ios - 如何使用 UIWebView 消除内存泄漏？

Question

我有一个 UIWebView，我必须在其中加载一个 url。

问题是打开 webView 后发生内存泄漏。我的意思是我无法消除内存泄漏。

下面是我的代码:-

import UIKit
import Toast_Swift


class WebViewController: UIViewController,UIWebViewDelegate {

//WebView
@IBOutlet weak var webView: UIWebView!

//URL
var strUrl : String? = nil

//Tag
var tag : Int! = 0

//ViewDidLoad
override func viewDidLoad() {
    super.viewDidLoad()

    //Delegate of web view
    webView.delegate = self
    //webView.stringByEvaluatingJavaScript(from: "localStorage.clear();")
    self.webView.loadRequest(URLRequest(url: URL(string: self.strUrl!)!))

    //Loading View
    self.view.makeToastActivity(.center)
}

//MARK :- Web view delegate.
func webViewDidFinishLoad(_ webView: UIWebView) {

    //ToastManager.shared.tapToDismissEnabled = true
    self.view.hideToastActivity()
}

//Button Back Action
@IBAction func btnBack(_ sender: Any) {


    if (tag == 1) {
        webView.delegate = nil
        self.strUrl = ""
        webView.removeCache()
        let gotoCreateView = self.storyboard?.instantiateViewController(withIdentifier: "CreateAccountView") as! CreateAccountView

        self.present(gotoCreateView, animated: true, completion: nil)

    } else {

        webView.delegate = nil
        self.strUrl = ""
        webView.removeCache()
        let gotoAboutUsView = self.storyboard?.instantiateViewController(withIdentifier: "AboutUsView") as! AboutUsView

        self.present(gotoAboutUsView, animated: true, completion: nil)
    }


    /*if (1 == tag)
    {
        webView.delegate = nil
        webView.removeCache()
        let gotoCreateView = self.storyboard?.instantiateViewController(withIdentifier: "CreateAccountView") as! CreateAccountView

        self.present(gotoCreateView, animated: true, completion: nil)

    }

    else
    {
        webView.delegate = nil
        webView.removeCache()
        let gotoAboutUsView = self.storyboard?.instantiateViewController(withIdentifier: "AboutUsView") as! AboutUsView

        self.present(gotoAboutUsView, animated: true, completion: nil)
    }*/
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    webView.delegate = nil
    webView.removeCache()
    webView.delegate = self
    self.webView.reload()
 }
}

extension UIWebView
{
 func removeCache()
 {
    URLCache.shared.removeAllCachedResponses()
    URLCache.shared.diskCapacity = 0
    URLCache.shared.memoryCapacity = 0

    if let cookies = HTTPCookieStorage.shared.cookies {
        for cookie in cookies {
            HTTPCookieStorage.shared.deleteCookie(cookie)
        }
    }
  }
}

如何消除内存泄漏？

谢谢

Answer 1

除了您的代码，您还需要获得以下几点:

1. 首先是尽量不要在主视图中添加 webView，您可以设置 alpha 或隐藏属性来代替它。如果您使用的是隐藏属性，那么在取消隐藏时将它们的委托(delegate)设置为 nil 并尝试管理 WebView 在隐藏时不会在后台运行。

2. 如果您在新的 ViewController 中显示，那么当我们推送 WebView 时，设置他们的委托(delegate)并重新加载请求。现在，当您尝试从该 View 中返回时。在弹出之前，将它们的委托(delegate)设置为 nil，将 nil 设置为其中使用的所有局部变量。

例如:

在 ViewDidLoad 上:您正在设置委托(delegate)，现在当你弹出时，意味着移动到上一个屏幕使用这些代码行:

  webView.delegate = nil
  webView.removeCache()

还有，

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    webView.delegate = nil
    webView.removeCache() 
    webView.delegate = self
    self.webView.reload()
 }

}

在后退按钮上:

@IBAction func btnBack(_ sender: Any) {
    if (tag == 1) {
        webView.delegate = nil
        self.strUrl = ""
        webView.removeCache()
        let gotoCreateView = self.storyboard?.instantiateViewController(withIdentifier: "CreateAccountView") as! CreateAccountView

        self.present(gotoCreateView, animated: true, completion: nil)

    } else {

        webView.delegate = nil
        self.strUrl = ""
        webView.removeCache()
        let gotoAboutUsView = self.storyboard?.instantiateViewController(withIdentifier: "AboutUsView") as! AboutUsView

        self.present(gotoAboutUsView, animated: true, completion: nil)
    }
}