作者：Dariel
原文鏈接：https://www.ctolib.com/topics-137696.html

1.簡單的實(shí)現(xiàn)

我們都知道 TableView 的刷新動(dòng)效是設(shè)置在 tableView(_:,willDisplay:,forRowAt:) 這個(gè)方法中的。

func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {

        cell.alpha = 0;
        UIView.animate(withDuration: duration, delay: delayFactor * Double(indexPath.row), options: [], animations: {
            cell.alpha = 1
        }, completion: nil)

    }

這樣一個(gè)簡單的淡入效果就OK了，但這樣顯然不夠優(yōu)雅，我們?nèi)绻诙鄠€(gè)TableView使用這個(gè)效果該怎樣封裝呢？

2.使用工廠設(shè)計(jì)模式進(jìn)行封裝

2.1 creator（創(chuàng)建者）：Animtor，用來傳入?yún)?shù)和設(shè)置動(dòng)畫

typealias Animation = (UITableViewCell, IndexPath, UITableView) -> ()

final class Animator {
    private var hasAnimatedAllCells = false
    private let animation: Animation

    init(animation: @escaping Animation) {
        self.animation = animation
    }

    func animate(cell: UITableViewCell, at indexPath: IndexPath, in tableView: UITableView) {
        guard !hasAnimatedAllCells else {
            return
        }

        animation(cell, indexPath, tableView)
    }
}

2.2 product（產(chǎn)品）：AnimtionFactory，用來設(shè)置不同的動(dòng)畫類型

enum AnimationFactory {
    static func makeFade(duration: TimeInterval, delayFactor: Double) -> Animation {
        return {cell, indexPath, _ in
            cell.alpha = 0;
            UIView.animate(withDuration: duration, delay: delayFactor * Double(indexPath.row), options: [], animations: {
                cell.alpha = 1
            }, completion: nil)
        }
    }

    static func makeLeft() -> Animation {
        return {cell, indexPath, _ in
            cell.frame = CGRect(x: cell.frame.size.width, y: cell.frame.origin.y, width: cell.frame.size.width, height: cell.frame.size.height)
            UIView.animate(withDuration: 0.5, delay: 0.05 * Double(indexPath.row), options: [], animations: {
                cell.frame = CGRect(x: 0, y: cell.frame.origin.y, width: cell.frame.size.width, height: cell.frame.size.height)
            }, completion: nil)
        }
    }

    static func makeDamping() -> Animation {
        return {cell, indexPath, _ in
            cell.transform = CGAffineTransform(scaleX: 1, y: 0)
            UIView.animate(withDuration: 0.5, delay: 0.05, usingSpringWithDamping: 1, initialSpringVelocity: 25, options: [], animations: {
                cell.transform = CGAffineTransform(scaleX: 1, y: 1)
            }, completion: nil)
        }
    }

    static func makeDampingAndFade() -> Animation {
        return {cell, indexPath, _ in
            cell.transform = CGAffineTransform(scaleX: 1, y: 0)
            UIView.animate(withDuration: 0.5, delay: 0.05 * Double(indexPath.row), usingSpringWithDamping: 1, initialSpringVelocity: 25, options: [], animations: {
                cell.transform = CGAffineTransform(scaleX: 1, y: 1)
            }, completion: nil)
        }
    }
}

將所有的動(dòng)畫設(shè)置封裝在Animation的閉包中。
最后我們就可以在tableview:(_:,willDisplay:,forRowAt:)這個(gè)方法中使用如下代碼，就實(shí)現(xiàn)最終效果

let animation = AnimationFactory.makeFade(duration: 0.5, delayFactor: 0.05)
let animator = Animator(animation: animation)
animator.animate(cell: cell, at: indexPath, in: tableView)

最終效果

注：原作者在Animator中animate方法中有一句

hasAnimatedAllCells = tableview.isLastVisibleCell(at: indexPath)

我在tableview中并未找到對應(yīng)的方法，因此沒有這一句，貌似對效果沒有什么影響

Demo地址:https://github.com/allstar456/TableViewAnimationDemo