cop 3503 fall 2012 shayan javed lecture 14

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COP 3503 FALL 2012SHAYAN JAVED

LECTURE 14

Programming Fundamentals using Java

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Graphical-User Interfaces

(GUIs)

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So far...

Only created text-based programs

No fancy graphics (buttons! menus! text-fields!)

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Graphical-User Interfaces (GUI)

Going to look at how to create GUIs in Java

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Use the SWING API (for desktop-programs)

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Use the SWING API (for desktop-programs)

Use the AWT API (for Java Applets – on the web)

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The SWING API

Used to create desktop applications.

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The SWING API

Used to create desktop applications.

Uses the Model-View-Controller software engineering design pattern.

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Model-View-Controller design

Model: Manages the behavior and data of the application. Changes state.

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View: Renders the model into a form for interaction.

(Button, textbox, checkbox, etc.)

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View: Renders the model into a form for interaction.

(Button, textbox, checkbox, etc.) Controller:

Receives user input and initiates a response by interacting with the model.

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The SWING API

Example:

Scrabble

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The GUI API

Use the NetBeans IDE for easy drag-and-drop creation.

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The GUI API

Use the NetBeans IDE for easy drag-and-drop creation.

But we are going to focus on basic code

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The GUI API

3 Groups of classes:

Component Classes: Buttons, Labels, TextFields, etc.

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The GUI API



Container Classes: Frames, Panels, Applets, etc.

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The GUI API



Container Classes: Frames, Panels, Applets, etc.

Helper Classes: Graphics, Color, Font, etc.

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The SWING API

Simple Window

Represented by the JFrame class

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The SWING API

import javax.swing.JFrame;

public static void main(String[] args) {JFrame frame = new JFrame(“A Title”);frame.setSize(400, 300);frame.setLocation(10, 300);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setVisible(true);}

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The SWING API – add components

import javax.swing.*;

public static void main(String[] args) {JFrame frame = new JFrame(“A Title”);

JButton button = new JButton(“OK”);frame.add(button);

frame.setSize(400, 300);...

}

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A JFrame containts a content pane.

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Content pane = instance of java.awt.Container;

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Objects are added to it frame.add( Component )

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Objects are added to it frame.add( Component ) frame.remove( Component )

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Layout Managers

Components in content pane are laid out by layout managers.

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Layout Managers

Components in content pane are laid out by layout managers.

Multiple types: FlowLayout GridLayout BorderLayout

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Layout Managers - FlowLayout

Components arranged left to right in order.

One row fills up, a new row is started

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java.awt.FlowLayout

Properties: alignment: int (CENTER/LEFT/RIGHT/etc.) hgap, vgap: int (the gaps – default: 5 pixels)

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java.awt.FlowLayout

Properties: alignment: int (CENTER/LEFT/RIGHT/etc.) hgap, vgap: int (the gaps – default: 5 pixels)

Constructors: FlowLayout() FlowLayout(alignment, hgap, vgap)

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public class ShowFlowLayout extends JFrame {public ShowFlowLayout() {

// set the flow layoutsetLayout(new FlowLayout(FlowLayout.LEFT,

10, 20);

add(new JButton(“Button”));add(new JTextField(8));

}}

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Layout Managers - GridLayout

Arrange components in a grid (matrix) formation. Placed left-to-right.

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Arrange components in a grid (matrix) formation. Placed left-to-right.

Properties: rows, columns: int hgap, vgap: int (the gaps – default: 5 pixels)

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public class ShowGridLayout extends JFrame {public ShowGridLayout() {

// set the Grid layout – 3 rows, 2 columnssetLayout(new GridLayout(3, 2, 10, 10);

add(new JButton(“Button”));add(new JTextField(8));

}}

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Layout Managers - BorderLayout

Default Layout for ContentPanes (Jframe)

Divides container into 5 areas: East, West, South, North, Center Components are added into one of these areas

Properties: hgap, vgap: int (the gaps – default: 5 pixels)

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Layout Managers - BorderLayout

public class ShowBorderLayout extends JFrame {public ShowBorderLayout() {

// set the Border LayoutsetLayout(new BorderLayout(10, 10);

add(new JButton(“Button”), BorderLayout.EAST);

add(new JTextField(8), BorderLayout.WEST);}

}

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The SWING API

Looked at adding Components to the Window (Frame).

