visualbasic lecture4.pdf

8/10/2019 visualbasic lecture4.pdf

1/20

Copyright 2011 Pearson Addison-Wesley

Addison Wesley

is an imprint of

2011 Pearson Addison-Wesley. All rights reserved.

Addison Wesley

is an imprint of

Chapter 3

Variables and Calculations


2/20


3/20


The TextBox Control

% text box is a rectangular area on a "or# that

accepts input "ro# a eyboard

Tutorial 3&1 pro'ides an exa#ple in the use o"a text box

Chapter 3& Slide 3


4/20


(sing the Text )roperty in Code

The TextBox control$s Text property can be

accessed in code the sa#e way you access

other properties

*or +xa#ple

The contents o" the Text property can be assigned

into a -abel control$s Text property

lblInfo.Text = txtInput.Text

The contents o" the Text property can be displayed

in a #essage box Chapter 3& Slide


5/20


6/20


String Concatenation

%ssu#e the user has entered their na#e into

the TextBox txt2a#e

-abel lblGreeting can say, 4ello5 to any na#e"ound in the TextBox

lblreeting.Text = !"ello ! # txt$ame.Text

%ppends user na#e in txt2a#e.Text to 4ello 5and stores result in text property o" lblGreeting

Chapter 3& Slide 6


7/20


String Concatenation

Tutorial 3&7 pro'ides another exa#ple o" how

to concatenate strings "ro# text boxes

Chapter 3& Slide 8

txtDayOfWee

ktxtMonth

txtDayOfMont

htxtYear

lblDateString

btnExitbtnClearbtnShowDate


8/20


%ligning Controls in 9esign /ode

!hen dragging a control to a "or#, it can be

aligned with a control already on the "or#

Blue guide lines appear "or 'ertical align#ent

-a'ender guide lines "or hori:ontal align#ent

Chapter 3& Slide ;


9/20


The *ocus /ethod

*or a control to ha'e the "ocus #eans that it is

ready to recei'e the user


10/20


The *ocus /ethod

?ou can tell which control has "ocus by its

characteristics

!hen a TextBox has "ocus, it will ha'e a blining

cursor or its text will be highlighted

!hen a button, radio button, or a chec box has

"ocus, you$ll see a thin dotted line around the

control

Tutorial 3&3 shows an exa#ple o" the *ocus

#ethodChapter 3& Slide1@


11/20


Controlling a *or#$s Tab =rder

with the TabIndex )roperty Tab ey steps "ocus "ro# one control to the

next

This order is set by the TabIndex property The Tab ey causes the "ocus to Au#p to the

control with the next highest TabIndex 'alue

The TabIndex property is best changed withthe Tab =rder option "ro# the View #enu

9isplays the "or# in tab order selection #ode

Set a new tab order by clicing the controls in theChapter 3& Slide11


12/20


%ssigning eyboard %ccess eys to Buttons

Say your "or# had a button with the text

+xit on it

?ou can allow the user to acti'ate the buttonusing %lt&D instead o" a #ouse clic

Eust change the button text property to

+Fxit The character "ollowing the


13/20



14/20


Setting the %ccept Button

The accept button is a button that is i#plicitly

acti'ated i" the user hits the +nter ey

The %cceptButton )roperty designates whichbutton on the "or# will beha'e in this #anner

The button cliced #ost "reuently on a "or#

is usually assigned as the accept button

Chapter 3& Slide1


15/20


Setting the Cancel Button

The cancel button is a button that is i#plicitly

acti'ated i" the user hits the +scape ey

The CancelButton )roperty designates whichbutton on the "or# will beha'e in this #anner

%ny exit or cancel button on a "or# is a

candidate to beco#e the cancel button Tutorial 3& pro'ides exa#ples o" setting

access eys, accept, and cancel buttons

Chapter 3& Slide1


16/20


Addison Wesley

is an imprint of

2011 Pearson Addison-Wesley. All rights reserved.

Addison Wesley

is an imprint of

Section 3.7

Variables and 9ata Types

Variables hold data that #ay be

#anipulated, used to #anipulate other data, or re#e#bered "or later use.


17/20


!hy 4a'e VariablesJ

% 'ariable is a storage location in the

co#puter$s #e#ory, used "or holding

in"or#ation while the progra# is running

The in"or#ation that is stored in a 'ariable

#ay change, hence the na#e 'ariable5

Chapter 3& Slide18


18/20


!hat Can ?ou 9o !ith VariablesJ

Copy and store 'alues entered by the user, so

they #ay be #anipulated

)er"or# arith#etic on 'alues Test 'alues to deter#ine that they #eet so#e

criterion

Te#porarily hold and #anipulate the 'alue o"a control property

Ke#e#ber in"or#ation "or later use in the

progra# Chapter 3& Slide1;


19/20


4ow to Thin %bout Variables

?ou the progra##er #ae up a na#e "or the

'ariable

Visual Basic associates that na#e with alocation in the co#puter


20/20


9eclaring Variables

% 'ariable declaration is a state#ent that creates a 'ariable in

#e#ory

The syntax is

im ariable$ame *s ataType

imshort "or 9i#ensionH is a eyword

ariable$ameis the progra##er designated na#e

*sis a eyword

ataTypeis one o" #any possible eywords "or the type

o" 'alue the 'ariable will contain

Chapter 3& Slide7@

visualbasic lecture4.pdf

Documents