Android

Question

任何人都可以帮助我理解这个错误吗？我尝试解析 xml 文件并获取内容。但每次我收到这个错误。有很多人有类似的错误，但还没有帮助我。

08-17 10:34:18.589 25213-25567/com.example.entwicklung1.designtestapp E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #2
                                                                                    Process: com.example.entwicklung1.designtestapp, PID: 25213
                                                                                    java.lang.RuntimeException: An error occurred while executing doInBackground()
                                                                                        at android.os.AsyncTask.done(AsyncTask.java:309)
                                                                                        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:354)
                                                                                        at java.util.concurrent.FutureTask.setException(FutureTask.java:223)
                                                                                        at java.util.concurrent.FutureTask.run(FutureTask.java:242)
                                                                                        at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234)
                                                                                        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
                                                                                        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
                                                                                        at java.lang.Thread.run(Thread.java:818)
                                                                                     Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'org.w3c.dom.NodeList org.w3c.dom.Node.getChildNodes()' on a null object reference
                                                                                        at com.example.entwicklung1.designtestapp.ReadRssZander.ProcessXml(ReadRssZander.java:66)
                                                                                        at com.example.entwicklung1.designtestapp.ReadRssZander.doInBackground(ReadRssZander.java:58)
                                                                                        at com.example.entwicklung1.designtestapp.ReadRssZander.doInBackground(ReadRssZander.java:29)
                                                                                        at android.os.AsyncTask.call(AsyncTask.java:295)
                                                                                        at java.util.concurrent.FutureTask.run(FutureTask.java:237)
                                                                                        at android.os.AsyncTask$SerialExecutor.run(AsyncTask.java:234) 
                                                                                        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113) 
                                                                                        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588) 
                                                                                        at java.lang.Thread.run(Thread.java:818)

这是我的代码的一部分。我什至无法使用 "item" 查找子项。我已经在这里得到错误：NodeList items = channel.getChildNodes();

@Override
protected Void doInBackground(Void... params) {
    ProcessXml(Getdata());
    return null;
}

private void ProcessXml(Document data) {
    if(data!=null) {
        Element root = data.getDocumentElement();
        Node channel = root.getChildNodes().item(1);
        NodeList items = channel.getChildNodes();

        //for(int i=0;i<items.getLength();i++){
        //    Node currentchild = items.item(i);
        //    Log.d("textcontent",currentchild.getTextContent());
           // if(currentchild.getNodeName().equalsIgnoreCase("item")){
           //     NodeList itemchilds=currentchild.getChildNodes();
           //     for(int j=0;j<itemchilds.getLength();j++){
           //         Node current= itemchilds.item(j);
           //         Log.d("textcontent",current.getTextContent());
           //     }
           // }
        //}
    }
}

public Document Getdata(){
    try {
        url = new URL(adress);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        InputStream inputStrem = connection.getInputStream();
        DocumentBuilderFactory builderFactory=DocumentBuilderFactory.newInstance();
        DocumentBuilder builder=builderFactory.newDocumentBuilder();
        Document xmlDoc =builder.parse(inputStrem);
        return xmlDoc;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

这是 XML 文件，我尝试解析：Link

Answer 1

我找到了解决问题的办法。我找错东西了。

我需要的正确项目是 Node channel = root.getChildNodes().item(0); 而不是 Node channel = root.getChildNodes().item(1);

Android - 空对象引用，正在解析 RSS 文件

Android - null object reference, Parsing RSS file

parsing

rss-reader