Container classes and objects

1
Container classes and objects

• Objects that hold information in a dependable
  form, used by other classes

2
Color

• Defined
• Color boxColor new Color( )
• boxColor Color.black
• Used
• g.setColor( boxColor )

3
Font

• Defined (needs constructor info)
• Font myFont new Font( Arial, Font.PLAIN, 12)
• Used
• g.setFont( myFont )
• g.setColor( Color.red)
• g.drawString( hello" ,160, 220)

Type
Style
Size
4
Polygon

• Defined
• int xValues 20, 40, 50, 30, 20, 15
• int yValues 50, 50, 60, 80, 80, 60
• Polygon shape1
• new Polygon( xValues, yValues, 6 )
• Used
• g.drawPolygon( shape1 )

Number of points
5
A push-button object

• JButton helloButton new JButton( "Hello" )
• Where can we place the pushbutton?
• On anything, really remember that!

6

• import javax.swing.
• import java.awt.
• public class Button extends JFrame
• public Button()
• setSize(400,400)
• JButton myButton new JButton(push")
• add( myButton)
• setVisible(true)
• public static void main(String args )
• Button app new Button()
• // end class

7
JFrame methods summary

• setSize (400, 400)
• setLocation (50, 75)
• add( someObject )
• setDefaultCloseOperation( EXIT_ON_CLOSE )
• setVisible( true )

8
Graphics method summary

• paint (Graphics g)
• g.setColor( boxColor )
• g.fillArc( x, y, width, height, 0, 360 )
• g.fillRect( x, y, width, height )
• g.setFont( myFont )
• g.drawString( hello" ,160, 220 )
• g.drawPolygon( shape1 )
• g.drawLine( x1,y1,x2,y2)

9
the Container class

• Holds a whole window context frames, scroll
  bars, buttons, menus, pop-ups, and operator
  actions mouse clicks, dragging dropping.
• Operator actions are called events.
• JFrame objects must be placed in a container, to
  be of any use.
• ContentPane is a special container that
  contains the current state of your computer.

10
A Container manages all PC resources

• Its brilliant, really

Content current PC state
Layout presentation
Events operator actions
Container
11
Creating a ContentPane container

• // a container to hold your computers info
• Container myPC new Container()
• // current state
• myPC getContentPane( )
• The Container myPC is now a Content
  environment, an Event environment, and a
  Layout environment
• which is an object that holds the current details
  of all screen, user, keyboard, mouse events and
  conditions, and further... is a place where we
  can build a Graphical User Interface (GUI),
  compatible with the computers configuration.

12
what does this do?

• Container myPC new Container()
• myPC getContentPane( )
• FlowLayout layout new FlowLayout( )
• myPC.setLayout( layout )

JFrame
Container
13
Computers, it turns out, are just a bunch of
containers
Contaner your PC
ContentPane its current state
JFrame a graphics pane
Layout organizes the graphics
14
more JFrame and Container methods

• setSize( w, h )
• setLocation( x, y )
• setDefaultCloseOperation( EXIT_ON_CLOSE )
  
• Container myPC new Container()
• myPC getContentPane()
• FlowLayout layout new FlowLayout()
• myPC.setLayout( layout )
• JButton helloButton new JButton( "Hello" )
• myPC.add( helloButton ) // note added to
  the Container
• setVisible( true )

15
the Container controls everything
We now shift from using JFrame as the Graphics
organizer, to using the Container