Computer Science A 11: 20/2

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Computer Science A 11 20/2

CS A
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Java and swing

• Graphics programming
• Windows with menus
• Buttons, textfields, scroll panels etc
• Animations, images,
• Events from mouse clicks, keyboard etc.
• Can be quite complicated

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EmptyFrame.java

• import javax.swing.JFrame
• public class EmptyFrame
• public static void main(String args)
• JFrame framenew JFrame("EmptyFrame")
• frame.setSize(600,600)
• frame.setDefaultCloseOperation(
• JFrame.EXIT_ON_CLOSE)
• frame.setVisible(true)

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EmptyFrame

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Add a canvas to the window

• public static void main(String args)
• JFrame framenew JFrame()
• frame.setSize(600,600)
• frame.setTitle("DrawShapes")
• frame.setDefaultCloseOperation(
• JFrame.EXIT_ON_CLOSE)
• JCanvas canvas new JCanvas()
• frame.add(canvas)
• frame.setVisible(true)
• ..

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Coordinate system

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drawLine(135,230,335,370)

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drawOval(135,230,200,140)

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What to draw on a canvas

• Line
• Oval/ellipsis
• Arcs (parts of an ellipsis
• Rectangles
• Curves, quadratic, qubic, bezier
• Images
• Text

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The state when drawing

• Current Font
• Current Stroke (width of lines)
• Current Paint (color of areas)
• Current Transform (scaling, rotation, deformation
  of drawings)
• Current Composite (new items can be made
  partially transparent
• Current clipping area. (limit the area in which
  you can draw)

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setFont(new Font("Serif",Font.BOLD,150))drawStri
ng("(GyÑ)",50,200)

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Paint

• canvas.setPaint(Color.red)
• canvas.fillRect(50,50,100,100)
• canvas.setPaint(Color.blue)
• canvas.fillOval(250,50,100,100)
• canvas.setPaint(Color.green)
• canvas.fillArc(450,50,100,100,45,270)
• canvas.setPaint(new GradientPaint(
• 50,350,Color.red,450,350,Color.blue))
• canvas.fillRect(50,300,500,100)

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Paint

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More to come

• Transformations
• Partially transparent
• Images
• Other components buttons etc
• Events from windows.

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Java swing components

• Windows and components

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Example

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JLabel

• A bit of text and/or an icon
• new JLabel(Label 1,new IconImage(..))

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JButton

• A button you can press.
• Text and/or an image (icon)

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Radiobutton and checkbox

• Press to select or de-select

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JTextField

• TextField a line where you can enter text using
  the keyboard.

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JTextArea

• TextArea a multi-line area for entering text

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JSlider

• A slider select a value
• By dragging a knob

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JSpinner

• Select a value
• by stepping through
• a bounded range
• of values

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JComboBox

• Select a value from
• a drop-down list

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JList

• Select an a value
• or an interval
• of values from
• a list