Lesson 5 GUI Programming AUBG ICoSCIS Team Assoc. Prof. Stoyan Bonev

Lesson 5GUI Programming

AUBG ICoSCIS TeamAssoc. Prof. Stoyan Bonev

March, 23 - 24, 2013 SWU, Blagoevgrad

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Lesson Contents:

Building Win apps technologies using Java & class libraries Swing AWT (Abstract Windows Toolkit)

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Java GUI programming

Java GUI programming has its own specific: Terminology Concept Philosophy Ideology Technologies:

• Hand-made programming (project:Java, Java application)• Visual, component programming (project:Java, Java

Desktop application)

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Terminology

Java Microsoft Frame Form Panel

Palette Toolbox

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Concept, Philosophy, Ideology

Based on class libraries, grouped in packagesWhen Java was introduced, GUI classes bundled in

AWT libraryThe AWT UI components were replaced by a more

robust and flexible library, known as Swing components.

To distinguish Swing components to their AWT counterparts, the Swing GUI components are named with a prefixed J.

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The Java GUI API – 3 groups of classes

Component classes – used for creating UI JButton, JLabel, JTextField, …

Container classes – used to contain other components JFrame, JPanel, JApplet

Helper classes – used to support GUI components. Graphics, Color, Font, FontMetrics, Dimension

GUI Class Hierarchy (Swing)

Dimension

Font

FontMetrics

Component

Graphics

Object Color

Container

Panel Applet

Frame

Dialog

Window

JComponent

JApplet

JFrame

JDialog

Swing Components in the javax.swing package

Lightweight

Heavyweight

Classes in the java.awt package

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LayoutManager

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Swing GUI Components

JMenuItem

JCheckBoxMenuItem

AbstractButton

JComponent

JMenu

JRadioButtonMenuItem

JToggleButton JCheckBox

JRadioButton

JComboBox

JInternalFrame

JLayeredPane

JList

JMenuBar

JOptionPane

JPopupMenu

JProgressBar

JFileChooser

JScrollBar

JScrollPane JSeparator JSplitPane

JSlider

JTabbedPane

JTable JTableHeader

JTextField JTextComponent

JTextArea

JToolBar JToolTip

JTree

JRootPane

JPanel

JPasswordField

JColorChooser

JLabel

JEditorPane

JSpinner

JButton

Frames

To create a UI, you need a container, i.e. a frame.

Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications.

The JFrame class can be used to create windows.

For Swing GUI programs, use JFrame class to create windows.

Frames

import javax.swing.*;

public class MyFrame {

public static void main(String[] args) {

JFrame frame = new JFrame("Test Frame");

frame.setSize(400, 300);

frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}

Frames javax.swing.JFrame

+JFrame()

+JFrame(title: String)

+setSize(width: int, height: int): void

+setLocation(x: int, y: int): void

+setVisible(visible: boolean): void

+setDefaultCloseOperation(mode: int): void

+setLocationRelativeTo(c: Component): void

+pack(): void

Creates a default frame with no title.

Creates a frame with the specified title.

Specifies the size of the frame.

Specifies the upper-left corner location of the frame.

Sets true to display the frame.

Specifies the operation when the frame is closed.

Sets the location of the frame relative to the specified component. If the component is null, the frame is centered on the screen.

Automatically sets the frame size to hold the components in the frame.

Frames – To create empty frame

Practice: Recommended IDE: NetBeans Create your own project: sbJavaWinEmptyForm

• Hand-made programming (project:Java, Java application)

Type import javax.swing.*; Type stmt within main() method to create a frame

JFrame mySBForm = new JFrame("Empty Form");

Run the project• No frame appears on the screen


Frame not visible if method setVisible() not invoked

Add one more stmt

mySBForm.setVisible(true);

Do you see the form? Look at the top left corner of the screen


Frame may move to the center of the screen using method setLocationRelativeTo()

Add one more stmt

mySBForm.setLocationRelativeTo(null);

Do you see the form? Look at the screen center


Frame sized to display just the title bar if method setSize() not used

Add one more stmt

mySBForm.setSize(900, 300); // dimensions in pixels

Do you see the effect of the change? Hint: setSize() to invoke before invoking setLocationRelativeTo()


How to tell the program to terminate when the frame gets closed?

