Swing II - GUI

Question 1

addWindowListener method

Answer 1

register a window listener for a window event
about 7 methods
create empty methods for methods that you dont want to use

Question 2

window adapter class

Answer 2

• when class doesn’t need most of the methods
• only heading defined
• inherit trivial implementation from windowadapter

can only be done when the JFrame doesnt need to be derived from any other class

Question 3

Icons

Answer 3

• small picture
  ImageIcon dukeIcon = new ImageIcon(“duke_waving.gif”);
  images must be in same directory

Question 4

scroll bars

Answer 4

when using a scroll bar the text is viewes through a view port that shows only part of the text at a time

ScrollPane scrolledText = newJScrollPane(memoDisplay);

Question 5

the horizontal and vertical scroll bar options/policies

Answer 5

Default - as needed
Never
Always

Question 6

where on the plane is the (0,0) co-ordinate

Answer 6

top left corner

positive x direction - left to right
positive y direction - top down

Question 7

adding elements to a frame using co-ord system

Answer 7

• everything is added with a rectangle (add a circle - the circle will be in a rectangle)
• adding a rectangle - location of upper left corner is stated

Question 8

bounding box

Answer 8

imaginary rectangle that encloses everything that is added to the frame

Question 9

paint method (only to be used for frames)

Answer 9

The method paint draws the component or container on the screen

public void paint(g){ super.paint(g); g.drawLine(dimension, dimension….,…)
}

Question 10

the graphics class

Answer 10

The object g of the class Graphics can be used as the calling object for a drawing method–The drawing will then take place inside the area of the screen specified by g

Question 11

what happens when the paint(g) method is invoked

Answer 11

g is replaced by the graphics object associated with the JFrame - therefore the images are drawn inside the JFrame

Question 12

draw an oval

Answer 12

g.drawOval(x,y,width,height)

Question 13

draw an arc

Answer 13

g.drawArc(int x, int y, int width, int height, int startAngle, int arcAngle)

Question 14

draw a rounded rectangle

Answer 14

g.drawRoundRect(x, y, width, height, arcWidth, arcHeight)

Question 15

what to use to draw figures on a panel

Answer 15

paintComponent

Question 16

jfram, jpanel and component vs jcomponent

Answer 16

A JPanelis a JComponent, but a JFrameis a Component, not a JComponent

Question 17

repaint method

Answer 17

The repaint method should be invoked when the graphics content of a window is changed

Question 18

how does repaint work

Answer 18

• The repaintmethod takes care of some overhead, and then invokes the method paint, which redraws the screen
  –Although the repaintmethod must be explicitly invoked, it is already defined
  –The paintmethod, in contrast, must often be defined, but is not explicitly invoked

Question 19

the validate method - google an explanation

Answer 19

causes a container to lay out its components again

It is a kind of “update” method that makes changes in the components shown on the screen–Every container class has the validatemethod, which has no arguments

Question 20

g.setColor(Color.BLUE)

Answer 20

changes the colour of the pen

Question 21

custom colours

Answer 21

Color brown = new Color(200, 150, 0);

only type int or type float (dont forget to use a type cast)

Question 22

the drawString

Answer 22

g.drawString(theText, X_START, Y_Start);

Question 23

fonts

Answer 23

the constructor for the Font class creaere a font in the given style and size

Font fontObject = new Font(“SansSerif”, Font.PLAIN, POINT_SIZE);

Question 24

hoe to set the font for the drawString() within the paint()

Answer 24

g.setFont(fontObject);