Visual Basic in 12 Easy Lessons vel05.htm

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Lesson 3, Unit 5


Using Labels, Buttons, and Text Boxes



What You'll Learn


This unit explores labels, command buttons, and text boxes in detail. It explains all the properties associated with those controls. The important thing to remember as you wade through the tables of properties is that you need to master these properties if you are going to master Visual Basic. Unless you understand how to set up each property to respond in the manner your application requires, you cannot use Visual Basic effectively or create the outstanding applications that Visual Basic is capable of creating. Once you learn about the properties available for these controls, the next unit will explain all the event procedures that are possible with the command button, label, and text box controls.


Note: From this unit through the end of the book, each lesson's project contains a complete application that uses the concepts taught in the two units. Each unit is descriptive, and the project takes what you learned in the two units and shows you what a real-world application of the material looks like. You get the best of both worlds of teaching: The theory comes in the units, and the practical applications appear in the end-of-lesson projects.

Focus In on Controls


Concept: As you learn about controls, you often hear the term focus. Learning about focus now saves you a lot of trouble later.


Definition: Focus refers to the control that is currently highlighted.

The control with the focus is the next control that will accept the user's response. Most Windows users instinctively understand focus even though very few have thought much about focus. The control with the focus is always the control that is highlighted. The focus often moves from control to control as the user works. The focus determines where the next action will take place.


Tip: In a way, a control's focus is much like a word processor's text cursor. The focus enables the user to know where the next action will take place unless he changes the focus, just as a text cursor tells the user where the next character will appear unless he moves the text cursor to a different location.

Only one control can have the focus at any one time, and not every control can get the focus. Figure 5.1 shows a form with four command buttons. The Third command button has the focus. You can tell this because the Third command button is highlighted, whereas the other command buttons are not. Not only is the button highlighted, but there is a dotted line around its caption.

Figure 5.1. The Third command button has the focus.


Definition: The focus order determines the control next in line for the focus.

Every form has a focus order that determines the next control that will receive the focus. In Figure 5.1, if the user presses Enter, the figure's Third command button will depress only because it has the focus. If the user pressed Tab before pressing Enter, the next control in sequence to receive the focus would be highlighted. If the Second command button were next in sequence to gain the focus, the user's Tab press would highlight the Second command button.

When you see a dialog box such as a File Open dialog box, the OK button is almost always the command button that has the focus. You can press Enter to select the OK command button, click a different command button (such as a Cancel command button), or press Tab until the command button that you want has the focus.

Through property settings, you can determine the focus order and whether a control can receive the focus. Your form might have some controls that you don't want the user to be able to highlight; therefore, you prevent them from getting the focus.

Review: The focus determines the control that triggers next. If a command button has the focus, it is highlighted and is the next button chosen if the user presses Enter. If a text box has the focus, it will receive the next keystroke's character even if there are five other text box controls on the form at the same time. If the user needs to enter text in a certain text box that does not have the focus, he must press Tab until the text box gets the focus, or he must click the text box that he wants with the mouse cursor.

The Command Button


Concept: The command button is the cornerstone of most Windows applications. With the command button, your user can respond to events, signal when something is ready for printing, and tell the program when to terminate. Although all command buttons work in the same fundamental way—they visually depress when the user clicks them, and they trigger events such as Click events—numerous properties for command buttons uniquely define each one and its behavior.

You are already familiar with several command button properties. You have seen that command buttons vary in size and location. Table 5.1 describes all the command button properties. You might want to open a new project, add a command button to the Form window by double-clicking the command button on the toolbox, and press F4 to scroll through the Properties window.

Several of the property settings can accept a limited range of numeric values. Most of these values are named in CONSTANT.TXT, and they are mentioned in this book as well. Some property settings accept either True or False values, indicating a yes or no condition. For example, if the Cancel property is set to True, that command button is the cancel command button and all other command buttons must contain a False Cancel property because only one command button on a form can have a True Cancel property.


Tip: As you read through the property tables in this book, familiarize yourself not only with the purpose of each property but also with its name. When you write code, you need to refer to these properties by their full and exact names.

Table 5.1. Command button properties.

