Download Inner classes, MVC, more GUI

GUI 2:
Inner classes & More Swing
OOP tirgul No. 5
2009
Inner classes
Suppose you write an applet, and you want your Applet subclass to contain some code
to handle mouse events. A solution is to define an inner class — a class inside of
your Applet subclass — that extends the MouseAdapter class. Inner classes can
also be useful for event listeners that implement one or more interfaces directly.
Example:
public class MyClass extends Applet {
...
someObject.addMouseListener(new MyAdapter());
...
class MyAdapter extends MouseAdapter {
public void mouseClicked(MouseEvent e) {
...//Event listener implementation goes here...
}
}
}
Anonymous inner classes
You can create an inner class without specifying
a name
public class MyClass extends Applet {
...
someObject.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
...//Event listener implementation goes here...
}
});
…
}
Nested & Inner classes
• Static (nested) and Non-Static (inner)
class OuterClass { ...
static class NestedClass { ... }
class InnerClass { ... }
}
• Access to nested/inner class from outside:
OuterClass.NestedClass
OuterClass out = …; out.InnerClass
• Instantiation of nested/inner class from outside the
outer class
… nested =new OuterClass.NestedClass(…);
out.InnerClass in = out.new InnerClass(…);
Nested & Inner classes 2
• Nested/inner class hides outer class methods and fields.
Access outer class methods/fields using OuterClass.staticMethod(…) or
OuterClass.this.anyMethod(…) in case of inner class
• Anonymous inner classes and local classes can access variables in
the surrounding scope only if the variables are final
void invokeAnon(final int number) {
final String word = “hello”;
someObject.pass(new Runnable() {
public void run() {
System.out.println(word.substring(number));
}
});
}
Nested & Inner classes 3
• Interfaces may have nested classes
• Generics parameters of outer class can be used within
inner classes
• Nested enums are equivalent to static nested classes
• Inner class cannot have static declarations in them
• Nested class is treated just as any other class by the
JVM, e.g. it is not loaded/initialized until used.
• Inner class holds a strong reference to the enclosing
instance
More… and further more…
Separating Data (model) from User
Interface (view)
Swing architecture, MVC
• Swing architecture is rooted in the model-viewcontroller (MVC) design that dates back to
Smalltalk.
• MVC architecture calls for a visual application to
be broken up into three separate parts:
– model that represents the data for the application.
– view that is the visual representation of that data.
– controller that takes user input on the view and
translates that to changes in the model.
Model-View-Controller (MVC)
UI:
refresh
View
Data display
Controller
events
refresh
Data:
User input
manipulate
Model
Data model
Swing’s Modified MVC
• MVC split didn't work well in practical terms
because the view and controller parts of a
component required a tight coupling
• So view and controller were collapsed into a
single UI (user-interface) object, controlled by
the “look-and-feel”
Look and Feel
• The architecture of Swing is designed so that you may
change the "look and feel" (L&F) of your application's
GUI
– Look refers to the appearance of GUI widgets
(JComponent-s)
– Feel refers to the way the widgets behave
• Swing's architecture enables multiple L&Fs by
separating every JComponent into two distinct classes:
a JComponent subclass and a corresponding
ComponentUI subclass (delegate).
Java L&F selection
Sun's JRE provides the following L&Fs:
•
•
•
CrossPlatformLookAndFeel "Java L&F" (a.k.a "Metal") looks the same on all
platforms. It is part of the Java API and is the default L&F.
SystemLookAndFeel the L&F that is native to the system it is running on. The
System L&F is determined at runtime, where the application asks the system to
return the name of the appropriate L&F.
…
Windows
Nimbus
(new in Java 6)
Metal
Motif
MV(C) Swing example: JList
Creating the list
listModel = new DefaultListModel();
JList list = new JList(listModel);
listModel.addElement("Debbie Scott");
listModel.addElement("Scott Hommel");
listModel.addElement("Sharon Zakhour");
int index = list.getSelectedIndex();
listModel.remove(index);
• Items are added \ removed from the
model and not directly from the list.
• There is no separate controller.
JList - Model
• Immutable: Vector / array (for static display)
• Mutable:
DefaultListModel (similar to vector)
• Mutable:
ListModel (interface):
–
–
–
–
int getSize()
Object getElementAt(int index)
void addListDataListener(ListDataListener l)
void removeListDataListener(ListDataListener l)
JList
ListDataListener
ListModel
JList - Model
Partial implementation of ListModel: AbstractListModel
ListModel bigData = new AbstractListModel() {
public int getSize() {
return Short.MAX_VALUE;
}
public Object getElementAt(int index) {
return "Index " + index;
}
};
• This list model has about 2^16 elements. Enjoy scrolling.
