下拉刷新和上拉加載 Swift

轉載自：http://iyiming.me/blog/2015/07/05/custom-refresh-and-loading/

 

關於下拉刷新和上拉加載，項目中一直使用MJRefresh（原先還用過EGOTableViewPullRefresh，MJRefresh更好用些），今天就分析下如何用Swift來實現這個功能。

關於如何下拉刷新和上拉加載，認識到兩點就可以了：

0.UIScrollViewDelegate

1.UIScrollView中的contentInset

直白一點說，就是在UIScrollView及其子類在下拉或者上拉到一定的偏移量時，設置contentInset，固定住UIScrollView，顯示動畫加載頁面，數據到達之后再恢復contentInset。

UIScrollView很強大，除了上面說的，我們有時用它來顯示放大縮小圖片。

今天來自定義一個下拉刷新視圖，並實現上拉加載功能。

前些天，一篇公眾號（Pinapps,里面的文章挺好）文章里推薦了一個iPhone上的RSS閱讀器Unread，軟件做的很棒，就把全部功能都買了下來（程序內購買）。其中里面的下拉刷新效果挺棒的，正好仿一下：

分析下這里面的效果：

一開始線條是隱藏的，有了偏移后，線條從原先的窄線條慢慢變成寬線條線條，其中線條的顏色和REFRESH顏色也是有變化的。為了能做出連續性的動畫我們使用POP(如果不是很了解POP的話，可以看一下我寫的這篇文章)

已傳至Github（時間倉促，沒有加以優化）：

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

下面是代碼的一些注釋：

前提：添加POP動畫，創建一個單視圖項目，在ViewController里面添加一個UITableView。

先來實現刷新視圖：即那三條紅線加上REFRESH。

我們創建Swift文件，繼承自UIView並命名為RefreshView：

代碼如下：

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import UIKit @IBDesignable class RereshView: UIView { var topLayer: CALayer?//頂部線 var middleLayer: CALayer?//中間線 var bottomLayer: CALayer?//底部線 var textLayer: CATextLayer?//REFRESH文字 override init(frame: CGRect) { super.init(frame: frame) setup()//設置 } required init(coder aDecoder: NSCoder) { super.init(coder: aDecoder) //fatalError("init(coder:) has not been implemented") setup()//設置 } /** 設置 */ func setup(){ //頂部線 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) //中間線 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) //底部線 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) } }

注意我們在Class前面加了一個@IBDesignable，這樣我們就能在Storyboard中查看我們自定義的視圖（如果想詳細了解的話，請看下Onevcat的可視化開發，IB新時代）。

在ViewController.swift中我們添加了如下代碼：

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import UIKit class ViewController: UIViewController,UITableViewDataSource,UIScrollViewDelegate { @IBOutlet weak var tableView: UITableView!//列表視圖 @IBOutlet weak var refreshView: RereshView!//下拉刷新視圖 @IBOutlet weak var refreshViewTopLayoutConstraint: NSLayoutConstraint!//下拉刷新居上的約束 var showBottomLayer:Bool = true//顯示刷新視圖的底部線 變寬 var hiddenBottomLayer:Bool = true//隱藏刷新視圖的底部線 即變窄 var showMiddleLayer:Bool = true//顯示刷新視圖的中間線 變寬 var hiddenMiddleLayer:Bool = true//隱藏刷新視圖的中間線 變窄 var showTopLayer:Bool = true//顯示刷新頭部的底部線 變寬 var hiddenTopLayer:Bool = true//隱藏刷新視圖的頭部線 變窄 var refreshing = false//是否在刷新中 var loadingAcitivityIndicatorView: UIActivityIndicatorView?//上拉加載指示菊花 var showFooterLoadingView:Bool = false//是否顯示上拉加載視圖 override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. settingUI()//設置界面 } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } //設置界面 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動畫 :param: layer 要添加動畫的layer :param: size 動畫到的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動畫 :param: layer 要添加動畫的layer :param: position 動畫到的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 //將要開始減速時 func scrollViewWillBeginDecelerating(scrollView: UIScrollView) { var contentOffsetY = scrollView.contentOffset.y if contentOffsetY > 0{ return } if contentOffsetY < -52{//偏移 52 時 我們顯示加載視圖 refreshing = true scrollView.contentInset = UIEdgeInsetsMake(62.0, 0.0, 0.0, 0.0) refreshViewTopLayoutConstraint.constant = 20//刷新視圖居上約束 //移除POP動畫 refreshView.topLayer?.pop_removeAllAnimations() refreshView.middleLayer?.pop_removeAllAnimations() refreshView.bottomLayer?.pop_removeAllAnimations() //設定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) }) } } } //滾動時 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; //添加上拉加載數據代碼 //... } } }

需要注明的是：

其中下拉刷新視圖和上拉加載視圖的父級視圖是ViewController.view。