12.

2019-04-15 16:57发布

站内文章 / PIC单片机
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多线程加载网络图片

let url = URL(string: "http://c.hiphotos.baidu.com/zhidao/pic/item/5ab5c9ea15ce36d3c704f35538f33a87e950b156.jpg") let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in guard let _ = data,error == nil else { return } //回到主线程 DispatchQueue.main.sync { self.headView.image = UIImage(data: data!) } } task.resume()

  • 学习代码:

    • ViewController.swift import UIKit let YHRect = UIScreen.main.bounds let YHHeight = YHRect.size.height let YHWidth = YHRect.size.width let HeadViewHeight = YHHeight/3.0 class ViewController: UIViewController { let datas = ["下","拉","可","以","出","现","很","神","奇","的","事","情","yo","yo","yo","yo","yo","yo"] let tableView = UITableView(frame: YHRect, style: .plain) let resueIdentifer = "CustomCell" let headView = UIImageView(frame: CGRect(x: 0.0, y: 0.0, width: YHWidth, height: HeadViewHeight)) override func viewDidLoad() { super.viewDidLoad() setupView() } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() } func setupView() { self.automaticallyAdjustsScrollViewInsets = false headView.backgroundColor = .white headView.contentMode = .scaleAspectFill headView.clipsToBounds = true view.addSubview(headView) //加载图片 let url = URL(string: "http://c.hiphotos.baidu.com/zhidao/pic/item/5ab5c9ea15ce36d3c704f35538f33a87e950b156.jpg") let task = URLSession.shared.dataTask(with: url!) { (data, response, error) in guard let _ = data,error == nil else { return } //回到主线程 DispatchQueue.main.sync { self.headView.image = UIImage(data: data!) } } task.resume() tableView.delegate = self tableView.dataSource = self tableView.tableFooterView = UIView() tableView.register(UITableViewCell.self, forCellReuseIdentifier: resueIdentifer) tableView.showsVerticalScrollIndicator = false //下面两句必不可少，否则会出现第一次加载时位置不对的情况 tableView.contentInset.top = HeadViewHeight tableView.contentOffset = CGPoint(x: 0.0, y: -HeadViewHeight) // tableView.scrollIndicatorInsets.top = HeadViewHeight//右边指示器的位置 view.addSubview(tableView) view.sendSubview(toBack: tableView) } } extension ViewController:UITableViewDataSource, UITableViewDelegate { //MARK: - DataSource func numberOfSections(in tableView: UITableView) -> Int { return 1 } func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return datas.count } func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: resueIdentifer, for: indexPath) cell.textLabel?.text = datas[indexPath.row] cell.textLabel?.textAlignment = .center return cell } //MARK: - Delegate func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat { return 50 } func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) { tableView.deselectRow(at: indexPath, animated: true) } func scrollViewDidScroll(_ scrollView: UIScrollView) { let offsety = scrollView.contentOffset.y + scrollView.contentInset.top if offsety <= 0 { headView.frame = CGRect(x: 0.0, y: 0.0, width: YHWidth, height: HeadViewHeight-offsety) }else { let height = (HeadViewHeight-offsety) <= 0.0 ? 0.0 : (HeadViewHeight-offsety) headView.frame = CGRect(x: 0.0, y: 0.0, width: YHWidth, height: height) headView.alpha = height/HeadViewHeight } } }

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