Chapter 3.1 Controls - PowerPoint PPT Presentation

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Chapter 3.1 Controls

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  1. Chapter 3.1Controls Programming In Visual Basic.NET

  2. Controls in the Toolbox Those controls that we will use in this class.

  3. The Name Property • How the programmer refers to a control in code • Name must begin with a letter • Must be less than 215 characters long • May include numbers and the underscore • Use appropriate 3 character naming prefix

  4. Control Name Prefixes

  5. Text Box (txt) • Used for user input/data entry • Text Property • What is displayed in text box • What user entered in text box • TextAlign Property • Controls alignment of text in the Text Box • Change Event

  6. TextBox Control – Properties • BorderStyle - defines the border surrounding the text box • ForeColor,BackColor - defines the text color and background color respectively • Enabled - controls whether the text box can get focus and will respond to events • Locked - controls whether user can change the text appearing in the text box • MultiLine - controls whether text will appear on multiple lines • MaxLength - defines the maximum number of characters that the user can enter into the text box

  7. TextBox Control – Properties • Name - defines name used to reference control instance with code • Again, use a standard prefix of "txt" • ScrollBars - defines whether vertical or horizontal scroll bars appear in text box • Text - contains the text appearing in text box • TextAlign - justifies text within the visible region of the control instance • X, Y, Height, Width properties define the position and size of the control instance

  8. TextBox - Methods and Events • Focus method sets input focus to a text box • Enter event fires when text box gets focus • Leave event fires when text box loses focus • TextChanged event fires when the the textual contents change at run time • The event fires for each character typed

  9. Button (btn) • Used to run/activate an Event Procedure • Click event • Properties • Text – Change the text property to display text to user • Image – change image to use a graphic button • Forecolor – changes the color of the text displayed • Backcolor – changes the color of the button

  10. Label (lbl) • Used for • Output on a form • Identification of objects • Directions/Information • Cannot by modified by user

  11. Label Properties • Text – used to display text or instructions to the user • Font – change font size, color, appearance • Image – use images to draw attention • Autosize – adjust the label object to text entered into the text property • textAlign – aligns the text displayed on the object

  12. Group Box (grp) • Used as containers for other controls such as radio buttons and check boxes • Improves readability of form • Text Property • What is displayed on the top edge of the group box • Splits the form object into separate planes • allows several groups of radio buttons on one form.

  13. Group box (grp) • Group boxes must be added to the form before other objects are added to them. • You can not drag checkboxes or radio buttons from the form to the group box • The group box must have the focus of the cursor before you draw your other objects inside them • Editing handles must be visible

  14. Check Box (chk) • Used for user input/data entry • Allows the user to select or deselect 1 or more in any group • Checked Property • Checked = True • Unchecked = False • CheckChanged Event – default event

  15. Radio Button (rdo) • Used for user input/data entry • Allows the user to select only 1 in any group • First create a group and then create each radio button inside the group • Checked Property • Checked = True • Unchecked = False • CheckChanged Event – default event

  16. Picture Box (pic) • Displays/contains a picture/graphic • Image Property • Complete path and filename of graphic • .bmp, .gif (including animated), .jpg, .png, .ico, .emf, .wmf • SizeMode Property • StretchImage causes graphic to be resized to match the size of the control • Visible Property

  17. Other Properties • BorderStyle Property –None, FixedSingle, Fixed3D • Forecolor – changes the color of text inside object • Backcolor – changes the color of object • Textalign – aligns text property • Enable • true (user can activate the object), • false (object us not available to user) • Visible • True (object appears on form) • False (object is hidden at run time) • TabIndex – set the order of the focus for controls on the form

  18. Properties and Methods • Properties can be set at design time in the property box • Or they be changed during program execution by statements in your code • txtHours.Text = "“ ‘ clears the content • Methods are action performed on objects • txtHours.focus

  19. Selecting Multiple Controls • SHIFT-Click or CTRL-Click to select/deselect multiple controls • Use the mouse to drag a selection box around multiple controls • To deselect all selected controls click elsewhere on the form

  20. Selecting Multiple Controls (cont.) Start here Drag to here Using mouse to drag a selection box around multiple controls Multiple selected controls, observe selection handles.

  21. What Can be Done with Multiple Selected Controls? • Use Format Menu or Layout Toolbar to • Align them to each other • Make same size • Modify the spacing between them • Move them as a group • Set their common properties

  22. Designing the User Interface • To the user the Interface should be • Easy to understand • Familiar • Comfortable • Organized • Sans Serif Fonts are best, not boldface or large • Color Neutral Overall • Keyboard Accessible

  23. Text=&OK Text=E&xit Keyboard Access Keys • Also referred to as Hot Keys • Underlined Letter • User presses ALT + underlined letter • Use Windows-Standard Keys • Defined using Text Property

  24. Default & Cancel Buttons • Default Button • Identified visually on Form by its darker outline • Responds to ENTER key • Form's AcceptButton Property • Cancel Button • Responds to ESC key • Form's CancelButton Property

  25. Focus • One control on a Form always has the Focus • Not all control types can receive the focus • TabStop Property (applicable only for controls that are capable of receiving the focus) • Designates whether a control is allowed to receive the focus; True or False

  26. Tab Order • User should be able to use TAB key to move the focus through a form in an organized manner; top to bottom, left to right • TabIndex Property • Number in tab sequence • 0 for first control to receive the focus when the form loads • In form’s graphic view – Use View Menu, Tab Order to set

  27. Setting TabIndex Property • View menu, TabOrder • Click on each control in sequence to set TabIndex property of controls automatically

  28. Form's Screen Location • StartPosition Property • Manual • CenterScreen • WindowsDefaultLocation • WindowsDefaultBounds • CenterParent

  29. ToolTips • Small label that is displayed when user places pointer on a control and pauses • Usually used with Command Buttons • Steps for creating ToolTips • Add a ToolTip Control to Form • Appears in the Component Tray, pane at bottom of Form Designer where nondisplay controls are shown • Set ToolTip on ToolTip1 Property of each control to the text of tip

  30. ToolTip Control Component Tray

  31. txtName.Text = "" lblMessage.Text = "" txtCourse.Clear( ) Clearing Text Boxes & Labels • Set Text Property equal to the Empty String • Empty String is 2 quotation marks with no space between them ("") • Use the Clear Method of a Text Box

  32. Resetting the Focus • Places the Insertion Point in a Text Box • Use the Focus Method txtName.Focus( )

  33. Checked Property of Check Boxes and Radio Buttons • Selects/Deselects Check Box or Radio Button • Set Checked Property • True = Checked, selected • False = Unchecked, deselected radRed.Checked = True chkBold.Checked = False

  34. VB Color Constants • ForeColor and BackColor Properties • Use VB Color Constants from the Color Class • View complete list in Help by using the keyword Color followed by a period txtName.ForeColor = Color.AliceBlue lblMessage.BackColor = Color.White

  35. With and End With • Change several properties at once in Code • Will run more efficiently With txtName .Visible = True .Text ="Lynne" . Focus( ) End With

  36. Concatenation • Think of it as "glueing" text strings together • Example: txtFName contains First Name txtLName contains Last Name lblFullName.Text = txtFName.Text & " " & txtLName.Text lblNote.Text = "Today's weather is " & txtWeather.Text & "."

  37. Continuing Lines of Code • For long lines of code it is more readable to continue them to the next line • At the end of the line type Line Continuation Character, a Space followed by an Underscore lblMessage.Text = txtFName.Text & "" & txtLName.Text & _ ", welcome to Aiken Technical College. Today is " & _ txtToday.Text