Add one more stmt

mySBForm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

If this stmt is not used, the program does not terminate when the frame is closed

Adding components to a frame

Modify the frame constructor argument

JFrame mySBForm = new JFrame("Empty Form");

ToJFrame mySBForm = new JFrame(“My frame with Components");

Adding components to a frame

To add a component, we must :• Create a component

• Add it to the frame (to the content pane of the frame) This may happen in Two steps

• JLabel myLabel1 = new Jlabel(“This is not Empty Frame”);

• mySBForm.add(myLabel1);

Or in one step creating anonymous component• mySBForm.add(new JLabel(“This is not Empty Frame”));

Removing components from a frame To remove a component, we must use method remove():

• mySBForm.remove(myLabel1);

Can we remove anonymous component?

Adding two or more components to a frame

To add more than one component, we must :• JLabel myLabel1 = new Jlabel(“This is not Empty Frame”);• mySBForm.add(myLabel1);• JLabel myLabel2 = new Jlabel(“This is Frame with components”);• mySBForm.add(myLabel2);• //JButton myBtn1 = new JButton(“My Button”);• //mySBForm.add(myBtn1);

Do you see more than one component on the screen? No. What’s the problem?

Adding two or more components to a frame

This is because components are put in the frame by the content pane’s layout manager and the default layout manager if not specified explicitly, allocates all the frame to the current component replacing/substituting the previous component if there is any.

It’s time to introduce several different layout managers to place components in the desired locations


Practice: Recommended IDE: NetBeans Create your own project: sbJavaWinEmptyForm

• Visual, component programming (project:Java, Java Desktop application)

Use the toolbox facility to configure your project

Run the project

Layout Managers

For more details open file

LayoutManagersAndMore.ppt

More on GUI programming

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Load file dialogs

JFileChooser chooser = new JFileChooser();chooser.setDialogTitle("Load which file?");

int result = chooser.showOpenDialog(enclosingJFrame);if (result != JFileChooser.APPROVE_OPTION) { File file = chooser.getSelectedFile(); // use file}

You could also test for CANCEL_OPTION or ERROR_OPTION

You will get back a File object; to use it, you must know how to do file I/O!

04/20/23 Assoc. Prof. Stoyan Bonev 27

Save file dialogs

JFileChooser chooser = new JFileChooser();chooser.setDialogTitle(“Save file as?");

int result = chooser.showSaveDialog(enclosingJFrame);if (result != JFileChooser.APPROVE_OPTION) { File file = chooser.getSelectedFile(); // use file}

You could also test for CANCEL_OPTION or ERROR_OPTION

You will get back a File object; to use it, you must know how to do file I/O!

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GUI BasicsorWindows Based Applications

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MotivationsTo build Windows application you need a frame (with

title bar and content pane) structured to contain components/controls such as

buttons,

labels,

text fields,

check boxes,

radio buttons,

combo boxes, and others.

See next slide for illustration

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Creating GUI Objects

// Create a button with text OK JButton jbtOK = new JButton("OK");

Button

Label Text field

Check Box

Radio Button

Combo Box

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// Create a label with text "Enter your name: "JLabel jlblName = new JLabel("Enter your name: ");

Button

Label Text field

Check Box

Radio Button

Combo Box

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// Create a text field with text "Type Name Here"JTextField jtfName = new JTextField("Type Name Here");

Button

Label Text field

Check Box

Radio Button

Combo Box

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// Create a check box with text boldJCheckBox jchkBold = new JCheckBox("Bold");

Button

Label Text field

Check Box

Radio Button

Combo Box

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// Create a radio button with text redJRadioButton jrbRed = new JRadioButton("Red");

