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

GUI API class hierarch – p371 Object Dimension,Font, FontMetrics, Color, Graphics, Component LayoutManager, Container Panel, Window, Jcomponent Applet, Frame, Dialog

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

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

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

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_CLOSE) ;  }

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().getScreenSize();  int width = screen.width;  int height = screen.height;  Dimension frmsize = frm.getSize();  int x = (width – frmsize.width)/2;  int y = (height – frmsize.height)/2;

Adding components to a frame Container container = frm.getContentPane(); JButton btn_ok = new JButton(“OK”); container.add(btn_ok);

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.

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

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.

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 < 10; I++) { container.add(new Jbutton(“Component”+I); }

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

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

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);

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));

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);

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.BOLD+Font.ITALIC, 12); JButton jbtOK = new JButton(“OK”); jbtOK.setFont(font1);