• Note: this is a static model: for remove / add some more code is
needed.
A class that listens to itself…
import javax.swing.*;
import java.awt.event.*;
public class FileChooserDemo extends JPanel implements
ActionListener {
JFileChooser fc;
}
public FileChooserDemo() {
fc = new JFileChooser();
JButton saveButton = new JButton("Save a File...");
saveButton.addActionListener(this);
//…
}
The actionPerformed method
public void actionPerformed(ActionEvent e) {
int returnVal =
fc.showOpenDialog(FileChooserDemo.this);
}
if (returnVal == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
print("Opening: " + file.getName() );
} else {
print("Open command cancelled by user.");
}
Dialogs and modality
• A Dialog window is an independent subwindow meant to carry temporary notice
apart from the main window.
• Most Dialogs present an error message or
warning to a user, but Dialogs can also
present images, directory trees, progress
bars and statuses, etc.
• A Dialog can be modal. When a modal
Dialog is visible, it blocks user input to all
other windows in the program.
JOptionPane creates modal dialogs, to create a nonmodal Dialog, you must use the JDialog directly.
Since Java 6, 4 types of modality are supported: none,
document, application, toolkit.
Simple dialogs
JOptionPane.showMessageDialog( frame,
"Eggs are not supposed to be green.",
"Inane error",
JOptionPane.ERROR_MESSAGE);
Object[] options = {"Yes, please", "No way!"};
int n = JOptionPane.showOptionDialog(frame,
"Would you like green eggs and ham?",
"A Silly Question",
JOptionPane.YES_NO_OPTION,
JOptionPane.QUESTION_MESSAGE,
null, //do not use a custom Icon
options, //the titles of buttons
options[0]); //default button title
http://java.sun.com/docs/books/tutorial/uiswing/components/dialog.html
Special dialogs - File Chooser
//Create a file chooser
final JFileChooser fc = new JFileChooser();
...
//In response to a button click:
int returnVal = fc.showOpenDialog(aComponent);
if (returnVal == JFileChooser.APPROVE_OPTION)
File file = fc.getSelectedFile();
Custom Dialog
• Our own class that extends JDialog,
dialog.setVisible(true)
• To intercept dialog closing:
dialog.addWindowListener(new WindowAdapter() { public void
windowClosing(WindowEvent we) { … } });
• Dialog can call back to the component that opened it when,
for example, Ok button was clicked
• Or dialog can store input in a local variable and provide public
access method to variable; when dialog is closed
(setVisible(false)) the creator of the dialog checks the input
values:
Custom Dialog example
public class CustomDialog
extends JDialog implements ActionListener
{
CustomDialog dialog = new CustomDialog(this);
final JTextField input;
dialog.setVisible(true);
…
String in = dialog.getInput();
public CustomDialog(JFrame frame) {
super(frame, true); //modal
input = new JTextField();
Dialogs don’t need to be created every
getContentPane().add(input);
time they are needed. A dialog instance
JButton okBut = new JButton("OK");
can be reused – stored in a local field,
getContentPane().add(okBut);
okBut.addActionListener(this);
initialized first time it is needed and
…
reset/customized before it is shown
}
public void actionPerformed(ActionEvent e) {
setVisible(false);
}
public String getInput() {
return input.getText();
}
http://zawoad.blogspot.com/2008/09/
showing-your-own-custom-dialog-boxin.html
Binding & Property Change Events
java.beans.PropertyChangeSupport, or even better for
UI: javax.swing.event.SwingPropertyChangeSupport
PropertyChangeSupport pc = new …(this);
PropertyChangeListener listen1, listen2;
…
pc.addPropertyChangeListener(listen1);
pc.addPropertyChangeListener(listen2);
pc.firePropertyChange(“changed”, false, true);
Listeners:
public void propertyChange(PropertyChangeEvent evt) { …}
Sun Tutorials,
Swing Visual index
Swing / AWT tutorial:
http://java.sun.com/docs/books/tutorial/uiswi
ng/
Swing Visual index :
http://java.sun.com/docs/books/tutorial/uiswi
ng/components/components.html
Java, GUI, Internet
Using Java for Rich Internet Applications (RIA)
Java Applets, Java Plug-in, Java Web-Start (JNLP)
Alternative GUI technologies in Java
Eclipse Rich Client Platform (RCP)
Google Web Toolkit (GWT)
Sun JavaFX
…
Web-based UI in Java
Servlet, JSP, JSF