Query returns null Pointer exception

Question

Hello I have a problem with a query. I guess I am missing something, but I do not know what, so I need your help

It returns java.lang.NullPointerException

 import android.annotation.TargetApi;
    import android.app.Activity;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.os.Bundle;
    import android.widget.TextView;
    import android.util.Log;

    @TargetApi(16)
    public class logged extends Activity{
        public TextView msg;
        private SQLiteDatabase myDB = null;
        public void onCreate(Bundle savedInstanceState){
             super.onCreate(savedInstanceState);
             setContentView(R.layout.logged);
             msg = (TextView) findViewById(R.id.msg);
             myDB.openDatabase("data/data/com.example.login2/databases/aeglea", null, SQLiteDatabase.OPEN_READONLY);

             try{
//here is the problem. Both kind of queries return the same error
                 //Cursor cur = myDB.query("user_login", new String[] {"username"}, null, null, null, null, null);
                 Cursor cur = myDB.rawQuery("SELECT username FROM user_login", null);
                 msg.setText("Hello");
             }catch (Exception e1){
                 Log.e("DATABAZA","hola "+e1);
                 msg.setText("No Hello you creep");
             }

        }


    }

And my database OnCreate is

public void onCreate(SQLiteDatabase db) {
        String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_NAME + "("
                + KEY_UID + " INTEGER PRIMARY KEY,"
                + KEY_NAME + " TEXT,"
                + KEY_LAST + " TEXT,"
                + KEY_EMAIL + " TEXT UNIQUE,"
                + KEY_USERNAME + " TEXT UNIQUE" + ")";

        db.execSQL(CREATE_LOGIN_TABLE);


    }

Thanks in advance

I think your path to your database file needs to be absolute: /data/data/com.example.login2/databases/aeglea (note the leading /) — xbakesx
– xbakesx, Commented Aug 23, 2012 at 18:40
@Peter sorry, yeah. The answer below from Sam is right. You never initialized myDB. — xbakesx
– xbakesx, Commented Aug 23, 2012 at 18:56

Sam · Accepted Answer · 2012-08-23 19:15:17Z

3

Rewrite

private SQLiteDatabase myDB = null;

mDB is null, you need to initialize it before referencing it.

Try using your extended SQLiteOpenHelper class:

Database openHelper = new Database(this);
myDB = openHelper.getWritableDatabase(); // or getReadableDatabase();

And remove:

myDB.openDatabase("data/data/com.example.login2/databases/aeglea", null, SQLiteDatabase.OPEN_READONLY);

Now mDB.query() should work!

edited Aug 23, 2012 at 19:15

answered Aug 23, 2012 at 18:52

Sam

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4 Comments

MayTheSchwartzBeWithYou Over a year ago

is this valid? I get the "Change type of myDB to SQLiteOpenHelper" private SQLiteDatabase myDB = null; myDB = new SQLiteOpenHelper(this, "aeglea", null, 1); this gets a weird error "; expected ,"

Sam Over a year ago

Sorry, that code is wrong. The advice about the error is correct, but as you noticed a SQLiteOpenHelper is not a SQLiteDatabase. Before I can give you a better answer: do you have a database adapter class? What about an OpenHelper where you define onCreate() for your database?

MayTheSchwartzBeWithYou Over a year ago

No I don;t think so. I have a class called Database extends SQLite helper where I first create the database "aeglea". You mean I need to define another class where it opens "aeglea"?

MayTheSchwartzBeWithYou Over a year ago

Daamn you are pro. Thanks. I go study to understand what you did :P

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