Android :: Cannot Open Database In Service Layer Class
Sep 15, 2010
When I create a instance of the SQLiteOpenHelper, I always need a "Context" to be passed as its constructor's argument. To use this "Context", in my service layer class, I extends Activity class, though I do not display this activity on the screen because it is my service layer. I always get NullPointer exception when I open the SQLiteOpenHelper in my service layer class, Is it because my service layer class extends the Activity class but I did not show this activity on mobile screen? (That's there is no intent to my service layer class), if it is so, how to get rid of it if I wanna open a SQLiteOpenHelper in my service layer class which do not need to extends Activity, but need a Context object to pass to SQLiteOpenHelper?
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Sep 22, 2009
Can a core class such as "AbsListView" access resources, such as xml files, and .png's, in a 3rd party app installed in the normal way (at the app level)?
I realize this is a change in framework code, and that is fine for my purposes. So, for example, if I know that I am going to install an app called "MyApp", could I go into frameworks/base/core/java/android/ widget/AbsListView.java and tell it to use an xml file and .png's that live in that app? Here is the line I would want to modify: setSelector(getResources().getDrawable( com.android.internal.R.drawable.list_selector_background));
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Jul 1, 2010
I have a ListActivity that uses a CursorAdapter to fill the rows in the view. I wrote a database helper class that gives me back results for common queries I make for my app, and it uses an SQLiteOpenHelper implementation I wrote to open the database. I use the open helper to open the database and get a cursor to pass to my CursorAdapter.
Here's a code snippet:
CODE:...................
The problem I'm having, that I didn't have before I implemented the open helper (before I just opened the database directly without a helper), is when I click on an item, which takes me to another activity, and then go back to this activity. When it initializes everything is fine, and my list is populated fine, but when I go back from the activity that follows, the list is empty and in the LogCat I see "Invalid statement in fillWindow()".
It appears from a few post I've seen that the reason is, when I requery the cursor, the database is closed. But I'm not closing it! I'm scratching my head on this one.
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Aug 23, 2010
I'm trying to deploy an application with an existing SQLite database.I've been reading though the examples that are posted but they are always missing some part of the class. I feel like I'm trying to bake muffins but no one told me to use baking powder.Can someone post a full database helper class for depoying an SQLite database on Android? Edit : Delete old code because it doesn't work.
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Dec 21, 2009
Ok so I know many are having battery issues. You, like me, probably have more battery life than you think. This is because the application layer of the phone is not receiving the hardware layer's data correctly (hold talk button, end call button, and middle button upon starting up your turned-off phone, this boots in test mode which shows you hardware layer battery power, aka the correct battery life estimate). It's causing another problem because some applications can't be run when the phone THINKS it's about to die.
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Jan 5, 2010
I am new to Android, and I haven't developed any app regarding databases on Android yet. So I have a few basic questions. I am after a good database class sample, that will let me to run the CRUD operations. I would like to use it as a static class
like: clsDB->Select("select * from clients");
or objClient->Delete(clientid);
I am wondering if someone, can share his database classes, if more people share the best. Also I have in mind to reuse this class in multiple ways, I will have services, activities etc...
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Sep 23, 2009
Can anybody suggest what functionality to provide in a query utility class/classes? The idea is to provide a database utility package for android developers. I just wanna do it for android community and of course for my learning.:-)
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Jul 1, 2010
Here is my code for my db class:
package one.two;
import java.util.List;
import android.app.ListActivity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import java.util.ArrayList;
public class DBAdapter extends ListActivity
{public String status = "status";
public String id = "id";
public String arrival = "arrival";
public String destination = "destination";
public String ferry = "ferry";
private static String DB_PATH = "/data/data/one.two/databases/";
private static final String DATABASE_NAME = "ferry.db";
private static final String DATABASE_TABLE = "port";
public static Context context;
public Cursor c;
public static SQLiteDatabase DbLib;
//overloaded non-null constructor
public DBAdapter(Context context) {
DbLib = context.openOrCreateDatabase(DATABASE_NAME,
SQLiteDatabase.CREATE_IF_NECESSARY,null);
System.out.println("OpenOrCreateDB Done");
} public class DatabaseHelper extends SQLiteOpenHelper {
Context context;
DatabaseHelper(Context context){