Button

Label Text field

Check Box

Radio Button

Combo Box

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// Create a combo box with choices red, green, and blueJComboBox jcboColor = new JComboBox(new String[]{"Red", "Green", "Blue"});

Button

Label Text field

Check Box

Radio Button

Combo Box

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Creating GUI Objects// Create a button with text OK JButton jbtOK = new JButton("OK"); // Create a label with text "Enter your name: "JLabel jlblName = new JLabel("Enter your name: ");

// Create a text field with text "Type Name Here"JTextField jtfName = new JTextField("Type Name Here"); // Create a check box with text boldJCheckBox jchkBold = new JCheckBox("Bold"); // Create a radio button with text redJRadioButton jrbRed = new JRadioButton("Red"); // Create a combo box with choices red, green, and blueJComboBox jcboColor = new JComboBox(new String[]{"Red", "Green", "Blue"});

Button

Label Text field

Check Box

Radio Button

Combo Box

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Swing vs. AWT

Swing class library

OR

AWT class library(Abstract Windows Toolkit)

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Swing vs. AWTSo why do the GUI component classes have a prefix J? Instead of JButton, why not name it simply Button? In fact, there is a class already named Button in the java.awt package.

When Java was introduced, the GUI classes were bundled in a library known as the Abstract Windows Toolkit (AWT). For every platform on which Java runs, the AWT components are automatically mapped to the platform-specific components through their respective agents, known as peers. AWT is fine for developing simple graphical user interfaces, but not for developing comprehensive GUI projects. Besides, AWT is prone to platform-specific bugs because its peer-based approach relies heavily on the underlying platform. With the release of Java 2, the AWT user-interface components were replaced by a more robust, versatile, and flexible library known as Swing components. Swing components are painted directly on canvases using Java code, except for components that are subclasses of java.awt.Window or java.awt.Panel, which must be drawn using native GUI on a specific platform. Swing components are less dependent on the target platform and use less of the native GUI resource. For this reason, Swing components that don’t rely on native GUI are referred to as lightweight components, and AWT components are referred to as heavyweight components.

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GUI Class Hierarchy (Swing)

Dimension

Font

FontMetrics

Component

Graphics

Object Color

Container

Panel Applet

Frame

Dialog

Window

JComponent

JApplet

JFrame

JDialog

Swing Components in the javax.swing package

Lightweight

Heavyweight

Classes in the java.awt package

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LayoutManager

*

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The Java GUI API

The Java GUI API contains classes that may classify in three groups:

Component classes Used to create interface

Container classes Used to contain components

Helper classes Used to support components

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AWT (Optional)AWTEvent

Font

FontMetrics

Component

Graphics

Object Color

Canvas

Button

TextComponent

Label

List

CheckBoxGroup

CheckBox

Choice

Container Panel Applet

Frame

Dialog FileDialog

Window

TextField

TextArea

MenuComponent MenuItem

MenuBar

Menu

Scrollbar

LayoutManager

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FramesTo create a user interface, you need to create a frame.

Frame is a window that is not contained inside another window. Frame is the basis to contain other user interface components in Java GUI applications.

The JFrame class can be used to create windows.

For Swing GUI programs, use JFrame class to create windows.

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Creating Frames(open file ProgPureFrame.java)

import javax.swing.*;public class MyFrame { public static void main(String[] args) { JFrame frame = new JFrame("Test Frame"); frame.setSize(400,300); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE); frame.setVisible(true); }

}

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Adding Components into a Frame// Add a button into the frameframe.getContentPane().add( new JButton("OK"));

Title bar

Content pane

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Content Pane Delegation in JDK 1.5// Add a button into the frameframe.getContentPane().add( new JButton("OK"));

Title bar

Content pane

// Add a button into the frameframe.add( new JButton("OK") );

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JFrame Class javax.swing.JFrame

+JFrame()

+JFrame(title: String)

+setSize(width: int, height: int): void

+setLocation(x: int, y: int): void

+setVisible(visible: boolean): void

+setDefaultCloseOperation(mode: int): void

+setLocationRelativeTo(c: Component): void

+pack(): void

Creates a default frame with no title.

