oracle 找到了这个很好的例子，它提供了一个创建RoundButton的类。
这是一个使用已编辑RoundButton类创建RoundedButton类的示例：
import java.awt.AWTEvent;
import java.awt.AWTEventMulticaster;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
initComponents();
}
private void initComponents() {
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final JTextField tf = new JTextField("");
RoundedButton rb = new RoundedButton("Go");
rb.setBackground(Color.yellow);
rb.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
JOptionPane.showMessageDialog(frame, "You said: " + tf.getText());
}
});
frame.add(tf, BorderLayout.NORTH);
frame.add(rb);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
new Test();
}
});
}
}
class RoundedButton 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 RoundedButton with no label.
*/
public RoundedButton() {
this("");
}
/**
* Constructs a RoundedButton with the specified label.
*
* @param label the label of the button
*/
public RoundedButton(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 RoundedButton
*/
@Override
public void paint(Graphics g) {
// paint the interior of the button
if (pressed) {
g.setColor(getBackground().darker().darker());
} else {
g.setColor(getBackground());
}
g.fillRoundRect(0, 0, getWidth() - 1, getHeight() - 1, 20, 20);
// draw the perimeter of the button
g.setColor(getBackground().darker().darker().darker());
g.drawRoundRect(0, 0, getWidth() - 1, getHeight() - 1, 20, 20);
// draw the label centered in the button
Font f = getFont();
if (f != null) {
FontMetrics fm = getFontMetrics(getFont());
g.setColor(getForeground());
g.drawString(label, getWidth() / 2 - fm.stringWidth(label) / 2, getHeight() / 2 + fm.getMaxDescent());
}
}
/**
* The preferred size of the button.
*/
@Override
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.
*/
@Override
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.
*/
@Override
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.
*/
@Override
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);
}
}
