GUI Programming with Java

Creating WindowsWindowsjavax.swing.JFrame – Empty windowBy default, JFrame is not visiblesetVisible(true)!Java Look And Feel (Metal) by default

Creating JFrameimport javax.swing.JFrame;class Testing { public static void main(String [] args) { JFrame mywin = new JFrame(); mywin.setVisible(true); }}

Inheritanceimport javax.swing.JFrame;class MyJFrame extends JFrame { public MyJFrame() { setTitle("My Window!"); }}class Testing { public static void main(String [] args) { MyJFrame mywin = new MyJFrame(); mywin.setVisible(true); }}

AWT vs. SwingAWT = Abstract Window Toolkitjava.awt.*;Old class library for JavaUses native GUI - componentsSwingjavax.swing.*;From Java 1.2 ->Extends AWTGUI – components 100% JavaPluggable look and feel

LayoutsUI is build on top of layoutsLayout determinates where UI-elements are layed.You can add a layout to JframeLayoutsFlowLayoutGridLayoutBorderLayoutGridBagLAyoutCardLayout

Layout and Componentsimport javax.swing.*;import java.awt.*;class MyJFrame extends JFrame { public MyJFrame() { setTitle("My Window!"); JButton clickMe = new JButton("Click me!"); FlowLayout layout = new FlowLayout(); setLayout(layout); add(clickMe); }}class Testing { public static void main(String [] args) { MyJFrame mywin = new MyJFrame(); mywin.setVisible(true); }}

BorderLayoutFive cellsnorthsoutheastwestcenter

Other layoutsBoxLayout- Components in row or columnCardLayoutWindow holds "cards", which can hold other componentsGridBagLayout- Lot of possibilities, hard to use

JPanelIt's possible to combine layouts using JPanelJPanel can have it's own layout. JPanel may hold other componentsJFrame can hold JPanels, that hold components..

Combining LayoutsJPanel left = new JPanel();left.setLayout(new GridLayout(2,1));JPanel right = new JPanel();right.setLayout(new GridLayout(3,1));leftrightsetLayout(new Gridlayout(1,2));add(left);add(right);MyJFrame

Combining Layoutspublic MyJFrame(){ setLayout(new GridLayout(1,2));JPanel left = new JPanel();left.setLayout(new GridLayout(2,1));left.add(new JButton("1"));left.add(new JButton("2"));JPanel right = new JPanel();right.setLayout(new GridLayout(3,1));right.add(new JButton("3"));right.add(new JButton("4")); right.add(new JButton("5"));add(left); add(right);}

ComponentsUI – components can be added to window (JFrame) using the add() – methodAll components derive from JComponentUI – components?JButtonJLabelJMenuItemJTableJTextAreaJTextField...

JComponentSome component's common methodssetVisible(boolean)setFont(Font)setEnabled(boolean)... See JComponent APIhttp://java.sun.com/javase/6/docs/api/javax/swing/JComponent.html

ComponentsJButtonJButton mybutton = new JButton("Click!");JLabelJLabel mylabel = new JLabel("Some text");JTextFieldJTextField myfield = new JTextField();String text = myfield.getText();JTextArea...

Delegation Event HandlingDelegation Event Model:Simple and easy to learnSupport a clean separation between application and GUI codeFacilitate the creation of robust event handling code which is less error-prone (strong compile-time checking)Flexible enough to enable varied application models for event flow and propagationFor visual tool builders, enable run-time discovery of both events that a component generates as well as the events it may observeSupport backward binary compatibility with the old model

Separation of GUI and BLSourceListenerRegistration

Concepts: Event SourceEvent source is usually some component that can raise eventsExamples of event sourceJButton (button is clicked)JMenuItemJTextField

ListenerAny class that can handle the events=> Any class that implements some interface

Recap on Polymorphisminterface AbleToMove { public void start(); public void stop();}class Car implements AbleToMove { public void start() { // do something } public void stop() { // do something }}

Recap on Polymorphismclass Test { public static void main(String [] args) { Airplane a = new Airplane(); someMethod(a); } public static void someMethod(AbleToMove x) { x.start(); }}You can pass whateverobject you desire as long asthe object implements AbleToMoveinterface!

ExampleJButton is a event source.JButton source = new JButton();When the button is clicked we want that something happensWe need a class that listens to the button.We register the source and the listener with each other!

Separation of GUI and BLJButtonListenerRegistration

RegistrationJButton holds a method addActionListenerpublic void addActionListener(ActionListener l)So you can call it likeJButton source = new JButton("Click!");source.addActionListener(...);Parameter ActionListener? What is it?It's an interface!This means that you can pass whatever object as long as the object implements the interface!

ActionListenerSo the listener can be what ever object as long as it implements the ActionListener.ActionListener:interface ActionListener {public void actionPerformed(ActionEvent e);}

ListenerSome class that implements the ActionListenerclass MyListener implements ActionListener { public void actionPerformed(ActionEvent e) { // do something }}

Separation of GUI and BLJButtonMyListeneraddActionListenerActionListener

Example Usage// Create the sourceJButton button = new JButton("click me");// Create the listenerMyListener listener = new MyListener();// Registrationbutton.addActionListener(listener);

RegistrationDifferent sources have different methods and interfaces for the registration.Registration:addXXXListenerExamplesaddMouseMotionListener(...)addMouseListener(...)addKeyListener(...)

Example: Listening to Mouse in Window// SourceJFrame a = new JFrame();// ListenerSomeClass listener = new SomeClass();// Registrationa.addMouseMotionListener(listener);

BL and GUI in the same classIn small programs it is usual that the GUI - and the application code is implemented in the same class.No the listener is the same class:class MyJFrame extends JFrame implements ActionListenerAnd registration:source.addActionListener(this);

MenuBarJFrame can contain MenuBarNeeded classesJMenuBarJMenuJMenuItemEvent handling the same as in JButton (addActionListener)

Creating MenuBarJMenuBar menubar = new JMenuBar();JMenu edit = new JMenu("Edit");JMenuItem pref = new JMenu("Preferen..edit.add(pref);menubar.add(edit);setJMenuBar(menubar);

About DialogsJFrame is used for windows, JDialog for dialogs.You can inherit the JDialog.Every dialog needs to know who the host window isdialog belongs to the window

Standard DialogsReally easy way to create dialogs is use standard dialogsJOptionPaneJFileChooserJColorChooser...

JOptionPaneWith one line of code, you can pop up a dialogJOptionPane.showMessageDialog(hostframe, "Hello!");Also availableshowConfirmDialogyes/no/cancelshowInputDialogprompt user

JFileChooserJFileChooser chooser = new JFileChooser(); int returnVal = chooser.showOpenDialog(parent); if(returnVal == JFileChooser.APPROVE_OPTION) String file = chooser.getSelectedFile().getName();

GUI Programming with Java

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