解析数据org.json.JSONException时出错：字符0的输入结束-Android
何博涛
问题内容：
问题答案：
我正在开发一个测试Android应用程序，该应用程序必须显示mysql数据库中的一些数据。这是我的日志：
05-22 17:10:56.865: E/JSON Parser(31648): Error parsing data org.json.JSONException: End of input at character 0 of
05-22 17:10:56.865: W/dalvikvm(31648): threadid=11: thread exiting with uncaught exception (group=0x418e3da0)
05-22 17:10:56.875: E/AndroidRuntime(31648): FATAL EXCEPTION: AsyncTask #1
05-22 17:10:56.875: E/AndroidRuntime(31648): Process: com.example.androidhive, PID: 31648
05-22 17:10:56.875: E/AndroidRuntime(31648): java.lang.RuntimeException: An error occured while executing doInBackground()
05-22 17:10:56.875: E/AndroidRuntime(31648): at android.os.AsyncTask$3.done(AsyncTask.java:300)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.lang.Thread.run(Thread.java:841)
05-22 17:10:56.875: E/AndroidRuntime(31648): Caused by: java.lang.NullPointerException
05-22 17:10:56.875: E/AndroidRuntime(31648): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:130)
05-22 17:10:56.875: E/AndroidRuntime(31648): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:1)
05-22 17:10:56.875: E/AndroidRuntime(31648): at android.os.AsyncTask$2.call(AsyncTask.java:288)
05-22 17:10:56.875: E/AndroidRuntime(31648): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
05-22 17:10:56.875: E/AndroidRuntime(31648): ... 3 more
05-22 17:10:57.436: D/AbsListView(31648): onDetachedFromWindow
05-22 17:10:57.436: D/AbsListView(31648): unregisterIRListener() is called
05-22 17:10:57.446: E/WindowManager(31648): android.view.WindowLeaked: Activity com.example.androidhive.AllProductsActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{42c02238 V.E..... R.....ID 0,0-914,346} that was originally added here
05-22 17:10:57.446: E/WindowManager(31648): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:456)
05-22 17:10:57.446: E/WindowManager(31648): at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:267)
05-22 17:10:57.446: E/WindowManager(31648): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.Dialog.show(Dialog.java:288)
05-22 17:10:57.446: E/WindowManager(31648): at com.example.androidhive.AllProductsActivity$LoadAllProducts.onPreExecute(AllProductsActivity.java:117)
05-22 17:10:57.446: E/WindowManager(31648): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587)
05-22 17:10:57.446: E/WindowManager(31648): at android.os.AsyncTask.execute(AsyncTask.java:535)
05-22 17:10:57.446: E/WindowManager(31648): at com.example.androidhive.AllProductsActivity.onCreate(AllProductsActivity.java:57)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.Activity.performCreate(Activity.java:5426)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2269)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.ActivityThread.access$900(ActivityThread.java:161)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
05-22 17:10:57.446: E/WindowManager(31648): at android.os.Handler.dispatchMessage(Handler.java:102)
05-22 17:10:57.446: E/WindowManager(31648): at android.os.Looper.loop(Looper.java:157)
05-22 17:10:57.446: E/WindowManager(31648): at android.app.ActivityThread.main(ActivityThread.java:5356)
05-22 17:10:57.446: E/WindowManager(31648): at java.lang.reflect.Method.invokeNative(Native Method)
05-22 17:10:57.446: E/WindowManager(31648): at java.lang.reflect.Method.invoke(Method.java:515)
05-22 17:10:57.446: E/WindowManager(31648): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
05-22 17:10:57.446: E/WindowManager(31648): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
05-22 17:10:57.446: E/WindowManager(31648): at dalvik.system.NativeStart.main(Native Method)
05-22 17:11:01.279: I/Process(31648): Sending signal. PID: 31648 SIG: 9
这里是JSONParser.java类
package com.example.androidhive;
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() {
}
// 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();
}
在这里，我用来显示所选数据的类：
package com.example.androidhive;
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.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.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>> productsList;
// url to get all products list
private static String url_all_products = "http://10.1.20.10/android/get_all_products.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 TAG_NAME = "name";
// products JSONArray
JSONArray products = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_products);
// Hashmap for ListView
productsList = new ArrayList<HashMap<String, String>>();
// Loading products in Background Thread
new LoadAllProducts().execute();
// Get listview
ListView lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),
EditProductActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, pid);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
}
});
}
// 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(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 {
// 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 name = c.getString(TAG_NAME);
// 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(TAG_NAME, name);
// adding HashList to ArrayList
productsList.add(map);
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getApplicationContext(),
NewProductActivity.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} 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, productsList,
R.layout.list_item, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
这里的PHP文件：
get_all_products.php
<?php
/*
* Following code will list all the products
*/
// array for JSON response
$response = array();
// include db connect class
require_once __DIR__ . '/db_connect.php';
// connecting to db
$db = new DB_CONNECT();
// get all products from products table
$result = mysql_query("SELECT *FROM products") or die(mysql_error());
// check for empty result
if (mysql_num_rows($result) > 0) {
// looping through all results
// products node
$response["products"] = array();
while ($row = mysql_fetch_array($result)) {
// temp user array
$product = array();
$product["pid"] = $row["pid"];
$product["name"] = $row["name"];
$product["price"] = $row["price"];
$product["created_at"] = $row["created_at"];
$product["updated_at"] = $row["updated_at"];
// push single product into final response array
array_push($response["products"], $product);
}
// success
$response["success"] = 1;
// echoing JSON response
echo json_encode($response);
} else {
// no products found
$response["success"] = 0;
$response["message"] = "No products found";
// echo no users JSON
echo json_encode($response);
}
?>
另外，这里主要活动：
package com.example.androidhive;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class MainScreenActivity extends Activity{
Button btnViewProducts;
Button btnNewProduct;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_screen);
// Buttons
btnViewProducts = (Button) findViewById(R.id.btnViewProducts);
btnNewProduct = (Button) findViewById(R.id.btnCreateProduct);
// view products click event
btnViewProducts.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Launching All products Activity
Intent i = new Intent(getApplicationContext(), AllProductsActivity.class);
startActivity(i);
}
});
// view products click event
btnNewProduct.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Launching create new product activity
Intent i = new Intent(getApplicationContext(), NewProductActivity.class);
startActivity(i);
}
});
}
}
我在互联网上阅读了有关此错误的各种线索，但它甚至是由差异问题引起的，我没有找到与我的情况类似的情况或解决了我问题的解决方案。
问题答案：
看起来您的PHP文件正在返回无效响应。
如果您正在编写返回JSON的处理程序，则它无论如何应返回有效的JSON响应。
应该是这样的：
$response = array();
$response["success"] = 0;
$response["message"] = "No products found";
// include db connect class
require_once __DIR__ . '/db_connect.php';
// connecting to db
$db = new DB_CONNECT();
// get all products from products table
$result = mysql_query("SELECT *FROM products");
// check for empty result
if ($result && mysql_num_rows($result) > 0) {
// looping through all results
// products node
$response["products"] = array();
while ($row = mysql_fetch_array($result)) {
// temp user array
$product = array();
$product["pid"] = $row["pid"];
$product["name"] = $row["name"];
$product["price"] = $row["price"];
$product["created_at"] = $row["created_at"];
$product["updated_at"] = $row["updated_at"];
// push single product into final response array
array_push($response["products"], $product);
}
// success
$response["success"] = 1;
}
// Echo JSON anyway!
echo json_encode($response);
die();
?>
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