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Chapter 13. Graphical User Interface
Concepts: Part 1
Continue from previouse lecture
 2007 Dr. Natheer Khasawneh
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Basic GUI components
Control
Description
Label
An area in which icons or uneditable text can be displayed.
TextBox
An area in which the user inputs data from the keyboard. The area also
can display information.
Button
An area that triggers an event when clicked.
CheckBox
A GUI control that is either selected or not selected.
ComboBox
A drop-down list of items from which the user can make a selection,
by clicking an item in the list or by typing into the box, if permitted.
ListBox
An area in which a list of items is displayed from which the user can
make a selection by clicking once on any element. Multiple elements
can be selected.
Panel
A container in which components can be placed.
ScrollBar
Allows the user to access a range of values that cannot normally fit in
its container.
Fig. 13.2
Some basic GUI components.
 2007 Dr. Natheer Khasawneh
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Windows Forms
• Component
– Class that implements IComponent interface
– Lacks visual parts
• Control
– Component with graphical part
• Such as button or label
– Are visible
• Event
– Generated by movement from mouse or keyboard
– Event handlers performs action
• Specifics written by programmer
 2007 Dr. Natheer Khasawneh
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Windows Forms
Components and controls for Windows Forms.
 2007 Dr. Natheer Khasawneh
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Windows Forms
Form Properties and
Description / Delegate and Event Arguments
Events
Common Properties
AcceptButton
Which button will be clicked when Enter is pressed.
AutoScroll
Whether scrollbars appear when needed (if data fills more than one
screen).
CancelButton
Button that is clicked when the Escape key is pressed.
FormBorderStyle
Border of the form (e.g., none, single, 3D, sizable).
Font
Font of text displayed on the form, as well as the default font of
controls added to the form.
Text
Text in the form’s title bar.
Common Methods
Close
Closes form and releases all resources. A closed form cannot be
reopened.
Hide
Hides form (does not release resources).
Show
Displays a hidden form.
Common Events
(Delegate EventHandler, event arguments EventArgs)
Load
Occurs before a form is shown. This event is the default when the
form is double-clicked in the Visual Studio .NET designer.
Fig. 13.4
Common Form properties and events.
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Finding Events
Class name
F
List of Form events.
 2007 Dr. Natheer Khasawneh
List of events
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Finding Events
Event name
Event delegate
Details of Click event.
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Finding Events
Argument class
Event delegate
Details of Click event.
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Control Properties and Layout
• Common properties
– Derive from class Control
– Text property
• Specifies the text that appears on a control
– Focus method
• Transfers the focus to a control
• Becomes active control
– TabIndex property
• Order in which controls are given focus
• Automatically set by Visual Studio .NET
– Enable property
• Indicate a control’s accessibility
 2007 Dr. Natheer Khasawneh
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Control Properties and Layout
• Visibility control
– Hide control from user
• Or use method Hide
• Anchor property
– Anchoring control to specific location
• Constant distance from specified location
– Unanchored control moves relative to the position
– Docking allows control to spread itself along and entire side
– Both options refer to the parent container
• Size structure
– Allow for specifying size range
• MinimumSize and MaximumSize property
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13.4 Control Properties and Layout
De sc rip tion
Cla ss Control
Pro p e rtie s a nd M etho d s
Common Properties
BackColor
Background color of the control.
BackgroundImage
Background image of the control.
Enabled
Whether the control is enabled (i.e., if the user can interact with it). A
disabled control will still be displayed, but “grayed-out”—portions of
the control will become gray.
Focused
Whether a control has focus. (The control that is currently being used
in some way.)
Font
Font used to display control’s Text.
ForeColor
Foreground color of the control. This is usually the color used to
display the control’s Text property.
TabIndex
Tab order of the control. When the Tab key is pressed, the focus is
moved to controls in increasing tab order. This order can be set by the
programmer.
TabStop
If true, user can use the Tab key to select the control.
Text
Text associated with the control. The location and appearance varies
with the type of control.
TextAlign
The alignment of the text on the control. One of three horizontal
positions (left, center or right) and one of three vertical positions (top,
middle or bottom).
Visible
Whether the control is visible.
Common Methods
Focus
Transfers the focus to the control.
Hide
Hides the control (sets Visible to false).
Show
Shows the control (sets Visible to true).
Fig. 12.10
C la ss Control p ro p e rtie s a nd m e tho d s.
