Creating Applications in Delphi 4

• brief overview
• getting started
• basic components for a Windows application
• see also:
  • Delphi Programming Main Index
  • Introduction to Delphi
  • Delphi Basics
  • Variable types
  • Relational database management systems
  • Database access solutions
  • Client Server middleware tools
  • Two-tier client server
  • Multi-tiered client server
  • Database systems
  • Delphi data validation
  • Client server techniques

Brief overview:

• Delphi is a fully object oriented programming tool that uses Object Pascal programming language for Windows (use Delphi 1 for 16 bit Win3.x applications and Kylix for Linux applications)
• It is not as easy as MS Access to create database applications but once the initial learning curve has been achieved, it has the tremendous advantage of vast flexibility, speed and power in the type of applications that one can create which are just not possible with MS Access.
• You do not need to load MS Access each time you access a database, just run your application!
• The files needed to deploy a delphi application on another computer are:
  • application exe file that you created
  • an application help file if you created one (Delphi does not create these, need other tools)
  • if using a database, then the Borland Database Engine files which need to be installed and registered in Windows Registry
  • any OCX ActiveX controls that you used (preferably dont use them) - these also need to be registered
  • NB. Delphi comes with a version of Installshield which can create floppy disk installations for you easily.
• database access options:
  • all versions:
    • use the Borland Database Engine to access database files, so that before one can access database files (apart from Paradox and dBase which it can access without an alias), one needs to create an alias to the database in the BDE configuration program.
  • Delphi 5 and higher (but not Kylix):
    • use MS ADO technology
  • Delphi 6, Kylix and higher:
    • dbXpress - small DLL file that allows unidirectional queries to databases via ODBC or JDBC
• As mentioned, Delphi can do almost anything that Windows can do, which makes it an extremely complex tool, but this complexity can be ignored for creating most applications which are very simple to create.

Getting started:

• use explorer to create:
  • a new subdirectory of Delphi 4 projects directory for each application you make
  • a new subdirectory of Delphi 4 called LibMine where you can store any shared units you make
  • a shortcut to any application dpr file you create so that it is easier to load each time you edit the application
  • a shortcut to any application exe file you create so that it is easier to run the application
• use the Borland Database Engine configuration tool to create aliases to any databases you wish to access.
• install any 3rd party components, highly recommended ones are:
  • Infopower (www.woll2woll.com)
    • fantastic database access components which makes it really easy to create:
      • functional grids with automatic record view dialogs, lookups, embedded images, checkboxes, etc
      • filter dialog boxes which allow users to narrow down the records seen
      • locate dialog boxes which allow users to locate a value in a field
      • incremental search control allows users to enter values and locate record as each value entered
      • keycombo control allows users to select an index which will the change to sort order and also the field that the incremental search works on
      • rich text editing controls
  • Teechart Pro (www.teemach.com):
    • this is an extension of the charting tool used in Delphi4 which provides additional functions:
      • stock market charts, etc
  • ReportBuilder Pro:
    • Delphi comes with a reporting tool "Quick Reports", but this is another reporting tool with even greater functionality and allows end-users to create their own reports
  • check out freebies and shareware components on the internet:
    • Delphi Super Page
    •  
• run Delphi 4 either via shortcut created above or from start menu/programs/Delphi4
• by default, Delphi 4 starts up the project you pointed to in shortcut, or if no shortcut used, a new project is opened which by default is called Project1 and the unit file is called Unit1. These should be renamed by selecting File:SaveAs, remembering that the application exe file name will be the same as the project name.
• you can change various options for the application by selecting Project:Options. This allows you to set the application title, icon, helpfile name (if you have made one), which forms are automatically created, etc.

