Swing II

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Swing II
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Swing II Topics

• WindowListener interface
• Icons
• Scrollbars
• The Graphics class
• Colors
• Fonts the drawString method

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WindowListener interface

• Must implement WindowListener interface
  (java.awt.event).
• All methods receive a WindowEvent
  (java.awt.event).
• Recall that the Jframe setDefaultCloseOperation
  is very limited.
• Instead, you may respond in any manner you wish
  by implementing the WindowListener inteface and
  then by using the setWindowListener method.

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WindowListener interface

• Method summary
• void windowActivated ( WindowEvent e )
• Invoked when the Window is set to be the active
  Window.
• void windowClosed ( WindowEvent e )
• Invoked when a window has been closed as the
  result of calling dispose on the window.
• void windowClosing ( WindowEvent e )
• Invoked when the user attempts to close the
  window from the window's system menu.

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WindowListener interface

• Method summary
• void windowDeactivated ( WindowEvent e )
• Invoked when a Window is no longer the active
  Window.
• void windowDeiconified ( WindowEvent e )
• Invoked when a window is changed from a minimized
  to a normal state.
• void windowIconified ( WindowEvent e )
• Invoked when a window is changed from a normal to
  a minimized state.

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WindowListener interface

• Method summary
• void windowOpened ( WindowEvent e )
• Invoked the first time a window is made visible.
• You do not need to fully implement all methods.
  You can simply define them with an empty block
• public void windowDeiconified ( WindowEvent e )
  

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Basic WindowListener template

• import java.awt.event.WindowEvent
• import java.awt.event.WindowListener
• public class MyWindowListener implements
  WindowListener
• public void windowActivated ( WindowEvent e )
  
• public void windowClosed ( WindowEvent e )
• public void windowClosing ( WindowEvent e )
• public void windowDeactivated ( WindowEvent e )
  
• public void windowDeiconified ( WindowEvent e )
  
• public void windowIconified ( WindowEvent e )
  
• public void windowOpened ( WindowEvent e )

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Extending JFrame and implementing some Listener

• We have 3 architectural options
• Class A extends JFrame class B implements some
  Listener.
• Class A extends JFrame and implements some
  Listener.
• Class A extends JFrame and class A contains an
  inner class B that implements some Listener.

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Inner classes

• Ex.
• public class MyOuterClass
• private class MyInnerClass

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Inner classes

• Advantages
• Can be used to make the outer class
  self-contained.
• Inner and outer classes have access to each
  others private members.
• Private inner classes cannot be accessed by name
  outside of the defining outer class.

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Extending JFrame implementing a WindowListener
in an inner class

• public class MyFrame extends JFrame
• private class MyWindowListener implements
  WindowListener
• public void windowActivated ( WindowEvent e )
  
• public void windowClosed ( WindowEvent e )
• public void windowClosing ( WindowEvent e )
• public void windowDeactivated ( WindowEvent e )
  
• public void windowDeiconified ( WindowEvent e )
  
• public void windowIconified ( WindowEvent e )
  
• public void windowOpened ( WindowEvent e )
• public MyFrame ( )
• addWindowListener( new MyWindowListener() )

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WindowAdapter class

• An abstract adapter class for receiving window
  events. The methods in this class are empty. This
  class exists as convenience for creating listener
  objects.
• Extend this class to create a WindowEvent
  listener and override the methods for the events
  of interest. (If you implement the WindowListener
  interface, you have to define all of the methods
  in it. This abstract class defines null methods
  for them all, so you can only have to define
  methods for events you care about.)
• Create a listener object using the extended class
  and then register it with a Window using the
  window's addWindowListener method. When the
  window's status changes by virtue of being
  opened, closed, activated or deactivated,
  iconified or deiconified, the relevant method in
  the listener object is invoked, and the
  WindowEvent is passed to it.

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Icons

• Simply a (typically small) picture.
• JLabels, JButtons, and JMenuItems can have
• icons
• strings
• icons and strings
• nothing at all
• If the item doesnt have any associated text, use
  the setActionCommand method to explicitly assign
  a command string to the item.

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Icons

• Creating icons from image files
• ImageIcon dukeIcon new ImageIcon(
  duke_waving.gif )
• Adding an icon to a label
• JLabel dukeLabel new JLabel( wood check )
• dukeLabel.setIcon( dukeIcon )
• JLabel dukeLabel new JLabel( dukeIcon )

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Icons

• Icons may be used with buttons and menu items
  too
• JButton happyButton new JButton( happy )
• ImageIcon happyIcon new ImageIcon(
  smiley.gif )
• happyButton.setIcon( happyIcon )

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Scrollbars

• Create the object to be scrolled
• JTextArea memo new JTextArea( 15, 30 )
• Create the JScrollPane
• public JScrollPane ( Component objectToBeScrolled
  )
• Add the JScrollPane to a container such as JPanel
  or JFrame.

