UISearchBar的使用

import UIKit

class ViewController: UIViewController {

    var searchBar: UISearchBar?
    
    override func viewDidLoad() {
        super.viewDidLoad()

        self.setupSearchBar()
    }
    
    func setupSearchBar() {
        self.searchBar = UISearchBar(frame: CGRect(x: 20, y: 64+10, width: UIScreen.main.bounds.width-2*20, height: 50))
        self.searchBar?.placeholder = "热门话题"
        /**
         public enum UISearchBarStyle : UInt {
         case `default` // currently UISearchBarStyleProminent  有背景 默认样式
         case prominent // used my Mail, Messages and Contacts  有背景 突出样式
         case minimal // used by Calendar, Notes and Music      无背景 最小样式
         }
         */
        self.searchBar?.searchBarStyle = .minimal
        
        /**
         public enum UIBarStyle : Int {
         case `default` 白色
         case black     黑色
         public static var blackOpaque: UIBarStyle { get } // Deprecated. Use UIBarStyleBlack   黑色
         case blackTranslucent // Deprecated. Use UIBarStyleBlack and set the translucent property to YES   黑色
         }
         */
        // 设置样式
        self.searchBar?.barStyle = .default
        // 设置背景色
        self.searchBar?.barTintColor = UIColor.red
        // 点击return自动搜索
        self.searchBar?.enablesReturnKeyAutomatically = true
        /**
         public enum UISearchBarIcon : Int {
         case search // The magnifying glass
         case clear // The circle with an x in it
         case bookmark // The open book icon
         case resultsList // The list lozenge icon
         }
         */
        // _的作用：忽略返回值，消除警告
        _ = self.searchBar?.image(for: .resultsList, state: .highlighted)
        
        self.searchBar?.delegate = self
        self.view.addSubview(self.searchBar!)
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        self.searchBar?.resignFirstResponder()
    }
}

// MARK: 搜索代理UISearchBarDelegate方法
extension ViewController: UISearchBarDelegate {
    
    func searchBarShouldBeginEditing(_ searchBar: UISearchBar) -> Bool {
        print("将要开始编辑")
        return true
    }
    func searchBarTextDidBeginEditing(_ searchBar: UISearchBar) {
        print("已经开始编辑")
    }
    func searchBarShouldEndEditing(_ searchBar: UISearchBar) -> Bool {
        print("将要结束编辑")
        return true
    }
    func searchBarTextDidEndEditing(_ searchBar: UISearchBar) {
        print("已经结束编辑")
    }
    func searchBar(_ searchBar: UISearchBar, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        print("文本改变的时候触发 text: \(text)")
        return true
    }
}