 2007 Dr. Natheer Khasawneh
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13.4 Control Properties and Layout
Before resize
After resize
Constant distance
to left and top sides
Fig. 13.11 Anchoring demonstration.
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13.4 Control Properties and Layout
Darkened bar indicates
to which wall control
is anchored
Click down-arrow
in Anchor property
to display
anchoring window
Fig. 13.12 Manipulating the Anchor property of a control.
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13.4 Control Properties and Layout
Control expands along
top portion of the form
Fig. 13.13 Docking demonstration.
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13.4 Control Properties and Layout
Common Layout
Properties
Description
Common Properties
Anchor
Side of parent container at which to anchor control—values can be
combined, such as Top, Left.
Dock
Side of parent container to dock control—values cannot be combined.
DockPadding (for
containers)
Sets the dock spacing for controls inside the container. Default is zero,
so controls appear flush against the side of the container.
Location
Location of the upper-left corner of the control, relative to it’s
container.
Size
Size of the control. Takes a Size structure, which has properties
Height and Width.
MinimumSize,
MaximumSize (for
Windows Forms)
The minimum and maximum size of the form.
Fig. 13.14 Class Control layout properties.
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13.5 Labels, TextBoxes and Buttons
• Labels
– Provide text instruction
• Read only text
– Defined with class Label1
• Derived from class Control
• Textbox
– Class TextBox
– Area for text input
• Password textbox
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13.5 Labels, TextBoxes and Buttons
• Button
– Control to trigger a specific action
• Checkboxes or radio buttons
– Derived from ButtonBase
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13.5 Labels TextBoxes and Buttons
Label
Description / Delegate and Event Arguments
Properties
Common
Properties
Font
The font used by the text on the Label.
Text
The text to appear on the Label.
TextAlign
The alignment of the Label’s text on the control. One of three horizontal positions
(left, center or right) and one of three vertical positions (top, middle or
bottom).
Fig. 13.15
Label properties.
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13.5 Labels TextBoxes and Buttons
TextBox Properties
Description / Delegate and Event Arguments
and Events
Common Properties
AcceptsReturn
If true, pressing Enter creates a new line if textbox spans multiple
lines. If false, pressing Enter clicks the default button of the form.
Multiline
If true, textbox can span multiple lines. Default is false.
PasswordChar
Single character to display instead of typed text, making the
TextBox a password box. If no character is specified, Textbox
displays the typed text.
ReadOnly
If true, TextBox has a gray background and its text cannot be
edited. Default is false.
ScrollBars
For multiline textboxes, indicates which scrollbars appear (none,
horizontal, vertical or both).
Text
The text to be displayed in the text box.
Common Events
(Delegate EventHandler, event arguments EventArgs)
TextChanged
Raised when text changes in TextBox (the user added or deleted
characters). Default event when this control is double clicked in the
designer.
Fig. 13.16
TextBox properties and events.
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13.5 Labels TextBoxes and Buttons
Button properties and
Description / Delegate and Event Arguments
events
Common Properties
Text
Text displayed on the Button face.
Common Events
(Delegate EventHandler, event arguments EventArgs)
Click
Raised when user clicks the control. Default event when this control is
double clicked in the designer.
Fig. 13.17
Button properties and events.
 2007 Dr. Natheer Khasawneh
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// Fig. 13.18: LabelTextBoxButtonTest.cs
// Using a Textbox, Label and Button to display
// the hidden text in a password box.
