我希望制作一个Android聊天室应用程序,使用PHP、MYSQL作为web服务,并在我的Android应用程序中解析JSON数据。一开始我能够查看数据,但即使在我的数据库中更新后,我也无法在我的应用程序中更新数据,必须重新运行应用程序才能获取更新的数据。我该如何解决这个问题。
代码:
package com.example.androidhive;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Timer;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
//import com.mekya.R;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
public class AllProductsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> all_chat;
// url to get all products list
private static String url_all_products = "http://url.com/chat-app/";
// JSON Node names
private static final String TAG_CHAT = "chat";
private static final String TAG_FROM = "from_u";
private static final String TAG_MESSAGE = "message";
private static final String TAG_DATE = "date";
// products JSONArray
JSONArray chat = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
// Hashmap for ListView
all_chat = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllProductsActivity.this);
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_products, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
// products found
// Getting Array of Products
chat = json.getJSONArray(TAG_CHAT);
// looping through All Products
for (int i = 0; i < chat.length(); i++) {
JSONObject c = chat.getJSONObject(i);
// Storing each json item in variable
String date = c.getString(TAG_DATE);
String from = c.getString(TAG_FROM);
String message = c.getString(TAG_MESSAGE);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_DATE, date);
map.put(TAG_FROM, from);
map.put(TAG_MESSAGE, message);
// adding HashList to ArrayList
all_chat.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AllProductsActivity.this, all_chat, R.layout.list_item, new String[] { TAG_FROM,TAG_DATE, TAG_MESSAGE },
new int[] { R.id.from,R.id.date, R.id.message });
// updating listview
setListAdapter(adapter);
}
});
}
}
}