Property Description
BackColor The command button is one of the few controls for which the background color property means very little. When you change the background color, only the dotted line around the command button's caption changes color.
Cancel If True, Visual Basic automatically clicks this command button when the user presses Esc. Only one command button can have a True Cancel property value at a time. All command buttons initially have their Cancel property set to False.
Caption The text that appears on the command button. If you precede any character in the text with an ampersand (&),it acts as the access key. Therefore, the access key for a command button with a Caption property set to E&xit is Alt+X. The default Caption value is the command button's Name value.
Default The command button with the initial focus when the form first activates has a Default property setting of True. All command buttons initially have False Default property values until you change one of them.

Definition: An icon is a picture on the screen.
DragIcon The icon that appears when the user drags the command button around on the form.

Because you only rarely enable the to user move a command button, you won’t use the Drag... property settings very much.
DragMode Contains either 1 for manual mouse dragging requirements—the user can press and hold the mouse button while dragging the control—or 0 (the default) for automatic mouse dragging—the user cannot drag the command button, but through code you can initiate the dragging if needed.
Enabled If True (the default), the command button can respond to events. Otherwise, Visual Basic halts event processing for that particular control.
FontBold If True (the default), the Caption displays in boldfaced characters.
FontItalic If True (the default), the caption displays in italicized characters.
FontName The name of the style of the command button caption. You typically use the name of a Windows True Type font.

(margin)Definition: A point is 1/72 of one inch.
FontSize The size, in points, of the font used for the command button's caption.
FontStrikethru If True (the default), the caption displays in strikethrough letters. In other words, characters have a line drawn through them.
FontUnderline If True (the default), the caption displays in underlined letters.
Height The height of the command button in twips.
HelpContextID If you add advanced context-sensitive help to your application, the HelpContextID provides the identifying number for the help text.
Index If the command button is part of a control array, the Index property provides the numeric subscript for each particular command button. (See Lesson 6.)
Left The number of twips from the left edge of the Form window to the left edge of the command button.
MousePointer The shape to which the mouse cursor changes if the user moves the mouse cursor over the command button. The possible values range from 0 to 12 and represent the different shapes that the mouse cursor can take on. (See Lesson 12.)
Name The name of the control. By default, Visual Basic generates the names Command1, Command2, and so on, as you add subsequent command buttons to the form.
TabIndex The focus tab order begins at 0 and increments every time you add a new control. You can change the focus order by changing the TabIndex values of the controls. No two controls on the same form can have the same TabIndex value.
TabStop If True, the user can press Tab to move the focus to this command button. If False, the command button cannot receive the focus.
Tag Not used by Visual Basic. The programmer can use it for an identifying comments applied to the command button.
Top The number of twips from the top edge of a command button to the top of the form.
Visible True or False, indicating whether the user can see and, therefore, use the command button.
Width The width of the command button in twips.

Warning: Table 5.1 lists only those command button properties that you can initialize and change in the Properties window. Other command button properties that you can change using Visual Basic code are available only at runtime.

Review: There are many command button properties. As you can see from Table 5.1, learning which properties are available tells you a lot about what you can do with command buttons later.

Label Properties


Concept: The label holds text on the form. Although there are several ways to display text, the label control enables you to post messages on the form that you can change by means of Visual Basic code. The user, however, cannot change the value of a text control.

Label controls are vital to Visual Basic applications because you are always putting text on the form for the user to read. Here are some of the uses for the label control:

Labels are extremely easy to place and initialize. If you don't want a message to appear in a label when the user first starts the application, be sure to delete all the text from the label's Caption property. Table 5.2 lists the properties available for labels within the Properties window.


Tip: Notice that many of the properties in Table 5.2 match those in Table 5.1. Many properties, such as Width and Height, apply to several different controls. Other properties, such as AutoSize, apply to only a few controls.

Table 5.2. label properties.

Property Description
Alignment Set to 0 for left-justification (the default), 1 for right-justification, or 2 for centering the Caption within the label. Putting a border around the label or shading the label a color often makes the justification stand out.
AutoSize If True, the control automatically adjusts its own size to shrinkwrap around the contents of its caption. If False (the default), the control clips off the right of the text if the label is not large enough to hold the entire caption.

