1. A Brief Overview of the Abstract Windowing Toolkit (AWT)
Motivation.
Typical Frame setup.
BorderLayout, FlowLayout, GridLayout.
Component class hierarchy
User events
Graphics contexts
Handling mouse events
CSE S. Tanimoto Java Abstract Windowing Toolkit

2. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
Motivation
1. A portable graphics model and window system (Unix, Microsoft Windows, Macintosh).
2. Support interaction in a general way (Mouse events, keyboard events).
3. Provide high-level building blocks (widgets like buttons and canvases in JDK1.0 and 1.1, and more complex interface components such as TreeView in JDK in “Swing”).
4. Permit integration with browsers (Netscape Navigator, Microsoft Internet Explorer)..
CSE S. Tanimoto Java Abstract Windowing Toolkit

3. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
Typical Frame Setup
// RecipeViewer.java Steve Tanimoto, 12 April 1999.
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class RecipeViewer extends Frame
implements WindowListener, ItemListener {
TextArea recipeTextArea;
Choice recipeSelector;
public static void main( String [] args) {
RecipeViewer rv = new RecipeViewer();
rv.init();
rv.show(); }
CSE S. Tanimoto Java Abstract Windowing Toolkit

4. RecipeViewer.java (Continued)
public void init() {
setSize(300, 200);
addWindowListener(this); // for the close box.
setLayout( new BorderLayout() );
add(new Label("The Recipe Viewer"),BorderLayout.NORTH);
recipeTextArea = new TextArea(100, 20);
add(recipeTextArea, BorderLayout.CENTER);
recipeSelector = new Choice();
recipeSelector.addItem("Select recipe");
recipeSelector.addItem("Limoncello");
recipeSelector.addItem("Salsa");
add(recipeSelector, BorderLayout.SOUTH);
recipeSelector.addItemListener(this); // for the Choice. }
CSE S. Tanimoto Java Abstract Windowing Toolkit

5. RecipeViewer.java (Continued)
public void itemStateChanged(ItemEvent e) {
String item = recipeSelector.getSelectedItem();
if (item.equals("Limoncello")) {
recipeTextArea.setText(
"To make limoncello, soak the zest of 15 lemons\n" +
"for 30 days in 1 liter of 100 proof vodka.\n" +
"Mix in 1 liter of cool sugar syrup made by cooking\n" +
"1 liter sugar in 1 liter water for 5 min.\n" +
"Add 1 more liter vodka, soak for 30 more days, and\n" +
"strain out into clean storage bottles."); }
else if (item.equals("Salsa")) {
"To make salsa, wash 3 lbs ripe tomatoes and dice.\n" +
"Add 3 minced jalapeno peppers, 1 bunch fresh cilantro\n" +
"also minced, 2 minced peeled onions, juice of 2 lemons,\n" +
"and 1 teaspoon salt."); }
else recipeTextArea.setText("Unknown choice"); }
CSE S. Tanimoto Java Abstract Windowing Toolkit

6. RecipeViewer.java (Continued)
public void windowClosing(WindowEvent e) {
dispose();
System.exit(0); }
public void windowClosed(WindowEvent e) {}
public void windowOpened(WindowEvent e) {}
public void windowIconified(WindowEvent e) {}
public void windowDeiconified(WindowEvent e) {}
public void windowActivated(WindowEvent e) {}
public void windowDeactivated(WindowEvent e) {}
CSE S. Tanimoto Java Abstract Windowing Toolkit

7. RecipeViewer.java (Continued)
CSE S. Tanimoto Java Abstract Windowing Toolkit

8. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
BorderLayout
NORTH
WEST
EAST
CENTER
SOUTH
CSE S. Tanimoto Java Abstract Windowing Toolkit

9. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
FlowLayout
setLayout(new FlowLayout(FlowLayout.LEFT, 10, 10))
CSE S. Tanimoto Java Abstract Windowing Toolkit

10. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
GridLayout
setLayout(new GridLayout(3, 2, 5, 5));
CSE S. Tanimoto Java Abstract Windowing Toolkit

11. Component Class Hierarchy
AWTEvent
Container
Panel
Applet
Button
Font
Window
Frame
Canvas
FontMetrics
TextComponent
ScrollPane
TextField
Object
Color
List
Dialog
TextArea
Choice
Graphics
FileDialog
Checkbox
Component
Label
Scrollbar
LayoutManager
CSE S. Tanimoto Java Abstract Windowing Toolkit

12. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
User Events
ActionEvent
ContainerEvent
AdjustmentEvent
FocusEvent
MouseEvent
EventObject
AWTEvent
ComponentEvent
InputEvent
KeyEvent
ItemEvent
PaintEvent
TextEvent
WindowEvent
CSE S. Tanimoto Java Abstract Windowing Toolkit

13. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
Graphics Contexts
void paint (Graphics g) {
int x=100; int y=50; int w=100; int h=50;
int x2=300; int y2=150;
g.drawString("Hello", x, y); // Draws text
g.setFont(new Font("Helvetica", Font.BOLD 20));
g.drawString("Hello again", x, y2);
g.setColor(Color.red);
g.drawLine(x1, y1, x2, y2);
g.drawRect(x, y, w, h);
g.fillRect(x, y, w, h);
g.drawOval(x, y, w, h); }
CSE S. Tanimoto Java Abstract Windowing Toolkit

14. CSE 341 -- S. Tanimoto Java Abstract Windowing Toolkit
Handling Mouse Events
1. Either define a class that implements one or both of the interfaces MouseListener or MouseMotionListener, or
2. Define a class that subclasses MouseAdapter (and, maybe which implements MouseMotionListener), or
3. Declare that your main class implements MouseListener and/or MouseMotionListener.
Then, if you have implemented a new class for handling the mouse, then create an instance of it and call one or both of
addMouseListener and/or addMouseMotionListener
Otherwise call addMouseListener and/or addMouseMotionListener with this.
CSE S. Tanimoto Java Abstract Windowing Toolkit

15. Example: LineSegments with Movable Endpoints
Let’s add interactivity to the LineSegmentCollection applet.
The user can click on the endpoint of any segment.
The user can drag the mouse and move the endpoint.
Any intersections with other line segments are updated, too.
(Note, this version leaves copies of some intersections until the other line is moved, too.)
CSE S. Tanimoto Java Abstract Windowing Toolkit

16. Handling Mouse Events (cont)
class MyMouseHandler extends MouseAdapter
implements MouseMotionListener {
public void mousePressed (MouseEvent e) {
for (Enumeration theEnum =
theSegments.elements();
theEnum.hasMoreElements();) {
selectedLS = (LineSegmentD)theEnum.nextElement();
selectedPoint =
selectedLS.getHit(e.getX(), e.getY());
if (selectedPoint != null) break;
selectedLS = null; }
CSE S. Tanimoto Java Abstract Windowing Toolkit

17. Handling Mouse Events (cont)
public void mouseReleased (MouseEvent e) {
selectedPoint = null; }
public void mouseDragged (MouseEvent e) {
if (selectedPoint != null) {
selectedLS.updateLocation(
selectedPoint, e.getX(), e.getY() );
repaint();
public void mouseMoved (MouseEvent e) {}
CSE S. Tanimoto Java Abstract Windowing Toolkit

18. Handling Mouse Events (cont)
public class LineSegmentCollectionD extends Applet {
Vector theSegments;
LSPointD selectedPoint = null;
LineSegmentD selectedLS = null;
public void init() {
MyMouseHandler mmh = new MyMouseHandler();
addMouseListener(mmh);
addMouseMotionListener(mmh);
theSegments = new Vector();
for (int i = 0; i < 10; i++) {
theSegments.addElement(new LineSegmentD(i,this)); }
CSE S. Tanimoto Java Abstract Windowing Toolkit