using
using
using
using
using
using
Outline
LabelTextBoxButt
onTest.cs
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
// namespace contains our form to display hidden text
namespace LabelTextBoxButtonTest
Visual Studio .NET adds
{
comments to our code
/// <summary>
/// form that creates a password textbox and
/// a label to display textbox contents
/// </summary>
Visual
The
IDE
Studio
manages
.NETthese
inserts
declaration
declarations
public class LabelTextBoxButtonTest :
System.Windows.Forms.Form
for the control we added to the form
{
private System.Windows.Forms.Button displayPasswordButton;
private System.Windows.Forms.Label displayPasswordLabel;
private System.Windows.Forms.TextBox inputPasswordTextBox;
Declare reference Reference
components
(an array)
is null
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
// default contructor
public LabelTextBoxButtonTest()
{
InitializeComponent();
}
Method InitializeComponent creates
Constructor
forand
thecontrols
form is created
for us
components
in the form
and
sets their properties
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/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if ( disposing )
{
Method Dispose
if ( components != null )
{
components.Dispose();
}
}
base.Dispose( disposing );
}
Outline
LabelTextBoxButt
onTest.cs
cleans up allocated resources
#region preprocessor directives allow
collapsible code in Visual Studio .NET
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.displayPasswordButton =
Create new objects
new System.Windows.Forms.Button();
control we added
this.inputPasswordTextBox =
new System.Windows.Forms.TextBox();
this.displayPasswordLabel =
new System.Windows.Forms.Label();
this.SuspendLayout();
for the
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//
// displayPasswordButton
//
this.displayPasswordButton.Location =
new System.Drawing.Point( 96, 96 );
this.displayPasswordButton.Name =
"displayPasswordButton";
this.displayPasswordButton.TabIndex = 1;
this.displayPasswordButton.Text = "Show Me";
this.displayPasswordButton.Click +=
new System.EventHandler(
this.displayPasswordButton_Click );
//
// inputPasswordTextBox
//
this.inputPasswordTextBox.Location =
new System.Drawing.Point( 16, 16 );
this.inputPasswordTextBox.Name =
"inputPasswordTextBox";
this.inputPasswordTextBox.PasswordChar = '*';
this.inputPasswordTextBox.Size =
new System.Drawing.Size( 264, 20 );
this.inputPasswordTextBox.TabIndex = 0;
this.inputPasswordTextBox.Text = "";
//
// displayPasswordLabel
//
this.displayPasswordLabel.BorderStyle =
System.Windows.Forms.BorderStyle.Fixed3D;
this.displayPasswordLabel.Location =
new System.Drawing.Point( 16, 48 );
this.displayPasswordLabel.Name =
"displayPasswordLabel";
Outline
LabelTextBoxButt
onTest.cs
Visual Studio .NET register
the event handler for us
Set the Name, PasswordChar
and Text properties for
inputPasswordTextBox
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Outline
this.displayPasswordLabel.Size =
new System.Drawing.Size( 264, 23 );
this.displayPasswordLabel.TabIndex = 2;
//
// LabelTextBoxButtonTest
//
this.AutoScaleBaseSize =
new System.Drawing.Size( 5, 13 );
this.ClientSize =
new System.Drawing.Size( 292, 133 );
this.Controls.AddRange(
new System.Windows.Forms.Control[] {
this.displayPasswordLabel,
this.inputPasswordTextBox,
this.displayPasswordButton});
this.Name = "LabelTextBoxButtonTest";
this.Text = "LabelTextBoxButtonTest";
this.ResumeLayout( false );
LabelTextBoxButt
onTest.cs
} // end method InitializeComponent
// end collapsible region started on line 53
#endregion
#endregion
signal the end
of the collapsible region
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run( new LabelTextBoxButtonTest() );
}
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Outline
// display user input on label
protected void displayPasswordButton_Click(
object sender, System.EventArgs e )
To show the text, set
{
User
must program this lineLabelTextBoxButt
manually
displayPasswordLabel’s
Text
to
// text has not changed
displayPasswordLabel.Text =
inputPasswordTextBox’sonTest.cs
Text
inputPasswordTextBox.Text;
Create an empty event handler named
}
displayPasswordButton_Click
} // end class LabelTextBoxButtonTest
} // end namespace LabelTextBoxButtonTest
Program Output
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13.6 GroupBoxes and Panels
• Arrange components on a GUI
– GroupBoxes can display a caption
• Text property determines its caption
– Panels can have scrollbar
• View additional controls inside the Panel
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13.6 GroupBoxes and Panels
GroupBox Properties
Description
Common Properties
Controls
The controls that the GroupBox contains.
Text
Text displayed on the top portion of the GroupBox (its caption).
Fig. 13.19
GroupBox properties.
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13.6 GroupBoxes and Panels
Panel Properties
Description
Common Properties
AutoScroll
Whether scrollbars appear when the Panel is too small to hold its
controls. Default is false.
BorderStyle
Border of the Panel (default None; other options are Fixed3D and
FixedSingle).
Controls
The controls that the Panel contains.
Fig. 13.20
Panel properties.
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13.6 GroupBoxes and Panels
Controls inside
panel
panel
panel
scrollbars
Fig. 13.21 Creating a Panel with scrollbars.
