1. Chapter 7-3 (Book Chapter 14)
Introduction to OOP with Java 4th Ed, C. Thomas Wu
Chapter 7-3 (Book Chapter 14)
GUI and
Event-Driven Programming
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2. Intro to OOP with Java, C. Thomas Wu
Layout Managers
The layout manager determines how the GUI components are added to the container (such as the content pane of a frame)
Among the many different layout managers, the common ones are
FlowLayout (see Ch14FlowLayoutSample.java)
BorderLayout (see Ch14BorderLayoutSample.java)
GridLayout (see Ch14GridLayoutSample.java)
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3. Intro to OOP with Java, C. Thomas Wu
FlowLayout
In using this layout, GUI components are placed in left-to-right order.
When the component does not fit on the same line, left-to-right placement continues on the next line.
As a default, components on each line are centered, but you can change it to left or right alignment.
When the frame containing the component is resized, the placement of components is adjusted accordingly.
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4. Intro to OOP with Java, C. Thomas Wu
FlowLayout Sample
This shows the placement of five buttons by using FlowLayout.
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5. FlowLayout
... contentPane = getContentPane( ); contentPane.setBackground( Color.WHITE ); contentPane.setLayout(new FlowLayout()); button1 = new JButton("button 1"); button2 = new JButton("button 2"); button3 = new JButton("button 3"); button4 = new JButton("button 4"); button5 = new JButton("button 5"); contentPane.add(button1); contentPane.add(button2); contentPane.add(button3); contentPane.add(button4); contentPane.add(button5);
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6. FlowLayout FlowLayout - Left Alignment FlowLayout - Right Alignment
To change the center alignment:
contentPane.setLayout(new FlowLayout(FlowLayout.LEFT));
contentPane.setLayout(new FlowLayout(FlowLayout.RIGHT));
FlowLayout - Left Alignment
FlowLayout - Right Alignment
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7. Intro to OOP with Java, C. Thomas Wu
BorderLayout
This layout manager divides the container into five regions: center, north, south, east, and west.
If the window is enlarged, the center area gets as much of the available space as possible.
The other areas expand only as much as necessary to fill all available space.
Not all regions have to be occupied.
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8. Intro to OOP with Java, C. Thomas Wu
BorderLayout Sample
contentPane.setLayout(new BorderLayout());
contentPane.add(button1, BorderLayout.NORTH);
contentPane.add(button2, BorderLayout.SOUTH);
contentPane.add(button3, BorderLayout.EAST);
contentPane.add(button4, BorderLayout.WEST);
contentPane.add(button5, BorderLayout.CENTER);
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9. BorderLayout
... contentPane = getContentPane( ); contentPane.setBackground( Color.WHITE ); contentPane.setLayout(new BorderLayout()); button1 = new JButton("button 1"); button2 = new JButton("button 2"); button3 = new JButton("button 3"); button4 = new JButton("button 4"); button5 = new JButton("button 5"); contentPane.add(button1, BorderLayout.NORTH); contentPane.add(button2, BorderLayout.SOUTH); contentPane.add(button3, BorderLayout.EAST); contentPane.add(button4, BorderLayout.WEST); contentPane.add(button5, BorderLayout.CENTER);
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10. Intro to OOP with Java, C. Thomas Wu
GridLayout
This layout manager placesGUI components on equal-size N by M grids.
Components are placed in top-to-bottom, left-to-right order.
The number of rows and columns remains the same after the frame is resized, but the width and height of each region will change.
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11. Intro to OOP with Java, C. Thomas Wu
GridLayout Sample
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12. GridLayout
... contentPane = getContentPane( ); contentPane.setBackground( Color.WHITE ); contentPane.setLayout(new GridLayout(2,3)); button1 = new JButton("button 1"); button2 = new JButton("button 2"); button3 = new JButton("button 3"); button4 = new JButton("button 4"); button5 = new JButton("button 5"); contentPane.add(button1); contentPane.add(button2); contentPane.add(button3); contentPane.add(button4); contentPane.add(button5);
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13. Absolute Positioning Here we do not use any layout manager.
We place the GUI objects on the frame’s content pane by explicitly specifying their position and size.
This is called absolute positioning
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14. Absolute Positioning
... private static final int BUTTON_WIDTH = 80; private static final int BUTTON_HEIGHT = 30; contentPane.setLayout( null ); contentPane.setBackground( Color.WHITE ); //create and place a button on the frame's content pane okButton = new JButton("OK"); okButton.setBounds(70, 125, BUTTON_WIDTH, BUTTON_HEIGHT); contentPane.add(okButton);
125 30 70 80
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15. Other Common GUI Components
Intro to OOP with Java, C. Thomas Wu
Other Common GUI Components
JCheckBox
Useful in representing a collection of binary (yes/no, true/false) options.
A JCheckBox object generates action events (like a JButton), but also generates item events, when the state of a check-box button changes (selected or deselected).
see Ch14JCheckBoxSample1.java and Ch14JCheckBoxSample2.java
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16. Other Common GUI Components
JRadioButton
The radio button is similar to the check-box, but only one button can be selected from the group.
When you select a new item, the currently selected radio button will get deselected.
Thus, the JRadioButton must be added to a group.
A JRadioButton generates both action events and item events.
see Ch14JRadioButtonSample.java
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17. Other Common GUI Components
JComboBox (drop-down list)
Similar to JRadioButton, but the choices are presented to the user in a form of a drop-down list
See Ch14JComboBoxSample.java
Jlist
Used to display a list of items
You can highlight one or more selection
see Ch14JListSample.java
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18. Intro to OOP with Java, C. Thomas Wu
Menus
The javax.swing package contains three menu-related classes: JMenuBar, JMenu, and JMenuItem.
JMenuBar is a bar where the menus are placed. There is one menu bar per frame.
JMenu (such as File or Edit) is a group of menu choices. JMenuBar may include many JMenu objects.
JMenuItem (such as Copy, Cut, or Paste) is an individual menu choice in a JMenu object.
Only the JMenuItem objects generate events.
Almost all nontrivial GUI programs support menus. By using these three menu-related classes, we can easily add menus to our Java programs.
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19. Intro to OOP with Java, C. Thomas Wu
Menu Components
Edit
View
Help
JMenuBar
Edit
View
Help
File
JMenu
The diagram shows how the menu-related objects correspond to the actual menus.
JMenuItem
separator
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20. Sequence for Creating Menus
Intro to OOP with Java, C. Thomas Wu
Sequence for Creating Menus
Create a JMenuBar object and attach it to a frame.
Create a JMenu object.
Create JMenuItem objects and add them to the JMenu object.
Attach the JMenu object to the JMenuBar object.
This is not the only valid sequence. Other sequences are possible. We list this sequence as one possible sequence you can follow in creating menus.
see Ch14MenueFrame.java
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21. Intro to OOP with Java, C. Thomas Wu
Handling Mouse Events
Mouse events include such user interactions as
moving the mouse
dragging the mouse (moving the mouse while the mouse button is being pressed)
clicking the mouse buttons.
The MouseListener interface handles mouse button
mouseClicked, mouseEntered, mouseExited, mousePressed, and mouseReleased
The MouseMotionListener interface handles mouse movement
mouseDragged and mouseMoved.
- See Ch14TrackMouseFrame.java and Ch14SketchPad.java
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22. Java Online Tutorial
More information about Java GUI can be found here:
General Java information can be found here
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