Creates a frame with the specified title.

Specifies the size of the frame.

Specifies the upper-left corner location of the frame.

Sets true to display the frame.

Specifies the operation when the frame is closed.

Sets the location of the frame relative to the specified component. If the component is null, the frame is centered on the screen.

Automatically sets the frame size to hold the components in the frame.

Demo: Open file ProgFrameAndControls.java

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Demo – different source text structure – same functionality

Open file ProgFrameAndControls.javaOpen file ProgFrameAndControlsStyleStandard.javaOpen file

ProgFrameAndControlsStyleRecommended.javaOpen file

ProgFrameAndControlsStyleSeparateClasses.java

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Demo Open file ProgFrameAndControls.javaYou cannot visualize more than one component.Each new component replaces the previous oneThe component occupies all the frame space

How to proceed with more components?You need a layout manager to associate with the

container using method setLayout() incontext <container>.setLayout(<arg>);

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Layout Managers Java’s layout managers provide a level of abstraction to

automatically map your user interface on all window systems.

The UI components are placed in containers. Each container has a layout manager to arrange the UI components within the container.

Layout managers are set in containers using the setLayout(LayoutManager) method in a container.

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Kinds of Layout ManagersFlowLayout

GridLayout

BorderLayout

Several other layout managers will be introduced in Chapter 33, “Containers, Layout Managers, and Borders”

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FlowLayout Example

The simplest layout manager. Components arranged from left to right row by

row in the order in which they were added.Possible alignment controlDemo: file ProgFrameAndLayout.java

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NetBeans – functionality Introduction to GUI Building

Contents Exercise 1: Creating a Project Exercise 2: Building the Front End Exercise 3: Adding Functionality Exercise 4: Running the Program How Event Handling Works

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Exercises/Tasks

Try to run ProgFrameAndLayout.java program

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FlowLayout ExampleRun the ProgFrameAndLayout.java program as it is set

without layout manager:

// with and/or without layout manager

// frame.setLayout(new FlowLayout(FlowLayout.LEFT,10,20));

// frame.setLayout(new GridLayout( 3, 2, 10, 15));

// frame.setLayout(new BorderLayout( 10, 20));

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FlowLayout ExampleRun the ProgFrameAndLayout.java program as it is set

with FlowLayout layout manager:

// with and/or without layout manager

frame.setLayout(new FlowLayout(FlowLayout.LEFT,10,20));

// frame.setLayout(new GridLayout( 3, 2, 10, 15));


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FlowLayout Example

Write a program that adds three labels and text fields into the content pane of a frame with a FlowLayout manager.

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The FlowLayout Class

java.awt.FlowLayout

-alignment: int

-hgap: int

-vgap: int

+FlowLayout()

+FlowLayout(alignment: int)

+FlowLayout(alignment: int, hgap: int, vgap: int)

The alignment of this layout manager (default: CENTER).

The horizontal gap of this layout manager (default: 5 pixels).

The vertical gap of this layout manager (default: 5 pixels).

Creates a default FlowLayout manager.

Creates a FlowLayout manager with a specified alignment.

Creates a FlowLayout manager with a specified alignment, horizontal gap, and vertical gap.

The get and set methods for these data fields are provided in the class, but omitted in the UML diagram for brevity.

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GridLayout Example

Components arranged in a grid (matrix)

formation. from left to right row by row in the order in which they were added.

Demo: file ProgFrameAndLayout.java

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GridLayout Example

Run the ProgFrameAndLayout.java program as it is set with GridLayout layout manager:

// with and/or without layout manager// frame.setLayout(new FlowLayout(FlowLayout.LEFT,10,20)); frame.setLayout(new GridLayout( 3, 2, 10, 15));


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GridLayout Example

Rewrite the program in the preceding example using a GridLayout manager instead of a FlowLayout manager to display the labels and text fields.