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Outline
// Fig. 13.22: GroupBoxPanelExample.cs
// Using GroupBoxes and Panels to hold buttons.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
GroupBoxPanelExa
mple.cs
/// form to display a groupbox versus a panel
public class GroupBoxPanelExample : System.Windows.Forms.Form
{
private System.Windows.Forms.Button hiButton;
GroupBox (name mainGroupBox)
private System.Windows.Forms.Button byeButton;
private System.Windows.Forms.Button leftButton;
private System.Windows.Forms.Button rightButton;
Panel (name mainPanel)
private System.Windows.Forms.GroupBox mainGroupBox;
private System.Windows.Forms.Label messageLabel;
private System.Windows.Forms.Panel mainPanel;
Control AutoScroll
property set to TRUE
messageLabel is initially blank
private System.ComponentModel.Container components = null;
// Visual Studio .NET-generated Dispose method
[STAThread]
static void Main()
{
Application.Run( new GroupBoxPanelExample() );
}
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Outline
// event handlers to change messageLabel
// event handler for hi button
private void hiButton_Click(
object sender, System.EventArgs e )
{
messageLabel.Text= "Hi pressed";
}
// event handler for bye button
private void byeButton_Click(
object sender, System.EventArgs e )
{
messageLabel.Text = "Bye pressed";
}
// event handler for far left button
private void leftButton_Click(
object sender, System.EventArgs e )
{
messageLabel.Text = "Far left pressed";
}
GroupBoxPanelExa
mple.cs
hiButton and byeButton
belong to GroupBox
Represent event handlers
Line messageLabel added to
customize the text
Panel has two buttons,
leftButton and rightButton
// event handler for far right button
private void rightButton_Click(
object sender, System.EventArgs e )
{
messageLabel.Text = "Far right pressed";
}
} // end class GroupBoxPanelExample
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Outline
GroupBoxPanelExa
mple.cs
Program Output
hiButton_Click
leftButton_Click
rightButton_Click
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13.7 Checkboxes and RadioButtons
• State buttons
– On/off or true/false state
– Derived from class ButtonBase
• CheckBox
– No restriction on usage
• RadioButton
– Grouped together
– Only one can be true
– Mutually exclusive options
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13.7 CheckBoxes and RadioButtons
CheckBox events and
Description / Delegate and Event Arguments
properties
Common Properties
Checked
Whether or not the CheckBox has been checked.
CheckState
Whether the Checkbox is checked (contains a black checkmark) or
unchecked (blank). An enumeration with values Checked,
Unchecked or Indeterminate.
Text
Text displayed to the right of the CheckBox (called the label).
Common Events
(Delegate EventHandler, event arguments EventArgs)
CheckedChanged
Raised every time the Checkbox is either checked or unchecked.
Default event when this control is double clicked in the designer.
CheckStateChanged Raised when the CheckState property changes.
Fig. 13.23
CheckBox properties and events.
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Outline
// Fig. 13.24: CheckBoxTest.cs
// Using CheckBoxes to toggle italic and bold styles.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
/// form contains checkboxes to allow
/// the user to modify sample text
public class CheckBoxTest : System.Windows.Forms.Form
{
private System.Windows.Forms.CheckBox boldCheckBox;
private System.Windows.Forms.CheckBox italicCheckBox;
private System.Windows.Forms.Label outputLabel;
CheckBoxTest.cs
When program start, both
Checkbox is unchecked
Text property set to Bold
The property
Label OutputLabel
Text
set to Italic is labeled
Watch the font style change
private System.ComponentModel.Container components = null;
// Visual Studio .NET-generated Dispose method
/// The main entry point for the application.
[STAThread]
static void Main()
{
Application.Run( new CheckBoxTest() );
}
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// make text bold if not bold,
// if already bold make not bold
private void boldCheckBox_CheckedChanged(
object sender, System.EventArgs e )
{
outputLabel.Font =
new Font( outputLabel.Font.Name,
outputLabel.Font.Size,
outputLabel.Font.Style ^ FontStyle.Bold );
}
Outline
CheckBoxTest.cs
Font constructor takes in the
font name, size, and style
Style is a member of the
//Style
make property
text italic if not italic,
Style
object’s
can
useStyle
bitwise
property
operators
is
FontStyle
enumeration
// if already Font
italic
make
not
italic
itself
is
read-only
set when object is created
private void italicCheckBox_CheckedChanged(
object sender, System.EventArgs e )
{
outputLabel.Font =
new Font( outputLabel.Font.Name,
outputLabel.Font.Size,
outputLabel.Font.Style ^ FontStyle.Italic );
}
} // end class CheckBoxTest
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Outline
CheckBoxTest.cs
Program Output
Result when bold is selected
Result when both styles are
selected
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13.7 CheckBoxes and RadioButtons
RadioButton
Description / Delegate and Event Arguments
properties and events
Common Properties
Checked
Whether the RadioButton is checked.
Text
Text displayed to the right of the RadioButton (called the label).
Common Events
(Delegate EventHandler, event arguments EventArgs)
Click
Raised when user clicks the control.
CheckedChanged
Raised every time the RadioButton is checked or unchecked.
Default event when this control is double clicked in the designer.
Fig. 13.25
RadioButton properties and events.
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Outline
// Fig. 13.26: RadioButtonsTest.cs
// Using RadioButtons to set message window options.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
RadioButtonsTest
.cs
/// form contains several radio buttons--user chooses one
/// from each group to create a custom MessageBox
public class RadioButtonsTest : System.Windows.Forms.Form
Label is used to prompt user
{
private System.Windows.Forms.Label promptLabel;
Label is used to display
private System.Windows.Forms.Label displayLabel;
which button was pressed
private System.Windows.Forms.Button displayButton;
Display the text Display
private System.Windows.Forms.RadioButton questionButton;
private System.Windows.Forms.RadioButton informationButton;
private System.Windows.Forms.RadioButton exclamationButton;
RadioButtons are
private System.Windows.Forms.RadioButton errorButton;
private System.Windows.Forms.RadioButton retryCancelButton;
created for the
private System.Windows.Forms.RadioButton yesNoButton;
enumeration options
private System.Windows.Forms.RadioButton yesNoCancelButton;
private System.Windows.Forms.RadioButton okCancelButton;
One event handling exists for
private System.Windows.Forms.RadioButton
okButton;
To store user’s choice
of
private System.Windows.Forms.RadioButton
all the
radio
buttons in
The
enumeration
options iconType is created. Object
iconType
is a
abortRetryIgnoreButton;
private System.Windows.Forms.GroupBox groupBox2;
private System.Windows.Forms.GroupBox groupBox1;
groupBox1
and groupBox2
name indicate
which
MessageBoxIcon
button to display
enumeration
private MessageBoxIcon iconType = MessageBoxIcon.Error;
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Outline
private MessageBoxButtons buttonType =
MessageBoxButtons.OK;
The enumeration
To
storebuttonType
user’s choice
Object
is of
a
name indicate
options
which
buttonType
is
created
MessageBoxButtom enumeration
/// The main entry point for the application.
button to display
RadioButtonsTest
[STAThread]
.cs
static void Main()
Handlers
compare
the
sender
object
{
Application.Run( new RadioButtonsTest()
); button to determine
with every radio
}
which button was selected
// change button based on option chosen by sender
private void buttonType_CheckedChanged(
object sender, System.EventArgs e )
Each radio button generates
{
a CheckedChanged when
if ( sender == okButton ) // display OK button
clicked
buttonType = MessageBoxButtons.OK;
// display OK and Cancel buttons
else if ( sender == okCancelButton )
buttonType = MessageBoxButtons.OKCancel;
// display Abort, Retry and Ignore buttons
else if ( sender == abortRetryIgnoreButton )
buttonType = MessageBoxButtons.AbortRetryIgnore;
// display Yes, No and Cancel buttons
else if ( sender == yesNoCancelButton )
buttonType = MessageBoxButtons.YesNoCancel;
// display Yes and No buttons
else if ( sender == yesNoButton )
buttonType = MessageBoxButtons.YesNo;
// only one option left--display
// Retry and Cancel buttons
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Outline
else
buttonType = MessageBoxButtons.RetryCancel;
Handlers compare the
} // end method
sender object
with every radio button to determine
buttonType_CheckedChanged
which button was selected
// change icon based on option chosen by sender
private void iconType_CheckedChanged(
object sender, System.EventArgs e )
{
if ( sender == errorButton ) // display error icon
iconType = MessageBoxIcon.Error;
RadioButtonsTest
.cs
// display exclamation point
else if ( sender == exclamationButton )
iconType = MessageBoxIcon.Exclamation;
// display information icon
else if ( sender == informationButton )
iconType = MessageBoxIcon.Information;
else // only one option left--display question mark
iconType = MessageBoxIcon.Question;
} // end method iconType_CheckedChanged
// display MessageBox and button user pressed
protected void displayButton_Click(
Result
Click
ofhandler
messagefor
box
displayButton
is a
object sender, System.EventArgs e )
DialogResult
creates a MessageBox
enumeration
{
DialogResult result =
Switch
statement tests for the result and
MessageBox.Show( "This is Your Custom MessageBox.",
set displayLabel.Text
appropriately
"Custom MessageBox",
buttonType, iconType, 0, 0 );
// check for dialog result and display it in label
switch ( result )
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{
case DialogResult.OK:
displayLabel.Text = "OK was pressed.";
break;
case DialogResult.Cancel:
displayLabel.Text = "Cancel was pressed.";
break;
case DialogResult.Abort:
displayLabel.Text = "Abort was pressed.";
break;
case DialogResult.Retry:
displayLabel.Text = "Retry was pressed.";
break;
Outline
RadioButtonsTest
.cs
The result input will help
determine which text to display
among the cases
case DialogResult.Ignore:
displayLabel.Text = "Ignore was pressed.";
break;
case DialogResult.Yes:
displayLabel.Text = "Yes was pressed.";
break;
case DialogResult.No:
displayLabel.Text = "No was pressed.";
break;
} // end switch
} // end method displayButton_Click
} // end class RadioButtonsTest
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Outline
RadioButtonsTest
.cs
Program Output
Radio button style allow user
to select one per column
Exclamation icon type
OKCancel button type
Error icon type
OK button type
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Outline
Information icon type
Question icon type
AbortRetryIgnore button type
YesNoCancel button type
YesNo button type
RadioButtonsTest
.cs
Program Output
RetryCancel button type
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Khasawneh
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13.8 PictureBoxes
• Class PictureBox
– Displays an image
• Image set by object of class Image.
– The Image property sets the Image object to use
– SizeMode property sets how the image is displayed
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13.8 PictureBoxes
PictureBox
Description / Delegate and Event Arguments
properties and events
Common Properties
Image
Image to display in the PictureBox.
SizeMode
Enumeration that controls image sizing and positioning. Values
Normal (default), StretchImage, AutoSize and
CenterImage. Normal puts image in top-left corner of
PictureBox and CenterImage puts image in middle (both cut
off image if too large). StretchImage resizes image to fit in
PictureBox. AutoSize resizes PictureBox to hold image.
Common Events
(Delegate EventHandler, event arguments EventArgs)
Click
Raised when user clicks the control. Default event when this control is
double clicked in the designer.
Fig. 13.27 PictureBox properties and events.
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Outline
// Fig. 13.28: PictureBoxTest.cs
// Using a PictureBox to display images.
using
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
System.IO;
/// form to display different images when clicked
public class PictureBoxTest : System.Windows.Forms.Form
{
private System.Windows.Forms.PictureBox imagePictureBox;
private System.Windows.Forms.Label promptLabel;
PictureBoxTest.c
s
PictureBox imagePicture
use to display
one of three bitmap images
private int imageNum = -1;
/// The main entry point for the application.
[STAThread]
static void Main()
{
Application.Run(
new PictureBoxTest()
);
Store
the image we want
to display
}
Includes instructions Click
On Picture Box to View
Images
To respond to the Click
// change image whenever PictureBox clicked
Modulus
calculation insures that
private void imagePictureBox_Click(
number is between 0 and 2
object sender, System.EventArgs e )
{
imageNum = ( imageNum + 1 ) % 3; // imageNum from 0 to 2
event
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// create Image object from file, display on PictureBox
imagePictureBox.Image = Image.FromFile(
Directory.GetCurrentDirectory() + "\\images\\image" +
imageNum + ".bmp" );
}
Method GetCurrentDirectory of Class Directory
} //the
end
class
PictureBoxTest
Set
Use
Image
imageNum
property
toofappend
Method
FromFile which
returns
current directory of file
as a string
imagePictureBox
the correct number
to an Image
takes a string and creates
an Image object
Outline
PictureBoxTest.c
s
Program Output
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13.9 Mouse Event Handling
• Class MouseEventArgs
–
–
–
–
–
–
Contain coordinates of the mouse pointer
The mouse pressed
Number of clicks
Number of notches the wheel turned
Passing mouse event
Mouse event-handling methods take an object and
MouseEventArgs object as argument
– The Click event uses delegate EventHandler and event
arguments EventArgs
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13.9 Mouse Event Handling
M ouse Eve nts, Dele g a te s
a nd Event Arg um e nts
Mouse Events (Delegate
EventHandler, event
arguments EventArgs)
MouseEnter
Raised if the mouse cursor enters the area of the control.
MouseLeave
Raised if the mouse cursor leaves the area of the control.
Mouse Events (Delegate
MouseEventHandler,
event arguments
MouseEventArgs)
MouseDown
Raised if the mouse button is pressed while its cursor is over the area of the
control.
MouseHover
Raised if the mouse cursor hovers over the area of the control.
MouseMove
Raised if the mouse cursor is moved while in the area of the control.
MouseUp
Raised if the mouse button is released when the cursor is over the area of the
control.
Class MouseEventArgs
Properties
Button
Mouse button that was pressed (left, right, middle or none).
Clicks
The number of times the mouse button was clicked.
X
The x-coordinate of the event, relative to the component.
Y
The y-coordinate of the event, relative to the component.
Fig. 12.29
Mo use e ve nts, d e le g a te s a nd e ve nt a rg um e nts.
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Outline
// Fig 13.30: Painter.cs
// Using the mouse to draw on a form.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
/// creates a form as a drawing surface
public class Painter : System.Windows.Forms.Form
{
bool shouldPaint = false; // whether to paint
Painter.cs
Creates variable shouldPaint to
determine whether to draw on
the form
/// The main entry point for the application.
[STAThread]
static void Main()
{
Application.Run( new Painter() );
}
// should paint after mouse button has been pressed
The event handler for
private void Painter_MouseDown(
MouseDown
object sender, System.Windows.Forms.MouseEventArgs eevent
)
{
shouldPaint
Mouse
cursor willis set to true
shouldPaint = true;
}
drawwhen this event occurs
// stop painting when mouse button released
The event handler of
private void Painter_MouseUp(
object sender, System.Windows.Forms.MouseEventArgs
e )mouse
shouldPaint set to false,
event MouseUp
{
cursor will not draw
shouldPaint = false;
 2007 Dr. Natheer
}
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Outline
// draw circle whenever mouse button
// moves (and mouse is down)
protected void Painter_MouseMove(
Painter.cs
object sender, System.Windows.Forms.MouseEventArgs e )
{
Creates
Program
the graphic
will draw only if
if ( shouldPaint )
object
shouldPaint
for the formis true
{
FillEllipse
draws a circle at every
Graphics graphics = CreateGraphics(); Method
Provides
method for
graphics.FillEllipse(
new
SolidBrush
object
point
theCreate
mouse
cursor
moves over
and by
drawing
various
shapes
new SolidBrush( Color.BlueViolet ),
passing
the constructor a Color
shouldPaint
is true
e.X, e.Y, 4, 4 );
value
}
} // end
Coordinates of x and y and the pixels height
Structure Color contain
SolidBrush
object
determines
andnumerous
width
are supplied
to the parameter list
Painter_MouseMove
predefined color the
constants
color of the shape drawn
} // end class Painter
Program Output
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Important Notes from MSDN
• Mouse events occur in the following order:
–
–
–
–
–
MouseEnter
MouseMove
MouseHover / MouseDown / MouseWheel
MouseUp
MouseLeave
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13.10 Keyboard Event Handling
• Key events
– Control that inherits from System.Windows.Forms.Control
– Delegate KeyPressEventHandler
• Event argument KeyPressEventArgs
• KeyPress
– ASCII character pressed
– No modifier keys
– Delegate KeyEventHandler
• Event argument KeyEventArgs
• KeyUp or KeyDown
– Special modifier keys
• Key enumeration value
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13.10 Keyboard Event Handling
Keyboard Events, Delegates and
Event Arguments
Key Events (Delegate
KeyEventHandler, event arguments
KeyEventArgs)
KeyDown
Raised when key is initially pushed down.
KeyUp
Raised when key is released.
Key Events (Delegate
KeyPressEventHandler, event
arguments KeyPressEventArgs)
KeyPress
Raised when key is pressed. Occurs repeatedly while
key is held down, at a rate specified by the operating
system.
