JEDI Slides-Intro2-Chapter19-Abstract Windowing Toolkit and Swing.pdf

Introduction to Programming 2 1
7 Abstract Windowing
Toolkit and Swing

Topics
? Abstract Windowing Toolkit (AWT) vs. Swing
? AWT GUI Components
– Fundamental Window Classes
– Graphics
– More AWT Components

Topics
? Layout Managers
– The FlowLayout Manager
– The BorderLayout Manager
– The GridLayout Manager
– Panels and Complex Layouts
? Swing GUI Components
– Setting Up Top-Level Containers
– A JFrame Example
– A JOptionPane Example

Abstract Windowing Toolkit
(AWT) vs. Swing
? Similarities:
– Tools provided by Java for developing interactive GUI applications
– Provides GUI components that can be used in creating Java
applications and applets
? Java Foundation Classes (JFCs)
– Important part of the Java SDK
– Collection of APIs that simplifies development Java GUI applications
– Primarily consists of five APIs
? AWT
? Swing
? Java2D
? Accessibility
? Drag and Drop

Abstract Windowing Toolkit
(AWT) vs. Swing
? AWT
– Some AWT components use native code
– Platform-dependent
– Ensure that the look and feel of an application run on different
machines be comparable
? Swing
– Written entirely using the Java programming language
– Platform-independent
– Ensures applications deployed across different platforms have the
same appearance
– Built around a number of APIs that implement various parts of the
AWT
? Can be used with AWT

AWT GUI Components:
Fundamental Window Classes
? GUI components such as buttons or text fields are placed in
containers.

AWT GUI Components:
Window Class Methods
? Setting the size of the window:
void setSize(int width, int height)
void setSize(Dimension d)
– Dimension d has width and height as fields
? A window by default is not visible. Setting its visibility:
void setVisible(boolean b)
– If b is true, window is set to be visible

AWT GUI Components:
Fundamental Window Classes
? Frame objects are usually used in designing GUI
applications
1 import java.awt.*;
2 /* Try the availble buttons in the frame */
3 public class SampleFrame extends Frame {
4 public static void main(String args[]) {
5 SampleFrame sf = new SampleFrame();
6 sf.setSize(100, 100); //Try removing this
7 sf.setVisible(true); //Try removing this
8 }
9 }

AWT GUI Components:
Graphics
? Graphics class (abstract) methods:
? Color class constructors

AWT GUI Components:
Graphics Example
2 public class GraphicPanel extends Panel {
3 GraphicPanel() {
4 setBackground(Color.black);
5 }
6 public void paint(Graphics g) {
7 g.setColor(new Color(0,255,0)); //green
8 g.setFont(new Font("Helvetica",Font.PLAIN,16));
9 g.drawString("Hello GUI World!", 30, 100);
10 g.setColor(new Color(1.0f,0,0)); //red
11 g.fillRect(30, 100, 150, 10);
12 }
13 //continued...

AWT GUI Components:
Graphics Example
14 /* need to place Panel in Frame or other Window */
16 Frame f = new Frame("Testing Graphics Panel");
17 GraphicPanel gp = new GraphicPanel();
18 f.add(gp);
19 f.setSize(600, 300);
20 f.setVisible(true);
21 }
22 }

More AWT Components
? AWT controls
– Components that allow the user to interact with a GUI application
– Subclasses of the component class

More AWT Components:
Example
2 class FrameWControls extends Frame {
4 FrameWControls fwc = new FrameWControls();
5 fwc.setLayout(new FlowLayout());
6 fwc.setSize(600, 600);
7 fwc.add(new Button("Test Me!"));
8 fwc.add(new Label("Labe"));
9 fwc.add(new TextField());
10 CheckboxGroup cbg = new CheckboxGroup();
11 fwc.add(new Checkbox("chk1", cbg, true));
12 fwc.add(new Checkbox("chk2", cbg, false));
13 fwc.add(new Checkbox("chk3", cbg, false));
14 //continued...

