问题
I'm developing an app in which data saved into database when there is no covered area of mobile signals. When service came back it will fetch all data from database and upload on server.
Now I have two problems.
- IntentService stops when 1st time data inserted into database.(When network service came back it also upload data on the server, for checking network connectivity I used timer.) I don't want to stop service.
- When 2nd time I start the service it created again and Gives Nullpointerexception. because there is no data in database so it also gives some other errors too about data retrivel.
Whats wrong in my code? I just want that when user starts the service it will run till last data in database and after that it will stop. I used threads in intentservice because earlier my app crash.
LogCat Error
10-14 20:44:02.135: E/Service(10042): Service Created..
10-14 20:44:02.505: E/Service Started(10042): Successful
10-14 20:44:03.585: E/Service Network(10042): Network is offline
10-14 20:44:08.656: E/Service Network(10042): Network is offline
10-14 20:44:13.616: E/Service Network(10042): Network is offline
10-14 20:44:18.646: E/Service Network(10042): Network is offline
10-14 20:44:23.595: E/Service Network(10042): Network is offline
10-14 20:44:29.526: E/Service Network(10042): Network is online
10-14 20:44:31.256: E/Data Sent(10042): Response 200
10-14 20:44:33.599: E/Service Network(10042): Network is online
10-14 20:44:34.446: E/Data Sent(10042): Response 200
10-14 20:44:38.646: E/Service Network(10042): Network is online
10-14 20:44:40.616: E/Data Sent(10042): Response 200
10-14 20:44:43.625: E/Service Network(10042): Network is offline
10-14 20:44:48.595: E/Service Network(10042): Network is offline
10-14 20:44:53.586: E/Service Network(10042): Network is offline
10-14 20:45:20.486: E/Service(10042): Service Created..
10-14 20:45:20.587: E/Service Started(10042): Successful
10-14 20:45:20.627: E/Insertion(10042): java.lang.NullPointerException
10-14 20:45:21.666: E/Service Network(10042): Network is offline
10-14 20:45:23.616: E/Service Network(10042): Network is offline
10-14 20:45:36.645: E/Service Network(10042): Network is offline
10-14 20:45:38.585: E/Service Network(10042): Network is offline
10-14 20:45:41.786: E/Service Network(10042): Network is online
10-14 20:45:42.026: E/AndroidRuntime(10042): FATAL EXCEPTION: Timer-1
10-14 20:45:42.026: E/AndroidRuntime(10042): java.lang.NullPointerException
10-14 20:45:42.026: E/AndroidRuntime(10042): at com.remote.synchronizer.haris.SQLiteAdapter.getAllContacts(SQLiteAdapter.java:93)
10-14 20:45:42.026: E/AndroidRuntime(10042): at com.remote.synchronizer.haris.OfflineDataService$1$1.run(OfflineDataService.java:80)
10-14 20:45:42.026: E/AndroidRuntime(10042): at java.util.Timer$TimerImpl.run(Timer.java:284)
10-14 20:45:43.646: E/Service Network(10042): Network is online
10-14 20:45:44.266: E/Data Sent(10042): Response 200
SQLiteAdapter.java
package com.remote.synchronizer.haris;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class SQLiteAdapter extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "Product";
public static final String TABLE_NAME = "Orders";
public static final int DATABASE_VERSION = 1;
public static final String KEY_ID = " _id"; //
public static final String KEY_NAME = "name";
public static final String KEY_SHOP = "shop";
private static final String KEY_CITY = "city";
private static final String KEY_DATE = "datee";
private static final String KEY_ORDER = "orderr";
private SQLiteDatabase sqLiteDatabase;
private SQLiteAdapter sqLiteHelper=this;
private static final String CREATE_TABLE =
"CREATE TABLE " + TABLE_NAME + " ("
+ KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ KEY_NAME + " VARCHAR,"
+ KEY_SHOP + " VARCHAR," + KEY_CITY + " VARCHAR, " + KEY_DATE + " VARCHAR, " + KEY_ORDER + " VARCHAR" +");";
public SQLiteAdapter(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
sqLiteDatabase=db;
}
/*public void close(){
sqLiteHelper.close();
}
*/
public void insert(String name, String shop, String city, String datee, String orderr){
try
{
ContentValues contentValues = new ContentValues();
contentValues.put(KEY_NAME, name);
contentValues.put(KEY_SHOP, shop);
contentValues.put(KEY_CITY, city);
contentValues.put(KEY_DATE, datee);
contentValues.put(KEY_ORDER, orderr);
sqLiteDatabase.insertOrThrow(TABLE_NAME, KEY_ID, contentValues);
//sqLiteDatabase.close();
}
catch(Exception e)
{
e.printStackTrace();
Log.e("Insertion", e.toString());
}
}
public void deleteAll(){
sqLiteDatabase.delete(TABLE_NAME, null, null);
}
public void delete_byID(int id){
sqLiteDatabase.delete(TABLE_NAME, KEY_ID+"="+id, null);
