SQLite and NullPointer in Android

Question

I'd like to use an sqlite database for my android application.First question, do I need to have a rooted device?! If i try adb shell sqlite3 on my Galaxy S, it will return "not found" error. Also, when I try to "ls /data/ " i get "No permission" error.

Second question, the NullPointer itself.

07-23 10:58:17.546: ERROR/AndroidRuntime(12815): Caused by: java.lang.NullPointerException
07-23 10:58:17.546: ERROR/AndroidRuntime(12815):     at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:203)
07-23 10:58:17.546: ERROR/AndroidRuntime(12815):     at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:98)
07-23 10:58:17.546: ERROR/AndroidRuntime(12815):     at com.gpachov.priorityqueue.database.Database.getAllRecords(Database.java:24)
07-23 10:58:17.546: ERROR/AndroidRuntime(12815):     at com.gpachov.priorityqueue.database.DatabaseAdapter.<init>(DatabaseAdapter.java:21)
07-23 10:58:17.546: ERROR/AndroidRuntime(12815):     at com.gpachov.priorityqueue.PriorityQueueActivity.<init>(PriorityQueueActivity.java:20)

It happens in the Context itself when trying to access the database.

Here is my code.

public class DatabaseHelper extends SQLiteOpenHelper {


    private final static String DATABASE_NAME="queue";

    private final static  int DATABASE_VERSION = 1;

    public DatabaseHelper(Context context){
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(ItemTable.CREATE_STRING);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        //nothing for now
    }

}

And the more important null pointer causing class:

public class Database {

    private DatabaseHelper mDatabaseHelper;

    public Database(Context context) {
        mDatabaseHelper = new DatabaseHelper(context);
    }

     List<Item> getAllRecords() {
        final SQLiteDatabase database = mDatabaseHelper.getReadableDatabase();

................. It blows with the NPE on the first line of getAllRecords().

Oh yeah, and here is my create string:

public static final String CREATE_STRING = "create table items (id integer primary key autoincrement, "+ "title text not null, description text not null, priority integer not null)";

George · Accepted Answer · 2011-07-23 09:33:46Z

1

Solved! An obvious and ridiculous mistake, though absolutely impossible to be seen from the text I posted.

I for some reason did instantiate my adapter before the onCreate() statement in the activity. Meaning the context passed below was not null, but not 'ready' yet. Therefore neithter the adapter nor the helper received null-contexts or stuff, but the earlier call with unprepared context results in unset fields and in-depth null-pointers.

Thanks everybody trying to catch this one, but as I did not post activity code, it was virtually incatchable from every other perspective than my own. Sorry about that.

answered Jul 23, 2011 at 9:33

George

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Ognyan · Accepted Answer · 2011-07-23 09:24:40Z

0

Answer to first question: No, you don't need rooted device.

About: adb shell sqlite3 what are you trying to accomplish here? It does not make sense as shown.

About "No permission": yep, that is normal. You can't access files belonging to app on real device like galaxy s (although it is perfectly possible on emulator).

Second question: obviously mDatabaseHelper is null and when you call mDatabaseHelper.getReadableDatabase(); in your getAllRecords() it causes the NPE. Do you have another constructor for your Database class? Like one that does not initialize mDatabaseHelper?

answered Jul 23, 2011 at 9:24

Ognyan

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George Over a year ago

Good try, but no. What am I trying to accomplish by calling the sqlite3? Actually trying to use sqlite to see if my database is successfully created, didn't feel I had to write that. Obviously if you had saw the stack trace I posted, you'd now that this is not the case and DatabaseHelper is 100% not null. Thanks for your feedback.

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