SQlite Database: Unable to find context

Question

Apparently there is some problem with the context and in the following line as I'm getting a NullPointerException. I think something is wrong with the context. Also when I"m trying to open and close database from two activities it's throwing CannotOpenORCloseDatabase Error. Please help.

DBHelper dbHelper = new DBHelper(this.getApplicationContext());

Any idea why? Or it'd be great if someone could suggest a workaround.

public static final String EXT_CATEGORY = "category";

public static final String EXT_URL = "url";

private String tableName = DBHelper.tableName;

private SQLiteDatabase MyDb;

private int category;
Cursor c = null;

public static final String EXT_POS = "position";
private String url;
private int position;
WebView mWebView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    Log.v(LOG_TAG, "onCreate() called");
    super.onCreate(savedInstanceState);

    openAndQueryDatabase();

}

private void openAndQueryDatabase() {

    position = 1;
    category = 0;
    Log.v(LOG_TAG, "onCreate() called 3");
    try {

        DBHelper dbHelper = DBHelper.getInstance(getBaseContext());
        MyDb = dbHelper.getWritableDatabase();


        c = MyDb.rawQuery("SELECT * FROM " + tableName
                + " where Category =" + category + "AND Position ="
                + position, null);
        Log.v(LOG_TAG, "onCreate() called 4");
        // url = c.getString(c.getColumnIndex("Image"));
        url = "www.google.com";
        Log.v(url, " URL in Recipe ");
    } catch (SQLiteException se) {
        Log.e(getClass().getSimpleName(),
                "Could not create or Open the database");
    }

try to use either this or just getApplicationContext() and then check — Usman Kurd, Dec 27 '12 at 08:21
`public DBHelper(Context context) { super(context, DBName, null, version); currentContext = context; DBPath = "/data/data/" + context.getPackageName() + "/databases"; createDatabase(); ` — buggydroid, Dec 27 '12 at 08:42

TouchBoarder · Accepted Answer · 2012-12-27T09:36:37.163

3

You should declare your DBHelper as a static instance (singleton) to ensure that only one DBHelper exist at any given time.

 public class DBHelper extends SQLiteOpenHelper { 

    private static DBHelper mInstance = null;

    public static DBHelper getInstance(Context activityContext) {

    // Get the application context from the activityContext to prevent leak
    if (mInstance == null) {
      mInstance = new DBHelper (activityContext.getApplicationContext());
    }
    return mInstance;
  }

  /**
   * Private, use the static method "DBHelper.getInstance(Context)" instead.
   */
  private DBHelper (Context applicationContext) {
    super(applicationContext, DATABASE_NAME, null, DATABASE_VERSION);
  }
}

To open the SQLiteDatabase use:

SQLiteDatabase mDataBase = DBHelper.getInstance(context).getWritableDatabase();

and to close it

mDataBase.close();

edited Dec 27 '12 at 09:36

answered Dec 27 '12 at 08:53

TouchBoarder

6,422
2
52
60

DBHelper dbHelper = DBHelper.getInstance(getBaseContext()); MyDb = dbHelper.getWritableDatabase(); The context is working but says unable to open or close the database. – buggydroid Dec 27 '12 at 09:28
`E/SQLiteDatabase(1025): android.database.sqlite.SQLiteCantOpenDatabaseException: unable to open database file 12-27 14:48:11.450: E/SQLiteDatabase(1025): at android.database.sqlite.SQLiteDatabase.dbopen(Native Method) 12-27 14:48:11.450: E/SQLiteDatabase(1025): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1013) 12-27 14:48:11.450: E/SQLiteDatabase(1025): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:986) 12-27 14:48:11.450: E/SQLiteDatabase(1025): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:962)` – buggydroid Dec 27 '12 at 09:30
@LilYoda see my updated answer for opening and closing the DB – TouchBoarder Dec 27 '12 at 09:37
1

@LilYoda use: SQLiteDatabase MyDb = DBHelper.getInstance(this).getWritableDatabase(); , and use "this" instead of "getBaseContext()" or "getApplicationContext()", the DBHElper.getInstance(this) method will handle the getApplicationContext for you. – TouchBoarder Dec 27 '12 at 09:46
@hsigmond- I've closed the DB but problem s with opening it! But that issue I came here for resolved thanks. I'll debug a li'l more. :) Appreciate your help. – buggydroid Dec 27 '12 at 10:05

score 2 · Answer 2 · answered Dec 27 '12 at 08:34

use constructor for this... While calling the DB class pass context as the parameter. like below.

    public class MyDB {

   private Context context;
    private DatabaseHelper DBHelper;
    private SQLiteDatabase db;

    public MyDB(Context ctx) 
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }
}

Hope this will help you.

Imtiaz Mamun · Answer 3 · 2016-12-27T21:55:24.630

2

Try this

db = new DbHelper(this.getContext());

It should work.

edited Dec 27 '16 at 21:55

answered Dec 27 '16 at 19:00

Imtiaz Mamun

51
9

score 1 · Answer 4 · edited May 23 '17 at 12:01

1

You are using, DBHelper dbHelper = new DBHelper(this.getApplicationContext());

Instead you should use,

DBHelper dbHelper = new DBHelper(getApplicationContext());

Edit-

Try using

MyDb = getApplicationContext().getWritableDatabase();

instead of

DBHelper dbHelper = new DBHelper(this.getApplicationContext());

MyDb = dbHelper.getWritableDatabase();

Also try removing the finally() block as suggested by this answer.

edited May 23 '17 at 12:01

Community

1
1

answered Dec 27 '12 at 08:21

Sahil Mahajan Mj

11,033
8
53
100

OK will try and get back. Thanks. :) – buggydroid Dec 27 '12 at 08:27
The above part doesn't work. I used without finally but still unable to open or close the database. Attaching the logcat and editing my code in the question. – buggydroid Dec 27 '12 at 09:22
You have already accepted the answer. so what's the issue now.? – Sahil Mahajan Mj Dec 27 '12 at 09:24
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/21754/discussion-between-lilyoda-and-sahil-mahajan-mj) – buggydroid Dec 27 '12 at 09:25
Ooh no worries. I'll try to debug a li'l more. The issue I came here for is resolved. – buggydroid Dec 27 '12 at 10:06
@LilYoda: It would be helpfull for future visitors, if you could post how your issue solved. – Sahil Mahajan Mj Dec 27 '12 at 10:12

SQlite Database: Unable to find context

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