NullPointerException when insertData() called in android

Question

I am currently working on android stenography project, but at registration time the error was occur

"java.lang.NullPointerException: Attempt to invoke virtual method 'boolean com.example.devd.stangnograpyonimage.DBHelper.insertData(java.lang.String, java.lang.String, java.lang.String, java.lang.String)' on a null object reference"

DataBaseHelper.java

public static final String DATABASE_NAME = "STAGNODB";
public static final String TABLE_NAME = "Satgno_Table";
//public static final String COLUUMN_ID  = "ID";
public static final String COLUUMN_USERNAME  = "UserName";
public static final String COLUUMN_PASSWORD = "Password";
public static final String COLUUMN_NAME = "Name";
public static final String COLUUMN_EMAIL = "Email";


public DBHelper(Context context) {

    super(context, DATABASE_NAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    try {
        db.execSQL("CREATE TABLE " + TABLE_NAME + "(" + COLUUMN_USERNAME + " VARCHAR(50),"
                + COLUUMN_PASSWORD + " VARCHAR(50),"
                + COLUUMN_NAME + " VARCHAR(50),"
                + COLUUMN_EMAIL + " VARCHAR(50));", null);
    }catch (Exception e){
        Log.e("SQL Table Creation ", "Table Not Created");
    }
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
}

public  boolean insertData(String userName, String password, String name, String email){
    SQLiteDatabase mydb = this.getWritableDatabase();
    ContentValues cv = new ContentValues();
    cv.put(COLUUMN_USERNAME, userName);
    cv.put(COLUUMN_PASSWORD, password);
    cv.put(COLUUMN_NAME, name);
    cv.put(COLUUMN_EMAIL, email);
    long result = mydb.insert(TABLE_NAME, null, cv);

    if(result == -1){
        return  false;
    }
    else {
        return  true;
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    DBHelper myDB;
    EditText etUserName, etPassword, etName, etEmail;
    Button btnRegister, btnLogin;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etUserName = (EditText) findViewById(R.id.etUserName);
        etPassword = (EditText) findViewById(R.id.etPassword);
        etName = (EditText) findViewById(R.id.etName);
        etEmail = (EditText) findViewById(R.id.etEmail);
        btnRegister = (Button) findViewById(R.id.btnRegister);
        btnLogin = (Button) findViewById(R.id.btnLogin);
        register();
    }
    public void register() {
        btnRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                boolean isInserted = myDB.insertData(etUserName.getText().toString(), etPassword.getText().toString(), etName.getText().toString(), etEmail.getText().toString());
                if(isInserted==true){
                    Toast.makeText(MainActivity.this,"Data Inserted", Toast.LENGTH_LONG).show();
                }
                else {
                    Toast.makeText(MainActivity.this,"Data not Inserted", Toast.LENGTH_LONG).show();
                }
            }
        });
    }
}

score 2 · Accepted Answer · answered Apr 17 '18 at 04:25

2

In your activity class, you have not initialized the variable DBHelper myDB. Thus when your activity calls

myDB.insertData(etUserName.getText().toString(), ...

You get a NullPointerException because myDB is null. To fix this, create the object in the onCreate method of your activity

myDB = new DBHelper(this);

answered Apr 17 '18 at 04:25

EJK

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i have initialized . check it below the class creation in 7th line of MainActivity – Dev Dhande Apr 17 '18 at 04:29
I looked at MainActivity and I do not see initialization on line 7. What is the content of this line? – EJK Apr 17 '18 at 04:32

MikeT · Answer 2 · 2018-04-17T04:38:51.143

You are declaring but not instantiating myDB so it is null.

i.e.

    DBHelper myDB;

Just declares myDB so it is null at this point as nothing has been assigned to the variable.

You need to add something like :-

    myDB = new DBHelper(this);

In the onCreate method of the MainActivity.

e.g. :-

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    etUserName = (EditText) findViewById(R.id.etUserName);
    etPassword = (EditText) findViewById(R.id.etPassword);
    etName = (EditText) findViewById(R.id.etName);
    etEmail = (EditText) findViewById(R.id.etEmail);
    btnRegister = (Button) findViewById(R.id.btnRegister);
    btnLogin = (Button) findViewById(R.id.btnLogin);
    myDB = new DBHelper(this); //<<<< ADDED
    register();
}

NullPointerException when insertData() called in android

2 Answers2