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The GridLayout Class

java.awt.GridLayout

-rows: int

-columns: int

-hgap: int

-vgap: int

+GridLayout()

+GridLayout(rows: int, columns: int)

+GridLayout(rows: int, columns: int, hgap: int, vgap: int)

The number of rows in this layout manager (default: 1).

The number of columns in this layout manager (default: 1).

The horizontal gap of this layout manager (default: 0).

The vertical gap of this layout manager (default: 0).

Creates a default GridLayout manager.

Creates a GridLayout with a specified number of rows and columns.

Creates a GridLayout manager with a specified number of rows and columns, horizontal gap, and vertical gap.


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The BorderLayout Manager

The BorderLayout manager divides the container into five areas: East, South, West, North, and Center. Components are added to a BorderLayout by using the add method.

add(Component, constraint), where constraint is BorderLayout.EAST, BorderLayout.SOUTH, BorderLayout.WEST, BorderLayout.NORTH, or BorderLayout.CENTER.

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BorderLayout ExampleFile ProgFrameAndLayout.java

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BorderLayout Example

Run the ProgFrameAndLayout.java program as it is set with BorderLayout layout manager:

// with and/or without layout manager// frame.setLayout(new FlowLayout(FlowLayout.LEFT,10,20));// frame.setLayout(new GridLayout( 3, 2, 10, 15)); frame.setLayout(new BorderLayout( 10, 20));

// uncomment this textframe.add(jbtOK1, BorderLayout.EAST);frame.add(jbtOK2, BorderLayout.CENTER);frame.add(jbtOK3, BorderLayout.WEST);frame.add(jbtOK4, BorderLayout.NORTH);frame.add(jbtOK5, BorderLayout.SOUTH);

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The BorderLayout Class

java.awt.BorderLayout

-hgap: int

-vgap: int

+BorderLayout()

+BorderLayout(hgap: int, vgap: int)

The horizontal gap of this layout manager (default: 0).

The vertical gap of this layout manager (default: 0).

Creates a default BorderLayout manager.

Creates a BorderLayout manager with a specified number of horizontal gap, and vertical gap.


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The Color ClassYou can set colors for GUI components by using the java.awt.Color class. Colors are made of red, green, and blue components, each of which is represented by a byte value that describes its intensity, ranging from 0 (darkest shade) to 255 (lightest shade). This is known as the RGB model.

Color c = new Color(r, g, b);

r, g, and b specify a color by its red, green, and blue components.

Example:Color c = new Color(228, 100, 255);

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Standard Colors

Thirteen standard colors (black, blue, cyan, darkGray, gray, green, lightGray, magenta, orange, pink, red, white, yellow) are defined as constants in java.awt.Color.

The standard color names are constants, but they are named as variables with lowercase for the first word and uppercase for the first letters of subsequent words. Thus the color names violate the Java naming convention. Since JDK 1.4, you can also use the new constants: BLACK, BLUE, CYAN, DARK_GRAY, GRAY, GREEN, LIGHT_GRAY, MAGENTA, ORANGE, PINK, RED, WHITE, and YELLOW.

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Setting ColorsYou can use the following methods to set the component’s background and foreground colors:

setBackground(Color c)

setForeground(Color c)

Example:

jbt.setBackground(Color.yellow);

jbt.setForeground(Color.red);

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The Font Class

Font myFont = new Font(name, style, size);Example:Font myFont = new Font("SansSerif ", Font.BOLD, 16);Font myFont = new Font("Serif", Font.BOLD+Font.ITALIC,12);

JButton jbtOK = new JButton("OK“);jbtOK.setFont(myFont);

Font NamesStandard font names that are supported in all platforms are: SansSerif, Serif, Monospaced, Dialog, or DialogInput.

