[kib77904]

/*
* Copyright 2002 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or
* without modification, are permitted provided that the following
* conditions are met:
*
* -Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* -Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any
* kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
* WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
* EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY
* DAMAGES OR LIABILITIES SUFFERED BY LICENSEE AS A RESULT OF OR
* RELATING TO USE, MODIFICATION OR DISTRIBUTION OF THE SOFTWARE OR
* ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE
* FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT,
* SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
* CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF
* THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN
* ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that Software is not designed, licensed or
* intended for use in the design, construction, operation or
* maintenance of any nuclear facility.
*/
package actual;

import java.applet.*;
import java.lang.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;

/**
* RoundButton - a class that produces a lightweight button.
*
* Lightweight components can have "transparent" areas, meaning that
* you can see the background of the container behind these areas.
*
*/
public class RoundButton extends Component {

ActionListener actionListener; // Post action events to listeners
String label; // The Button's text
protected boolean pressed = false; // true if the button is detented.


/**
* Constructs a RoundButton with no label.
*/
public RoundButton() {
this("");
}

/**
* Constructs a RoundButton with the specified label.
* @param label the label of the button
*/
public RoundButton(String label) {
this.label = label;
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
}

/**
* gets the label
* @see setLabel
*/
public String getLabel() {
return label;
}

/**
* sets the label
* @see getLabel
*/
public void setLabel(String label) {
this.label = label;
invalidate();
repaint();
}

/**
* paints the RoundButton
*/
public void paint(Graphics g) {
int s = Math.min(getSize().width - 1, getSize().height - 1);

// paint the interior of the button
if(pressed) {
g.setColor(getBackground().darker().darker());
} else {
g.setColor(getBackground());
}
g.fillArc(0, 0, s, s, 0, 360);

// draw the perimeter of the button
g.setColor(getBackground().darker().darker().darker());
g.drawArc(0, 0, s, s, 0, 360);

// draw the label centered in the button
Font f = getFont();
if(f != null) {
FontMetrics fm = getFontMetrics(getFont());
g.setColor(getForeground());
g.drawString(label,
s/2 - fm.stringWidth(label)/2,
s/2 + fm.getMaxDescent());
}
}

/**
* The preferred size of the button.
*/
public Dimension getPreferredSize() {
Font f = getFont();
if(f != null) {
FontMetrics fm = getFontMetrics(getFont());
int max = Math.max(fm.stringWidth(label) + 40, fm.getHeight() + 40);
return new Dimension(max, max);
} else {
return new Dimension(100, 100);
}
}

/**
* The minimum size of the button.
*/
public Dimension getMinimumSize() {
return new Dimension(100, 100);
}

/**
* Adds the specified action listener to receive action events
* from this button.
* @param listener the action listener
*/
public void addActionListener(ActionListener listener) {
actionListener = AWTEventMulticaster.add(actionListener, listener);
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
}

/**
* Removes the specified action listener so it no longer receives
* action events from this button.
* @param listener the action listener
*/
public void removeActionListener(ActionListener listener) {
actionListener = AWTEventMulticaster.remove(actionListener, listener);
}

/**
* Determine if click was inside round button.
*/
public boolean contains(int x, int y) {
int mx = getSize().width/2;
int my = getSize().height/2;
return (((mx-x)*(mx-x) + (my-y)*(my-y)) <= mx*mx);
}

/**
* Paints the button and distribute an action event to all listeners.
*/
public void processMouseEvent(MouseEvent e) {
Graphics g;
switch(e.getID()) {
case MouseEvent.MOUSE_PRESSED:
// render myself inverted....
pressed = true;

// Repaint might flicker a bit. To avoid this, you can use
// double buffering (see the Gauge example).
repaint();
break;
case MouseEvent.MOUSE_RELEASED:
if(actionListener != null) {
actionListener.actionPerformed(new ActionEvent(
this, ActionEvent.ACTION_PERFORMED, label));
}
// render myself normal again
if(pressed == true) {
pressed = false;

// Repaint might flicker a bit. To avoid this, you can use
// double buffering (see the Gauge example).
repaint();
}
break;
case MouseEvent.MOUSE_ENTERED:

break;
case MouseEvent.MOUSE_EXITED:
if(pressed == true) {
// Cancel! Don't send action event.
pressed = false;

// Repaint might flicker a bit. To avoid this, you can use
// double buffering (see the Gauge example).
repaint();

// Note: for a more complete button implementation,
// you wouldn't want to cancel at this point, but
// rather detect when the mouse re-entered, and
// re-highlight the button. There are a few state
// issues that that you need to handle, which we leave
// this an an excercise for the reader (I always
// wanted to say that!)
}
break;
}
super.processMouseEvent(e);
}

}


希望懂JAVA的大大能幫個忙，能告訴小弟上面程式的意思嗎，因為研究很久一直搞不懂，先謝謝囉