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}//end constructor DatabaseHelper
// ---closes the database---
public void close() {
DBHelper.close();
}//end close()
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion){
}//end onUpgrade()
@Override
public void onCreate(SQLiteDatabase db){
}//end onCreate()
}// end class DatabaseHelper
private static DatabaseHelper DBHelper;
private static final int DATABASE_VERSION = 1;
public static ArrayList<String> getAllTitles(){
ArrayList<String> port = new ArrayList<String>();
Cursor c=null;
c = DbLib.query("port"
new String[] { "status", "id", "arrival",
"destination", "ferry" }, null, null,
null, null, null);
try {
if (c!=null) { // start - when there is at least 1 record
System.out.println("Cursor is NOT NULL");
int i =0;
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext())
{// Debug Stm
System.out.println("Record No. "+i);
System.out.println(c.getString(0));
System.out.println(c.getString(1));
System.out.println(c.getString(2));
System.out.println(c.getString(3));
System.out.println(c.getString(4));
// Assign database cursor.records to arraylist
port.add(i,c.getString(0));
port.add(i,c.getString(1));
port.add(i,c.getString(2));
port.add(i,c.getString(3));
port.add(i,c.getString(4));
i = i + 1;
} } // end - where there is at least 1 record
} finally {
if (c!=null) {
c.close();
} } return port;
}//end getAllTitles()
public void open() {
//Open the database
String myPath = DB_PATH + DATABASE_NAME;
DbLib = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
} }//end class DBAdapter
My Arrival class
package one.two;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
public class Arrival extends ListActivity
{ private ListView listView;
/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState)
{ ArrayList<String> retList = new ArrayList<String>();
System.out.println("Start onCreate Function");
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
System.out.println("In onCreate Function");
System.out.println("In of GetData");
DBAdapter db = new DBAdapter(this);
System.out.println("DB Open");
db.open();
System.out.println("DB Opened");
retList = getData();
System.out.println("Out of GetData");
// force count no. of records in table
// dump to check index
int cnt = 2;
int i=0;
for (i = 0; i<cnt; i++)
System.out.println(retList.toString());
listView = (ListView) findViewById(android.R.id.list);
SimpleCursorAdapter mAdapter = new SimpleCursorAdapter(this, android.R.id.list, null, null, null);
this.setListAdapter(mAdapter);
// db.close();
} @SuppressWarnings("static-access")
public static ArrayList<String> getData()
{ ArrayList<String> items = DBAdapter.getAllTitles();
// titles ???? redundant
//ArrayList<String> titles = new ArrayList<String>(items);
System.out.println("Return a LIST titles");
return items;
} }
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Aug 21, 2010
According to my application i create the database with two tables. when i inserting the data in 1 table then it runs correctly after that when i save data in the second table then it gives the exception of illegal state exception (database cannot be open). Please give me the solution.
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May 1, 2010
Everything is in the title.
On the official documentations it is stated that Note that services, like other application objects, run in the main thread of their hosting process and AsyncTask only works if it is executed in the UIThread.
So is it possible to use AsyncTask in a Service class? code...
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Sep 26, 2010
Did a fresh install of Eclipse, JDK and android-sdk.
I am currently receiving this error when creating a new project
[2010-09-26 16:07:56 - Test] ERROR: Unable to open class file C:workspaceTestgencomexample estR.java: No such file or directory
What's the reason for this and how I fix it?
Eclipse Helios 32 bit
java version "1.6.0_21"
Android sdk API 8
P.S. Im new to Android development.
EDIT: I tried most of you solutions, but nothing worked. So I started using my frineds install of Eclipse Ganymeade.
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Apr 18, 2010
I am trying to use
SQLiteDatabase.openDatabase( "/data/data/edwin11.myapp/databases/myapp.db", null, (SQLiteDatabase.CREATE_IF_NECESSARY | SQLiteDatabase.NO_LOCALIZED_COLLATORS));
To create/open a database instead of making use of the SQLiteOpenHelper (because I want to pass in the flag SQLiteDatabase.NO_LOCALIZED_COLLATORS. However, I am getting this exception for that line of code:
04-18 09:50:03.585: ERROR/Database(3471): sqlite3_open_v2("/data/data/edwin11.myapp/databases/myapp.db", &handle, 6, NULL) failed
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): java.lang.RuntimeException: An error occured while executing doInBackground()
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at android.os.AsyncTask$3.done(AsyncTask.java:200)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.util.concurrent.FutureTask.run(FutureTask.java:122)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at java.lang.Thread.run(Thread.java:1060)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): Caused by: android.database.sqlite.SQLiteException: unable to open database file
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at android.database.sqlite.SQLiteDatabase.dbopen(Native Method)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1584)
04-18 09:50:03.665: ERROR/AndroidRuntime(3471): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:638)...
