又是一个关于多线程的作业,老样子,先看需求
这次作业具体要做成什么样子没有指定,那我们就做一个加载成都的天气信息吧。
具体的运行效果如下:
要实现这个功能很简单,首先我们先声明一个显示信息的UITextView
var textView: UITextView!
然后分别将UITextView和一个按钮添加到视图上
self.view.backgroundColor = UIColor.white
let loadButton = UIButton(frame: CGRect(x: 100, y: 100, width: 150, height: 40))
loadButton.setTitle("加载成都天气", for: .normal)
loadButton.setTitleColor(UIColor.cyan, for: .normal)
loadButton.setTitleColor(UIColor.brown, for: .highlighted)
loadButton.addTarget(self, action: #selector(loadImage), for: .touchUpInside)
self.view.addSubview(loadButton)
textView = UITextView(frame: CGRect(x: 10, y: 200, width: 300, height: 300))
textView.font = UIFont.systemFont(ofSize: 44)
textView.layer.borderWidth = 1
self.view.addSubview(textView)
最后再实现按钮的action即可
@objc func loadImage() {
DispatchQueue.global().async {
let url = URL(string: "http://www.weather.com.cn/data/sk/101270101.html")
let request = URLRequest(url: url!)
let session = URLSession.shared
let dataTask = session.dataTask(with: request, completionHandler: { (data, response, error) in
if error == nil {
if let json = try? JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.allowFragments) as? [String: Any] {
if let dict = json!["weatherinfo"] as? [String: String] {
var text = ""
text += "城市:" + dict["city"]! + "\n"
text += "温度:" + dict["temp"]! + "\n"
text += "风向:" + dict["WD"]! + "\n"
text += "风力:" + dict["WS"]! + "\n"
DispatchQueue.main.async {
self.textView.text = text
}
}
}
}
})
dataTask.resume()
}
}
在刚进入这个方法时,我们使用系统设定好的全局队列来加载线程,使用异步的方式加载不会造成界面的卡顿,然后初始化一个URL和URLRequest,这两个变量用于获取json数据。
然后再使用URLSession的单例shared初始化一个URLSession的对象,再调用它的dataTask方法来进行网络获取到的数据的解析。在闭包中,我们将获取到的data以json的格式解析出来,并将最后的结果显示在UITextView中,因为涉及到对界面组件的操作,所以对主界面元素的操作必须放在主线程中。
最后我们需要调用dataTask的resume()方法来开始网络服务。
所有代码如下:
import UIKit
class ViewController: UIViewController {
var textView: UITextView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.view.backgroundColor = UIColor.white
let loadButton = UIButton(frame: CGRect(x: 100, y: 100, width: 150, height: 40))
loadButton.setTitle("加载成都天气", for: .normal)
loadButton.setTitleColor(UIColor.cyan, for: .normal)
loadButton.setTitleColor(UIColor.brown, for: .highlighted)
loadButton.addTarget(self, action: #selector(loadImage), for: .touchUpInside)
self.view.addSubview(loadButton)
textView = UITextView(frame: CGRect(x: 10, y: 200, width: 300, height: 300))
textView.font = UIFont.systemFont(ofSize: 44)
textView.layer.borderWidth = 1
self.view.addSubview(textView)
}
@objc func loadImage() {
DispatchQueue.global().async {
let url = URL(string: "http://www.weather.com.cn/data/sk/101270101.html")
let request = URLRequest(url: url!)
let session = URLSession.shared
let dataTask = session.dataTask(with: request, completionHandler: { (data, response, error) in
if error == nil {
if let json = try? JSONSerialization.jsonObject(with: data!, options: JSONSerialization.ReadingOptions.allowFragments) as? [String: Any] {
if let dict = json!["weatherinfo"] as? [String: String] {
var text = ""
text += "城市:" + dict["city"]! + "\n"
text += "温度:" + dict["temp"]! + "\n"
text += "风向:" + dict["WD"]! + "\n"
text += "风力:" + dict["WS"]! + "\n"
DispatchQueue.main.async {
self.textView.text = text
}
}
}
}
})
dataTask.resume()
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}