Definition: A hexadecimal number is a base-16 number.
BackColor The background color of the label. It is a hexadecimal number that represents one of thousands of possible Windows color values. You can select from a palette of colors displayed by Visual Basic when you are ready to set the BackColor property. The default background color is the same as the form's default background color.
BackStyle If set to 0, meaning transparent, the form’s background color comes through the label’s background. If set to 1 (the default), the label's background color hides the form behind the label.
BorderStyle Either 0 (the default) for no border or 1 for a fixed single-line border.
Caption The text that appears on a label.
DragIcon The icon that appears when the user drags the label control around on the form.

Because you only rarely enable the to user move a label control, you won’t use the Drag... property settings very much.
DragMode Contains either 1 for manual mouse dragging requirements—the user can press and hold the mouse button while dragging the control—or 0 (the default) for automatic mouse dragging—the user cannot drag the label control, but through code you can initiate the dragging if needed.
Enabled If True (the default), the label control can respond to events. Otherwise, Visual Basic halts event processing for that particular control.
FontBold If True (the default), the Caption displays in boldfaced characters.
FontItalic If True (the default), the caption displays in italicized character.
FontName The name of the label control’s style. You typically use the name of a Windows True Type font.
FontSize The size, in points, of the font used for the label control's caption.
FontStrikethru If True (the default), the caption displays in strikethrough letters. In other words, the characters have a line drawn through them.
FontUnderline If True (the default), the caption displays in underlined letters.
ForeColor The color of the text inside the caption.
Height The height of the label control in twips.
Index If the label control is part of a control array, the Index property provides the numeric subscript for each particular label control. (See Lesson 6.)
Left The number of twips from the left edge of the Form window to the left edge of the label control.

Definition: DDE stands for Dynamic Data Exchange.
LinkItem Contains the data to be passed to an advanced DDE application.
LinkMode Set to 0 (the default) for no DDE allowance, 1 for automatic DDE allowance, 2 for a code-based DDE, or 3 for a code-based notify requirement.
LinkTimeout The count of tenths of seconds that a sent DDE message is to wait for a response.
LinkTopic Specifies the source application and topic for a DDE application.
MousePointer The shape to which the mouse cursor changes if the user moves the mouse cursor over the label control. The possible values range from 0 to 12 and represent the different shapes that the mouse cursor can take on. (See Lesson 12.)
Name The name of the control. By default, Visual Basic generates the names Label1, Label2, and so on, as you add subsequent label controls to the form.
TabIndex The focus tab order begins at 0 and increments every time you add a new control. You can change the focus order by changing value of the TabIndex of the control. No two controls on the same form can have the same TabIndex value.
Tag Not used by Visual Basic. The programmer can use it for identifying comments applied to the label control.
Top The number of twips from the top edge of a label control to the top of the form.
Visible True or False, indicating whether the user can see and, therefore, use the label control.
Width The width of the label control in twips.
WordWrap If True, the text wraps to hold the entire caption. If False (the default), the text does not wrap but is truncated to fit the caption.

Warning: Table 5.2 lists only those label properties that you can initialize and change in the Properties window. Other label properties that you can change using Visual Basic code are available only at runtime.

Rarely, and more probably never, will you have to specify every property value when you create a new control. Most of the default values work well without any modification.

Review: The label properties display text on the form that the user can read.

Text Box Controls


Concept: Text box controls display default values and accept user input. Text box controls enable you to determine how the user enters data and responds to questions and controls that you display.

When you display a text box on a form, you give the user a chance to accept a default value—the text box's initial Text property—or to change it to something else. The user can enter text of any data type—numbers, letters, and special characters. He can scroll left and right by using the arrow keys, and he can use the Ins and Del keys to insert and delete text within the text box control.

Most of the text box's properties work like the label control's properties. Unlike the label, however, the text box properties describe data-entry properties so that the control can deal with user input instead of simple text display. Table 5.3 describes the property values for the text box control.

Table 5.3. Text box properties.

Property Description
Alignment Set to 0 for left-justification (the default), 1 for right-justification, or 2 for centering the Caption within the text box. If MultiLine contains False, Visual Basic ignores the Alignment setting.
BackColor The background color of the text box. It is a hexadecimal number that represents one of thousands of possible Windows color values. You can select from a palette of colors displayed by Visual Basic when you are ready to set the BackColor property. The default background color is the same as the form's default background color.
BorderStyle Either 0 (the default) for no border or 1 for a fixed single-line border.
DragIcon The icon that appears when the user drags the text box around on the form.

