Ancora su repaint…
Quando si modifica la composizione di un
container, per mostrare le variazioni NON
BASTA chiamare la repaint(), prima occorre
chiamare la validate().
Ancora su repaint…
p.addButton();
p.validate();
p.repaint();
Animazione in Java
Problemi che possono nascere,
e loro soluzione
Animazione in Java
Application
MyFrame
(JFrame)
ClockPanel
(JPanel)
public class ClockPanel extends JPanel { …
public void paintComponent(Graphics g) {
Date d=new Date();
int sec=d.getSeconds(); OBSOLETO, ma funziona
double angle=sec*Math.PI/30;
int w=this.getWidth();
int h=this.getHeight();
g.setColor(Color.YELLOW);
g.fillRect(0,0,w,h);
g.setColor(Color.GREEN);
g.fillOval(0,0,w,h);
g.setColor(Color.BLACK);
g.drawLine(w/2,h/2,
(int)(w/2*(1+Math.cos(angle)))
,(int)(h/2*(1+Math.sin(angle))));
} …
ClockPanel - paintComponent
public class MyFrame extends JFrame {
//Component initialization
private void jbInit() throws Exception {
contentPane=new ClockPanel();
this.setContentPane(contentPane);
contentPane.setLayout(borderLayout1);
this.setSize(new Dimension(400, 300));
this.setTitle("Frame Title");
while (true) {
try {
Thread.sleep(1000);
}
catch (InterruptedException ex) {
}
contentPane.repaint();
}
}
...
MyFrame – version 1
Animazione e Threads in Java
Application
Runner
(Runnable)
MyFrame
(JFrame)
ClockPanel
(JPanel)
public class Runner implements Runnable {
ClockPanel cp;
public Runner(ClockPanel cp) {
this.cp=cp;
}
public void run() {
while (true) {
try {
Thread.sleep(1000);
}
catch (InterruptedException ex) {
}
cp.repaint();
}
}
Runner
}
MyFrame – version 2
public class MyFrame extends JFrame {
//Component initialization
private void jbInit() throws Exception {
contentPane=new ClockPanel();
this.setContentPane(contentPane);
contentPane.setLayout(borderLayout1);
this.setSize(new Dimension(400, 300));
this.setTitle("Frame Title");
Runner r=new Runner(contentPane);
new Thread(r).start();
}
...
Applicativi in Java
Come distribuire un applicativo fatto in Java?
Vedi anche
http://www.excelsior-usa.com/articles/java-to-exe.html
JRE? What is that? What version?
the author of a Java program has to ensure that the
proper version of the JRE is installed on an end user
system.
In a general case you may not expect that your end users
will know what a JRE is, how to check its version, and
how to download and install it.
A .bat file (or a .sh file)
Even if you can make sure the right version of the JRE is properly
installed on enduser systems, which is quite possible in a
classroom or enterprise environment, the command line required
to launch your Java application can be quite long:
java -Xmx200m -cp whatever.jar -Dsome.property MyApp
Yes, you may put that line into a batch file and call it runme.bat, but
it looks so much easier to give your program to a friend, teacher
or colleague as a single file that can be run by a double-click. Or,
even better, enable it to be installed and uninstalled in a native
manner without affecting other applications.
executable jar
you can make your Java application runnable via a
double-click by packaging it into a so called
executable jar
You do that by specifying the main class of your
application, any extra jar files it may require and so on
in the jar's manifest file
MANIFEST.MF
Manifest-Version: 1.0
Main-Class: animation.Application1
executable jar
Crea un jar:
jar cvfm MyApp.jar MyApp.mf *.class *.gif
Esegui un jar:
java -jar MyApp.jar
the Java launcher will read the manifest from MyApp.jar and invoke
the main method from the class specified in the Manifest.
If you double-click that jar file on a system that has JRE installed, the
java launcher will be invoked automatically.
JAR problems
The major problem with executable jars is
compatibility.
The default JRE may be of an older version than
is required by your application or may not have
the necessary Java Optional Packages installed.
