BIS 335 Chapter 6

Applets

- GUI program that runs in a rectangular area on a web page - provide interactivity on web pages - does not have a main method

Stand-alone

- GUI program that runs on its own without a web browser - any class that has a main() is stand alone

frame

- a container used to display a GUI-based java application - most common = JFrame object which is independent and main window of application

JCheckBox

- component has two states, selected or unselected - represented by boolean value (true if selected, false if not) - constructor: JCheckBox showTime = new JCheckBox("Show Time");

3 kinds of objects in GUIs

- components - events - listeners

panel

- container that cannot be displayed on its own but used to organize other components - most common = JPanel - must be added to another container (usually JFrame) to be displayed

FlowLayout constructors

- default: new FlowLayout() - to specify other gaps and alignment: public FlowLayout(int align, int hgap, int vgap) - values for alignment = FlowLayout.LEFT, FlowLayout.RIGHT, FlowLayout.CENTER

BorderLayout

- designed to display one large, central component with up to four smaller components arranged around the edge

containers

- hold and organize other components - frames, panels, applets, dialog boxes

JTextField

- holds a single line of text - constructor: public JTextField(int columns) - columns = preferred width of text field

JTextArea

- holds multiple lines of text - constructor: public JTextArea(String contents, int rows, int columns)

GridLayout

- lays out components in grid containing rows and columns of equal sized rectangles - add components: cntr.add(comp) - constructor = new GridLayout(R,C)

Borders

- leave border around outside of container, not handled by layout manager - can be added to ANY component - use setBorder() method to apply to an object

BorderFactory.createLineBorder(top, left, bottom, right)

- leaves empty border around edges of component - parameter = integers

FLowLayout

- lines up components in a row - default layout for JPanel - uses preferred size of components

event

- object that represents some activity that we may want to respond to - ex. we want program to perform some action when the following occurs: - mouse is moved - keyboard key clicked - a timer expires

Listeners

- objects designed to respond to events generated by component objects - as event occurs, the component calls the appropriate method of the listener and passes the object that describes the event

components

- objects that represent screen elements (labels, buttons, text fields, menus, etc.) - organized in containers

JSlider

- provides way for user to select integer value from range of possible values - constructor: public JSlider(int minimum, int maximum, int value)

JButton

- push button that users clicks to trigger some action - constructor: JButton button = new JButton("Exit");

JLabel

- simplest type of component, exists just to display lines of text that can't be changed by user - constructor: JLabel message = new JLabel("Click Here", JLabel.CENTER);

ActionEvent

- when user clicks button, generates an event of type ActionEvent - event sent to listener that must be registered with button as ActionListener - to register: buttonName.addActionListener(buttonHandler)

JFrame

- where stand-alone apps are created - blank content pane, you can add things or replace entirely with a new component - can add one or more panels

2 main GUI-related packages

1. Abstract Windowing Toolkit (AWT): original java GUI package - import java.awt.*; 2. Swing: provides additional/more versatile components - import javax.swing.*;

If you want to display the "Clear" button to the user & do perform some action if the user clicks on it, you must do the following steps:

1. Create a JButton object 2. add a JButton object to a JPanel object 3. add a Listener object to the JButton, 4. write the code in actionPerformed to do what you want to do

Steps for setting up GUI

1. create container and assign layout manager 2. create components 3. add components to container 4. use container as the content pane of a window or applet

every container has:

1. default layout manager 2. instance method, setLayout(), that takes a parameter of type LayoutManager 3. add a component with the add() method

Steps to use Listener

1. put implements ActionListener on JPanel class definition 2. make component and add to panel in the constructor 3. attach a listener to component in constructor for the panel using addActionListener(this) 4. write action performed method in class for JPanel as "public void actionPerformed(ActionEvent e)"

4 main methods of JOptionPane

1. showConfirmDialog 2. showInputDialog 3. showMessageDialog 4. showOptionDialog

AWT stands for:

Abstract Windowing Toolkit

Which layout manager divides a container object into North, South, East, West and Center regions?

BorderLayout

BorderLayout positions

BorderLayout.CENTER BorderLayout.NORTH BorderLayout.SOUTH BorderLayout.EAST BorderLayout.WEST

What is the default layout for JPanel?

FlowLayout

Font constructor

Font plainFont = new Font ("Serif", Font.BOLD, 12);

GUI

Graphical User Interface

how to create JFrame or JPanel

JFrame window = new JFrame("Title"); JPanel content = new JPanel();

What is the simplest type of component?

JLabel

I want to display a JButton to the user. As taught in class, I should add the JButton to a:

JPanel

Add components to BorderLayout

Suppose container = cntr, component = comp cntr.add(comp, BorderLayout.SOUTH);

If you want your program to pop up a JOptionPane dialog box when a user clicks a button, you put the code that pops up the window into which method?

actionPerformed

comp.setVisible(true) comp.setVisible(false)

called to hide or show component

BorderFactory.createMatteBorder(top, left, bottom, right)

can specify individual thickness for each individual edge

JOptionPane

class that provides basic built in windows so you don't have to build them yourself

BorderFactory.createEtchedBorder()

creates border that looks like groove etched around the component

BorderFactory.createTitledBorder(title)

creates border with title of type String, displayed in upper left corner

BorderFactory.createLineBorder(color, thickness)

draws a line around all four edges of a component

comp.getWidth() comp.getHeight()

functions that give current size of the component in pixels

BorderFactory.createLoweredBevelBorder()

gives 3D effect that makes it look lowered into the computer screen

layout manager

helps you layout the components you are adding to a container

What is the difference between objectname1.length & objectname2.length()?

length = length of an array called objectname1 length() = length of a String called objectname2

Specifying horizontal/vertical gaps in GridLayout

new GridLayout(R, C, H, V)

Specifying horizontal/vertical gaps in BorderLayout

panel.setLayout(new BorderLayout(5,7));

comp.setBackground(color) comp.setForeground(color)

sets background/foreground color

comp.setFont(font)

sets font used for text

pixel

smallest point addressable on a screen

Size settings

use setSize() if parent has no layout manager use setPreferredSize() if parent has layout manager

comp.setEnabled(true) comp.setEnabled(false)

used to enable and disable components