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Scrollbars

• JScrollPane
• public JScrollPane ( Component objectToBeScrolled
  )
• public void setHorizontalScrollBarPolicy ( int
  policy )
• policies
• JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS
• JScrollPane.HORIZONTAL_SCROLLBAR_NEVER
• JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED
• public void setVerticalScrollBarPolicy ( int
  policy )
• policies
• JScrollPane.VERTICAL_SCROLLBAR_ALWAYS
• JScrollPane.VERTICAL_SCROLLBAR_NEVER
• JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED

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The Graphics class

• Coodinate system and origin
• (0,0) ----------gt x
• v
• y
• JFrames paint method draws whatever needs to be
  drawn.
• public void paint ( Graphics g )

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Graphics class methods

• Method summary
• void clearRect ( int x, int y, int width, int
  height )
• Clears the specified rectangle by filling it with
  the background color of the current drawing
  surface.
• void draw3DRect ( int x, int y, int width, int
  height, boolean raised )
• Draws a 3-D highlighted outline of the specified
  rectangle.
• void drawArc ( int x, int y, int width, int
  height, int startAngle, int arcAngle )
• Draws the outline of a circular or elliptical arc
  covering the specified rectangle.

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Graphics class methods

• Method summary
• void drawLine ( int x1, int y1, int x2, int y2 )
• Draws a line, using the current color, between
  the points (x1, y1) and (x2, y2) in this graphics
  context's coordinate system.
• void drawOval ( int x, int y, int width, int
  height )
• Draws the outline of an oval.
• void drawPolygon ( int xPoints, int yPoints,
  int nPoints )
• Draws a closed polygon defined by arrays of x and
  y coordinates.
• void drawPolyline ( int xPoints, int yPoints,
  int nPoints )
• Draws a sequence of connected lines defined by
  arrays of x and y coordinates.

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Graphics class methods

• Method summary
• void drawRect ( int x, int y, int width, int
  height )
• Draws the outline of the specified rectangle.
• void drawRoundRect ( int x, int y, int width, int
  height, int arcWidth, int arcHeight )
• Draws an outlined round-cornered rectangle using
  this graphics context's current color.
• void drawString ( String str, int x, int y )
• Draws the text given by the specified string,
  using this graphics context's current font and
  color.
• void fill3DRect ( int x, int y, int width, int
  height, boolean raised )
• Paints a 3-D highlighted rectangle filled with
  the current color.

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Graphics class methods

• Method summary
• void fillArc ( int x, int y, int width, int
  height, int startAngle, int arcAngle )
• Fills a circular or elliptical arc covering the
  specified rectangle.
• void fillOval ( int x, int y, int width, int
  height )
• Fills an oval bounded by the specified rectangle
  with the current color.
• void fillPolygon ( int xPoints, int yPoints,
  int nPoints )
• Fills a closed polygon defined by arrays of x and
  y coordinates.
• void fillPolygon ( Polygon p )
• Fills the polygon defined by the specified
  Polygon object with the graphics context's
  current color.
• void fillRect ( int x, int y, int width, int
  height )
• Fills the specified rectangle.

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Graphics class methods

• Method summary
• void fillRoundRect ( int x, int y, int width, int
  height, int arcWidth, int arcHeight )
• Fills the specified rounded corner rectangle with
  the current color.
• Color getColor ( )
• Gets this graphics context's current color.
• Font getFont ( )
• Gets the current font.
• FontMetrics getFontMetrics ( )
• Gets the font metrics of the current font.
• FontMetrics getFontMetrics ( Font f )
• Gets the font metrics for the specified font.

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Graphics class methods

• Method summary
• void setColor ( Color c )
• Sets this graphics context's current color to the
  specified color.
• void setFont ( Font font )
• Sets this graphics context's font to the
  specified font.
• void translate ( int x, int y )
• Translates the origin of the graphics context to
  the point (x, y) in the current coordinate system.