Because you only rarely enable the user to move a text box, you won’t use the Drag... property settings very much.
DragMode Contains either 1 for manual mouse dragging requirements—the user can press and hold the mouse button while dragging the control—or 0 (the default) for automatic mouse dragging—the user cannot drag the text box, but through code you can initiate the dragging if needed.
Enabled If True (the default), the text box can respond to events. Otherwise, Visual Basic halts event processing for that particular control.
FontBold If True (the default), the Text displays in boldfaced characters.
FontItalic If True (the default), the Text displays in italicized characters.
FontName The name of the text box's style. You typically use the name of a Windows True Type font.
FontSize The size, in points, of the font used for the text box control's Text value.
FontStrikethru If True (the default), the text value displays in strikethrough letters. In other words, the characters have a line drawn through them.
FontUnderline If True (the default), the text value displays in underlined letters.
ForeColor The color of the text inside the Text property.
Height The height of the text box in twips.
HelpContextID If you add advanced context-sensitive help to your application, the HelpContextID provides the identifying number for the help text.
HideSelection Keeps text highlighted even when the text box loses its focus.
Index If the text box is part of a control array, the Index property provides the numeric subscript for each particular text box. (See Lesson 6.)
Left The number of twips from the left edge of the Form window to the left edge of the text box.
LinkItem Contains the data to be passed to an advanced DDE application.
LinkMode Set to 0 (the default) for no DDE allowance, 1 for automatic DDE allowance, 2 for a code-based DDE, or 3 for a code-based notify requirement.
LinkTimeout The count of tenths of seconds that a sent DDE message is to wait for a response.
LinkTopic Specifies the source application and topic for a DDE application.
MaxLength If set to 0 (the default), the limit of the Text value can be as great as approximately 32,000 characters. Otherwise, the MaxLength specifies how many characters the user can enter in the text box.
MousePointer The shape to which the mouse cursor changes if the user moves the mouse cursor over the text box. The possible values range from 0 to 12 and represent the different shapes that the mouse cursor can take on. (See Lesson 12.)

Definition: A carriage return character sends the text cursor to the next line.
MultiLine If True, the text box can display more than one line of text. If False (the default), the text box contains a single, and often long, line of text. The text can contain a carriage return.
Name The name of the control. By default, Visual Basic generates the names Text1, Text2, and so on, as you add subsequent text boxes to the form.
PasswordChar If you enter a character, such as an asterisk (*) for the PasswordChar, Visual Basic does not display the user's text but instead displays the PasswordChar as the user types the text. Use text boxes with a PasswordChar set when the user needs to enter a password and you don't want others looking over his shoulder to peek at the password. Figure 5.2 shows a password-entry form that uses an asterisk for the password character. Even though the text box receives the user's actual typed characters, the screen displays only the PasswordChar typed.
ScrollBars Set to 0 (the default) for no scroll bars, 1 for a horizontal scroll bar, 2 for a vertical scroll bar, or 3 for both kinds of scroll bars.
TabIndex The focus tab order begins at 0 and increments every time you add a new control. You can change the focus order by changing the value of the TabIndex of the control. No two controls on the same form can have the same TabIndex value.
TabStop If True, the user can press Tab to move the focus to this label control. If False, the label control cannot receive the focus.
Tag Not used by Visual Basic. The programmer can use it for identifying comments applied to the text box.
Text The initial value that the user sees in the text box. The default value is the name of the control. The value continues to update as the user enters new text at runtime.
Top The number of twips from the top edge of a text box to the top of the form.
Visible True or False, indicating whether the user can see and, therefore, use the text box.
Width The width of the text box in twips.

Figure 5.2. The password character appears instead of the characters that the user types.


Warning: Table 5.3 lists only those text box properties that you can initialize and change in the Properties window. Other text box properties that you can change using Visual Basic code are available only at runtime.

Review: The text box control enables you to display default values and to accept the changes and additions that the user makes to those values when he enters text from the keyboard. Once the user enters text in a text box control, you can check the Text property to access that text.

Setting Properties


Concept: The Properties window makes its easy for you to set properties when you place controls on the form and build your application.

