无法使用 SqliteDatabaseHelper 在 Android 工作室中开始活动

Question

I'm trying to create a simple application and I'm storing my data in a SQLiteDatabase, but the problem is when I type my credentials the application shut down immediatly without showing anything on logcat. Is it possible to call our database and work on it out of onCreate method in our main activiy? Here's my MainActivity code:

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.username)
    EditText username;
    @BindView(R.id.password)
    EditText password;
    @BindView(R.id.buttonConnect)
    Button buttonConnect;

    //Calling our database
    final DatabaseHelper dbHelper = new DatabaseHelper(this);


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
    }

    @OnClick(R.id.buttonConnect)
    public void onConnect() {
        if (!emptyFields()) {
            User user = dbHelper.queryUser(username.getText().toString(), password.getText().toString());
            if (user != null) {
                Intent intent = new Intent(MainActivity.this, RestaurantCategories.class);
                startActivity(intent);
                Toast.makeText(MainActivity.this, "Welcome " + user.getUsername(), Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(MainActivity.this, "User not found", Toast.LENGTH_SHORT).show();
                password.setText("");
            }
        }else{
            Toast.makeText(MainActivity.this, "Empty Fields", Toast.LENGTH_SHORT).show();
        }
    }

    private boolean emptyFields() {
        if (TextUtils.isEmpty(username.getText().toString()) || TextUtils.isEmpty(password.getText().toString())) {
            return true;
        }else {
            return false;
        }
    }
}

and this My Database queries codes:

public class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseHelper(Context context) {
        super(context,DatabaseOptions.DB_NAME, null,DatabaseOptions.DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //Create table
        db.execSQL(DatabaseOptions.CREATE_USERS_TABLE_);

        // Inserting our login credentials
        initialInsertion(db,"aladin","alloallo123");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + DatabaseOptions.USERS_TABLE);
        // Create tables again
        onCreate(db);
    }


    public void initialInsertion(SQLiteDatabase db,String username,String password) {
        ContentValues values = new ContentValues();
        values.put(DatabaseOptions.USERNAME,username);
        values.put(DatabaseOptions.PASSWORD,password);
        db.insert(DatabaseOptions.USERS_TABLE,null,values);
        db.close();
    }

    // To verify credentials in our login page !
    public User queryUser(String username, String password) {

        SQLiteDatabase db = this.getReadableDatabase();
        User user = null;

        Cursor cursor = db.query(DatabaseOptions.USERS_TABLE, new String[]{DatabaseOptions.ID,
                        DatabaseOptions.USERNAME, DatabaseOptions.PASSWORD}, DatabaseOptions.USERNAME
                        + "=? and " + DatabaseOptions.PASSWORD + "=?",
                new String[]{username, password}, null, null, null, "1");
        if (cursor != null)
            cursor.moveToFirst();
        if (cursor != null && cursor.getCount() > 0) {
            user = new User(cursor.getString(1), cursor.getString(2));
        }
        // return user
        return user;
    }


}

The Idea is since I don't have a register page I want to insert directly to my database in the methode OnCreate that's why I'm calling the function initialInsertion

Ps: DatabaseOptions is a different class where I create database & tables..

Answer 1

If there is a crash in JVM code, there's also a stacktrace to go with it. You might have a logcat filter or something that hides it though.

In your initialInsertion() you're closing the database you didn't open yourself. That's an error. Remove the close() call there.

(That database onCreate() code path gets triggered by the getReadableDatabase() in your queryUser() - that's what you'd be seeing in the stacktrace.)