Question

花了好几个小时试图找出为什么＆＃34; finalURL ＆＃34; ＆＃34; fetch＆＃34;中的变量方法无法通过＆＃34; 下载程序＆＃34; 上课？非常感谢任何指针......

它是一个词汇表改进应用程序，因此它从字典api中获取XML数据。

public class DefineWord extends Activity {

    static final String head = new String("http://www.dictionaryapi.com/api/v1/references/collegiate/xml/");
    static final String apikey = new String("?key=xxxxxx-xxx-xxx-xxxx-xxxxx");

    TextView src;
    EditText searchBar;

OnCreate中：

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.defineword);

        src=(TextView)findViewById(R.id.textFromWeb);
        searchBar = (EditText)findViewById(R.id.searchBar);
    }

获取方法：

    public void fetch(View v){                                              //onClick in xml starts this "fetch" method

        String w = searchBar.getText().toString();                          // get the text the user enters into searchbar
        String finalURL = head.trim() + w.trim() + apikey.trim();           //concatenate api url 

        Downloader d = new Downloader(); 
        d.execute(finalURL);                                                // Calls AsyncTask to connect in the background.    
}

的AsyncTask：

    class Downloader extends AsyncTask<String,Void,String>{

        ArrayList<String> information = new ArrayList<String>();    // Store fetched XML data in ArrayList

        public String doInBackground(String... urls) {
            String result = null;

            try {

                DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
                DocumentBuilder builder = factory.newDocumentBuilder();

问题出在这里。＆＃34;的 finalURL ＆＃34;无法解析为变量。

                Document doc = builder.parse(finalURL);  //finalURL cannot be resolved to a variable ??? 

                doc.getDocumentElement().normalize();

                NodeList nList = doc.getElementsByTagName("entry"); // Make a list of all elements in XML file with tag name "entry" 

                for (int temp = 0; temp < nList.getLength(); temp++) {   //Iterate over elements and get their attributes (Definition, etymology...)  

                    Node nNode = nList.item(temp);

                    if (nNode.getNodeType() == Node.ELEMENT_NODE){


                        Element eElement = (Element) nNode;

                        String element = ("\nCurrent Element : " + eElement.getAttribute("id"));
                        information.add(element);  //

                        String definitions = ("\nDefinition : \n" + eElement.getElementsByTagName("dt").item(0).getTextContent());
                        information.add(definitions);
                    }

                }

            }catch (ParserConfigurationException e){
                e.printStackTrace();

            }catch(SAXException e){
                e.printStackTrace();
            }catch(IOException e){
                e.printStackTrace();
            }

            return result;
        }

        protected void onPostExecute (String result){

            String finalresult = information.toString();
            src.setText(finalresult);
        }

    }
}

感谢您的时间。

Answer 1

这称为参数。使用asyncTask.execute(parameter)将对象传递给doInBackground(String... arrayOfParameters)。

因此，要再次访问该值，您应该使用builder.parse(urls[0]);

Answer 2

finalURL在fetch方法中声明，因此只能在此函数中访问。

如果您希望在整个程序中可以访问它，请在函数之外声明它，如此。

class MyClass{
    public static String finalURL;    // variable declaration

    public void fetch(View v){ 
        finalURL = head.trim() + w.trim() + apikey.trim();   // variable assignment
    }    

    public void otherFunction(){
        Document doc = builder.parse(finalURL);    // retrieves static class variable
    }
}

我希望这能回答你的问题。如果没有，请告诉我这是一种混乱。

如何从另一个类访问变量？ android java

2 个答案: