ENGR/CS 101 CS Session
Lecture 4
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Log into Windows/ACENET (reboot if in Linux)
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Start Microsoft Visual Studio 2010
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Finish exercise from last time
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Outline
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Problem: Use a GUI to enter user input
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Microsoft Visual Studio GUI designer
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Forms, textboxes, buttons, labels
C# programming language
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Properties
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Events and handlers
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Problem Specification
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Today's program will be a GUI application that
has the same functionality as the console
program from last time.
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Allow the user to enter a shift key letter in
uppercase
Allow the user to enter a plaintext letter in
uppercase to be enciphered
Have a button for the user to click to have the
plaintext letter enciphered
Display the ciphertext letter
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Interface Mockup
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Textboxes to enter
plaintext and shift
key, and to display
ciphertext
Button to encipher
plaintext.
Labels to identify the
textboxes
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Creating a GUI Project
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Create a new project. Make sure the language
template is Visual C#.
Select "Windows Form Application". Give the
project a name like "cs101gui".
Click on OK. You will get the GUI designer with
a blank form.
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Creating a GUI Project
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GUI Designer
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GUI Designer
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Every GUI application has a base form that
contains all other GUI elements. Change size
by pulling on the handles.
GUI elements are available in the Toolbox.
Click on form, then roll mouse over the Toolbox
tab, click on Common Controls.
Select and place GUI elements
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E.g., Textbox, Button, Label
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GUI Designer
Toolbox Tab
GUI element
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GUI Designer
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Properties
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Each GUI element has properties that control
its appearance. E.g., Text, Font, Size
Values for the selected element are shown in
Properties Window (View -> Properties
Window), usually in the lower right corner
You can change the initial values in the
Properties Window. Can also change them in
program code (i.e., while program is running).
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Properties
Properties Window
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Properties
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Each GUI element is an object with a Name
property that is its variable name in the code.
Always change the Name of manipulated
elements so they have meaningful variables
names. E.g. plaintextBox rather than
textbox1.
Almost every GUI element has a Text property.
E.g., the main form's Text property is its
titlebar. We can change it to give the
application a title.
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Properties
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Properties are accessed in programs using a
dot (.):
<element name>. <property name>
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For example, textboxes have a Text property
that is a string containing the contents of the
box. To access this string in the plaintext box
use: plaintextBox.Text
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In-class Exercise, Part 1
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Create a simple form with three Textboxes for
the plaintext, ciphertext, and shift key, and a
Button.
After changing the properties as described on
the next slide, label and arrange these
elements however you like on the form.
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In-class Exercise, Part 1
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Change the following properties:
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For the Textboxes, change their Name property to
"plaintextBox", "ciphertextBox", and "keyBox"
(without the quotes), respectively. For plaintextBox
and ciphertextBox, change Multiline property to
True. After this, pull on the handles to make them
as large as you like.
For the Button, change its Name to "encipher" and
its Text to "Encipher".
Change Font properties to the font and size of your
choice.
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Events and Handlers
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Unlike console programs, which require the
programmer to prompt and read in user data,
GUI programs have form elements that are
always waiting for data, but computation only
happens when an event occurs.
Input devices cause events that the GUI then
handles. For example:
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Mouse events include: Click, DoubleClick,
MouseDown, MouseMove, MouseUp, Rollover
Keyboard events include: KeyPress
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Events and Handlers
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Double-clicking on a form element in the GUI
designer brings up the code view of the form.
As with console programs, MSVS has created a
skeleton program.
It also creates a handler function stub for the
most common event for the element type and
attaches it to the element. E.g., Click event for
our Encipher button.
When a user clicks the Encipher button, this
handler function is run to respond to the event.
We'll have it encipher a plaintext letter.
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Events and Handlers
Handler code goes here!
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Events and Handlers
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A handler function can access any of the GUI
elements and their properties.
We will get the user data from the keyBox and
plaintextBox using the Text property like so:
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keyBox.Text
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plaintextBox.Text
Just as with the user input from the console, we
need to convert a string into a char using
char.Parse( )
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Handler Design
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The design of the handler code for the Encipher
button basically is the same as the console
program. However, the details of how the user
input is received and the result displayed are
different since we are using Textboxes. (New
or modified steps in bold.)
1. Clear the ciphertext box
2. Get the shift key from keyBox.Text
3. Get the plaintext letter from plaintextBox.Text
4. Compute the ciphertext letter
5. Append the cipher letter to the ciphertext box.
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In-class Exercise, Part 2
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For our program, we want to handle a mouse
click on the Encipher button. Double-click on
the button to get to the handler function stub, if
you haven't done so already.
Add the handler function code shown on the
next two slides. It basically is the same as the
console program code, except the user
interaction uses the textboxes rather than the
console.
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Encipher Button Handler Code
// This code goes in the place indicated on Slide 19
// The modified parts from the console program are bold
// Variable declarations ­ same as console program
char shiftKey, // key letter plainLetter, // user input
cipherLetter; // result
int shiftNumber, // # of shift places
index; // of cipher letter
// Clear the result box
ciphertextBox.Text = "";
// Get the key letter and a letter to encipher from user
shiftKey = char.Parse(keyBox.Text);
plainLetter = char.Parse(plaintextBox.Text);
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Encipher Button Handler Code
// Compute the corresponding ciphertext letter
// Same as the console program
shiftNumber = shiftKey ­ 'A';
index = (plainLetter ­ 'A' + shiftNumber) % 26;
cipherLetter = (char)((int)'A' + index);
// Display the results
// Append the enciphered letter to ciphertext box
// Need to convert it to a string first
ciphertextBox.AppendText(cipherLetter.ToString());
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