是否可以在 webview 上显示之前预加载 html

Question

我搜索了整个互联网，但找不到解决方案，所以决定请教专家是否可行。

我有一个正在为其开发 iOS 应用程序的博客，但加载内容需要花费太多时间。

那么是否可以在用户打开文章之前预加载所有文章的html（不是图像），就像FB即时文章一样。 FB 即时文章已预加载和缓存，当用户打开它时，它会在 Flash 中打开，但图像除外，图像会在用户打开它时下载。

目前我正在使用 uiwebview，我打算将其替换为 wkwebview。

提前感谢您的帮助。

调用缓存

CachedArticles.shared.cacheArticles(self.articles) { success 
    print("cache creation finished, success: \(success)")
}

调用网络视图

tableView.deselectRow(at: indexPath, animated: true)
let webVC = storyboard!.instantiateViewController(withIdentifier:"NewsReaderViewController") as! NewsReaderViewController
webVC.article = self.articles?[indexPath.row]
navigationController?.pushViewController(webVC, animated: true)

缓存class

import UIKit

class CachedArticles: NSObject {

static let shared: CachedArticles = CachedArticles()

let cachePath = NSSearchPathForDirectoriesInDomains(.cachesDirectory, .userDomainMask, true).first!

func cacheArticles(_ articles: [ArticalClass]?, completion: @escaping (Bool)->() ) {

    guard let articles = articles else { return }

    DispatchQueue.global().async {
        DispatchQueue.main.async {
            UIApplication.shared.isNetworkActivityIndicatorVisible = true
        }

        var success = true

        for article in articles {
            guard let path = article.url, let url = URL(string: path), self.webArchive(forHeadline: article.headline!.replacingOccurrences(of: " ", with: "")) == nil else { continue }

            print("caching article: \(article)")
            do {
                let data = try Data(contentsOf: url)
                let url = self.cacheFileURL(forHeadline: article.headline!)
                STWebArchiver().archiveHTMLData(data, textEncoding: "UTF-8", baseURL: url, completionBlock: { data in
                    (data! as NSData).write(toFile: url.path, atomically: true)
                })
            } catch let error {
                success = false
                print("Error: \(error)")
            }
        }

        DispatchQueue.main.async {
            UIApplication.shared.isNetworkActivityIndicatorVisible = false
            completion(success)
        }
    }
}

func webArchive(forHeadline: String?) -> URL? {
    let url = cacheFileURL(forHeadline: forHeadline!)
    return FileManager.default.fileExists(atPath: url.path) ? url : nil
}

private func cacheFileURL(forHeadline: String) -> URL {
    let url = URL(fileURLWithPath: self.cachePath).appendingPathComponent(forHeadline.replacingOccurrences(of: " ", with: "")+".webarchive")
    return url
}

}

Answer 1

您可以采用 "greedy" webview 方法，方法是在将它们添加到视图层次结构并开始请求之前预先创建它们。这假设每个 webview 实例将显示一个页面，该页面不会导航到其他 html 页面。 appDidFinishLaunching 将是进行设置的地方。

Answer 2

您可以在预览时通过HTTP请求获取html文件并保存到缓存中，真正进入时检查是否在缓存中。

============================================= ====

4.24 更新有两个因素

首先，我不知道 'articles' 数组是如何生成的，是否包含 src url。

其次，我查看了 STWebArchiver 代码，发现它：

- (void)archiveHTMLData:(NSData *)aData
       textEncoding:(NSString *)anEncoding
            baseURL:(NSURL *)anURL
    completionBlock:(void (^)(NSData *))completion {
htmlDocPtr doc = htmlParseDoc((xmlChar *)[aData bytes], [anEncoding UTF8String]);
NSArray *pathsForImagesAndScripts = [self valueForAttributeName:@"src" withEvaluatingXPath:@"//script[@src]|//img[@src]" inDocument:doc];
NSArray *pathsForStylesheets = [self valueForAttributeName:@"href" withEvaluatingXPath:@"//link[@rel='stylesheet'][@href]" inDocument:doc];
NSArray *resourcesPaths = [pathsForImagesAndScripts arrayByAddingObjectsFromArray:pathsForStylesheets];
NSArray *resourceUrls = [self absoluteURLsForPaths:resourcesPaths baseURL:anURL];
dispatch_async(dispatch_queue_create("Downloads", 0), ^{
    NSMutableDictionary *resources = [NSMutableDictionary dictionary];
    dispatch_apply([resourceUrls count], dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^(size_t i) {
        NSURL *url = [resourceUrls objectAtIndex:i];
        NSString *urlString = [url absoluteString];
        BOOL unfetched = NO;
        @synchronized (resources) {
            unfetched = ![resources objectForKey:urlString];
            if (unfetched) {
                [resources setObject:[NSNull null] forKey:urlString];
            }
        }
        if (unfetched) {
            NSURLResponse *response;
            NSError *error;
            NSURLRequest *request = [NSURLRequest requestWithURL:url];
            NSData *data = [NSURLConnection sendSynchronousRequest:request
                                                 returningResponse:&response
                                                             error:&error];
            NSMutableDictionary *resourceArchive = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                                    urlString, @"WebResourceURL",
                                                    [response MIMEType], @"WebResourceMIMEType",
                                                    data, @"WebResourceData", nil];
            if ([response textEncodingName]) {
                [resourceArchive setObject:[response textEncodingName] forKey:@"WebResourceTextEncodingName"];
            }
            @synchronized (resources) {
                [resources setObject:resourceArchive forKey:urlString];
            }
        }
    });
    NSMutableDictionary *archiveSource = [NSMutableDictionary dictionaryWithObject:[resources allValues] forKey:@"WebSubresources"];
    NSMutableDictionary *mainResource = [NSMutableDictionary dictionary];
    [mainResource setObject:aData forKey:@"WebResourceData"];
    [mainResource setObject:@"" forKey:@"WebResourceFrameName"];
    [mainResource setObject:@"text/html" forKey:@"WebResourceMIMEType"];
    [mainResource setObject:anEncoding forKey:@"WebResourceTextEncodingName"];
    [mainResource setObject:[anURL absoluteString] forKey:@"WebResourceURL"];
    [archiveSource setObject:mainResource forKey:@"WebMainResource"];
    NSData *webArchive = [NSPropertyListSerialization dataFromPropertyList:archiveSource
                                                                    format:NSPropertyListBinaryFormat_v1_0
                                                          errorDescription:NULL];
    completion(webArchive);
});
xmlFreeDoc(doc);
}

这意味着 STWebArchiver 不仅缓存纯 HTML 文件而且还缓存请求的资源。

是否可以在 webview 上显示之前预加载 html

is it possible to preload html before displaying on webview

uiwebview

ios

wkwebview