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?

Android :: cannot open database in service layer class


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Android :: Core Class Access Resources At The App Layer

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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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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

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May 1, 2010

Everything is in the title.

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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

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Jun 23, 2010

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Aug 20, 2010

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May 8, 2009

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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.
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} @Override
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Jul 2, 2010

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}
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@Override
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} @Override
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