android - Jsoup.parse 在 19 种以上的 Android 设备上花费 10 倍以上的时间

Question

出于某种原因，在 kitkat 设备上使用 Jsoup.parse 比在旧设备上花费的时间多 10 倍，起初我认为这与 ART 运行时有关，但改回 dalvik 并没有帮助

这是我使用的代码:

        downloadedHtml = NetworkHelper.downloadString("https://en.m.wikipedia.org/wiki/Dusseldorf");

        AppLog.i("Downloaded data, Jsoup is parsing the html");

        hDoc = Jsoup.parse(downloadedHtml);

        Element htmlElement = hDoc.select("html").first();

        String langCode = htmlElement.attributes().get("lang");

        ArticleInfo articleInfo = new ArticleInfo(getWikiLanguage(langCode), langCode, href);

        article = new Article(articleInfo, href);

        String title = hDoc.getElementById("section_0").text();

        article.set_title(title);

        Document documentNode = hDoc.ownerDocument(); 

        Elements contents = documentNode.getElementsByClass("content");

        if (contents == null || contents.isEmpty())
            throw new IllegalArgumentException("content");

        Element content = contents.first();

        Elements imgElements = content.select("img");

        Element htmlNode;

        for (int i = 0; i < imgElements.size(); i++)
        {
            htmlNode = imgElements.get(i);

            if (!htmlNode.hasAttr("src"))
                continue;

            String src = htmlNode.attr("src");

            if (src.startsWith("//"))
                htmlNode.attr("src", String.format("http:%s", src));
            //else
            //throw new UnsupportedOperationException();
        }

        //get section headings

        Elements headlines = documentNode.getElementsByClass("mw-headline");

        if (headlines != null)
        {
            Element headline;

            for (int i = 0; i < headlines.size(); i++)
            {
                headline = headlines.get(i);

                String headline_link = headline.id();
                String headline_title = headline.text();

                SectionHeadline sectionHeadline = new SectionHeadline(headline_title, headline_link);
                article.get_sectionHeadlines().add(sectionHeadline);
            }
        }

        article.set_html(content.outerHtml());

        //get languages
        //language list

        Element languageSection = content.getElementById("mw-mf-language-section");

        if (languageSection != null)
        {
            Elements languageLinks = languageSection.select("li");

            Element languageLink;

            for (int i = 0; i < languageLinks.size(); i++)
            {
                languageLink = languageLinks.get(i);

                Element link = null;
                Elements ls = languageLink.select("a");

                if (ls == null || ls.size() == 0)
                    continue;

                link = ls.first();

                if (!link.hasAttr("href"))
                    continue;

                String linkHref = link.attr("href");

                if (linkHref != null && link.text() != null)
                {
                    String languageCode = link.attr("lang");

                    if (linkHref.startsWith("//"))
                        linkHref = String.format("http:%s", linkHref);

                    ArticleInfo languageInfo = new ArticleInfo(getWikiLanguage(languageCode), languageCode, linkHref);

                    if (languageInfo.get_language() == "Unknown")
                        continue;

                    article.get_languages().add(languageInfo);
                }
            }

        }

知道问题出在哪里吗？

Answer 1

问题中的代码选择文档的一部分，将其保存到一个变量，选择该变量的一部分，将其保存到一个新变量，等等。另一种可能的实现是使用 selector syntax更严格地只选择需要的元素，而不是将这些中间步骤保存在新对象中。

下面的代码在我的机器上执行了 2 秒。上面的类似摘录在大约 4 秒内执行。随后的时间更接近，相差大约 50 毫秒，因此请对此持保留态度。

我不知道 kitkat 是否存在性能问题。您可能会发现将计时器添加到您的 kitkat 和 dalvik 版本以隔离是否存在性能瓶颈以及在何处存在性能瓶颈很有帮助。

这是我的代码:

long start = System.currentTimeMillis();
Document hDoc = Jsoup.
    connect("https://en.m.wikipedia.org/wiki/Dusseldorf").
    userAgent("Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.57 Safari/537.17").
    get();

//select the first html element, then take the value of the lang attribute
String langCode = hDoc.select("html:eq(0)").attr("lang");
String title = hDoc.getElementById("section_0").text();

Document documentNode = hDoc.ownerDocument();

//select all the image elements having the attribute src which are
//descended from the first element with the content class
Elements imgElementsHavingSrcAttr = documentNode.select("*.content:eq(0) img[src]");
Element htmlNode;

//for each img element
for (Element img : imgElementsHavingSrcAttr)
{
    htmlNode = img;
    String src = img.attr("src");

    if (src.startsWith("//"))
    {
        htmlNode.attr("src", String.format("http:%s", src));
    }
}
System.out.println("Function took " + (System.currentTimeMillis()-start) + "ms");