java - Android Mysql从表中获取特定数据

Question

我这里有我的java代码。

package com.atthesis.ticmip;

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.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;

public class Mainusersdictionary extends ListActivity {
    // Progress Dialog
    private ProgressDialog pDialog;

    // Creating JSON Parser object
    JSONParser jParser = new JSONParser();

    ArrayList<HashMap<String, String>> dilist;

    // url to get all products list
    private static String url_all_dictionary = "http://10.0.2.2/android/get_dictionary.php";

    // JSON Node names
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_dictionary = "disease";
    private static final String TAG_RID = "rid";
    private static final String TAG_NAME = "disease";

    // products JSONArray
    JSONArray diseases = null;


        public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_usersdictionary);
        setTitle("Mga Sakit");

        StrictMode.enableDefaults();
     // Hashmap for ListView
        dilist = new ArrayList<HashMap<String, String>>();

        // Loading products in Background Thread
        new LoadAlldisease().execute();

        // Get listview
        //ListView lv = getListView();
        ListView lv =(ListView)findViewById(android.R.id.list);





    }


        /**
         * Background Async Task to Load all product by making HTTP Request
         * */
        class LoadAlldisease extends AsyncTask<String, String, String> {

            /**
             * Before starting background thread Show Progress Dialog
             * */
            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                pDialog = new ProgressDialog(Mainusersdictionary.this);
                pDialog.setMessage("Loading diseases. 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_dictionary, "GET", params);

                // Check your log cat for JSON reponse
                Log.d("Diseases: ", json.toString());

                try {
                    // Checking for SUCCESS TAG
                    int success = json.getInt(TAG_SUCCESS);

                    if (success == 1) {
                        // products found
                        // Getting Array of Products
                        diseases = json.getJSONArray(TAG_dictionary);

                        // looping through All Products
                        for (int i = 0; i < diseases.length(); i++) {
                            JSONObject c = diseases.getJSONObject(i);

                            // Storing each json item in variable
                            String rid = c.getString(TAG_RID);
                            String reg = 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_RID, rid);
                            map.put(TAG_NAME, reg);

                            // adding HashList to ArrayList
                            dilist.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);*/
                        Toast.makeText(getApplicationContext(), "No Region", Toast.LENGTH_LONG).show();

                    }
                } 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(
                                Mainusersdictionary.this, dilist,
                                R.layout.ctxtview, new String[] { TAG_RID,
                                        TAG_NAME},
                                new int[] { R.id.rid, R.id.name });
                        // updating listview
                        ListView lv =(ListView)findViewById(android.R.id.list);
                        lv.setAdapter(adapter);
                        //setListAdapter(adapter);

                    }
                });

            }

        }





}

和一个可以从 mysql 检索数据的 php 文件

<?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 rid, disease FROM ddictionary") or die(mysql_error());

// check for empty result
if (mysql_num_rows($result) > 0) {
    // looping through all results
    // products node
    $response["diseases"] = array();

    while ($row = mysql_fetch_array($result)) {
        // temp user array
        $diseases = array();
        $diseases["rid"] = $row["rid"];
        $diseases["disease"] = $row["disease"];



        // push single product into final response array
        array_push($response["diseases"], $regions);
    }
    // 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);
}
?>

我收到错误

01-28 20:48:26.517: E/JSON Parser(5033): Error parsing data org.json.JSONException: Value <br of type java.lang.String cannot be converted to JSONObject
01-28 20:48:26.582: I/Choreographer(5033): Skipped 427 frames!  The application may be doing too much work on its main thread.
01-28 20:48:26.991: I/Choreographer(5033): Skipped 104 frames!  The application may be doing too much work on its main thread.
01-28 20:48:27.096: E/AndroidRuntime(5033): FATAL EXCEPTION: AsyncTask #1
01-28 20:48:27.096: E/AndroidRuntime(5033): Process: com.atthesis.ticmip, PID: 5033
01-28 20:48:27.096: E/AndroidRuntime(5033): java.lang.RuntimeException: An error occured while executing doInBackground()
01-28 20:48:27.096: E/AndroidRuntime(5033):     at android.os.AsyncTask$3.done(AsyncTask.java:300)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.FutureTask.run(FutureTask.java:242)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.lang.Thread.run(Thread.java:818)
01-28 20:48:27.096: E/AndroidRuntime(5033): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String org.json.JSONObject.toString()' on a null object reference
01-28 20:48:27.096: E/AndroidRuntime(5033):     at com.atthesis.ticmip.Mainusersdictionary$LoadAlldisease.doInBackground(Mainusersdictionary.java:97)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at com.atthesis.ticmip.Mainusersdictionary$LoadAlldisease.doInBackground(Mainusersdictionary.java:1)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
01-28 20:48:27.096: E/AndroidRuntime(5033):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
01-28 20:48:27.096: E/AndroidRuntime(5033):     ... 4 more

此错误导致我的应用程序停止。那么解决这个问题的解决方案或方法是什么。我在这里制作了所有谷歌的东西，但对我的应用程序没有影响。请帮我解决这个问题，或者这里有什么更好的代码？预先感谢先生

Answer 1

您能否发布服务器调用的输出？ IE。打开这个网址:

http://10.0.2.2/android/get_dictionary.php

在您的浏览器中查看您得到的内容。

留言

"Value <br of type java.lang.String"

表明应用程序收到的响应的起始字符是 HTML 代码而不是 JSON 数组。可能是服务器端的一些错误/警告/通知输出。

<小时/>

编辑 1

我只是想查看实际的服务器响应，看看您的服务器是否返回有效的 JSON 对象。我看到的方式是，在 JSONParser 类(我假设是您自己编写的类)中的某个位置，您正在使用不是真正的 JSON 数据的数据创建 JSONObject，或者至少不被识别为 JSON 数据。

我会探索两个选项:

1. 创建一个静态 .json 文件，其中包含您确信内容正确的内容，并在应用程序中使用该文件而不是 PHP 文件输出。如果工作正常，您就知道问题出在服务器上，而不是应用程序中。

2. 从您发布的 php 文件中，不清楚您是否已将服务器的输出 header 设置为 app/json。尽管这不是强制性的，但我建议您始终指定生成的输出 header ，例如:

   header('内容类型:application/json');

将其放在 echo json_encode(...) 行的前面。 (但是，在发送 header 之前，您不能从服务器获得任何其他输出(回显或错误消息)，否则您将收到错误消息。)

我建议您尝试这两个选项，并让我们知道发生了什么/发生了变化。