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Drawing with the graphics class

• public class Face extends JFrame
• public void paint ( Graphics g )
• super.paint( g )
• g.setColor( Color.BLUE )
• g.drawLine( 55, 60, 75, 60 )

Typically, one overrides paint but never calls it
directly. Additionally, there is a repaint
method. Typically, one calls repaint when it is
necessary to redraw the contents of the frame
(but one never overrides repaint).
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Colors

• We saw how we can call setColor in our paint
  method to change colors.
• We may use the predefined colors such as
  Color.BLUE, Color.CYAN, etc.
• Colors are represented by triples of RGB values
• Color brown new Color( 200, 150, 0 )
• where each int component is in 0..255

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Colors

• Other useful methods
• public Color brighter ( )
• Returns a brighter version of the calling
  objects color.
• public Color darker ( )
• Returns a darker version of the calling objects
  color.
• new Color ( 0.5f, 1.0f, (float)0.2 )
• Where each float rgb component is in 0.0 .. 1.0

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Colors

• Color c JColorChooser.showDialog( null,
  "JColorChooser", null )

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Fonts the drawString method

• Recall the drawString method
• g.drawString( hello, x, y )
• To change the current font
• Font f new Font( SansSerif, Font.PLAIN, 24
  )
• g.setFont( f )
• g.drawString( hello, x, y )

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Fonts the drawString method

• Say the user picks a different font from a menu.
• What sequence of events occur?
• How do we then change the appearance of the text
  in our paint/drawing program?

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Additional information

• Not in the text

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Additional listeners

• MouseListener
• MouseMotionListener
• MouseWheelListener
• KeyListener
• WindowStateListener
• WindowFocusListener

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MouseListener interface

• Method summary
• void mouseClicked ( MouseEvent e )
• Invoked when the mouse button has been clicked
  (pressed and released) on a component.
• void mouseEntered ( MouseEvent e )
• Invoked when the mouse enters a component.
• void mouseExited ( MouseEvent e )
• Invoked when the mouse exits a component.

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MouseListener interface

• Method summary
• void mousePressed ( MouseEvent e )
• Invoked when a mouse button has been pressed on a
  component.
• void mouseReleased ( MouseEvent e )
• Invoked when a mouse button has been released on
  a component.
• Also MouseAdapter MouseInputAdapter classes.

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MouseEvent class

• Method summary
• int getButton ( )
• Returns which, if any, of the mouse buttons has
  changed state.
• int getClickCount ( )
• Returns the number of mouse clicks associated
  with this event.
• int getX ( )
• Returns the horizontal x position of the event
  relative to the source component.

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MouseEvent class

• Method summary
• int getY ( )
• Returns the vertical y position of the event
  relative to the source component.
• String paramString ( )
• Returns a parameter string identifying this
  event.
• int getModifiersEx ( ) (inherited from
  InputEvent)
• Returns the extended modifier mask for this
  event. Extended modifiers represent the state of
  all modal keys, such as ALT, CTRL, META, and the
  mouse buttons just after the event occurred.

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MouseMotionListener interface

• Method summary
• void mouseDragged ( MouseEvent e )
• Invoked when a mouse button is pressed on a
  component and then dragged.
• void mouseMoved ( MouseEvent e )
• Invoked when the mouse cursor has been moved onto
  a component but no buttons have been pushed.
• Also MouseMotionAdapter MouseInputAdapter
  classes.

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MouseWheelListener interface

• Method summary
• void mouseWheelMoved ( MouseWheelEvent e )
• Invoked when the mouse wheel is rotated.
• No MouseWheelAdapter!

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MouseWheelEvent class

• Method summary
• int getScrollAmount ( )
• Returns the number of units that should be
  scrolled in response to this event.
• int getWheelRotation ( )
• Returns the number of "clicks" the mouse wheel
  was rotated.

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KeyListener interface

• Added to a component by its addKeyListener
  method.
• KeyAdapter class available as well.
• Method summary
• void keyPressed ( KeyEvent e )
• Invoked when a key has been pressed (low level).
• void keyReleased ( KeyEvent e )
• Invoked when a key has been released (low level).
• void keyTyped ( KeyEvent e )
• Invoked when a key has been typed (higher level).

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KeyEvent class

• Indicates what key was pressed.
• Defines constants for function and arrow keys.
• Allows one to detect if modifiers (Alt, Ctrl,
  Shift) were also pressed.

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WindowStateListener interface

• Method summary
• void windowStateChanged ( WindowEvent e )
• Invoked when window state is changed.
• WindowEvent WindowAdapter classes were already
  discussed.

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WindowFocusListener interface

• Method summary
• void windowGainedFocus ( WindowEvent e )
• Invoked when the Window is set to be the focused
  Window, which means that the Window, or one of
  its subcomponents, will receive keyboard events.
• void windowLostFocus ( WindowEvent e )
• Invoked when the Window is no longer the focused
  Window, which means that keyboard events will no
  longer be delivered to the Window or any of its
  subcomponents.
• WindowEvent WindowAdapter classes were already
  discussed.