1.下拉刷新

refreshControl = UIRefreshControl()
        
        let otherView = UIView()
        otherView.frame = CGRect(x: 0, y: 0, width: 400, height: 44)
        otherView.backgroundColor = UIColor.purpleColor()
        refreshControl?.addSubview(otherView)
        /*
        1.UIRefreshControl只要拉到一定程度无论是否松手会都触发下拉事件
        2.触发下拉时间之后, 菊花不会自动隐藏
        3.想让菊花消失必须手动调用endRefreshing()
        4.只要调用beginRefreshing, 那么菊花就会自动显示
        5.如果是通过beginRefreshing显示菊花, 不会触发下拉事件
        */
        refreshControl?.addTarget(self, action: Selector("loadMoreData"), forControlEvents: UIControlEvents.ValueChanged)



RefreshView.swift

import UIKit
import SnapKit

class XMGRefreshControl: UIRefreshControl {
    override init() {
        super.init()
        // 1.添加子控件
        addSubview(refreshView)
        // 2.布局子控件
        refreshView.snp_makeConstraints { (make) -> Void in
            make.size.equalTo(CGSize(width: 150, height: 50))
            make.center.equalTo(self)
        }
        
        // 3.监听UIRefreshControl frame改变
        addObserver(self, forKeyPath: "frame", options: NSKeyValueObservingOptions.New, context: nil)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    deinit
    {
        removeObserver(self, forKeyPath: "frame")
    }
    override func endRefreshing() {
        super.endRefreshing()
        refreshView.stopLoadingView()
    }
    
    /// 记录是否需要旋转
    var rotationFlag = false
    // MARK: - 内部控制方法
    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        
        if frame.origin.y == 0 || frame.origin.y == -64
        {
            // 过滤掉垃圾数据
            return
        }
        
        // 判断是否触发下拉刷新事件
        if refreshing
        {
            // 隐藏提示视图, 显示加载视图, 并且让菊花转动
            refreshView.startLoadingView()
            return
        }
        
        // 通过观察发现: 往下拉Y越小, 往上推Y越大
        if frame.origin.y < -50 && !rotationFlag
        {
            rotationFlag = true
            NJLog("往上旋转")
            refreshView.rotationArrow(rotationFlag)
        }else if frame.origin.y > -50 && rotationFlag
        {
            rotationFlag = false
            NJLog("往下旋转")
            refreshView.rotationArrow(rotationFlag)
        }
    }
    
    // MARK: -懒加载
    private lazy var refreshView: RefreshView = RefreshView.refreshView()
}

class RefreshView: UIView {
    /// 菊花
    @IBOutlet weak var loadingImageView: UIImageView!
    /// 提示视图
    @IBOutlet weak var tipView: UIView!
    /// 箭头
    @IBOutlet weak var arrowImageView: UIImageView!
    
    class func refreshView() -> RefreshView {
        return NSBundle.mainBundle().loadNibNamed("RefreshView", owner: nil, options: nil).last as! RefreshView
    }
    
    // MARK: - 外部控制方法
    /// 旋转箭头
    func rotationArrow(flag: Bool)
    {
        var angle: CGFloat = flag ? -0.01 : 0.01
        angle += CGFloat(M_PI)
        /*
        transform旋转动画默认是按照顺时针旋转的
        但是旋转时还有一个原则, 就近原则
        */
        UIView.animateWithDuration(2.0) { () -> Void in
            self.arrowImageView.transform = CGAffineTransformRotate(self.arrowImageView.transform, angle)
        }
    }
    
    /// 显示加载视图
    func startLoadingView()
    {
        // 0.隐藏提示视图
        tipView.hidden = true
        
        if let _ = loadingImageView.layer.animationForKey("lnj")
        {
            // 如果已经添加过动画, 就直接返回
            return
        }
        // 1.创建动画
        let anim =  CABasicAnimation(keyPath: "transform.rotation")
        
        // 2.设置动画属性
        anim.toValue = 2 * M_PI
        anim.duration = 5.0
        anim.repeatCount = MAXFLOAT
        
        // 3.将动画添加到图层上
        loadingImageView.layer.addAnimation(anim, forKey: "lnj")
    }
    
    /// 隐藏加载视图
    func stopLoadingView()
    {
        // 0.显示提示视图
        tipView.hidden = false
        
        // 1.移除动画
        loadingImageView.layer.removeAllAnimations()
    }
}

2.显示提醒消息

/// 显示刷新提醒
    private func showRefreshStatus(count: Int)
    {
        // 1.设置提醒文本
        tipLabel.text = (count == 0) ? "没有更多数据" : "刷新到\(count)条数据"
        tipLabel.hidden = false
        // 2.执行动画
        UIView.animateWithDuration(1.0, animations: { () -> Void in
//            UIView.setAnimationRepeatAutoreverses(true)
            self.tipLabel.transform = CGAffineTransformMakeTranslation(0, 44)
            }) { (_) -> Void in
                UIView.animateWithDuration(1.0, delay: 2.0, options: UIViewAnimationOptions(rawValue: 0), animations: { () -> Void in
                    self.tipLabel.transform = CGAffineTransformIdentity
                    }, completion: { (_) -> Void in
                        self.tipLabel.hidden = true
                })
        }
    }

3.缓存行高

 /// 缓存行高
    private var rowHeightCaches =  [String: CGFloat]()

 // 返回行高
    override func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
        
        let viewModel = statuses![indexPath.row]
        let identifier = (viewModel.status.retweeted_status != nil) ? "forwardCell" : "homeCell"
        
        // 1.从缓存中获取行高
        guard let height = rowHeightCaches[viewModel.status.idstr ?? "-1"] else
        {
            NJLog("计算行高")
            // 缓存中没有行高
            // 2.计算行高
            // 2.1获取当前行对应的cell
            let cell = tableView.dequeueReusableCellWithIdentifier(identifier) as! HomeTableViewCell
            
            // 2.1缓存行高
            let  temp = cell.calculateRowHeight(viewModel)
            
            rowHeightCaches[viewModel.status.idstr ?? "-1"] = temp
            
            // 3.返回行高
            return temp
        }
        
        // 缓存中有就直接返回缓存中的高度
        return height
    }


override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // 释放缓存数据
        rowHeightCaches.removeAll()
    }