Class KeyPressEventArgs
Properties
KeyChar
Returns the ASCII character for the key pressed.
Handled
Whether or not the KeyPress event was handled.
Class KeyEventArgs Properties
Alt
Indicates whether the Alt key was pressed.
Control
Indicates whether the Control key was pressed.
Shift
Indicates whether the Shift key was pressed.
Handled
Whether the event was handled.
KeyCode
Returns the key code for the key, as a Keys
enumeration. This does not include modifier key
information. Used to test for a specific key.
KeyData
Returns the key code as a Keys enumeration,
combined with modifier information. Used to
determine all information about the key pressed.
KeyValue
Returns the key code as an int, rather than as a Keys
enumeration. Used to obtain a numeric representation
of the key pressed.
Modifiers
Returns a Keys enumeration for any modifier keys
pressed (Alt, Control and Shift). Used to determine
modifier key information only.
Fig. 13.31 Keyboard events, delegates and event arguments.
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Outline
// Fig. 13.32: KeyDemo.cs
// Displaying information about the key the user pressed.
using
using
using
using
using
using
System;
System.Drawing;
System.Collections;
System.ComponentModel;
System.Windows.Forms;
System.Data;
KeyDemo.cs
// form to display key press
// information--contains two labels
public class KeyDemo : System.Windows.Forms.Form
{
private System.Windows.Forms.Label charLabel;
private System.Windows.Forms.Label keyInfoLabel;
Label for key pressed
Forms contain
Initially
empty two Labels
Label for modifier information
private System.ComponentModel.Container components = null;
/// The main entry point for the application.
[STAThread]
static void Main()
{
Application.Run( new KeyDemo() );
}
KeyPress
event
Accesses
the KeyChar property of
If key pressed
ishandler
not ASCII,
the KeyPressEventArgs
object
remains
empty
keycharLabel
char
// display the character pressed using
protected void KeyDemo_KeyPress(
object sender, System.Windows.Forms.KeyPressEventArgs e )
{
Key pressed
charLabel.Text = "Key pressed: " + e.KeyChar;
}
Display the key pressed
as a char
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Outline
// display modifier keys, key code, key data and key value
private void KeyDemo_KeyDown(
object sender, System.Windows.Forms.KeyEventArgs e )
{
KeyDemo.cs
Uses Alt, Shift, and Control
keyInfoLabel.Text =
KeyEventArgs object
"Alt: " + ( e.Alt ? "Yes" : properties
"No") + '\n' +
"Shift: " + ( e.Shift ? "Yes"KeyCode
: "No" ) returns
+ '\n'the
a+Keys
key enumeration
pressed
This block test for special
"Ctrl: " + ( e.Control ? "Yes"Displays
: "No" )
+ KeyCode,
'\n' +
the
KeyData,
and bool if matched
KeyData
property
returns
akeys,
Keys
converted
without
modifier
into a string
keys
information
using
ToString
return
"KeyCode: " + e.KeyCode + '\n'KeyValue
+
properties
enumeration
with data about modifier keys
"KeyData: " + e.KeyData + '\n'
+
"KeyValue: " + e.KeyValue;
}
KeyValue
key code
as ankey
integer
Integer
valuereturns
is the the
Windows
virtual
code
KeyUp event handler clears both labels
// clear labels when key released
private void KeyDemo_KeyUp(
object sender, System.Windows.Forms.KeyEventArgs e )
{
keyInfoLabel.Text = "";
charLabel.Text = "";
}
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Outline
Keys enumeration can test for
specific keys by comparing key
pressed to KeyCode
KeyDemo.cs
Program Output
KeyDown event still raised so
KeyPress eventdisplays
was notinformation
engaged
keyInfoLabel
 2007 Dr. Natheer
Khasawneh
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Important Notes From MSDN
• Key events occur in the following order:
– KeyDown
– KeyPress
– KeyUp
• The KeyPress event is not raised by noncharacter keys;
however, the noncharacter keys do raise the KeyDown and
KeyUp events.
• Use the KeyChar property to sample keystrokes at run time
and to consume or modify a subset of common keystrokes.
• To handle keyboard events only at the form level and not
enable other controls to receive keyboard events, set the
KeyPressEventArgs.Handled property in your form's
KeyPress event-handling method to true.
 2007 Dr. Natheer Khasawneh