NPE in Android Studio when communicating with database

Question

I am new to Android Development and I get a NullPointerException when trying to get a writable database. Here is the code:

Main Activity

public class MainActivity extends AppCompatActivity {

    MyDatabase myDatabase;
    SQLiteDatabase sqLiteDatabase;
    EditText textOne;
    EditText textTwo;
    Context context;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textOne = (EditText) findViewById(R.id.textOne);
        textTwo = (EditText) findViewById(R.id.textTwo);

    }

    public void addInfo(View view) {
        String name = textOne.getText().toString();
        String address = textTwo.getText().toString();
        myDatabase = new MyDatabase(context);
        sqLiteDatabase = myDatabase.getWritableDatabase();
        myDatabase.addData(name, address, sqLiteDatabase);
        myDatabase.close();

        textOne.setText("");
        textTwo.setText("");

    }
}

My database code:

public class MyDatabase extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "info.db";
    private static final String TABLE_NAME = "Personal_Info";
    private static final String NAME_COLUMN = "names";
    private static final String ADDRESS_COLUMN = "address";
    private static final String ROW_IDENTIFIER = "_id";
    private static int DATABSE_VERSION = 1;
    private static String query = "CREATE TABLE " + TABLE_NAME + "(" + ROW_IDENTIFIER + " INTEGER PRIMARY KEY AUTOINCREMENT, " + NAME_COLUMN + " TEXT, " + ADDRESS_COLUMN + " TEXT);";

    public MyDatabase(Context context) {
        super(context, DATABASE_NAME, null, DATABSE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        try {
            db.execSQL(query);
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    public void addData(String name, String address, SQLiteDatabase db) {

        ContentValues contentValues = new ContentValues();
        contentValues.put(NAME_COLUMN,name);
        contentValues.put(ADDRESS_COLUMN,address);
        db.insert(TABLE_NAME,null,contentValues);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        try {
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME );
        } catch (SQLException e) {
            e.printStackTrace();
        }

        onCreate(db);
    }
}

The error is thrown on this line in MainActivity:

myDatabase = new MyDatabase(context);

All input is welcome.

Can you post your logcat snippet too. From which line is the NPE coming from ? — Nishant Srivastava, Sep 09 '15 at 01:21

score 0 · Answer 1 · answered Sep 09 '15 at 02:26

You never initialized the variable context, so it is null. Since you have an Activity, you might as well just do this:

myDatabase = new MyDatabase(this);

where this refers to the Activity instance. You can do this inside of onCreate() if you like, or leave it where it is inside of addItem().

NPE in Android Studio when communicating with database

1 Answers1