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  • 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:

    下拉刷新

    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。

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  • 原文地址:https://www.cnblogs.com/Jenaral/p/5626787.html
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