java - 解析数据时出错 org.json.JSONException : End of input at character 0 of - Android

Question

我正在开发一个测试 Android 应用程序，它必须显示来自 mysql 数据库的一些数据。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();
            }

这里是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);
                }
            });

        }

    }
}

这里是 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，这里主要的Activity:

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帖子，但它甚至是由不同的问题引起的，而且我没有找到与我类似的案例或解决我的问题的解决方案。

Answer 1

看起来您的 PHP 文件正在返回无效响应。

如果您正在编写一个返回 JSON 的处理程序，它无论如何都应该返回有效的 JSON 响应。

它应该是这样的:

$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();
?>