java - Android XML Reader 读取一次

Question

我只是想制作一个 XML 阅读器，但遇到了一些麻烦。当我解析 XML 文件时，它说只有一个标签并只读取这个标签。但是不止一个。这是我的代码:

    @Override
    protected Void doInBackground(Void... voids) {

        try {
            URL url = new URL(QuizActivity.fileUrl);
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();

            Document document = builder.parse(new InputSource(url.openStream()));
            document.getDocumentElement().normalize();

            NodeList sorular = document.getElementsByTagName("sorular");
            Log.d("Soru Sayısı", String.valueOf(sorular.getLength()));
            for(int i = 0; i < sorular.getLength(); i++){
                Node sorularNode = sorular.item(i);
                Element sorularElement = (Element) sorularNode;

                NodeList siraNodeList = document.getElementsByTagName("sira");
                Element siraElement = (Element) siraNodeList.item(i);

                NodeList textNodeList = document.getElementsByTagName("text");
                Element textElement = (Element) textNodeList.item(i);

                NodeList aNodeList = document.getElementsByTagName("a");
                Element aElement = (Element) aNodeList.item(i);

                NodeList bNodeList = document.getElementsByTagName("b");
                Element bElement = (Element) bNodeList.item(i);

                NodeList cNodeList = document.getElementsByTagName("c");
                Element cElement = (Element) cNodeList.item(i);

                NodeList dNodeList = document.getElementsByTagName("d");
                Element dElement = (Element) dNodeList.item(i);

                NodeList eNodeList = document.getElementsByTagName("e");
                Element eElement = (Element) eNodeList.item(i);

                NodeList dogruNodeList = document.getElementsByTagName("dogru");
                Element dogruElement = (Element) dogruNodeList.item(i);

                int sira = Integer.parseInt(siraElement.getChildNodes().item(i).getNodeValue());

                SinavActivity.soruText.put(sira, textElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.cevap_a.put(sira, aElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.cevap_b.put(sira, bElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.cevap_c.put(sira, cElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.cevap_d.put(sira, dElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.cevap_e.put(sira, eElement.getChildNodes().item(i).getNodeValue());
                SinavActivity.dogruCevap.put(sira, dogruElement.getChildNodes().item(i).getNodeValue().trim());

            }

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        }
        return null;
    }

XML 文件:

<?xml version="1.0" encoding="utf-8"?>
<sorular>
<Matematik>
    <soru>
        <sira>1</sira>
        <text>Bir sınıftaki öğrencilerin % 40 ı kız öğrencidir. Kız öğrencilerin % 90 ı, erkek öğrencilerin %80 matematik dersinden başarılıdır. Buna göre, bu sınıfın matematik dersinden başarısı yüzde kaçtır?</text>
        <a>84</a>
        <b>46</b>
        <c>20</c>
        <d>12</d>
        <e>50</e>
        <dogru>A</dogru>
    </soru>
    <soru>
        <sira>2</sira>
        <text>A ve B boş olmayan 2 kümedir 2.s(A)=3.s(B)= 5.s(A ∩ B) olduğuna göre s(A-B) en az kaçtır?</text>
        <a>8</a>
        <b>10</b>
        <c>2</c>
        <d>9</d>
        <e>12</e>
        <dogru>D</dogru>
    </soru>
</Matematik>

如果我写 NodeList sorular = document.getElementsByTagName("sorular"); 它表示计数 NodeList = 1 但如果我写 NodeList sorular = document .getElementsByTagName("soru"); 它说 count = 2 但它给了我一个 NullPointerException

Answer 1

因为 siraElement.getChildNodes().getLength() 将始终返回 1 元素，所以当

siraElement.getChildNodes().item(i).getNodeValue() //i=0

所以第一个节点将位于 0 索引处，但是当 i=1 时，索引 1< 处将没有 Node/

siraElement.getChildNodes().item(i).getNodeValue() //i=1  error

所以你可以从 0 索引中获取 always

 int sira = Integer.parseInt(siraElement.getChildNodes().item(0).getNodeValue());
//                                                           ^^

对下面的所有值做同样的事情

textElement.getChildNodes().item(0).getNodeValue()
...
dogruElement.getChildNodes().item(0).getNodeValue().trim()