CMPUT 301 Lecture 01

CMPUT 301 Lecture 01

Java Swing, Events Readings: Just Java 2: Chap 19 & 21, or Eckels Thinking in Java: Chap 14 Slide credits to CMPUT 301, Department of Computing Science University of Alberta Java Foundation Classes JFC: Abstract Window Toolkit (AWT)

original user interface toolkit dont go there! Swing package javax.swing.*, introduced in Java 1.2 2 Swing Portable API: The appearance and behavior (look-andfeel) of the user interface components are

implemented in Java might work slightly differently from any host platform pluggable look-and-feels e.g., Motif, windows, 3 Containment Hierarchy Top-level container: place for other Swing components to paint themselves

e.g., JFrame, JDialog, Japplet Intermediate container: simplify positioning of atomic components e.g., JPanel, JSplitPane, JTabbedPane 4 Containment Hierarchy Atomic components: self-sufficient components that present

information to and get input from the user e.g., JButton, JLabel, JComboBox, JTextField, JTable 5 Swing Components and containers: superclasses and interfaces

extends and implements OReilly 1999 6 Swing Java Documentation:

1.4.1/docs/api/javax/swing/ package-summary.html SwingSet: javawebstart/demos.html Quick tutorial: books/tutorial/uiswing/start/ swingTour.html

7 Containers Notes: Container objects group components, arranging them for display with a layout manager. 8 Top-Level Containers

JFrame example: contains a single component JRootPane, which has a JMenuBar (optional) and a content pane theFrame.setJMenuBar( theMenuBar ) theFrame.setContentPane( thePanel ) add non-menu components to this content pane theFrame.getContentPane().add( aButton ) 9

Events Two approaches to event handling read-evaluation loop (client-written loop) notification-based (callbacks) Swing uses the 2nd approach 10 Events

Swing: objects communicate by firing and handling events (event objects) (conventional method call) events are sent from a single source object to one or more registered listener objects 11 Events Swing:

different event sources produce different kinds of events e.g., a JButton object, when clicked, generates an ActionEvent object, which is handled by an ActionListener (an object whose class implements this interface) 12 Events

listener interface event source 1..* 1..* event listener 13

Events Handling: create a component e.g., a JButton add it to the GUI e.g., to a JPanel register a listener to be notified when the component generates an event

e.g., interface ActionListener define the callback method e.g., actionPerformed() 14 Event Handling class MyListener implements ActionListener { public void actionPerformed( ActionEvent event ) { // react to event

} } // instantiate event listener ActionListener listener = new MyListener(); // instantiate event source JButton button = new JButton( Hello ); // register event listener with event source

button.addActionListener( listener ); 15 UML Sequence Diagram :MyPanel new :JButton

new :MyListener addActionListener () actionPerformed () 16

Event Handling Options for implementing listeners: listener class anonymous inner classes named inner classes 17 Event Handling Listener class:

18 Event Handling Anonymous inner listener class: 19 Event Handling Named inner listener class:

20 Event Handling Note: A class could potentially be both an event source and event listener. Good or bad idea? 21 Event Handling

public class MyButton extends JButton implements ActionListener { public MyButton() { addActionListener( this ); } public void actionPerformed( ActionEvent event ) { }

} JButton button = new MyButton() 22 Dependencies 23 Dependencies Problems:

need to maintain consistency in the views (or observers) need to update multiple views of the common data model (or subject) need clear, separate responsibilities for presentation (look), interaction (feel), computation, persistence 24 Model/View/Controller MVC roles:

model complete, self-contained representation of object managed by the application e.g., spreadsheet document provides a number of services to manipulate the data e.g., recalculate, save computation and persistence issues 25

Model/View/Controller MVC roles: view tracks what is needed for a particular perspective of the data e.g., bar chart view presentation issues controller gets input from the user, and uses appropriate

information from the view to modify the model e.g., get slider value, trigger chart modify interaction issues 26 Model/View/Controller 27 Model/View/Controller Separation:

you can modify or create views without affecting the underlying model the model should not need to know about all the kinds of views and interaction styles available for it separate threads? 28 Model/View/Controller In Swing: in practice, views and controllers are

implemented with Swing components and listeners both views and controllers will be dependent on Swing APIs 29 Model/View/Controller In Swing: still, try to separate the model and its services so that it is Swing-free

model is like a virtual machine or kernel specific to the application 30 Model/View/Controller Smalltalk: originated the MVC concept integral support in interactive applications with MVC classes

31 Model/View/Controller Java and Swing: concept is still valid to help structure interactive applications e.g., use a framework that supports MVC Swing internally uses a variant of MVC for its pluggable look-and-feel capability 32

Pluggable Look-and-Feel Swing: the look-and-feel is implemented in Java, but could mimic Windows, Motif, Classic, Aqua, etc. UIManager.setLookAndFeel( ); UIManager.setLookAndFeel( javax.swing.plaf.metal.MetalLookAndFeel

); 33 Pluggable Look-and-Feel SwingSet: 34 Pluggable Look-and-Feel Idea:

similar to skins, themes, schemes, etc., but must include feel as well as look 35 Pluggable Look-and-Feel Swing internals: each component uses a user interface delegate object (responsible for view and controller roles) component

model object user interface object user interface manager 36

Pluggable Look-and-Feel Swing internals: each component specifies a model interface that an associated model class must implement 37 Model/View/Controller CRC cards for MVC: discuss what models, views, and

controllers there are in the system be a design critic 38

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