//kvc方法，字典转模型
setValuesForKeys(dic)
}
//获取的数据中没定义的键值在这里处理
override func setValue(_ value: Any?, forUndefinedKey key: String) {
// print("undefined key : \(key), value : \(value)")
}
}
创建自定义cell
自定义 cell包括两部分：
1>展示图片用的imageView
2>展示文字title的Label
import UIKit
import SDWebImage
class CarouselCollectionViewCell: UICollectionViewCell {
var imageView = UIImageView()
var titleLabel = UILabel()
var carouselModel : CarouselModel? {
didSet {
//设置属性时给label和imageView赋值
titleLabel.text = carouselModel?.title
//使用SDWebImage设置imageView图片
imageView.sd_setImage(with: URL(string: (carouselModel?.pic_url ?? "")!), placeholderImage: UIImage(named: "placehold"))
}
}
override init(frame: CGRect) {
super.init(frame: frame)
setupUI()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
extension CarouselCollectionViewCell {
func setupUI() {
imageView.frame = self.bounds
titleLabel.frame = CGRect(x: 0, y: self.bounds.size.height - 30, width: self.bounds.size.width, height: 30)
titleLabel.backgroundColor = UIColor(white: 0.4, alpha: 0.3)
titleLabel.textColor = .white
self.addSubview(imageView)
self.addSubview(titleLabel)
}
}
自定义CarouselView遵循 DataSource 协议
//MARK:- collectionViewDataSource
extension CarouselView : UICollectionViewDataSource {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
//返回10000倍item实现无限轮播，因为collectionView的重用机制，并不会创建这么多item，不用担心内存问题
return 10000*(carouselModelArr?.count ?? 0);
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
//使用自定义item：CarouselCollectionViewCell
let collectionItem = collectionView.dequeueReusableCell(withReuseIdentifier: CellIdentifier, for: indexPath) as! CarouselCollectionViewCell
let index = indexPath.item % carouselModelArr!.count
collectionItem.carouselModel = carouselModelArr![index]
return collectionItem
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let item = collectionView.cellForItem(at: indexPath) as! CarouselCollectionViewCell
print("title : \(item.titleLabel.text)")
}
}
自定义CarouselView遵循Delegate协议
//MARK:- collectionViewDelegate
extension CarouselView : UICollectionViewDelegate {
func scrollViewDidScroll(_ scrollView: UIScrollView) {
//当偏移超过page的一半时pageControl调到下一个
let offset = scrollView.contentOffset.x + kViewWidth / 2
pageControl.currentPage = Int(offset / kViewWidth) % (carouselModelArr?.count ?? 1)
}
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
//用户开始拖拽时，移除定时器
removeTimer()
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
//用户停止拖拽时，打开定时器
addTimer()
}
}
添加计时器，使collection View滚动起来
//MARK:- 添加计时器
extension CarouselView {
func addTimer() {
timer = Timer(timeInterval: 3.0, target: self, selector: #selector(scrollToNextPage), userInfo: nil, repeats: true)
RunLoop.main.add(timer!, forMode: .commonModes)
}
func removeTimer() {
timer?.invalidate()
timer = nil
}
func scrollToNextPage() {
let offsetX = carouselCollectionView.contentOffset.x + kViewWidth//当前偏移量加上一页的宽度
carouselCollectionView.setContentOffset(CGPoint(x: offsetX, y: 0), animated: true)
}
}
此时，一个简单的轮播图就完成了！
下面是轮播图的使用：
import UIKit
import AFNetworking
class ViewController: UIViewController {
//创建自定义carousView
// let carouselView = CarouselView(Y: 64, H: 200)//需要毛玻璃效果时Y为64
let carouselView = CarouselView(Y: 0, H: 200)//不需要毛玻璃效果时Y，为0。
var modelArr = [CarouselModel]()
override func viewDidLoad() {
super.viewDidLoad()
setupUI()
getArrayFromWeb()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
extension ViewController {
func setupUI() {
// self.automaticallyAdjustsScrollViewInsets = false//需要毛玻璃效果时设置（是否根据所在界面的navigationbar与tabbar的高度，自动调整scrollview的inset.默认是true）
self.navigationController?.navigationBar.isTranslucent = false//不需要毛玻璃效果时设置
self.view.addSubview(carouselView)
}
//使用AFN解析数据
func getArrayFromWeb() {
let manager = AFHTTPSessionManager()
manager.get("http://www.douyutv.com/api/v1/slide/6", parameters: ["version" : "2.300"], progress: nil, success: { (task:URLSessionDataTask, json:Any) in
// print("jsonData: \(json)")
guard let dataDic = json as? [String : NSObject] else { return }
guard let dataArr = dataDic["data"] as? [[String : NSObject]] else { return }
for dic in dataArr {
self.modelArr.append(CarouselModel(dic: dic))
}
//获取完数据，将数组赋给carouselView的carouselModelArr
self.carouselView.carouselModelArr = self.modelArr
}) { (task:URLSessionDataTask?, error:Error) in
print("error : \(error)")
}
}
}
