下拉刷新和上拉加载 Swift

转载自：http://iyiming.me/blog/2015/07/05/custom-refresh-and-loading/

关于下拉刷新和上拉加载，项目中一直使用MJRefresh（原先还用过EGOTableViewPullRefresh，MJRefresh更好用些），今天就分析下如何用Swift来实现这个功能。

关于如何下拉刷新和上拉加载，认识到两点就可以了：

0.UIScrollViewDelegate

1.UIScrollView中的contentInset

直白一点说，就是在UIScrollView及其子类在下拉或者上拉到一定的偏移量时，设置contentInset，固定住UIScrollView，显示动画加载页面，数据到达之后再恢复contentInset。

UIScrollView很强大，除了上面说的，我们有时用它来显示放大缩小图片。

今天来自定义一个下拉刷新视图，并实现上拉加载功能。

前些天，一篇公众号（Pinapps,里面的文章挺好）文章里推荐了一个iPhone上的RSS阅读器Unread，软件做的很棒，就把全部功能都买了下来（程序内购买）。其中里面的下拉刷新效果挺棒的，正好仿一下：

分析下这里面的效果：

一开始线条是隐藏的，有了偏移后，线条从原先的窄线条慢慢变成宽线条线条，其中线条的颜色和REFRESH颜色也是有变化的。为了能做出连续性的动画我们使用POP(如果不是很了解POP的话，可以看一下我写的这篇文章)

已传至Github（时间仓促，没有加以优化）：

https://github.com/iYiming/MyDemo/tree/master/Weibo

下面是代码的一些注释：

前提：添加POP动画，创建一个单视图项目，在ViewController里面添加一个UITableView。

先来实现刷新视图：即那三条红线加上REFRESH。

我们创建Swift文件，继承自UIView并命名为RefreshView：

代码如下：

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import UIKit @IBDesignable class RereshView: UIView { var topLayer: CALayer?//顶部线 var middleLayer: CALayer?//中间线 var bottomLayer: CALayer?//底部线 var textLayer: CATextLayer?//REFRESH文字 override init(frame: CGRect) { super.init(frame: frame) setup()//设置 } required init(coder aDecoder: NSCoder) { super.init(coder: aDecoder) //fatalError("init(coder:) has not been implemented") setup()//设置 } /** 设置 */ func setup(){ //顶部线 topLayer = CALayer() topLayer!.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor topLayer!.frame = CGRectMake(98, 0, 4, 4) topLayer!.cornerRadius = 2 self.layer.addSublayer(topLayer) //中间线 middleLayer = CALayer() middleLayer!.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor middleLayer!.frame = CGRectMake(98, 14, 4, 4) middleLayer!.cornerRadius = 2 self.layer.addSublayer(middleLayer) //底部线 bottomLayer = CALayer() bottomLayer!.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor bottomLayer!.frame = CGRectMake(98, 28, 4, 4) bottomLayer!.cornerRadius = 2 self.layer.addSublayer(bottomLayer) //REFRESH textLayer = CATextLayer() textLayer!.foregroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor textLayer!.fontSize = 10 textLayer!.contentsScale = UIScreen.mainScreen().scale textLayer!.string = "REFRESH" textLayer!.opacity = 0 textLayer!.frame = CGRectMake(75, 62, 50, 20) self.layer.addSublayer(textLayer) } }

注意我们在Class前面加了一个@IBDesignable，这样我们就能在Storyboard中查看我们自定义的视图（如果想详细了解的话，请看下Onevcat的可视化开发，IB新时代）。

