我目前正在学习构建一个通过我网站上的php webservice连接到mySQL数据库的Android应用程序，并从中提取有关不同商店的信息。
我一直在从一个教程中学习并且遇到错误'java.lang.RuntimeException：执行doInBackground时发生错误'。我在这里搜索了很多年，已经回答的问题似乎对我的情况没有帮助。因此想知道你是否可以提供帮助？
我的代码：
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
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.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 AllShopsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> shopsList;
// url to get all shops list
private static final String url_all_shops = "http://www.mywebsitename.biz/android_connect/get_all_shops.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_SHOPS = "shops";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
// shops JSONArray
JSONArray shops = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_shops);
// Hashmap for ListView
shopsList = new ArrayList<HashMap<String, String>>();
// Loading shops in Background Thread
new LoadAllshops().execute();
// Get listview
ListView lv = getListView();
// on seleting single shop
// launching Edit shop 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(),
EditshopAcivity.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 shop 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 shop
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all shop by making HTTP Request
* */
class LoadAllshops extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(AllShopsActivity.this);
pDialog.setMessage("Loading shops. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All shops 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_shops, "GET", params);
// Check your log cat for JSON reponse
//Log.d("All shops: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// shops found
// Getting Array of shops
shops = json.getJSONArray(TAG_SHOPS);
// looping through All shops
for (int i = 0; i < shops.length(); i++) {
JSONObject c = shops.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
shopsList.add(map);
}
} else {
// no shops found
// Launch Add New shop Activity
Intent i = new Intent(getApplicationContext(),
NewshopActivity.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 shops
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
AllShopsActivity.this, shopsList,
R.layout.list_item, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
我注意到行protected String doInBackground(String... args)有'字符串......'我之前没有看到过这是一个问题，还是意味着
退出投注：
08-24 23:44:50.837: E/AndroidRuntime(1709): FATAL EXCEPTION: AsyncTask #1
08-24 23:44:50.837: E/AndroidRuntime(1709): java.lang.RuntimeException: An error occured while executing doInBackground()
08-24 23:44:50.837: E/AndroidRuntime(1709): at android.os.AsyncTask$3.done(AsyncTask.java:299)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
08-24 23:44:50.837: E/AndroidRuntime(1709): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.lang.Thread.run(Thread.java:856)
08-24 23:44:50.837: E/AndroidRuntime(1709): Caused by: java.lang.NullPointerException
08-24 23:44:50.837: E/AndroidRuntime(1709): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:138)
08-24 23:44:50.837: E/AndroidRuntime(1709): at com.example.androidhive.AllProductsActivity$LoadAllProducts.doInBackground(AllProductsActivity.java:1)
08-24 23:44:50.837: E/AndroidRuntime(1709): at android.os.AsyncTask$2.call(AsyncTask.java:287)
08-24 23:44:50.837: E/AndroidRuntime(1709): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
08-24 23:44:50.837: E/AndroidRuntime(1709): ... 5 more
我检查了我的db_config.php文件，服务器，密码和用户都是正确的。有什么建议吗？
编辑： 添加清单详细信息：
<!-- Internet Permissions -->
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:configChanges="keyboardHidden|orientation"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- All Product Activity -->
<activity
android:name=".AllProductsActivity"
android:label="All Products" >
</activity>
编辑2：JSONPARSER
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();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
答案 0 :(得分：3)
鉴于您的JSONParser代码，似乎返回值保持为null并返回如下：jObj
您正在捕捉大多数例外并打印出一些消息，请检查它们。
此外，主要原因似乎是您的网址没有返回任何内容，就像您在评论中所说的那样。
所以，基本上，只需确保URL确实返回您所期望的并调试JSONParser组件。