}
/*public Cursor queueAll(){
String[] columns = new String[]{KEY_ID, KEY_NAME, KEY_SHOP, KEY_CITY, KEY_DATE, KEY_ORDER};
Cursor cursor = sqLiteDatabase.query(TABLE_NAME, columns,
null, null, null, null, null);
return cursor;
}*/
public List<NameValuePair> getAllContacts() {
List<NameValuePair> postParameters = new ArrayList<NameValuePair>();
String selectQuery = "SELECT * FROM " + TABLE_NAME;
sqLiteHelper.getReadableDatabase();
Cursor cursor = sqLiteDatabase.rawQuery(selectQuery, null);
if(cursor.moveToFirst()){
while(!cursor.isAfterLast())
{
postParameters.add(new BasicNameValuePair("User", cursor.getString(cursor.getColumnIndex(KEY_NAME))));
postParameters.add(new BasicNameValuePair("ShopName", cursor.getString(cursor.getColumnIndex(KEY_SHOP))));
postParameters.add(new BasicNameValuePair("city", cursor.getString(cursor.getColumnIndex(KEY_CITY))));
postParameters.add(new BasicNameValuePair("OrderDate", cursor.getString(cursor.getColumnIndex(KEY_DATE))));
postParameters.add(new BasicNameValuePair("OrderDetail", cursor.getString(cursor.getColumnIndex(KEY_ORDER))));
cursor.moveToNext();
}
}
//cursor.close();
return postParameters;
};
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(SQLiteAdapter.class.getName(),
"Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + CREATE_TABLE);
onCreate(db);
}
}
OfflineDataService.java
package com.remote.synchronizer.haris;
import java.util.ArrayList;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;
import org.apache.http.NameValuePair;
import android.app.IntentService;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.util.Log;
public class OfflineDataService extends IntentService {
boolean wifi,edge;
private Timer timer= new Timer();
SQLiteDatabase db;
String un,shop,city,date,order;
private SQLiteAdapter mySQLiteAdapter;
Cursor cursor;
public OfflineDataService() {
super("OfflineDataService");
}
@Override
public void onCreate() {
super.onCreate();
Log.e("Service", "Service Created.. ");
mySQLiteAdapter = new SQLiteAdapter(this);
mySQLiteAdapter.getWritableDatabase();
}
@Override
protected void onHandleIntent(final Intent intent) {
final Handler threadHandler;
threadHandler = new Handler();
new Thread(new Runnable(){
@Override
public void run() {
Bundle bundle=intent.getExtras();
un=bundle.getString("un");
shop=bundle.getString("shop");
city=bundle.getString("city");
date=bundle.getString("date");
order=bundle.getString("order");
Log.e("Service Started", "Successful");
//Inserting New Record
mySQLiteAdapter.insert(un,shop,city,date,order);
timer.scheduleAtFixedRate(new TimerTask(){
@Override
public void run() {
//Checking network connectivity
wifi=NetworkInfo.Wifi(OfflineDataService.this);
edge=NetworkInfo.EDGE(OfflineDataService.this);
if(wifi==true||edge==true)
{
Log.e("Service Network", "Network is online");
List<NameValuePair> contacts=new ArrayList<NameValuePair>();
contacts=mySQLiteAdapter.getAllContacts();
String url="http://10.0.2.2:3325/Product/Create?";
int response = 0;
try
{
response = CustomHttpClient.executeHttpPost(url, contacts);
if(response==200)
{
Log.e("Data Sent", "Response 200");
}
else{
Log.e("Service Data", "Faield to upload data" );
}
}
catch (Exception e)
{
Log.e("Data Sending", e.toString());
e.printStackTrace();
}
}
else
{
Log.e("Service Network", "Network is offline");
}
}
}, 1000, 5000);
}
}).start();
}
/*@Override
public void onDestroy() {
super.onDestroy();
// mySQLiteAdapter.deleteAll();
Log.e("Service Destroy", "Successful");
}*/
}
Do I need to use onStartCommand instead of onHandleIntent or do I need to use service instead of IntentService to control them?
回答1:
This might be the problem, I don't see where you are saving the readable database... Change this:
sqLiteHelper.getReadableDatabase();
Cursor cursor = sqLiteDatabase.rawQuery(selectQuery, null);
To this:
if(sqLiteDatabase == null || !sqLiteDatabase.isOpen()) {
sqLiteDatabase = sqLiteHelper.getReadableDatabase();
}
Cursor cursor = sqLiteDatabase.rawQuery(selectQuery, null);
Addition
For a SQLiteOpenHelper, onCreate() is only called when you are creating a new database not just opening an existing one... Change your constructor to:
public SQLiteAdapter(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
sqLiteDatabase = this.getWritableDatabase();
}
(and remove sqLiteDatabase=db from onCreate())
Also, I forgot that this was a two part question. IntentServices are not designed to run indefinitely, you should use a Service instead (or switch to using a ContentProvider).
来源：https://stackoverflow.com/questions/12884050/intentservice-stops-after-data-insertion-into-sqlite-and-gives-nullpointer-excep