在ViewController.swift中我们添加了如下代码：

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import UIKit class ViewController: UIViewController,UITableViewDataSource,UIScrollViewDelegate { @IBOutlet weak var tableView: UITableView!//列表视图 @IBOutlet weak var refreshView: RereshView!//下拉刷新视图 @IBOutlet weak var refreshViewTopLayoutConstraint: NSLayoutConstraint!//下拉刷新居上的约束 var showBottomLayer:Bool = true//显示刷新视图的底部线 变宽 var hiddenBottomLayer:Bool = true//隐藏刷新视图的底部线 即变窄 var showMiddleLayer:Bool = true//显示刷新视图的中间线 变宽 var hiddenMiddleLayer:Bool = true//隐藏刷新视图的中间线 变窄 var showTopLayer:Bool = true//显示刷新头部的底部线 变宽 var hiddenTopLayer:Bool = true//隐藏刷新视图的头部线 变窄 var refreshing = false//是否在刷新中 var loadingAcitivityIndicatorView: UIActivityIndicatorView?//上拉加载指示菊花 var showFooterLoadingView:Bool = false//是否显示上拉加载视图 override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. settingUI()//设置界面 } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } //设置界面 func settingUI(){ let screenWidth = CGRectGetWidth(UIScreen.mainScreen().bounds) let screenHeight = CGRectGetHeight(UIScreen.mainScreen().bounds) loadingAcitivityIndicatorView = UIActivityIndicatorView(activityIndicatorStyle: UIActivityIndicatorViewStyle.Gray) loadingAcitivityIndicatorView?.hidesWhenStopped = true loadingAcitivityIndicatorView?.frame = CGRectMake((screenWidth - 20)/2.0,screenHeight - 40, 20, 20) self.view.addSubview(loadingAcitivityIndicatorView!) } /** 添加size动画 :param: layer 要添加动画的layer :param: size 动画到的size */ func addSizeAnimation(layer: CALayer,size: CGSize){ var springAnimation = POPSpringAnimation(propertyNamed: kPOPLayerSize) springAnimation.toValue = NSValue(CGSize: size); springAnimation.springBounciness = 18 layer.pop_addAnimation(springAnimation, forKey: "layerSpringAnimation") } /** 添加position动画 :param: layer 要添加动画的layer :param: position 动画到的position */ func addPositionAnimation(layer: CALayer,position: CGPoint){ var springAnimation = POPSpringAnimation(propertyNamed: kPOPLayerPosition) springAnimation.toValue = NSValue(CGPoint: position); springAnimation.springBounciness = 18 layer.pop_addAnimation(springAnimation, forKey: "layerSpringAnimation") } //UITableViewDataSource func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return 100 } func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { var cell = tableView.dequeueReusableCellWithIdentifier("Cell") as! UITableViewCell cell.textLabel?.text = "\(indexPath.row)" return cell } //UIScrollViewDelegate //将要开始减速时 func scrollViewWillBeginDecelerating(scrollView: UIScrollView) { var contentOffsetY = scrollView.contentOffset.y if contentOffsetY > 0{ return } if contentOffsetY < -52{//偏移 52 时 我们显示加载视图 refreshing = true scrollView.contentInset = UIEdgeInsetsMake(62.0, 0.0, 0.0, 0.0) refreshViewTopLayoutConstraint.constant = 20//刷新视图居上约束 //移除POP动画 refreshView.topLayer?.pop_removeAllAnimations() refreshView.middleLayer?.pop_removeAllAnimations() refreshView.bottomLayer?.pop_removeAllAnimations() //设定layer位置 refreshView.topLayer?.frame = CGRectMake(121, 0, 4, 4) refreshView.middleLayer?.frame = CGRectMake(98, 14, 4, 4) refreshView.bottomLayer?.frame = CGRectMake(75, 28, 4, 4) refreshView.textLayer?.opacity = 0 self.addPositionAnimation(self.refreshView.topLayer!,position: CGPointMake(121, 14)) self.addPositionAnimation(self.refreshView.middleLayer!,position: CGPointMake(98, 14)) self.addPositionAnimation(self.refreshView.bottomLayer!,position: CGPointMake(75, 14)) let delayTime = dispatch_time(DISPATCH_TIME_NOW,Int64(1 * Double(NSEC_PER_SEC))) dispatch_after(delayTime,dispatch_get_main_queue()) { UIView.animateWithDuration(0.3, animations: { () -> Void in scrollView.contentInset = UIEdgeInsetsMake(0.0, 0.0, 0.0, 0.0) self.refreshViewTopLayoutConstraint.constant = -52 }, completion: { (Bool) -> Void in self.refreshing = false self.refreshView.topLayer!.frame = CGRectMake(98, 0, 4, 4) self.refreshView.middleLayer!.frame = CGRectMake(98, 14, 4, 4) self.refreshView.bottomLayer!.frame = CGRectMake(98, 28, 4, 4) }) } } } //滚动时 func scrollViewDidScroll(scrollView: UIScrollView) { var contentOffsetY = scrollView.contentOffset.y if contentOffsetY <= 0 { if refreshing{ return; } self.refreshView.hidden = false refreshViewTopLayoutConstraint.constant = -contentOffsetY - 52 if contentOffsetY < -30{ self.hiddenBottomLayer = true if showBottomLayer{ showBottomLayer = false self.addSizeAnimation(refreshView.bottomLayer!, size: CGSizeMake(50, 4)); refreshView.bottomLayer?.backgroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor } if contentOffsetY < -46{ self.hiddenMiddleLayer = true if showMiddleLayer{ showMiddleLayer = false self.addSizeAnimation(refreshView.middleLayer!, size: CGSizeMake(50, 4)); refreshView.middleLayer?.backgroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor } if contentOffsetY < -62{ self.hiddenTopLayer = true if showTopLayer{ showTopLayer = false self.addSizeAnimation(refreshView.topLayer!, size: CGSizeMake(50, 4)); refreshView.topLayer?.backgroundColor = UIColor(red: 192/255.0, green: 47/255.0, blue: 46/255.0, alpha: 1.0).CGColor refreshView.middleLayer?.backgroundColor = UIColor(red: 192/255.0, green: 47/255.0, blue: 46/255.0, alpha: 1.0).CGColor refreshView.bottomLayer?.backgroundColor = UIColor(red: 192/255.0, green: 47/255.0, blue: 46/255.0, alpha: 1.0).CGColor refreshView.textLayer?.foregroundColor = UIColor(red: 192/255.0, green: 47/255.0, blue: 46/255.0, alpha: 1.0).CGColor } }else{ self.showTopLayer = true if hiddenTopLayer{ hiddenTopLayer = false self.addSizeAnimation(refreshView.topLayer!, size: CGSizeMake(4, 4)); refreshView.topLayer?.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor refreshView.middleLayer?.backgroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor refreshView.bottomLayer?.backgroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor refreshView.textLayer?.foregroundColor = UIColor(red: 64/255.0, green: 64/255.0, blue: 64/255.0, alpha: 1.0).CGColor } } }else{ self.showMiddleLayer = true if hiddenMiddleLayer{ hiddenMiddleLayer = false self.addSizeAnimation(refreshView.middleLayer!, size: CGSizeMake(4, 4)); refreshView.middleLayer?.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor } } }else{ self.showBottomLayer = true if hiddenBottomLayer{ hiddenBottomLayer = false self.addSizeAnimation(refreshView.bottomLayer!, size: CGSizeMake(4, 4)); refreshView.bottomLayer?.backgroundColor = UIColor(red: 200/255.0, green: 200/255.0, blue: 200/255.0, alpha: 1.0).CGColor } } refreshView.textLayer?.opacity = Float(-contentOffsetY/62.0) }else{ self.refreshView.hidden = true let screenWidth = CGRectGetWidth(UIScreen.mainScreen().bounds) } if scrollView.contentOffset.y + scrollView.frame.size.height < scrollView.contentSize.height{ loadingAcitivityIndicatorView?.stopAnimating() tableView.contentInset = UIEdgeInsetsMake(0, 0, 0, 0); showFooterLoadingView = false }else{ tableView.contentInset = UIEdgeInsetsMake(0, 0, 60, 0); loadingAcitivityIndicatorView?.startAnimating() showFooterLoadingView = true; //添加上拉加载数据代码 //... } } }

需要注明的是：

其中下拉刷新视图和上拉加载视图的父级视图是ViewController.view。