EPITA Première Année Cycle Ingénieur Atelier ... - wiki-prog - Epita

EPITA Première Année Cycle Ingénieur 

Atelier Java - J5 

Marwan Burelle 

marwan.burelle@lse.epita.fr 

http://www.lse.epita.fr 



Going Graphics 

Swing And 

Concurrency

Overview 

1 Going Graphics 

2 Swing And Concurrency 




Swing And 

Concurrency






Swing And 

Concurrency

Different toolkits 

• AWT: the good-old one, lakes some features and has 

a plateform specific look’n’feel (anyway, AWT is 

deprecated) 

• Swing: a better AWT with a unified Look’n’feel and 

better drawing algorithms. 

• SWT: the toolkit from Eclipse backed on native 

toolkits. 




Swing And 

Concurrency

Swing 

• Swing could have been a demonstration of classical 

design patterns in action, the whole concept heavily 

relies on: 

• Decorator 

• Composite 

• Facade 

• Chain of responsibility (internal) 

• A graphical application in Java can be seen as tree 

(Composite) rooted by a JFrame and where nodes are 

widget and layout. 

• The layout concept help you hierarchically describes 

your interface and provide a nive way to organize 

your widget 

• The whole API is event-driven meaning that all you 

have to do is to connect event and operations 

triggered by those events. 




Swing And 

Concurrency

SwingSet2 demo 




Swing And 

Concurrency

Exploring The BorderLayout 

SimpleFrame 

import javax.swing.*; 

import java.awt.BorderLayout; 

import java.awt.Container; 

import java.awt.Dimension; 

public class SimpleFrame { 

public static void main(String[] args) { 

javax.swing.SwingUtilities.invokeLater( 

new Runnable() { 

public void run() { show(); } 

} 

); 

} 

} 




Swing And 

Concurrency

Exploring The BorderLayout 

SimpleFrame 

private static void show() { 

JFrame frame = new JFrame("BorderLayout"); 

frame.setDefaultCloseOperation( 

JFrame.EXIT_ON_CLOSE); 

JButton labelT = new JButton("Top"); 

JButton labelB = new JButton("Bottom"); 

JButton labelC = new JButton("Center"); 

JButton labelL = new JButton("Left"); 

JButton labelR = new JButton("Right"); 

Container pane = frame.getContentPane(); 

pane.add(labelT, BorderLayout.PAGE_START); 

pane.add(labelB, BorderLayout.PAGE_END); 

pane.add(labelC, BorderLayout.CENTER); 

pane.add(labelL, BorderLayout.LINE_START); 

pane.add(labelR, BorderLayout.LINE_END); 

frame.pack(); 

frame.setVisible(true); 

} 




Swing And 

Concurrency

Adding an Event Listener 

SimpleFrame 

static void addButtonEvent(final JButton b) { 

final String name = b.getText(); 

ActionListener listener = 

new ActionListener() { 

int c = 0; 

public void actionPerformed(ActionEvent e) { 

out.println(name); 

c++; 

b.setText(name + " clicked (" + c + ")"); 

} 

}; 

b.addActionListener(listener); 

} 




Swing And 

Concurrency

Swing And Concurrency 

Swing And Concurrency 




Swing And 

Concurrency

We Got Threads ? 

• A swing application always runs with 3 threads 

doing separate works in order to keep the 

application the most responsible as possible: 

• Initial Thread: the threads that execute initial 

application code. 

• Event Dispatch Thread: where all the stuff about event 

is done. 

• Worker Threads: where the background heavy work is 

done. 

• These threads are created directly by the framework, 

the only things you need to know is how to interract 

with them. 




Swing And 

Concurrency

Initial Threads 

• The only role of the initial thread is to launch the 

invoke the GUI creation that will be run by the Event 

Dispatch Thread. 

Syntax: invokeLater 

javax.swing.SwingUtilities.invokeLater( 

new Runnable() { 

public void run() { BuildGUI(); } 

} 

); 




Swing And 

Concurrency

Event Dispatch Thread 

• The place for all event and swing activities 

• Almost all swing action must be done in that thread: 

swing operations are not thread safe, so we must 

keep them bound to one thread. 

• Task in the Event Dispatch Thread must be short: if a 

task take too long, it will make the interface 

unresponsive or freezing 

• Globaly, if you start your GUI with the previous 

method, it will run on the wrigth thread. 




Swing And 

Concurrency

Worker Threads 

• Background taskes (often long one) are supposed to 

run asynchronously with the GUI and thus run on 

one or more Worker Threads. 

• javax.swing.SwingWorker is an abstract class used 

to build task to be scheduled on the worker threads. 

• You must define a method doInBackground that 

launch the work 

• You may define also a method called done that will 

be executed by the Event Dispatch Thread. 

• javax.swing.SwingWorker implements the 

Futur interface and thus we are able to wait for 

result using method get. 

• Beware, get is blocking and you’ll probably invoke it 

from the Event Dispatch Thread, it then can freeze your 

interface. There’s an overloaded variant of get 

taking a time-out value to avoid long waiting. 




Swing And 

Concurrency

Live Updates 

• We sometime need to push update to the interface 

before the end of the computation. 

• javax.swing.SwingWorker provides a method 

publish that let you make values available for the 

Event Dispatch Thread. 

• The Event Dispatch Thread will access these values 

through the method process that you thus need to 

override. 




Swing And 

Concurrency

Workers 

Syntax: SwingWorker 

class MyWorker extends SwingWorker { 

O doInBackground() { 

// do your job here 

// and public sometimes ... 

publish(new I(...)); 

} 

void process(List values) { 

// display things here 

} 

} 




Swing And 

Concurrency

Other Tools 

• You can cancel a running job from the Event Dispatch 

Thread using the method worker.cancel(true) 

• The worker will be able to test the cancelation state 

using the method isCancelled() 

• You can use the progress property (an int ranging 

from 0 to 100) to indicate progression (using 

setProgress and getProgress) 

• You also have the state variable indicating the 

current state through the possible values: PENDING, 

STARTED, DONE 




Swing And 

Concurrency

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