JWS - Java Web Start
Using Java Web Start technology, standalone Java software applications can
be deployed with a single click over the network. Java Web Start ensures
the most current version of the application will be deployed, as well as
the correct version of the Java Runtime Environment (JRE).
Java Web Start downloads, installs, and manages one or more Java
Runtime Environments as required by the applications the user
runs.
JWS - Java Web Start
After running the application for the first time from the web page as
described above, the application is cached. This both improves
application performance and enables the user to access it without
returning to the web page.
The application is added to the Java Application Cache Viewer. Users can
simplify running a Java Web Start application further by adding a shortcut
to the desktop, by selecting Install Shortcuts from the Application menu
in the Java Application Cache Viewer.
JWS - Java Web Start
Developer responsibilities:
- Crea un JAR file
- Crea un JNLP file
- Crea una Web Page
- Metti il tutto su un Web Server
JWS - JNLP file
<?xml version="1.0" encoding="utf-8"?>
<jnlp spec="1.0“ codebase="URL of application on your Web server"
href="Notepad.jnlp">
<information>
<title>Notepad Demo</title>
<vendor>Sun Microsystems, Inc.</vendor>
<offline-allowed/>
</information>
<resources>
<jar href="Notepad.jar"/>
<j2se version="1.3+"
href="http://java.sun.com/products/autodl/j2se"/>
</resources>
<application-desc main-class="Notepad"/>
</jnlp>
JWS - Java Web Start
Where Do You Get Java Web Start?
Java Web Start is included in the Java Runtime
Environment (JRE) as part of J2SE 5.0.
Vedi
http://java.sun.com/products/javawebstart/
Custom wrappers
When a Java program is invoked the operating system runs a Java
launcher from the JRE. The Windows version of the JRE has
separate launchers for command-line and GUI apps, called
java.exe and javaw.exe respectively.
As a result, all running Java applications have the same Taskbar/AltTab icons and appear in the Windows Task Manager as either
java.exe or javaw.exe. If you have two or more Java apps
running, you have no means to distinguish between multiple
instances of the standard Java launcher in the Task Manager.
Custom wrappers
A Java wrapper in essentially a custom Java launcher that is also a
self-extracting archive containing all the application's classes, jars
and auxiliary files. Some wrapper provide additional features such
as instant splash screen, stdout and stderr redirection.
A wrapper normally looks up the JRE upon startup. If the JRE is not
present or its version does not match the application's
compatibility requirements, some wrappers may install the JRE (if
you have included it when wrapping your application) and/or
download and install the required version of the JRE.
The most sophisticated wrappers may also setup file associations and
create shortcuts on first run.
Custom wrappers
Pro
 JRE version check
 JRE download or bundling
 Unique process name and icon
 No end-user training
Contro
 Platform specific
 Desktop integration capabilities absent or very limited
Per una lista di Wrappers (free o commerciali) vedi
http://www.excelsior-usa.com/articles/java-to-exe.html
Installers
Installer tools may give you the following
benefits:
* Install-time JRE detection and download
* Generation of native launchers
* User-editable JVM parameter files
* Redirection of stderr and stdout for saving
logs and exception stack traces.
* Registration of Java applications as Windows
services and Unix daemons
Platform-centric, Multi-Platform, Cross-Platform
free: IzPack, Advanced Installer for Java
Ahead-Of-Time Compilers
AOT compilers are known also as "static
compilers" and "native code compilers". The
latter term is the most used and, as it often
happens, the least correct from the technical
standpoint, because JIT compilers also produce
native code.
An Ahead-Of-Time (AOT) compiler takes as input
your jars and class files and produces a
conventional native executable for the target
platform, such as Windows EXE or Linux ELF
binary.
NON SERVE LA JRE!
Ahead-Of-Time Compilers
Pro
 Peformance increase
 IP protection
 Better user perception
Contro
 Disk footprint increase
 Limited applicability
1 prodotto commerciale, 1 open source (immaturo)
Vedi: http://www.excelsior-usa.com/articles/java-to-exe.html