在listview中显示数据库中的项目,问题

currently I am working on an application that will allow the user to login/register and then post a comment/view comments. I am testing the data on a local host using XAMPP and Myphpadmin. I know the php side of things work as I have created mock interfaces and ran them via the web browser. They all interact with the database fine and display results when requested. The application so far will allow the user to sign in or register. These are registered to the database and work fine. The user can add a message to the database once signed in this is semi working as it is adding the message to the database but then this should display all messages in a listview. For some reason the listview does not seem to be functioning. If anybody has the time to have a look through and explain why it's failing to show the data then it would be greatly appreciated.

Once a comment has been posted, the user should be directed to a read comments page, this will have the option to post another comment, via the post comment button. It should also show the most recent comments in a list format. Within here is my list activity that seems to be wrong.

 package com.example.mysqltest;

 import java.util.ArrayList;
 import java.util.HashMap;
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
 import android.app.ListActivity;
 import android.app.ProgressDialog;
 import android.content.Intent;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.AdapterView;
 import android.widget.AdapterView.OnItemClickListener;
 import android.widget.ListAdapter;
 import android.widget.ListView;
 import android.widget.SimpleAdapter;

 public class ReadComments extends ListActivity {

// Progress Dialog
private ProgressDialog pDialog;

// php read comments script

// localhost :
// testing on your device
// put your local ip instead, on windows, run CMD > ipconfig
// or in mac's terminal type ifconfig and look for the ip under en0 or en1
private static final String READ_COMMENTS_URL = "http://192.168.10.112:80/webservice/comments.php";

// testing on Emulator:
// private static final String READ_COMMENTS_URL =
// "http://192.168.10.112:80/webservice/comments.php";

// testing from a real server:
// private static final String READ_COMMENTS_URL =
// "http://www.mybringback.com/webservice/comments.php";

// JSON IDS:
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";
// it's important to note that the message is both in the parent branch of
// our JSON tree that displays a "Post Available" or a "No Post Available"
// message,
// and there is also a message for each individual post, listed under the
// "posts"
// category, that displays what the user typed as their message.

// An array of all of our comments
private JSONArray mComments = null;
// manages all of our comments in a list.
private ArrayList<HashMap<String, String>> mCommentList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // note that use read_comments.xml instead of our single_post.xml
    setContentView(R.layout.read_comments);
}

@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
    // loading the comments via AsyncTask
    new LoadComments().execute();
}

public void addComment(View v) {
    Intent i = new Intent(ReadComments.this, AddComment.class);
    startActivity(i);
}

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

    // Instantiate the arraylist to contain all the JSON data.
    // we are going to use a bunch of key-value pairs, referring
    // to the json element name, and the content, for example,
    // message it the tag, and "I'm awesome" as the content..

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

    // Bro, it's time to power up the J parser
    JSONParser jParser = new JSONParser();
    // Feed the beast our comments url, and it spits us
    // back a JSON object. Boo-yeah Jerome.
    JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);

    // when parsing JSON stuff, we should probably
    // try to catch any exceptions:
    try {

        // I know I said we would check if "Posts were Avail." (success==1)
        // before we tried to read the individual posts, but I lied...
        // mComments will tell us how many "posts" or comments are
        // available
        mComments = json.getJSONArray(TAG_POSTS);

        // looping through all posts according to the json object returned
        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);

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

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

            // adding HashList to ArrayList
            mCommentList.add(map);

            // annndddd, our JSON data is up to date same with our array
            // list
        }

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

/**
 * Inserts the parsed data into the listview.
 */
private void updateList() {
    // For a ListActivity we need to set the List Adapter, and in order to
    // do
    // that, we need to create a ListAdapter. This SimpleAdapter,
    // will utilize our updated Hashmapped ArrayList,
    // use our single_post xml template for each item in our list,
    // and place the appropriate info from the list to the
    // correct GUI id. Order is important here.
    ListAdapter adapter = new SimpleAdapter(this, mCommentList,
            R.layout.single_post, new String[] { TAG_TITLE, TAG_MESSAGE,
                    TAG_USERNAME }, new int[] { R.id.title, R.id.message,
                    R.id.username });

    // I shouldn't have to comment on this one:
    setListAdapter(adapter);

    // Optional: when the user clicks a list item we
    // could do something. However, we will choose
    // to do nothing...
    ListView lv = getListView();
    lv.setOnItemClickListener(new OnItemClickListener() {

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

            // This method is triggered if an item is click within our
            // list. For our example we won't be using this, but
            // it is useful to know in real life applications.

        }
    });
}

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

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(ReadComments.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();
    }
}
    }

Finally here is my JSON parser,

    package com.example.mysqltest;

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.UnsupportedEncodingException;
 import java.util.List;

 import org.apache.http.HttpEntity;
 import org.apache.http.HttpResponse;
 import org.apache.http.NameValuePair;
 import org.apache.http.client.ClientProtocolException;
 import org.apache.http.client.entity.UrlEncodedFormEntity;
 import org.apache.http.client.methods.HttpGet;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.utils.URLEncodedUtils;
 import org.apache.http.impl.client.DefaultHttpClient;
 import org.json.JSONException;
 import org.json.JSONObject;

 import android.util.Log;

 public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(final String url) {

    // Making HTTP request
    try {
        // Construct the client and the HTTP request.
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);

        // Execute the POST request and store the response locally.
        HttpResponse httpResponse = httpClient.execute(httpPost);
        // Extract data from the response.
        HttpEntity httpEntity = httpResponse.getEntity();
        // Open an inputStream with the data content.
        is = httpEntity.getContent();

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

    try {
        // Create a BufferedReader to parse through the inputStream.
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        // Declare a string builder to help with the parsing.
        StringBuilder sb = new StringBuilder();
        // Declare a string to store the JSON object data in string form.
        String line = null;

        // Build the string until null.
        while ((line = reader.readLine()) != null) {
            sb.append(line + "
");
        }

        // Close the input stream.
        is.close();
        // Convert the string builder data to an actual string.
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // Try to parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // Return the JSON Object.
    return jObj;

}

// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
        List<NameValuePair> params) {

    // Making HTTP request
    try {

        // check for request method
        if (method == "POST") {
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);
            httpPost.setEntity(new UrlEncodedFormEntity(params));

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } else if (method == "GET") {
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }

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

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "
");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;

}
  }
douningqiu4991
douningqiu4991 谢谢,我已编辑它以使其更精确,但仍有很多内容,但我不确定问题是我的列表还是解析器。你有什么主意吗?
6 年多之前 回复
dsxi70423
dsxi70423 没问题,但我认为最好提一下代码的主要部分。事实上,它比缺乏信息更好,但它只是让一些人忽略了你的问题,而且一般来说缺乏吸引力。
6 年多之前 回复
douyi8732
douyi8732 对不起,我想我会尝试尽可能清楚,第三段代码是列表的实现位置。
6 年多之前 回复
douzhangbao2187
douzhangbao2187 它真的太长了,所有这些都是必要的吗?
6 年多之前 回复
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