CIS205 - Visual Basic

Objectives of the Week

Familiarize yourself with a selection of new controls
Easily size and locate controls on the form
Understand the keyboard interface
Use of the With statement to easily address control properties
String Concatenation

New Controls

	Text Box	User input. Multiple Lines if necessary. Control over the font properties
	Frame	Container. Used to hold related controls, especially Option Buttons
	Check Box	Boolean (True or False, On or Off, Checked or Unchecked)
	Option Button	Boolean, but only one Option Button per Container can be True
	Image	Holds a Picture. The image can be stretched to the size of the control.
	Shape	Display a Rectangular or Circular image
	Line	Primarily to enhance the user interface

See the chart of some of the Properties, Methods and Events of this week's controls

Naming Conventions

Remember that you only give a control a name when you will reference it in the Event Handler code. Here are the three character prefixes for today's new controls. The format of the control name, as specified in the control Name property is three character prefix in lower case, followed by a descriptive name with the first character capitalized.

Examples:
txtName, fraColors, chkBold, optSophomore

Text Box	txt
Frame	fra
Check Box	chk
Option Button	opt
Image	img
Shape	sha
Line	lin

Command Button	cmd
Form	frm
Label	lbl

Much of the discussion will refer to this graphic

Example 1

Alignment of Controls

Visual Basic gives you tools necessary to assist you in building a consistent user interface. Your form will look much nicer if the controls are sized and aligned properly. The Format selection on the Menu Bar provides access to these features. To make use of these tools, you must select multiple controls. Click on a control, then hold down the Control Key, and click on a second and a third control. The selections under the Format Menu selection describe the operations you can perform on these selected controls.

Align	Match up the left or top properties.
Make the Same Size	Same Height or Width. Especially for Command Buttons.
Horizontal Spacing	Move the selected controls close or farther apart
Vertical Spacing	Move the selected controls close or farther apart
Center in Form	Vertically or Horizontally
Lock Controls	When you are all done, this prevents you from accidentally moving a control

In addition, the location of the form on the desktop when your application starts can be positioned using the Form Layout window located in the bottom right corner of the VB Development Environment. "Grab" the form in this window and position it on the simulated desktop.

Keyboard Interface

In most situations, especially when you have a user that has experience using your application, a good Keyboard Interface will make your program much easier to use. Here are some things you need to consider:

Tab Order

	Each control on the form has a TabStop and a TabIndex property.

	The TabStop is a Boolean (True or False) Indicator. When the user presses the tab key to jump between fields on the user interface, it will or will not stop on the selected control.

	The TabIndex property describes the sequence in which the Tab Key will jump from field to field.

Alt-Key Combinations

	Want Fast and Direct access to a field on the form?

	Modify the Caption of the control to include an Ampersand (&) character. Notice how the Bold Checkbox appears as Bold (Underscore B). The Caption is coded as &Bold. This allows direct access to this check box by pressing Alt-B

	The Label and Text Box controls have a special relationship. When the Label and TextBoxes have TabIndexes in sequence, you can code an Alt Key selection on the Label, and pressing that combination will position to the associated text box.

	The key combinations must be unique on the form

Default and Cancel Keys

	Another Keyboard Shortcut for Command Buttons

	Set the Default property to True and when the user presses the Enter Key, this Command Button Click Event is triggered. The exception to this is when another Command Button has Focus

	Set the Cancel property to True and when the user presses the Escape Key, this Command Button Click Event is triggered. The exception to this is when another Command Button has Focus

	Only one Command Button can be the Default button and only one can be the Cancel button

General User Interface Considerations

Tool Tips	Use the ToolTipText property to trigger helpful hints as the user positions the mouse pointer over the control
Font	Select the proper Font and Color combination for the control at design time. This can also be modified at run time.

Very Important

The Frame Control is used as a Container. A set of Option Buttons can only have one control set to true per container. For each set of option buttons, use a frame to separate them. In the example above, the Frame as a Container is required to isolate the Graphics selection and the Shape selection. The Frame is used with the Font Checkboxes only to provide a consistency to the user interface.

Some Coding Considerations

Intrinsic Constants	VB uses literal indicators to represent certain properties in controls. You have seen two examples of this today: CheckBox.Value = 0 means False or Not Checked CheckBox.Value = 1 means True or Checked Shape.Shape = 0 means Rectangle Shape.Shape = 3 means Circle There are more here for the shape control VB provides a set of constants so we don't have to remember that a zero means rectangle, etc. To set a Checkbox on or off, code: CheckBox.Value = vbChecked or CheckBox.Value = vbUnchecked To change a Shape control to a circle code: Shape.Shape = vbShapeCircle Intrinsic Constants are documented in the Help for the specific control.
With - End With	When referencing multiple properties of a control, it is cumbersome to have to fully qualify each property. The With - End With Block provides a shortcut. Without a With Block: txtText.Font.Underline = chkUnderline.Value txtText.Font.Italic = chkItalic.Value txtText.Font.Bold = chkBold.Value Using a With Block: With txtText.Font .Underline = chkUnderline.Value .Italic = chkItalic.Value .Bold = chkBold.Value End With This can save you a bit of typing and at the same time, provide some good structure to your Event Handler as you can easily set all necessary control properties at the same time
Default Properties	Many controls have what is known as a Default Property This means that rather that having to specify the property in full Object.Property notation, that you can specify the Default Property by specifying only the Object Name. Example: txtText.Text = "Hello" chkBox.Value = vbChecked The Default Property for the TextBox is Text and the Default Property for the CheckBox is Value. Coding the example using the Default Properties would look like this: txtText = "Hello" chkBox = vbChecked If you are referencing the Default Property of a control, you do not have to specify the property name. After having said all of this: Don't EVER Use The Default Properties ALWAYS specify the reference using the full Object.Property notation This is a bad habit as future versions of VB will probably not support this feature and it is currently not supported in VBScript (which is used in coding for web pages under Windows Internet Explorer)
Concatenation of strings	Joining strings literals together is an example of Concatenation. The String Concatenation operator is the Ampersand (&). txtFullName.Text = txtLastName.Text & ", " & txtFirstName.Text This example joins the First and Last Name fields into a "Last, First" format
Code Continuation	Often, a line of code can become so long that it scrolls off the screen and it is difficult to read. Visual Basic is not at all concerned with this. VB has no problem reading a line of code no matter what the length. In situations like this, it comes in handy to split a line in two (or three or four ....) The operator to perform this Continuation is the Underscore (see the Shift - Dash on the keyboard) txtText.Text = "This is " & _ "a very " & _ "long string" Use the Continuation to make your Event Handler code easier to read.