DataBaseHelper.java

package com.example.finaleapp;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

 class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "UserDatabase.db";
    public static final int DATABASE_VERSION = 1;

    public static final String TABLE_NAME = "Users";
    public static final String COLUMN_ID = "id";
    public static final String COLUMN_USERNAME = "username";
    public static final String COLUMN_PASSWORD = "password";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME + "(" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                COLUMN_USERNAME + " TEXT, " +
                COLUMN_PASSWORD + " TEXT)";
        db.execSQL(CREATE_TABLE);
    }

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

    // Register user
    public boolean registerUser(String username, String password) {
        if (checkUserExists(username)) return false;

        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_USERNAME, username);
        values.put(COLUMN_PASSWORD, password);

        long result = db.insert(TABLE_NAME, null, values);
        db.close();
        return result != -1;
    }

    // Check login
    public boolean loginUser(String username, String password) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_NAME, null, COLUMN_USERNAME + "=? AND " + COLUMN_PASSWORD + "=?",
                new String[]{username, password}, null, null, null);
        boolean result = cursor.getCount() > 0;
        cursor.close();
        db.close();
        return result;
    }

    // Update password
    public boolean updatePassword(String username, String newPassword) {
        if (!checkUserExists(username)) return false;

        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_PASSWORD, newPassword);

        int rows = db.update(TABLE_NAME, values, COLUMN_USERNAME + "=?", new String[]{username});
        db.close();
        return rows > 0;
    }

    // Check if user exists
    public boolean checkUserExists(String username) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_NAME, null, COLUMN_USERNAME + "=?", new String[]{username}, null, null, null);
        boolean exists = cursor.getCount() > 0;
        cursor.close();
        db.close();
        return exists;
    }
}