Doing some testing just before that line of code (using File.isExists) shows that the file /data/data/edwin11.myapp/databases/myapp.db does not exist. Would that be the cause of the error? (Or am I just using SQLiteDatabase.openDatabase the wrong way?) Would it help if I create the file beforehand? (Shouldn't that be taken care of by the SQLiteDatabase.CREATE_IF_NECESSARY flag that I passed in?) If creating the file manually is the way to go, is it just an empty file, or do I have to write something to it?
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Nov 8, 2010
Recently I very often get error reports from users that upgrade their OS. > This includes at least 1.5, 1.6, 2.1 and custom ROMs. Anybody else seeing these? Any idea what to do about it?
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Jun 23, 2010
In my app, I'm supporting the backup and restoration of the Sqlite db file. I need to close and re-open my database connection after the restore. How can I do this?
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Sep 1, 2010
What is the class name of media scanner service?
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Oct 2, 2009
if the inner UpdateService class is not static, it cannot start the service. The ActivityManager complains "Unable to start service Intent"...
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Jun 18, 2010
In Android, if I want to do some background work, what is the difference between
Creating a Service to do the work, and having the Activity start the Service VS. Creating a standard java class to do the work, and having the Activity create an object of the class and invoke methods, to do the work in separate thread.
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Aug 20, 2010
I'm watching the 2010 Google I/O video on this topic and I have a few questions to make sure I understand properly. Google I/O 2010 - Android REST client applications Please note I also have a very limited understanding of CursorAdapters Right now my application just has a UI layer. I've created an object called DbAdapter using some Google tutorials to create a small database and a table in that database. I've created a class I'm calling DataBroker (extending ContentProvider) to manage retrieving data from the database and calling web services to update data. Scenarios:
1) Suppose I want to display a list of items in my ListActivity. Am I correct in assuming I will write a function in my DataBroker that creates a Cursor to the table in my database that holds those items, fire up a service which launches a thread which calls a web service to get additional items, then return the Cursor to my UI thread? Doing this would likely return the Cursor to my UI thread before the web service finished, but, I'm assuming, once the CursorAdapter has a Cursor, it will automatically show any changes made to that database table, yes?
2) Now I have a list of items in my ListView. Suppose I give the user some functionality to delete an item. The user executes this functionality. It should call a function in my DataBroker which updates the row in my database corresponding to that item, setting the status column to STATE_DELETING (which will remove the row from the ListView because the Cursor has a clause excluding this state), then fire off a service that fires a thread that hits my web service, then deletes the row in the database when finished? Also, suppose I have multiple Activities, am I looking at having a static Cursor for each Activity with a list, grabbing that Cursor in the Activity's onCreate, and if that Cursor is null, hitting my DataBroker?
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May 8, 2009
I'm posting this to share the lessons I learned while working with IntentService. IntentService has a single constructor that takes a string argument "name". The documentation has no description of what name is used for. In looking at the sources, I found that its only use is in naming the worker thread for the IntentService. This thread is named IntentService [name].
I initially implemented the constructor of the derived class to also take a String argument and passed it along to the derived class. This is wrong. This will cause the startService() call to generated a java.lang.InstantiationException in the application containing the service i.e. you don't get the exception in the application calling startService(). A clue to the actual problem is a little further up in the logs:"newInstance failed: no <init>()"
The derived class must have a Default constructor and that constructor must call super() passing a string for the name component of the worker thread name.
public class MyIntentService extends IntentService {
public MyIntentService() { super("MyIntentService");
} @Override
protected void onHandleIntent(Intent intent) {
// Handle events on worker thread here }
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Jul 2, 2010
I am trying to call my service class's stopService() method from my activity. But I don't know how to access stopservice method from my activity class. I have the below code but its not working. This is HomeScreen class:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
enablecheck = (CheckBox)findViewById(R.id.enablecheck);
enablecheck.setOnCheckedChangeListener(new OnCheckedChangeListener(){
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// TODO Auto-generated method stub
if(enablecheck.isChecked()){
startService(new Intent(HomeScreen.this, AutoService.class));
} else {
stopService(new Intent(HomeScreen.this, AutoService.class));
} } });
}
This is Service Class:
public class AutoService extends Service {
private static final String TAG = "AutoService";
private Timer timer;
private TimerTask task;
@Override
public IBinder onBind(Intent intent) {
return null;
} @Override
public void onCreate() {
Toast.makeText(this, "Auto Service Created", Toast.LENGTH_LONG).show();
Log.d(TAG, "onCreate");
int delay = 5000; // delay for 5 sec.
