SQLite android login and register - sql

Question

From the previous question I asked, I am still having the same question. I do not know how to use database (SQLite) to 'sync' with my application to log in or register
package log1.log2;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class Login extends Activity {
UserDB db = new UserDB(this);
/** Called when the activity is first created. */
private EditText etUsername;
private EditText etPassword;
private Button btnLogin;
private Button btnRegister;
private TextView lblResult;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Get the EditText and Button References
etUsername = (EditText)findViewById(R.id.usernametxt);
etPassword = (EditText)findViewById(R.id.passwordtxt);
btnLogin = (Button)findViewById(R.id.btnLogin);
btnRegister = (Button)findViewById(R.id.btnRegister);
lblResult = (TextView)findViewById(R.id.msglbl);
//Cursor c = (Cursor) db.getAllTitles();
//Button btnArrival = (Button) findViewById(R.id.btnRegister);
//btnArrival.setOnClickListener(this);
// Set Click Listener
btnRegister.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent intent=new Intent(Login.this,Register.class);
startActivity(intent);
}
});
btnLogin.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
db.open();
// Check Login
String username = etUsername.getText().toString();
String password = etPassword.getText().toString();
if(username.equals("select username from Users")){
if(password.equals("select password from users where username = username"))
{
Intent intent=new Intent(Login.this,Test.class);
startActivity(intent);
}
else
{
lblResult.setText("Wrong password");
}
} else {
lblResult.setText("Username does not exist. Please register.");
}
db.close();
}
});
}
}
Should I use the 'select' 'from' 'where' statement? Or there is another way?

Answer 1

Where you have
username.equals("select username from Users")
you are actually testing if what the user entered is literally the same object (which it is not). To authenticate against a local database of Users, you would want to try something more like this:
Cursor c = db.rawQuery("SELECT username FROM Users WHERE username='?' AND password='?'", new String[] {username, password});
if(c.moveToFirst()) {
// at least one row was returned, this should signal success
} else {
// authentication failed
}
Where 'db' is the SQLiteDatabase object you are working with. If you need any kind of security, I would also hash the password before you store it in the database!