WKWebView（一）资源缓存

前言

iOS开发过程中，有些页面是用H5进行开发，原生使用WebView打开H5页面的链接，但是这种方式有一个很大的缺陷，就是打卡H5页面会很慢；因为H5页面一般都会引入各种各样的资源，有js、css、图片等等；这些资源在每一次打开H5页面的时候，会逐步通过网络请求下载到页面上，所以导致每一次打卡页面都比较慢；
那有没有一种办法处理呢？
那就是把这些资源进行缓存，只在第一次打开的时候，进行下载，并缓存到本地；后面再次打开的时候，就直接取缓存中的数据；

一、WKURLSchemeHandler介绍

WKURLSchemeHandler是iOS11后开放出来的API，可通过WKURLSchemeHandler检测到WKWebView中的网络请求，通过原生进行处理；

二、WKURLSchemeHandler使用

1、WKWebview添加Catetory

#import <objc/runtime.h>

@implementation WKWebView(WIICustomer)


+ (void)load 
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Method originalMethod1 = class_getClassMethod(self, @selector(handlesURLScheme:));
        Method swizzledMethod1 = class_getClassMethod(self, @selector(bbhandlesURLScheme:));
        method_exchangeImplementations(originalMethod1, swizzledMethod1);
    });
}
 
+ (BOOL)bbhandlesURLScheme:(NSString *)urlScheme {
    if ([urlScheme isEqualToString:@"http"] ||
        [urlScheme isEqualToString:@"https"]) {
        return NO;  //这里让返回NO,不走系统断言，走自己的handler处理
    } else {
        return [self bbhandlesURLScheme:urlScheme];
    }
}

@end

2、创建WKURLSchemeHandler类

class WIIWebViewSchemeHandler: NSObject & WKURLSchemeHandler {
    
    public var module = "Test"

    func webView(_ webView: WKWebView, start urlSchemeTask: WKURLSchemeTask) {
        guard let url = urlSchemeTask.request.url else {
            urlSchemeTask.didFinish()
            return
        }
        let urlPath = url.absoluteString
        let key = urlPath.md5()
        guard let localFilePath = self.getLocalFilePath(key: key) else {
            urlSchemeTask.didFinish()
            return
        }
        if FileManager.default.fileExists(atPath: localFilePath) {
            let fileHandle = FileHandle(forReadingAtPath: localFilePath)
            if let data = fileHandle?.readDataToEndOfFile() {
                let mimeType = self.getMimeType(key: key)
                let response = self.createURLResponse(url: url, data: data, mimeType: mimeType)
                urlSchemeTask.didReceive(response)
                urlSchemeTask.didReceive(data)
                urlSchemeTask.didFinish()
                try? fileHandle?.close()
                return
            }
            try? fileHandle?.close()
        }
        let session = URLSession.shared
        let task = session.dataTask(with: url) { data, response, err in
            if let data = data, let response = response {
                let mimeType = response.mimeType ?? "text/plain"
                self.saveMimeType(mimeType, key: key)
                
                let urlResponse = self.createURLResponse(url: url, data: data, mimeType: mimeType)
                urlSchemeTask.didReceive(urlResponse)
                urlSchemeTask.didReceive(data)
                urlSchemeTask.didFinish()
                
                try? data.write(to: URL(fileURLWithPath: localFilePath), options: Data.WritingOptions.atomic)
            } else {
                urlSchemeTask.didFailWithError(err ?? NSError())
            }
        }
        task.resume()
    }
    
    func webView(_ webView: WKWebView, stop urlSchemeTask: WKURLSchemeTask) {
        
    }
}

extension WIIWebViewSchemeHandler {
    func createURLResponse(url: URL, data: Data, mimeType: String) -> URLResponse {
        return URLResponse(url: url, mimeType: mimeType, expectedContentLength: data.count, textEncodingName: nil)
    }
}
extension WIIWebViewSchemeHandler {
    func getLocalFilePath(key: String) -> String? {
        guard let rootPath = self.urlCacheRootFilePath() else {
            return nil
        }
        return "\(rootPath)/\(key)"
    }
    
    func urlCacheRootFilePath() -> String? {
        guard let path = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first else {
            return nil
        }
        let directoryPath = "\(path)/\(self.module)"
        if FileManager.default.fileExists(atPath: directoryPath) {
            return directoryPath
        }
        try? FileManager.default.createDirectory(atPath: directoryPath, withIntermediateDirectories: true)
        return directoryPath
    }
}

extension WIIWebViewSchemeHandler {
    func getMimeType(key: String) -> String {
        return UserDefaults.standard.string(forKey: key) ?? ""
    }
    
    func saveMimeType(_ type: String, key: String) {
        UserDefaults.standard.setValue(type, forKey: key)
    }
}

3、WKWebView设置URLScheme

let config = WKWebViewConfiguration()
let handler = WIIWebViewSchemeHandler()
config.setURLSchemeHandler(handler, forURLScheme: "http")
config.setURLSchemeHandler(handler, forURLScheme: "https")
self.webview = WIIWebView(frame: self.view.bounds, configuration: config)