Layout Managers

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Layout Managers
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A Container manages all PC resources

• Its brilliant, really

Content current PC state
Layout presentation
Events operator actions
Container
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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.

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what does this do?

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

JFrame
Container
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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 )

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the Container controls everything
We now shift from using JFrame as the Graphics
organizer, to using the Container
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Using Layout Managers

• A layout manager is an object that determines the
  size and position of the components within a
  container. Although components can provide size
  and alignment hints, a container's layout manager
  has the final say on the size and position of the
  components within the container.

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From Sun

• Although we recommend that you use layout
  managers, you can perform layout without them. By
  setting a container's layout property to null -
  myPC.setLayout( null ) - you make the container
  use no layout manager. With this strategy, called
  absolute positioning, you must specify the size
  and position of every component within that
  container. One drawback of absolute positioning
  is that it doesn't adjust well when the top-level
  container is resized. It also doesn't adjust well
  to differences between users and systems, such as
  different font sizes.

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Adding components

• When you add components to a container, the
  arguments you specify to the add method depend on
  the layout manager that the container is using.
  For example, BorderLayout requires that you
  specify the area to which the component should be
  added, using code like this
• myPC.add( aComponent, BorderLayout.NORTH)

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Flow Layout

• Container myPC new Container()
• myPC getContentPane()
• FlowLayout layout new FlowLayout()
• myPC.setLayout( layout )
• JButton helloButton new JButton( "Hello" )
• myPC.add( helloButton )

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Grid Layout

• Container myPC new Container()
• myPC getContentPane()
• GridLayout layout new GridLayout()
• myPC.setLayout( layout )
• JButton helloButton new JButton( "Hello" )
• myPC.add( helloButton )

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Border Layout

• Container myPC new Container()
• myPC getContentPane()
• BorderLayout layout new BorderLayout()
• myPC.setLayout( layout )
• JButton helloButton new JButton( "Hello" )
• myPC.add( helloButton, BorderLayout.NORTH )