And how to lay them out.

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The SWING API

Looked at adding Components to the Window (Frame).

And how to lay them out.

But often need “sub-windows” to create more complex interfaces.

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Using JPanels as Subcontainers

Panels are subcontainers.

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Can add components to them

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Also set layouts (default: FlowLayout)

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Also set layouts (default: FlowLayout)

JPanel panel = new JPanel();panel.add(new JButton(“OK”));

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Using JPanels// set the Border Layout of the JFramesetLayout(new BorderLayout(10, 10);

// add a Panel to the West and EastJPanel p1 = new JPanel(); add(p1, BorderLayout.WEST);JPanel p2 = new JPanel(); p2.setLayout(new GridLayout(2, 2, 5, 5));add(p2, BorderLayout.EAST);

// add components to the east panelp2.add(new JTextField(8)); p2.add(new JButton(“Button1”));p2.add(new JTextField(8)); p2.add(new JButton(“Button2”));

// one button to the west panelp1.add(new JButton(“Button3”));

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Adding Components

Need to add components for interaction.

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Adding Components

Need to add components for interaction.

Some useful ones: JButton JTextField JCheckBox JComboBox JMenuBar etc...

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Model: (ALREADY IMPLEMENTED) Manages the behavior and data of the application. Changes state.

View: DONE Renders the model into a form for interaction.

(Button, textbox, checkbox, etc.) Controller:

Receives user input and initiates a response by interacting with the model.

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Interaction and Events

Need to handle events from various GUI components.

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Button clicks, text field changes, menu selection, etc.

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Button clicks, text field changes, menu selection, etc.

Event-driven programming

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Components generate different kinds of Events

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ActionEvent, ItemEvent, ChangeEvent, MouseEvent, KeyEvent

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Example: JButton generates ActionEvent

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Example: JButton generates ActionEvent Mouse pressed/moved/dragged: MouseEvent

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Example: JButton generates ActionEvent Mouse pressed/moved/dragged: MouseEvent JCheckBox: ItemEvent, ActionEvent

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Need to “listen” for Events.

Source object fires an event, and an object interested in the event handles it. Latter object called a “listener”

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For an object to be a listener, it needs to implement an interface.

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Interface should correspond to the Event. ActionListener for ActionEvent MouseListener for MouseEvent KeyListener for KeyEvent

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Interface should correspond to the Event. ActionListener for ActionEvent MouseListener for MouseEvent KeyListener for KeyEvent

object.addXListener(...)

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ActionListener interface

class AClass implements ActionListener {public void actionPerformed(ActionEvent e) {

// do whatever you want}

}

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class AClass implements ActionListener {public void actionPerformed(ActionEvent e) {


}

JButton button = new JButton(“OK”);button.addActionListener(new AClass());

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ActionEvent methods:

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ActionEvent methods: Object getSource(): returns the object on which

the Event initially occurred. (in java.util.EventObject)

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ActionEvent methods: Object getSource(): returns the object on which

the Event initially occurred. (in java.util.EventObject)

String getActionCommand(): returns the command string

(text of the button for ex.)

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ItemListener interface

Used for check boxes, toggle buttons, etc.

class AClass implements ItemListener {public void itemStatechanged(ItemEvent e) {


}

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ItemListener interface

ItemEvent methods:

Object getItem(): Component-specific object.

int getStateChange(): The new state of the associated object.

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Look at some other useful Events:

MouseEvent KeyEvent WindowEvent

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Look at some other useful Events:

MouseEvent KeyEvent WindowEvent

Experiment!

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Summary

Windows and Panels Layouts Add Components

Add Listeners Handle Events

cop 3503 fall 2012 shayan javed lecture 14

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