More AWT Components:
Example
15 List list = new List(3, false);
16 list.add("MTV");
17 list.add("V");
18 fwc.add(list);
19 Choice chooser = new Choice();
20 chooser.add("Avril");
21 chooser.add("Monica");
22 chooser.add("Britney");
23 fwc.add(chooser);
24 fwc.add(new Scrollbar());
25 fwc.setVisible(true);
26 }
27 }

Layout Managers
? Definition:
– Determines the position and size of the components within a
container
– Governs the layout of the components in the container
? Some of the layout managers in Java
– FlowLayout
– BorderLayout
– GridLayout
– GridBagLayout
– CardLayout

Layout Managers: Methods
? Setting the layout manager:
void setLayout(LayoutManager mgr)
– Can pass null, no layout manger in use
? If no layout manager is used, need to position the elements
manually
public void setBounds(int x, int y, int width, int
height)
– Method of the Component class
– Quite difficult and tedious if you have several Component objects
? Need to call this method for each object

Layout Managers:
The FlowLayout Manager
? Default manager for the Panel class and its subclasses
– The Applet class is a subclass of Panel
? Positions the components in a left to right and top to bottom
manner, starting at the upper-lefthand corner
– Typing using a word editor

Layout Managers:
? Has three constructors:

Layout Managers:
? Gap
– Spacing between the components
– Measured in pixels
? Possible alignment values:
FlowLayout.LEFT
FlowLayout.CENTER
FlowLayout.RIGHT

Layout Managers:
2 class FlowLayoutDemo extends Frame {
4 FlowLayoutDemo fld = new FlowLayoutDemo();
5 fld.setLayout(new FlowLayout(FlowLayout.RIGHT,
6 10, 10));
7 fld.add(new Button("ONE"));
8 fld.add(new Button("TWO"));
9 fld.add(new Button("THREE"));
10 fld.setSize(100, 100);
11 fld.setVisible(true);
12 }
13 }

Layout Managers:
? Sample output:

Layout Managers:
The BorderLayout Manager
? Default layout for Window objects and its subclasses
– Includes those of Frame and Dialog type
? Divides Container object into five parts where Component
objects are added
– North - stretch horizontally
– South - stretch horizontally
– East - adjust vertically
– West - adjust vertically
– Center - adjusts in both directions

Layout Managers:
? Has two constructors
– Parameters hgap and vgap refers to the spacing between the
components within the container

Layout Managers:
? Adding a component to a specified region:
– Use the add method and pass two arguments:
?
Component to add
? Region where the component is to be positioned
– Only one component can be placed in one region
? Valid regions:
– BorderLayout.NORTH
– BorderLayout.SOUTH
– BorderLayout.EAST
– BorderLayout.WEST
– BorderLayout.CENTER

Layout Managers:
2 class BorderLayoutDemo extends Frame {
4 BorderLayoutDemo bld = new BorderLayoutDemo();
5 bld.setLayout(new BorderLayout(10, 10));
6 bld.add(new Button("NORTH"), BorderLayout.NORTH);
7 bld.add(new Button("SOUTH"), BorderLayout.SOUTH);
8 bld.add(new Button("EAST"), BorderLayout.EAST);
9 bld.add(new Button("WEST"), BorderLayout.WEST);
10 bld.add(new Button("CENTER"), BorderLayout.CENTER);
11 bld.setSize(200, 200);
12 bld.setVisible(true);
13 }
14 }

Layout Managers:
? Sample output: ? After resizing:

Layout Managers:
The GridLayout Manager
? Like FlowLayout
– Positions components from left to right and top to bottom
– Starts adding components at the upper-lefthand corner
? Divides the container into a number of rows and columns
– Regions are equally sized
– Ignores the component's preferred size

Layout Managers:
? Has the following constructors:

Layout Managers:
2 class GridLayoutDemo extends Frame {
4 GridLayoutDemo gld = new GridLayoutDemo();
5 gld.setLayout(new GridLayout(2, 3, 4, 4));
6 gld.add(new Button("ONE"));
7 gld.add(new Button("TWO"));
8 gld.add(new Button("THREE"));
9 gld.add(new Button("FOUR"));
10 gld.add(new Button("FIVE"));
11 gld.setSize(200, 200);
12 gld.setVisible(true);
13 }
14 }

Layout Managers:
? Sample output: ? After resizing:

Panels and Complex Layouts
? For more complex layouts
– Can combine the different layout managers
– Use of panels at the same time
? Recall:
– A Panel is a Container and a Component
– Can insert Components into the Panel
– Can add Panel to a Container

2 class ComplexLayout extends Frame {
4 ComplexLayout cl = new ComplexLayout();
5 Panel panelNorth = new Panel();
6 Panel panelCenter = new Panel();
7 Panel panelSouth = new Panel();
8 /* North Panel */
9 //Panels use FlowLayout by default
10 panelNorth.add(new Button("ONE"));
11 panelNorth.add(new Button("TWO"));
12 panelNorth.add(new Button("THREE"));
13 //continued...

