add the value in Arraylist in hashmap android

问题

I have to fetch the lis of data.

So i have used the arraylist of string with list.here how can i add the value on map.

I have used below code:

       static final String KEY_TITLE = "Category";
         static final String KEY_ARTICLE = "article";
          static final String KEY_IMAGE = "image";


 final ArrayList<HashMap<String,  List<String>>> songsList = new ArrayList<HashMap<String,  List<String>>>();
        XMLParser parser = new XMLParser();
        String xml = parser.getXmlFromUrl(URL); // getting XML from URL
        Document doc = parser.getDomElement(xml); // getting DOM element

        NodeList nl = doc.getElementsByTagName(KEY_TITLE);
        NodeList nl1 = doc.getElementsByTagName(KEY_ARTICLE);
        NodeList nl2 = doc.getElementsByTagName(KEY_IMAGE);
        System.out.println(nl.getLength());
        for (int i = 0; i < nl.getLength(); i++) {
           //System.out.println(nl.getLength());
            HashMap<String, List<String>> map = new HashMap<String, List<String>>();
            map.put( KEY_TITLE,((Element)nl.item(i)).getAttribute("name"));
           for (int j = 0; j < nl1.getLength(); j++) {
              map.put( KEY_ARTICLE,((Element)nl1.item(j)).getAttribute("title"));
              map.put( KEY_IMAGE,((Element)nl2.item(j)).getAttribute("url"));
             }
           songsList.add(map);
          }

Here am getting the below error on these (map.put( KEY_TITLE,((Element)nl.item(i)).getAttribute("name"));) line:

The method put(String, List<String>) in the type HashMap<String,List<String>> is not applicable for the arguments (String, String)

How can i clear these error ..pls provide me solution for these ...

回答1:

at this line

 map.put( KEY_TITLE,((Element)nl.item(i)).getAttribute("name"));

you are adding a single string to instead of List

You have to create a List of String at that point and add your String to it and at the list to your map.

e.g.:

  List<String> myList= new ArrayList<String>();
  myList.add((Element)nl.item(i)).getAttribute("name"));
  map.put( KEY_TITLE,myList);

you have a loop. I think that i know what you want to achieve i'll update my code. This can help you avoiding overriding the map input

HashMap<String, List<String>> map = new HashMap<String, List<String>>();

        for(int i = 0; i < nl.getLength(); i++) {
             String name = (Element) nl.item(i)).getAttribute("name");
             populateMap(map, name, KEY_TITLE);
            for(int j = 0; j < nl1.getLength(); j++) {
                String title=(Element) nl1.item(j)).getAttribute("title");
                populateMap(map, title, KEY_ARTICLE);

                String url=(Element) nl2.item(j)).getAttribute("url");
                populateMap(map, url, KEY_IMAGE);
            }
            songsList.add(map);
        }

Method populateMap()

void populateMap(HashMap<String, List<String>> map, String value, String key) {
        List<String> myList;
        if(!map.containsKey(key)) {
            myList = new ArrayList<String>();
            myList.add(value);
            map.put(key, myList);
        } else {
            myList = map.get(key);
            myList.add(value);
        }
    }

回答2:

You get that error because a String is not a List<String>.

Either change your map declaration to HashMap<String, String> or enclose your String into a List<String> and give it to the method.

回答3:

The key you're passing in is wrong. You're passing in a string, you need to pass in a list of strings. So create a list, stick the value you're trying to pass into the hash map into the list, then put that list into the hash map.

来源：https://stackoverflow.com/questions/15738659/add-the-value-in-arrayliststring-liststring-in-hashmap-android

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java