Basic components needed for a Windows application:

• the Windows application:
  • when you create a new application in Delphi, it automatically creates for you, in addition to a blank form with its pascal unit file, the following objects which are not immediately obvious to the developer:
    • the project source code file:
      • Delphi adds the various units you use into this pascal file and in its implementation section, places code to run your application and create any forms that need to be created automatically
      • you can view this file by selecting View Source from the menu
    • the application object:
      • this is in fact a form which is not seen as it has been sized with width = 0 and height = 0, but keeps all the other forms you create together at run time by managing the global event loop and thus controls events such as onHint
      • specify its title property so that users can see the name of your application in the task bar
      • specify a help file name so that when users click on help or F1, the help file will be activated
    • the screen object: 
      • this gives you access to the user's screen resolution, etc as well as all the forms you have created
    • the thread object:
      • each Window application needs a thread to get access to the CPU, as a developer you can ignore this object unless you wish to create multiple threads to allow tasks to run in the background or utilise multiple CPU's.
• the Form (or "window"):
  • this is already created for you by default. You can create additional forms for use in the application via File: New Form or File:New.
  • consider setting the following properties for the form:
    • renaming the form by editing the name property
    • showhints = true (this allows hints to be displayed when user leaves mouse over an object)
    • windowstate = wsMaximised (if you wish form to be automatically maximised)
    • windowpostition = poSreencenter (to centre the form on the screen by default)
    • forms can be MDI forms which means they can contain child forms in a way that MS Word does, where each document that is opened is a child form which can be minimised, if you create applications like these, you need to create a menu item called "Windows" which allows user to select one of the open child forms.
    • to ensure automatic scaling of the form and its components according to differing user screen resolutions:
      • set Scaled property of forms to True
      • use only True Type fonts (ie. don't use MS Sans Serif)
      • use Windows small fonts on the computer you use to develop the forms
      • set the Autoscroll property to false, if you want to scale the form and not just the controls in it
      • set the form position to either: upper-left corner or windowpostition = poScreenCenter
    • to ensure the user doesn't close the application without saving data, write code in the main form's OnCloseQuery event (not the OnClose event which may not always be called)
• from the component palette which sits at the top of the Delphi screen, you can select a component and add to form by clicking on the form, the components that should be considered are:
  • menu (on the "Standard" controls tab):
    • double click on it to edit the menu then either:
      • right click and select insert from template to insert ready made menu items such as the usual Windows "File", "Edit", "Help" menus, these can then be edited as needed.
      • type a caption in the blank caption property:
        • this will create a new menu item
        • if you enter a hyphen alone, this will create a separator bar on your menu
        • if you prefix any letter with &, this will create the underlined keyboard accelerator key
    • once a menu item has been created:
      • you can create a keyboard shortcut (eg. Ctrl-S or F4) to a menu item by selecting one from the shortcut property drop down list
      • you can add a hint that displays when the user selects the item via the hint property
      • you can create a submenu by right clicking on the item and selecting "Submenu"
      • you can drag and drop menu items from one spot on the menu to another
      • if you double click a menu item you can insert code to tell the computer what to do when the user clicks on this item (eg. for the E&xit item, add code "close;" which instructs form to close, and if the form is the main form, it will also mean the application is closed otherwise it will just hide the form)
      • many standard menu items are made easier to implement by dropping a TActionList component on the form and using this to allocate an action for the menu item (eg. cut, paste, copy, etc), others will need code attached to their OnClick event.
  • status bar:
    • this has its align property set to alBottom to force it to always be at the bottom of the form
    • select the panels property to add panels to the bar and customise these
    • select autoHint to display the hints from the form objects in the 1st panel
  • tool bar or top panel for containing speed buttons, etc:
    • I tend to use a panel component as this is easiest and set its caption to blank and its align to alTop, to drop buttons onto this just select the button component from the pallette and click on the panel - NOT the form.
    • for win98 look, you can create dockable tool bars, etc from the palette
  • scrollbox (if not an MDI form):
    • I prefer to drop a scrollbox component in the space between the top panel and the status bar and set its align property to alClient which means it will fill up all the space available between those components.
    • This allows me to drop other components onto the scrollbox such as database grids and then when the user resizes the form smaller, the user can access the entire grid using the scrollbars.
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