我正在使用 AsyncTask 来显示通过 PHP 和 JSON 从数据库提供的数据，所以当我尝试用完我的应用程序时，我得到了那个错误：
09-20 15:31:51.330: E/Buffer Error(4484): Error converting result java.lang.NullPointerException
09-20 15:31:51.330: E/JSON Parser(4484): Error parsing data org.json.JSONException: End of input at character 0 of
这是我的 Java 类：
package com.androidhive.dashboard;
import android.app.Activity;
import android.app.ListActivity;
import android.os.Bundle;
import androidhive.dashboard.R;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.NameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.util.Log;
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;
import android.widget.TextView;
public class PlacesActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> productsList;
// url to get all products list
private static String url_all_products = "http://192.168.1.74/test/focus.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "products";
private static final String TAG_PID = "pid";
private static final String LIB_ART = "LibArt";
private static final String COD_ART = "CodArt";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.places_layout);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
}//onCreate finish
// Response from Edit Product Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* 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(PlacesActivity.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 {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String LibArt = c.getString(LIB_ART);
String CodArt = c.getString(COD_ART);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(LIB_ART, LibArt);
map.put(COD_ART,CodArt);
// adding HashList to ArrayList
productsList.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(
PlacesActivity.this, productsList,
R.layout.list_item, new String[] { COD_ART,TAG_PID,
LIB_ART},
new int[] { R.id.codart ,R.id.pid, R.id.libart });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
这里是 PHP 文件：
<?php
require 'FastJSON.class.php';
$db = mssql_connect ('HPWALID', '', '');
$ret = mssql_select_db ('Focus', $db) or die ('Echec lors de la connexion: '.mysql_error ());
$result = mssql_query("SELECT * FROM TabStock");
if (mssql_num_rows($result) > 0) {
// looping through all results
// products node
$response["products"] = array();
while ($row = mssql_fetch_array($result)) {
// temp user array
$product = array();
$product["CodArt"] = $row["CodArt"];
$product["LibArt"] = $row["LibArt"];
$product["pid"] = $row["pid"];
// push single product into final response array
array_push($response["products"], $product);
}
// success
$response["success"] = 1;
// echoing JSON response
$var = FastJSON::encode($response);
echo $var;
} else {
// no products found
$response["success"] = 0;
$response["message"] = "No products found";
// echo no users JSON
// echo json_encode($response);
$var = FastJSON::encode($response);
echo $var;
}
?>