Font StyleFont.PLAIN (0), Font.BOLD (1), Font.ITALIC (2), and Font.BOLD + Font.ITALIC (3)

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Finding All Available Font Names

GraphicsEnvironment e = GraphicsEnvironment.getLocalGraphicsEnvironment();

String[] fontnames = e.getAvailableFontFamilyNames();

for (int i = 0; i < fontnames.length; i++)

System.out.println(fontnames[i]);

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Using Panels as Sub-ContainersPanels act as sub-containers for grouping user interface

components.

It is recommended that you place the user interface components in panels and place the panels in a frame. You can also place panels in a panel.

To add a component to JFrame, you actually add it to the content pane of JFrame.

To add a component to a panel, you add it directly to the panel using the .add method.

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Creating a JPanel

You can use new JPanel() to create a panel with a default FlowLayout manager or

new JPanel(LayoutManager) to create a panel with the specified layout manager. Use the add(Component) method to add a component to the panel. For example,

JPanel p = new JPanel();

p.add(new JButton("OK"));

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Demo

Open file ProgTestPanels.java

Open file ProgTestPanels2.java

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Testing Panels ExampleThis example uses panels to organize components. The program creates a user interface for a Microwave oven.

A button

A textfield

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buttons

frame

p2

p1

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Common Features of Swing Components

java.awt.Container

+add(comp: Component): Component

+add(comp: Component, index: int): Component

+remove(comp: Component): void

+getLayout(): LayoutManager

+setLayout(l: LayoutManager): void

+paintComponents(g: Graphics): void

Adds a component to the container.

Adds a component to the container with the specified index.

Removes the component from the container.

Returns the layout manager for this container.

Sets the layout manager for this container.

Paints each of the components in this container.

java.awt.Component

-font: java.awt.Font

-background: java.awt.Color

-foreground: java.awt.Color

-preferredSize: Dimension

-visible: boolean

+getWidth(): int

+getHeight(): int

+getX(): int

+getY(): int

The font of this component.

The background color of this component.

The foreground color of this component.

The preferred size of this component.

Indicates whether this component is visible.

Returns the width of this component.

Returns the height of this component.

getX() and getY() return the coordinate of the component’s upper-left corner within its parent component.

javax.swing.JComponent

-toolTipText: String

-border: javax.swing.border.Border

The tool tip text for this component. Tool tip text is displayed when the mouse points on the component without clicking.

The border for this component.



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BordersYou can set a border on any object of the JComponent class. Swing has several types of borders. To create a titled border, use

new TitledBorder(String title).

To create a line border, use new LineBorder(Color color, int width),

where width specifies the thickness of the line. For example, the following code displays a titled border on a panel:

JPanel panel = new JPanel();panel.setBorder(new TitledBorder(“My Panel”));

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Test Swing Common FeaturesComponent Properties

font backgroundforegroundpreferredSizeminimumSizemaximumSize

JComponent Properties

toolTipTextborder

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Image IconsJava uses the javax.swing.ImageIcon class to represent an icon. An icon is a fixed-size picture; typically it is small and used to decorate components. Images are normally stored in image files. You can use new ImageIcon(filename) to construct an image icon. For example, the following statement creates an icon from an image file us.gif in the image directory under the current class path: ImageIcon icon = new ImageIcon("image/us.gif");

TestImageIconTestImageIcon RunRun

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Splash Screen

A splash screen is an image that is displayed while the application is starting up. If your program takes a long time to load, you may display a splash screen to alert the user. For example, the following command:

java –splash:image/us.gf TestImageIcon

displays an image while the program TestImageIcon is being loaded.

Task

Write JAVA program to support a frame with three labels Three text fields Two buttons

Scheme of the pane:label1 textfield1label2 textfield2label3 textfield3button1 button2

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Questions? And/Or

Thank You For

Your Attention!

Lesson 5 GUI Programming AUBG ICoSCIS Team Assoc. Prof. Stoyan Bonev

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