int period = 5000; // repeat every sec.
timer = new Timer();
timer.scheduleAtFixedRate(task = new TimerTask(){
public void run() {
System.out.println("done");
} }, delay, period);
}
@Override
public boolean stopService(Intent name) {
// TODO Auto-generated method stub
timer.cancel();
task.cancel();
return super.stopService(name);
} }
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Jun 22, 2010
Hi, custom classes which are part of a framework, so nothing graphical. One of those (singleton) classes is a Logging class which send logs to my server. I noticed that even though I can call the classes methods in my service it actually won't be logging anything... In my specific example it's osmething like : Logger.getInstance().log("Whatever I want to Log"); Obviously the getInstance is a static method so it can be accessed from anywhere within my project right away.. I was wondering though why this method for example isn't getting called ? Also how do I debug a Service ? Btw I am using of IPC from one of my Activities which gets bound to the service and can start/stop the music for example...
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Mar 25, 2009
I have created a threaded service the following way. code...
After I close the application the phone works really slow and I guess it is due to thread termination failure.
Does anyone know what is the best way to terminate all threads before terminating the application?
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Jun 1, 2010
I was wondering if it's possible to call specific methods defined within the AsynTask class from another class and/or service ?
In my specific case I have a Service playing some sounds, but the sound is selected from a List with available sounds...
When a sounds is selected it is downloaded from my home server, this takes some time (not much, let's say around the 3-4 seconds, the sounds/effects aren't big in size)...
So my problem at the moment is that I have a service to play those sounds, and when I select one I wanted to show a progressdialog... The way (if I understood correctly) is to use an AsyncTask, but the only thing the AsyncTask will do is telling my Service to play a specific sound from my server... So there is no "callback" from the service to the Asynctask...
How can I call a running AsyncTask, which sits in another class, and tell him all work is done and thus he can stop showing the ProgressDialog ? Or am I over-engineering it and there are other ways ?
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Mar 27, 2009
I am having problem using webview in my application. When ever the webviewclient and webview is trying to load, it will throw me and uncaugh exception. Code...
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Nov 20, 2010
My app uses two databases (separate files). To handle these databases I have created two Helper classes which extend SQLiteOpenHelper, one for each database.
I am now going to add a third database and wonder whether I need to create yet another Helper class (and if I used a 4th and a 5th database would I need even more Helper classes), or can I use the same Helper class for multiple databases?
The problem that I see with trying to use just one Helper class is that I can't see how to pass the name of the individual database files to the Helper. At present the name of the database is hard-coded as a Static field of each of the Helper classes, but if I had only one Helper class I would need to be able to pass the different names in to the Constructor when creating the separate Helper objects; the problem is that the SQLiteOpenHelper Constructor seems to be called by Android with just one parameter: the Context.
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May 19, 2010
The problem seems to be that the Service class does not inherit the > findViewById() method.
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Jun 8, 2010
I have android application and service that runs in separate process. Application and service read and write to same database (and same table).
What is the best way to work with database? How to prevent locks?
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Jun 6, 2011
I am trying to create a drools app on android using eclipse. It compiles /builds correctly in Eclipse. But when I run it in emulator or android device, it says
W/System.err( 322): java.lang.IllegalArgumentException: Unable to instantiate service for Class 'org.drools.builder.KnowledgeBuilderFactoryService '
I have the required jars added to "libs" directory of the project and the jars are also added to the build path in eclipse.
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Apr 30, 2010
I am trying to execute a {public void} method in Service, from scheduled TimerTask which is periodically executing.This TimerTask periodically checks a condition. If it's true, it calls method via {className}.{methodName};However, as Java requires, the method needs to be {pubic static} method, if I want to use {className} with {.dot}.The problem is this method is for notification using Toast(Android pop-up notification) and Status Bar.But for this to work, the method must not have {static} modifier and resides in Service class.So, basically, I want background Service to evaluate condition from scheduled TimerTask, and execute a method in Service class.Can anyone help me what's the right way to use Service, invoking a method when certain condition is satisfied while looping evaluation?
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Aug 6, 2010
I have a C/S solution, which take Android as its client and PHP as its server.
I have my own account system.
I'm wondering whether I could provide my user to login my system with Google Account?
I saw there are web-solution for this, like this stackoverflow.com could use Google Account to directly login.
Is there a solution for C/S system?
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