//activity
public class MainActivity extends AppCompatActivity {
    DatabaseHelper db;
    EditText editText_Lusername, editText_Lpassword;
    Button button_login, button_redirectregister;
    String TAG = "TESTER";


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

        db = new DatabaseHelper(this);
        editText_Lusername = (EditText)findViewById(R.id.editText_Lusername);
        editText_Lpassword = (EditText)findViewById(R.id.editText_Lpassword);
        button_login = (Button)findViewById(R.id.button_login);
        button_redirectregister = (Button)findViewById(R.id.button_redirectregister);

    }

// DB helper
package com.example.xanderd.trafficbase;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME    = "trafficbase.db";
    public static final String TABLE_NAME       = "users_table";
    public static final String ID               = "id";
    public static final String USERNAME         = "username";
    public static final String PASSWORD         = "password";
    public static final String EMAIL            = "email";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table "+TABLE_NAME+"("+ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+USERNAME+" TEXT,"+PASSWORD+" TEXT," +
                ""+EMAIL+" TEXT)");
    }

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

    }

    public void insertUser(String username, String password, String email) {
        SQLiteDatabase db = getWritableDatabase();
        db.execSQL("INSERT INTO users_table ('"+USERNAME+"','"+PASSWORD+"','"+EMAIL+"')" +
                "VALUES ('"+username+"','"+password+"','"+email+"');");


    }

    public Cursor authRegister(String username){
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT username FROM users_table WHERE username = '"+username+"' ",null);
        return cursor;
    }

    public Cursor authLogin(String username, String password){
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT username FROM users_table WHERE username = '"+username+"' AND password = '"+password+"' ",null);
        return cursor;

    }
}