14 /* Center Panel */
15 panelCenter.setLayout(new GridLayout(4,4));
16 panelCenter.add(new TextField("1st"));
17 panelCenter.add(new TextField("2nd"));
18 panelCenter.add(new TextField("3rd"));
19 panelCenter.add(new TextField("4th"));
20 /* South Panel */
21 panelSouth.setLayout(new BorderLayout());
22 panelSouth.add(new Checkbox("Choose me!"),
BorderLayout.CENTER);
23 panelSouth.add(new Checkbox("I'm here!"),
24 BorderLayout.EAST);
25 panelSouth.add(new Checkbox("Pick me!"),
26 BorderLayout.WEST);
27 //continued...

28 /* Adding the Panels to the Frame container */
29 //Frames use BorderLayout by default
30 cl.add(panelNorth, BorderLayout.NORTH);
31 cl.add(panelCenter, BorderLayout.CENTER);
32 cl.add(panelSouth, BorderLayout.SOUTH);
33 cl.setSize(300,300);
34 cl.setVisible(true);
35 }
36 }

? Sample output:

Swing GUI Components
? Package is found in javax.swing
? Written entirely using Java
– Have the same look and feel even when executed on different
platforms
? Provides more interesting components
– Color chooser
– Option pane

? Names of the Swing GUI components are almost similar to
that of AWT
– Name of AWT components but prefixed with J
– Example:
? AWT: Button class
? Corresponding Swing component: JButton class

Swing: Setting Up Top-Level
Containers
? Top-level containers in Swing are slightly incompatible with
those in AWT
– In terms of adding components to the container
? Adding a component to the container:
– Get the content pane of the container
? Use the getContentPane method
– Add components to the content pane
? Still use the add method

Swing: A JFrame Example
1 import javax.swing.*;
3 class SwingDemo {
4 JFrame frame;
5 JPanel panel;
6 JTextField textField;
7 JButton button;
8 Container contentPane;
10 SwingDemo sd = new SwingDemo();
11 sd.launchFrame();
12 }
13 //continued...

14 void launchFrame() {
15 /* initialization */
16 frame = new JFrame("My First Swing Application");
17 panel = new JPanel();
18 textField = new JTextField("Default text");
19 button = new JButton("Click me!");
20 contentPane = frame.getContentPane();
21 //add components to panel–FlowLayout by default
22 panel.add(textField);
23 panel.add(button);
24 /* add components to contentPane– BorderLayout */
25 contentPane.add(panel, BorderLayout.CENTER);
26 frame.pack(); //Size of frame based on components
27 frame.setVisible(true);
28 }
29 }

? The java.awt package is still imported
– The layout managers in use are defined in this package
– Giving a title to the frame and packing the components within the
frame is applicable for AWT frames too
? Coding convention:
– Declare components as fields
– A launchFrame method is defined:
? Initialization and addition of components
– No longer just extend the Frame class
– Advantage: organized and easier to add event handling codes

? Sample output:

Swing: A JOptionPane Example
1 import javax.swing.*;
2 class JOptionPaneDemo {
3 JOptionPane optionPane;
4 void launchFrame() {
5 optionPane = new JOptionPane();
6 String name = optionPane.showInputDialog(
7 "Hi, what's your name?");
8 optionPane.showMessageDialog(null,
9 "Nice to meet you, " + name + ".",
10 "Greeting...",optionPane.PLAIN_MESSAGE);
11 System.exit(0);
12 }
14 new JOptionPaneDemo().launchFrame(); } }

? Sample output:

Summary
? Abstract Windowing Toolkit (AWT) vs. Swing
– Similarities
– Differences
? AWT GUI Components
– Fundamental Window Classes
?
Component, Container, Window, Frame, Panel
– Graphics
?
Methods and the Color class
– More AWT Components
?
Label, TextField, TextArea, Button, Checkbox, CheckboxGroup, Choice,
List, Scrollbar

Summary
? Layout Managers
– The FlowLayout Manager
– The BorderLayout Manager
– The GridLayout Manager
– Creating Complex Layouts
? Swing GUI Components
– Setting Up Top-Level Containers
?
Use getContentPane method
?
Use add method
– JFrame, JOptionPane

JEDI Slides-Intro2-Chapter19-Abstract Windowing Toolkit and Swing.pdf

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