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   ► KBProgrammingDelphi for W...Language Basics   Print This     
 
Delphi Language Basics:
20 Minute Delphi Primer: Displaying Things
 
Posted 11 years ago on 2/26/2008 and updated 10/24/2009
Take Away:

This primer is intended for those just getting started in Delphi and focuses on displaying things.

KB100883



Displaying Things in Delphi

One of the easiest ways to learn a language is to jump right in and make it do things. You can take this tutierial right on-line. Just task switch beween your browser and Delphi. In this tutorial, you will create a form with several buttons on it. Each button will demonstrate a technique for displaying information to the user. Lets get started by doing the following to do steps.

To do:

  1. Start Delphi

Note We strongly recommend that you type in and run each exercise. Just reading about something isn't nearly as good as doing it.

1. Using ShowMessage

ShowMessage displays a simple dialog box with the text you provide it. It is one of the most used ways of displaying information.

To do:

  1. Create a new application by selecting File | New Application.
  2. Place a button on the form and change its Caption property to ShowMessage.
  3. Double click on the button to bring up the editor.
  4. Type line 3 from the code listing (on the right) between the begin and end.
  5. Run and test the program by selecting the Run VCR style button (looks like a play button).

Notes

  1. The user has no way to modify the text.
  2. Notice the semi-colon at the end of the line you typed in.
  3. If you have trouble compiling, try the copy/paste method to typing.

Code Listing

procedure TForm1.Button1Click(Sender: TObject); 
begin 
	ShowMessage('Hello World!'); 
end; 

2. Using MessageBox - Part I

MessageBox is similar to ShowMessage but gives you more control over how it displays. This one is a favorite of developers because it is a Windows API function wrapped in a Delphi method. This is important because many Windows development languages support the MessageBox function.

To do:

  1. Add a button to our form (this time change its Caption to MessageBox1).
  2. Double click on the button to bring up the editor.
  3. Type line 3 from the code listing between the begin and end.
  4. Run and test the program.

Notes:

  1. The begin and end mark this methods code. Notice that the end has a ; after it.
  2. There is a main begin and end that mark the applications code. Notice the final end has a . after it. (You can see this by switching back to Delphi.)

Code Listing

procedure TForm1.Button2Click(Sender: TObject);
begin
    Application.MessageBox('Hello World!', 'My First App', 0);
end;

3. Using MessageBox - Part II

MessageBox also allows you to display multiple buttons and know which the user pressed. This is very usefull for limited yes/no type user interaction.

To do:

  1. Add a button to our form (set its Caption to MessageBox2).
  2. Double click on the button to bring up the editor.
  3. Type lines 2 and 3 from the code listing above begin.
  4. Type Lines 5 and 6 between the begin and end.
  5. Run and test the program.

Notes:

  1. Notice we declared sAns to be an integer. Then assigned the return value from MessageBox to it.
  2. Because Pascal is a highly typed language, we must use methods like IntToStr to convert a value to the correct type for the given method (as in line 6).

Code Listing

procedure TForm1.Button3Click(Sender: TObject); 
	var 	
iAns : Integer; 
begin 	
	iAns := Application.MessageBox('Is this fun?', 'Question', MB_YESNO); 	
	ShowMessage(IntToStr(iAns)); 
end; 

4. Using InputBox

InputBox allows you to set a value, display it to the user, and have the user change it. Although InputBox generally isnt flashy enough for finished applications, it is great for debugging and smaller in-house applications.

To do:

  1. Add a button to our form (set its Caption to InputBox).
  2. Double click on the button to bring up the editor.
  3. Add lines 2, 3, 5, and 6 from the code listing to it.
  4. Run and test the program.

Notes:

  1. Notice we used to the + symbol to concatenate two strings (a literal and a variable).
  2. Because themethod Button4Click belongs to the class TForm1, the first line must include both to uniquely identify the method. Youll learn a lot more about object oriented programming as you learn Delphi. For now, this simple definition will work.

Code Listing

procedure TForm1.Button4Click(Sender: TObject);
var 	
	sAns : String; 
begin 	
	sAns := InputBox('Question', 'What is your name?', 'Tiger Woods'); 	
	ShowMessage('Hello ' + sAns); 
end; 

5. Using the StatusBar Component

The StatusBar component allows you to write text to the status bar. This is one of the most common ways to display information to a user without stopping their work.

To do:

  1. Add a StatusBar component from the Win95 tab to the form.
  2. Change the SimplePanel property of the StatusBar to True.
  3. Add a button to our form (set its Caption to StatusBar).
  4. Add lines 2 and 3 from the code listing to the Click event of the button.
  5. Run and test the program.

Notes:

  1. Notice we used two apostrophies in a row to represent one apostrophe in a literal string.
  2. Notice the use of dot notation in line 3 to set a property of an object.

Code Listing

procedure TForm1.Button3Click(Sender: TObject); 
begin 	
	StatusBar1.SimpleText := 'Isn''t this cool!'; 
end;

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