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Observer Pattern Times Four:
JTextField: ActionListener receives event after you hit <return>.
The ActionListener updates the Data (Model) object.
JTextField
anonymousobject
ActionListener
addActionListener
actionPerformed
Observer Pattern Times Four:
Data: Is observed by the BarGraph (ChangeListener) for any changes to the model.
Data
BarGraph
ChangeListener
attach
stateChanged
Observer Pattern Times Four:
BarGraph: MouseListener receives event when you click on the bar graph.
mousePressed() moves the bar and updates Data object.
BarGraph
MouseAdapter
MouseListeneraddMouseListener
mousePressed
Observer Pattern Times Four:
Data: Is observed by TextFrame (ChangeListener) for any changes to data.
Data
TextFrame
ChangeListener
attachstateChanged
Data.java
public class Data {public Data(ArrayList<Double> d) { data = d; listeners = new ArrayList<ChangeListener>(); }
public ArrayList<Double> getData() { return (ArrayList<Double>) (data.clone()); }
public void attach(ChangeListener c) { listeners.add(c); }
}
Data.java
public class Data {
public void update(int loc, double val) {
if (val > MAX) val = MAX;
if (val < 0) val = 0;
data.set(loc, new Double(val)); // for each listener, let the listener know a change has occurred for (ChangeListener l : listeners) { l.stateChanged(new ChangeEvent(this)); } }
public Double get(int i) { return data.get(i);
} private ArrayList<Double> data; private ArrayList<ChangeListener> listeners; public static final double MAX = 100.0;
}
TextFrame:
public class TextFrame extends JFrame implements ChangeListener {public TextFrame (Data md) {
d = md; ActionListener l = new ActionListener()
{ public void actionPerformed(ActionEvent e) { JTextField c = (JTextField) e.getSource(); int ndx = findBox(c); if (ndx >= 0) d.update(ndx,Double.parseDouble(c.getText().trim())); } };
JPanel tPanel = new JPanel();tPanel.setLayout(new BoxLayout(tPanel,BoxLayout.PAGE_AXIS));
tf = new JTextField[5];for (int i = 0; i < 5; i++) {
tf[i] = new JTextField(10);tf[i].addActionListener(l);tPanel.add(tf[i]);
}add(tPanel, BorderLayout.CENTER);setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);pack();setVisible(true);
}...}
TextFrame:
@Overridepublic void stateChanged(ChangeEvent e) {
// how I notify the text frame if the bar graph changesfor (int i = 0; i < 5; i++){
double d1 = d.get(i).doubleValue();String s = tf[i].getText().trim();double d2;try {
d2 = Double.parseDouble(s);} catch(NumberFormatException nfe ) {
d2 = 0.0;}if (Math.abs(d1 - d2) > 0.01)
tf[i].setText(new Double(d1).toString());}
}
public int findBox(JTextField t) {int i = 0;while (i < 5) {
if (t == tf[i])return i;
i++;}return -1;
}
private Data d; private JtextField[ ] tf;
}
BarGraph:
public class BarGraph extends JFrame implements ChangeListener { public BarGraph(Data md) { d = md; setLocation(0,300); Icon barIcon = new Icon() { public int getIconWidth() { return WIDTH; } public int getIconHeight() { return HEIGHT; }
public void paintIcon(Component c, Graphics g , int x, int y) { Graphics2D g2 = (Graphics2D) g; Color cl = g2.getColor(); for (int i = 0; i < 5; i++) { Rectangle2D.Double rectangle =
new Rectangle2D.Double(0, (HEIGHT/6)*i,
WIDTH*(d.get(i).doubleValue()/Data.MAX), (HEIGHT/6));
g2.setPaint(Color.cyan); g2.fill(rectangle); g2.setColor(Color.black);
g2.draw(rectangle); } Rectangle2D.Double rectangle =
new Rectangle2D.Double(0,375,WIDTH,(HEIGHT/6)); g2.setPaint(cl); g2.fill(rectangle);g2.setColor(cl);g2.draw(rectangle);
} }; // end of barIcon panel ...}
BarGraph:
public class BarGraph extends JFrame implements ChangeListener {
public BarGraph(Data md) { ...
add(new JLabel(barIcon)); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); MouseListener m = new MouseAdapter() {
public void mousePressed(MouseEvent e){ Point2D p = e.getPoint(); double dy = p.getY(); int barToMove = (int)(dy / BARHEIGHT); if (barToMove < 0 || barToMove > 4) return; double dx = p.getX(); double newV = (dx/WIDTH)* Data.MAX; d.update(barToMove, newV); }
}; addMouseListener(m); pack(); setVisible(true); } // end constructor
} // end class