GUI programming

1
GUI programming

• AWT(Abstract Windows Toolkit)-GUI components
  library when Java was introduced
• AWT was replaced by Swing components
• import javax.swing.

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GUI API class hierarch p371

• Object
• Dimension,Font, FontMetrics, Color, Graphics,
  Component
• LayoutManager, Container
• Panel, Window, Jcomponent
• Applet, Frame, Dialog

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GUI Container classes

• Container classes are GUI components that are
  used as containers to contain other GUI
  components
• Container, JFrame, JDialog, JApplet, and JPanel

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Java GUI API container classes

• Container used to group components. A layout
  manager is used to position and place components
  in a container
• Frames, panels and applets are examples of
  containers
• JFrame window not contained inside another
  window. It is the container that holds other
  Swing user-interface components
• JDialog popup window or message box
• JApplet subclass of Applet. You must extend
  JApplet to create a Swing-based Java applet.
• JPanel invisible container that holds
  user-interface components. Panel can be nested.
  JPanle also can be used as a canvas to draw
  graphics

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GUI helper classes

• Helper classes are not subclass of Component.
  They are used to describe the properties of GUI
  components
• Graphics abstract class that provides a
  graphical context for drawing strings, lines, and
  simple shapes
• Color deals with colors of GUI components
• Font specifies fonts for the text and drawings
  on GUI components
• FontMetrics is an abstract class used to get the
  properties of the font
• Dimension encapsulates the width and height of a
  component
• LayoutManager specify how components are
  arranged in a container

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Frame

• Create a Frame
• import javax.swing.
• public class MyFrame
• public static void main( String args)
• JFrame frm new JFrame(Test Frame)
• frm.setSize(400, 300)
• frm.setVisible(true)
• frm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS
  E)

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Centering a Frame

• To display the frame at specific location -up
  left corner at (x,y)
• frm.setLocation(x,y)
• Centering a frame
• Dimension screen Toolkit.getDefaultToolkit().get
  ScreenSize()
• int width screen.width
• int height screen.height
• Dimension frmsize frm.getSize()
• int x (width frmsize.width)/2
• int y (height frmsize.height)/2

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Adding components to a frame

• Container container frm.getContentPane()
• JButton btn_ok new JButton(OK)
• container.add(btn_ok)

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Layout Managers

• FlowLayout is the simplest layout manager. The
  components are arranged in the container from
  left to right in the order in which they were
  added
• public FlowLayout(int align, int hgap, int vgap)
  construct a new FlowLayout with the specified
  alignment, horizontal gap and vertical gap.
• public FlowLayout( int alignment) with Hgap and
  vGap 5 pixels
• public FlowLayout() center alignment and 5
  pixels gaps.

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GridLayout

• The GridLayout manager arranges components in a
  grid with number of rows and columns defined by
  the constructor.
• public GridLayout(int rows, int columns, int
  hgap, int vgap)
• public GridLayout(int rows, int columns)- 0 gaps
• public GridLayout() one column in a single row

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• The number of row or column can be zero but not
  both
• If 0 rows and 3 columns for a grid with 10
  components, GridLayout creates 3 columnds and 4
  rows
• If both the number of rows and columns are
  nonzero, the number of rows is the dominating
  parameter that is, the number of rows is fixed,
  and the layout manager dynamically calculate the
  number of columns.

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example

• Container container getContentPane()
• container.setLayout(new FlowLayout(FlowLayout.LEFT
  ,10,20))
• container.setLayout(new GridLayout(4,3,10,20))
• for( int I 0 I lt 10 I)
• container.add(new Jbutton(ComponentI)

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BorderLayout

• The BorderLayout manager divides the window into
  five areas
• East, South, West, North and Center
• public BorderLayout(int hgap, int vgap)
• public BorderLayout construct a new
  BorderLayout without horizontal or vertical gaps
• North and south can stretch horizontally
• West and east can stretch vertocally
• Center can stretch both horizontally and
  vertically to fill any empty space
• Components are added to a BorderLayout by using
  add(component, index), where index is a constant
  BorderLayout.East, South, North, and West

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panel

• You can divide window into panels
• Panels can act like smaller container to group
  user-interface components
• You can add button in a panel and add the panel
  into the frame.
• You also can use layout manger to set layout of
  components I the panel

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panel

• Create a panel and add buttons to the panel
• Panel p1 new Panel()
• p1.setLayout(new GridLayout(3,3))
• p1.add(new Button(OK)
• Add the panel to the container
• container.add(p1)

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Color class java.awt.Color

• Colors are made of red, green and blue, each of
  which is represented by a byte value
  0(darkest)-255(lightest), known as RGB model
• Constructor
• public Color( int r, int g, int b)
• Color color new Color(128, 100,100)
• JButton jbtOK new JButton(OK)
• jbtOK.setBackground(color)
• Jbt.setForeground(new Color(100,1,1))

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Alternative

• You can use one of 13 standard colors
• black, blue, cyan, darkGray, gray, green,
  lightGray, magenta, orange, pink, red, white,
  yellow
• They are defined as constants in java.awt.Color
• jbtOK.setForeground(Color.red)

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Font class java.awt.Font

• Constructor
• public Font(String name, int style, int size)
• You can choose a font name from
• SansSerif, Serif, Monospaced, Dialog, or
  DialogInput
• You can choose a style from
• Font.PLAIN, Font.BOLD, Font.ITALIC and Font.BOLD
  Font.ITALIC
• Specify a font size of any positive integer.
• Font font1 new Font(SansSerif, Font.BOLD,
  16)
• Font font2 new Font(Serif, Font.BOLDFont.ITAL
  IC, 12)
• JButton jbtOK new JButton(OK)
• jbtOK.setFont(font1)