UITableView頭部下拉放大網(wǎng)上很多實(shí)現(xiàn)方式问芬，使用過(guò)程會(huì)感覺(jué)很炫酷册倒，實(shí)際實(shí)現(xiàn)起來(lái)成本確很低蔫耽，兩種實(shí)現(xiàn)方式供參考.

ContentInset實(shí)現(xiàn)

自定義UITableView见秤，數(shù)據(jù)初始化:
<pre><code>` tableView = UITableView(frame: CGRect.init(x: 0, y: 64, width:self.view.bounds.width, height: self.view.bounds.height - 64), style: .plain)
tableView?.register(UITableViewCell.classForCoder(), forCellReuseIdentifier: "UITableViewCell")
tableView?.delegate = self
tableView?.dataSource = self

    setUpTableHeader1()
    
    self.view.addSubview(tableView!)
    
    sections = [
        ExpandSection(title: "簡(jiǎn)書(shū)", items: ["FlyElephant", "keso"]),
        ExpandSection(title: "編程語(yǔ)言", items: ["Swift", "Objective-C", "JavaScript", "Python"]),
        ExpandSection(title: "地區(qū)", items: ["北京", "河南", "江西"]),
    ]`</code></pre>

頂部頭部設(shè)置:
<pre><code>let frame:CGRect = CGRect(x: 0, y: -200, width: self.view.bounds.width, height: 200) headerImgView = UIImageView.init(image: UIImage.init(named: "Header.jpeg")) headerImgView.frame = frame headerImgView.contentMode = .scaleAspectFill tableView?.contentInset = UIEdgeInsetsMake(200, 0, 0, 0) tableView?.addSubview(headerImgView)</code></pre>

實(shí)現(xiàn)UIScrollViewDelegate:
<pre><code>` func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offsetY:CGFloat = scrollView.contentOffset.y

    if offsetY < 0 {
        headerImgView.y = offsetY
        headerImgView.height = -offsetY
    }
}`</code></pre>

實(shí)現(xiàn)效果下拉放大效果能實(shí)現(xiàn)控乾，UITableView向上互動(dòng)會(huì)有瑕疵幔欧，效果如下:

FlyElephant-ContentInset.gif

自定義UITableHeaderView

初始化數(shù)據(jù)不變，自定UITableHeaderView丽声，添加子視圖UIImageView
<pre><code>` func setUpTableHeader() {
let frame:CGRect = CGRect(x: 0, y: 0, width: self.view.bounds.width, height: 200)

    tableHeaderView = UIView.init(frame: frame)
    headerImgView = UIImageView.init(image: UIImage.init(named: "Header.jpeg"))
    headerImgView.frame = frame
    headerImgView.contentMode = .scaleAspectFill
    
    tableHeaderView.addSubview(headerImgView)
    tableView?.tableHeaderView = tableHeaderView
}`</code></pre>

UIScrollViewDelegate中下拉過(guò)程需要對(duì)視圖進(jìn)行等比例放大及平移礁蔗，停止下來(lái)的時(shí)候置為初始狀態(tài):
<pre><code>` func scrollViewDidScroll(_ scrollView: UIScrollView) {
let offsetY:CGFloat = scrollView.contentOffset.y

    if offsetY < 0 {
        let originalHeight:CGFloat = tableHeaderView.height
        
        let scale:CGFloat = (originalHeight - offsetY) / originalHeight
        let transformScale3D:CATransform3D = CATransform3DMakeScale(scale, scale, 1.0)
        let translation3D:CATransform3D = CATransform3DMakeTranslation(0, offsetY/2, 0)
        headerImgView.layer.transform = CATransform3DConcat(transformScale3D, translation3D)

    } else {
        headerImgView.layer.transform = CATransform3DIdentity
    }
}

`</code></pre>

效果圖如下:

scroll2.gif