如何在Android的ListView中显示来自MySQL的数据？

Question

I can insert data into database but now face the problem that cannot retrieve data from the database and display in listview in android. Here is my coding part for retrieve data. Hope someone can help to solve this, thank you.

package com.example.iuum;


private ProgressDialog pDialog;


private static final String READ_COMMENTS_URL = "http://10.19.229.212/webservice/comments.php";


private static final String TAG_SUCCESS = "success";
private static final String TAG_TITLE = "title";
private static final String TAG_POSTS = "posts";
private static final String TAG_POST_ID = "post_id";
private static final String TAG_USERNAME = "username";
private static final String TAG_MESSAGE = "message";

private JSONArray mComments = null;

private ArrayList<HashMap<String, String>> mCommentList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_forum1a);
}

@Override
protected void onResume() {

    super.onResume();

    new LoadComments().execute();
}

public void clickbtnWrite(View v) {
    Intent i = new Intent(Forum1a.this, AddForum.class);
    startActivity(i);
}

/**
 * Retrieves recent post data from the server.
 */
public void updateJSONdata() {


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


    JSONParser jParser = new JSONParser();

    JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);


    try {


        mComments = json.getJSONArray(TAG_POSTS);


        for (int i = 0; i < mComments.length(); i++) {
            JSONObject c = mComments.getJSONObject(i);

            // gets the content of each tag
            String title = c.getString(TAG_TITLE);
            String content = c.getString(TAG_MESSAGE);
            String username = c.getString(TAG_USERNAME);


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

            map.put(TAG_TITLE, title);
            map.put(TAG_MESSAGE, content);
            map.put(TAG_USERNAME, username);


            mCommentList.add(map);


        }

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

/**
 * Inserts the parsed data into the listview.
 */
private void updateList() {

    ListAdapter adapter = new SimpleAdapter(this, mCommentList,
            R.layout.singelpost, new String[] { TAG_TITLE, TAG_MESSAGE,
                    TAG_USERNAME }, new int[] { R.id.title, R.id.message,
                    R.id.username });


    setListAdapter(adapter);


    ListView lv = getListView();    
    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {



        }
    });
}



public class LoadComments extends AsyncTask<Void, Void, Boolean> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(Forum1a.this);
        pDialog.setMessage("Loading Comments...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected Boolean doInBackground(Void... arg0) {
        updateJSONdata();
        return null;

    }

    @Override
    protected void onPostExecute(Boolean result) {
        super.onPostExecute(result);
        pDialog.dismiss();
        updateList();
    }
}
}

Answer 1

Add ListView in activity_forum1a.xml

<ListView
    android:id="@+id/list_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"></ListView>

Take ListView reference

    private ListView mList;

Initialize it in onCreate

    mList = (ListView) findViewById(R.id.list_view);

Take ListAdapter class Refernce

private ListAdapter listAdapter;

Add setListAdapter method

public void setListAdapter(ListAdapter listAdapter) {
    this.listAdapter = listAdapter;
    mList.setAdapter(listAdapter);
}

Change updateList method to

    /**
     * Inserts the parsed data into the listview.
     */
    private void updateList() {

        ListAdapter adapter = new SimpleAdapter(this, mCommentList,
                R.layout.test, new String[] { TAG_TITLE, TAG_MESSAGE,
                TAG_USERNAME }, new int[] { R.id.title, R.id.message,
                R.id.username });

        setListAdapter(adapter);
}

and perform item click operation outside from the method, by implementing onItemClickListener