The Properties window contains a list of every property that you can specify at design time. For example, there are 25 command button properties—refer to Table 5.1 for the complete list—that you can set when you place a command button on a form at design time. You can also read and change many of them when you run the program. Three properties that you can set at runtime through code are not available at design time. There are additional properties that you can set at runtime through code but not set at design time.

The Properties window offers several ways of setting property values. Figure 5.3 shows the Properties window for a label control. Notice that the Properties window contains a scrolling list of properties available at design time for labels, a data entry and dropdown list for setting property values, and a dropdown list for selecting another control's properties.

Figure 5.3. The Properties window offers you several ways to change property values.

As you found out in the previous unit, you can change a property value by clicking the property’s row in the Properties window and entering a new value. The window’s data entry text box receives the new property as you type the name. If you clicked the Name property and typed a new name, you would see the name in the data-entry text box.

The Properties window also offers you multiple-choice selections from which to choose if a property can assume a limited number of values. For example, the MousePointer property can hold the only values 0-Default through 7-Size NS. These are the various shapes in which the mouse can appear. Instead of typing one of these values, simply click the MousePointer property and then the down arrow that opens the data-entry text box's dropdown list, shown in Figure 5.4. You can select one of the values from the list without having to type a value.

Figure 5.4. Visual Basic offers a choice of property values.


Note: You don't have to select a control first to see its properties in the Properties window.

Some programmers prefer to place several controls on a form before they set any property values. Once you place several controls on the form, each control has its own set of properties that you can set from the Properties window. Use the window's control dropdown selection box to display all the controls in the application, as shown in Figure 5.5. Select from the list of controls that drops down to see the control's property settings appear in the Properties window.

Figure 5.5. Select the control whose properties you want changed.


Tip: The Properties window’s dropdown list of controls shows the type and the name of each control.

Definition: A palette is a set of colors from which you choose.

When you set a color property, such as a label's BackColor property, you can type the hexadecimal color value, but it is much easier to select the color from a palette of colors that Visual Basic displays for you. If you clicked the BackColor property of a control such as a label, the Properties window data-entry text box changes to ellipses (...) instead of the arrow that normally accompanies a dropdown box. When you click the ellipses, Visual Basic displays a color selection palette like the one shown in Figure 5.6. Click one of the palette's colors to select it for the BackColor property. Visual Basic assigns the appropriate color hexadecimal value to match the color that you select.

Figure 5.6. Select a color from the palette of colors.

Review: The Properties window offers all kinds of helpful shortcuts that you can use when you set property values for your form’s controls. You can move from control to control and set properties along the way by choosing the control from the Properties window. You also can select a value for properties that is based on a fixed list of possible values.

Homework



General Knowledge


  1. What is meant by focus?

  2. What is the focus order?

  3. Which property controls the focus order?

  4. Which property is common for all controls and names the controls?

  5. True or false: You can set or change all properties at program design time.

  6. True or false: Only one control can have the focus at any one time.

  7. If a property can accept only a limited range of values, which text file holds descriptions for those ranges?

  8. What is an icon?

  9. What meant by the measurement term point?

  10. What is a palette?

  11. Which of the following can the user enter in text box controls?

    1. Numbers

    2. Letters

    3. Special characters

    4. All of the above

  12. Which property disables a text box control from triggering event procedures?

  13. What is the range of values that the Alignment property can hold?

  14. True or false: You often must set most of the property values every time you place a control on a form.

  15. What is a carriage return character?

  16. What does DDE stand for?

  17. True or false: A control can appear on the form but not be seen by the user.

  18. Which four properties available for most controls describe the two measurement indicators to the right of the toolbar?


Write Code That...


  1. What is the best control for titles and instructions?

  2. Which text box property setting would you use for a secret message that the user must enter?

  3. Suppose that you were writing a Visual Basic program that needs to perform a specific task when the user presses Esc. Which property do you have to set?


Find the Bug


  1. Julie is unhappy. She just began programming in Visual Basic so she can use some help to overcome her frustration. Julie places all her controls on the form before setting property values for the controls. The only problem that Julie has is that she thinks she must close the Properties window, highlight another control, and display the Properties window once again to set that control's property settings. Show Julie a better way.


Extra Credit


  1. Even though only one control at a time can have the focus, there is a property that can make the user think that a text box still has the focus when the focus is really elsewhere. What is the name of this text box property?

Which text box control property works the most like the Caption property of a command button or label?

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