获取JSOUP索引不起作用

时间:2016-10-01 01:54:57

标签: java android attributes jsoup

try {
    String url = "http://www.billboard.com/charts/artist-100";
    String urlFound;
    String closing = ")";
    String start = "h";
    Document doc = Jsoup.connect(url).get();
    Elements urls = doc.getElementsByClass("chart-row__image");
    for (Element u : urls) {
        urlFound = u.attr("style");
        String sub =  urlFound.substring(urlFound.indexOf(start), urlFound.indexOf(closing));
        System.out.println(sub);
        //Log.d("URLS,", attr.substring(attr.indexOf("http://"), attr.indexOf(")")));
    }
}
catch(IOException ex){
}

我尝试过多次调试,但我一直收到错误,Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1我不知道为什么会发生这种情况?有人能让我知道可能出现的问题吗?

1 个答案:

答案 0 :(得分:1)

您从所有div class="chart-row__image元素中提取样式属性字符串,但要了解该组中的许多元素都没有样式属性。在这种情况下,JSoup返回一个空字符串,这会搞乱你的程序。解决方案不是这样做,而是让jsoup只选择那些具有style属性的元素。

例如,不是:

Elements urls = doc.getElementsByClass("chart-row__image");

而是:

Elements urls = doc.select(".chart-row__image[style]");

是的,不要忽视例外。

所以

    String url = "http://www.billboard.com/charts/artist-100";
    String urlFound;
    String closing = ")";
    String start = "h";
    Document doc;
    try {
        doc = Jsoup.connect(url).get();
        // Elements urls = doc.getElementsByClass("chart-row__image");
        Elements urls = doc.select(".chart-row__image[style]");
        for (Element u : urls) {
            urlFound = u.attr("style");
            int startingIndex = urlFound.indexOf(start);
            int endingIndex = urlFound.indexOf(closing);
            if (startingIndex > 0 && endingIndex > 0) {
                String sub = urlFound.substring(startingIndex, endingIndex);
                System.out.println(sub);
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }