Lecture Notes: Creating a User Login Screen in Delphi

Introduction

• Practical assessment task (PAT) is required for RT subject.
• Demonstration of how to create a login screen in Delphi.
• Login screens are common in many projects.
• This lecture provides tips and suggestions for creating a login screen.

Database Setup

• Simple database with a table named tbl_users.
• Fields in tbl_users:
  • username (primary key)
  • password
  • first_name
  • surname
  • user_type (e.g., admin, general user)
• Admin example (username: admin, password: qwerty).
• Populate the database with user data for testing.

Delphi Program Setup

• Main form becomes visible after successful login.
• Add a data module (dm_pat_example) to access the ADO table (ado_users).
• Initial state hides main form content behind a login panel.
• Login panel contains UI components for username and password.
• Pre-populate fields with test data to simplify testing.
• Name UI components clearly to avoid confusion (e.g., edt_login_username, edt_register_username).

Code Implementation

• Code to handle login button click event:
  1. Extract values from edit controls into variables.
  2. Search the database for matching username and password.
  3. Iterate through the ADO table using a while loop.
  4. Use a boolean flag (b_found) to indicate if a matching record is found.
  5. Show an error message if no match is found.
  6. Hide login panel and record user details if match is found.
• Example search algorithm in Delphi:

  if ado_users['username'] = s_username then
    if ado_users['password'] = s_password then
      b_found := true;
  

• Store user details in global variables (s_user, s_user_type) for later use.
• Customize welcome message to user on successful login.

Testing and Debugging

• Ensure fields are correctly populated for reliable testing.
• Test with various user credentials to validate login functionality.

Conclusion

• Login screen is a fundamental feature in many programs.
• Follow the tips for a smooth user experience.
• Additional resources available on YouTube, Facebook, and Twitter.