主线程网络

问题描述

当我尝试实现以下代码时收到 NetworkOnMainThreadException:

I get a NetworkOnMainThreadException when I try to implement the following code:

public class HandlingXMLStuff extends ListActivity{
static final String URL = "xml_file";

 static final String ITEM = "item"; //parent
    static final String Id = "id";
    static final String Name = "name";
    static final String Desc = "desc";
    static final String Link = "Link";

@Override
public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.xmllist);

ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();

xmlparser parser = new xmlparser();
String xml = parser.getXmlFromUrl(URL);
Document doc = parser.getDomElement(xml);


NodeList nl = doc.getElementsByTagName(ITEM);


//START: loop through all item nodes <item>
for (int i = 0;i<nl.getLength();i++){
    //lets create our HASHMAP!! (feeds items into our ArrayList)
    HashMap<String, String> map = new HashMap<String, String>();
    Element e = (Element) nl.item(i);
    //add each child node to the HashMap (key, value/<String, String>)
    map.put(Name, parser.getValue(e, Name));
    map.put(Desc, parser.getValue(e, Desc));
    map.put(Link, parser.getValue(e, Link));


    menuItems.add(map);

}//DONE


ListAdapter adapter = new SimpleAdapter(this, menuItems, R.layout.list_item,
        new String[] {Name, Desc, Link}, new int []{R.id.name, R.id.description, R.id.link});

setListAdapter(adapter);
        }
}

和处理程序:

public class xmlparser{

public String getXmlFromUrl(String url) {
String xml = null;

try {

    DefaultHttpClient httpClient = new DefaultHttpClient();
    HttpPost httpPost = new HttpPost(url);

    HttpResponse httpResponse = httpClient.execute(httpPost);
    HttpEntity httpEntity = httpResponse.getEntity();
    xml = EntityUtils.toString(httpEntity);

} catch (UnsupportedEncodingException e) {
    e.printStackTrace();
} catch (ClientProtocolException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

return xml;
}
public Document getDomElement(String xml){
    Document doc = null;
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    try {

        DocumentBuilder db = dbf.newDocumentBuilder();

        InputSource is = new InputSource();
            is.setCharacterStream(new StringReader(xml));
            doc = db.parse(is);

        } catch (ParserConfigurationException e) {
            Log.e("Error: ", e.getMessage());
            return null;
        } catch (SAXException e) {
            Log.e("Error: ", e.getMessage());
            return null;
        } catch (IOException e) {
            Log.e("Error: ", e.getMessage());
            return null;
        }

        return doc;
  }

public String getValue(Element item, String str) {
        NodeList n = item.getElementsByTagName(str);
        return this.getElementValue(n.item(0));
    }

public final String getElementValue( Node elem ) {
         Node child;
         if( elem != null){
             if (elem.hasChildNodes()){
                 for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){
                     if( child.getNodeType() == Node.TEXT_NODE  ){
                         return child.getNodeValue();
                     }
                 }
             }
         }
         return "";
  }

}

知道为什么吗?它应该可以工作，我读过的所有教程都将其视为工作代码，但它不会运行，只会引发异常.我读过我可能需要实现 asynctask 但我不熟悉它并且不确定哪些部分需要他们自己的线程.感谢您的任何帮助、批评(建设性)、建议等.

Any idea why? It should work, all the tutorials I've read treat this as working code but it doesn't run and only throws the exception. I've read I might need to implement asynctask but im new to it and not sure what parts need their own thread. Thanks for any help, critique (constructive), suggestions, etc.

推荐答案

因为，如果那段代码正在主应用程序线程上执行，那么您就是在主应用程序线程上进行网络 I/O.

Because, if that hunk of code is being executed on the main application thread, you are doing network I/O on the main application thread.

我读过我可能需要实现 asynctask 但我不熟悉它并且不确定哪些部分需要他们自己的线程.

我会将网络 I/O 和解析放在 doInBackground() 中，并将 setListAdapter() 调用放在 onPostExecute() 中一个 AsyncTask.

I would put the network I/O and the parsing in doInBackground() and the setListAdapter() call in onPostExecute() of an AsyncTask.

这篇关于主线程网络的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！