Date post: | 06-Jan-2018 |
Category: |
Documents |
Upload: | patrick-morgan |
View: | 217 times |
Download: | 2 times |
1
Chapter 4 – Decisions4.1 Relational and Logical Operators (see
other set of slides)4.2 If Blocks (see other set of slides)4.3 Select Case Blocks (see other set of
slides)4.4 Input via User Selection
4.4 Input via User Selection• Using a List Box for Input• Using Radio Buttons for Input• Using Check Boxes for Input• Events Raised by Selections
2
The Three Types of Controls Used for Selection
3
list box
radio buttons check
boxes
Which would you use for:
Age? Ethnicity?
Fill a List Box at Design Time via its String Collection Editor
4
Tasks button
click here to invoke string collection editor
String Collection Editor
5
Fill by direct typing or by copying and pasting from a text editor or a spreadsheet.
List Box at Run Time
6
lstMonths
selected item
The value of lstMonths.Text is the string consisting of the selected item.
Example 4.4.1– Form Designer
Items property
Collections editor
Code
8
Selection by user
Output
10
The Group Box Control• Group boxes are passive objects used to
group other objects together.• When you drag a group box, the attached
controls follow as a unit.• To attach controls to a group box, create
the group box and then place the controls into the group box.
11
Group Box Example
Three attached controls:
Button1Button2Button3
12
Radio Button Properties• To determine if the button is on or off
radButton.Checked
has value True if button is on.
• To turn a radio button on radButton.Checked = True
Question: what is the data type of the RadioButton’s Checked property?
13
Example 3: Form
radChild
radAdult
radSenior
radMinor
Radio buttons are intended for mutually exclusive choices.By placing them in a GroupBox control, you guarantee only one will be selected.
14
Example 4.4.3If radChild.Checked Then txtFee.Text = FormatCurrency(0)ElseIf radMinor.Checked Then txtFee.Text = FormatCurrency(5)ElseIf radAdult.Checked Then txtFee.Text = FormatCurrency(10)ElseIf radSenior.Checked Then txtFee.Text = FormatCurrency(7.5)Else MessageBox.Show("Must make a selection.")End If
15
Example 4.4.3: Output
16
The Check Box Control• Consists of a small square and a caption• Presents the user with a Yes/No choice• During run time, clicking on the check box
toggles the appearance of a check mark.• Checked property has value True when check
box is checked and False when not• CheckedChanged event is raised when the
user clicks on the check box
17
Example 4.4.4: Form
chkDrug
chkDentalchkVision
chkMedical
Check boxes are intended for allowing multiple selections. This happens regardless of whether or not they are placed in a GroupBox.
Example 4.4.4: Code for ButtonDim sum As Double = 0If chkDrugs.Checked Then sum += 39.15End IfIf chkDental.Checked Then sum += 10.81End IfIf chkVision.Checked Then sum += 2.25End IfIf chkMedical.Checked Then sum += 55.52End IftxtTotal.Text = FormatCurrency(sum)
18
Example 4.4.4: Output
19
Events Raised by a Selection
• SelectedIndexChanged – raised when a new item of a list box is selected
• CheckedChanged - raised when the user clicks on an unchecked radio button or a check box; that is, when the value of the Checked property is changed.
20
21
Example 5: Code
Here, a single event procedure is handling multiple events. In this case, whichever CheckBox’s Checked status gets changed will trigger the procedure to execute.
22
Example 5: Output