这大概是个初级问题。但是，我已经阅读了《Java 编程绝对初学者》的第 12 章，并进入了挑战部分。我不能完全让程序显示带有扩展类的标记按钮。
该规范指出：
扩展 JPRButton3D 类以创建一个显示标签的按钮，就像您现在非常熟悉的 AWT Button 类一样。作为一个额外的测试，重写 isFocusable() 方法，以便可以遍历您的按钮类，并确保您绘制一些特殊的图形，以便在您的按钮具有焦点时使其明显。
如何编辑我的 LabelButton3D 和 LabelButton3DTest 代码来完成此任务？
对本规范的回答可能有助于许多新的 Java 程序员扩展他们自己的类。
非常感谢您在此问题上的时间和合作。
这是 JPRButton3D 的代码：
package jpr.lightweight;
import java.awt.*;
import java.awt.event.*;
/**
* A lightweight 3D Button class that fires actions when clicked.
* When it is enabled it appears {@link #RAISED RAISED}, when
* it is pressed it appears {@link #SUNK SUNK}, and when it is
* not enabled, it appears {@link #FLAT FLAT}.
*/
public class JPRButton3D extends JPRRectComponent3D {
private boolean pressed;
/**
* This <code>JPRButton3D</code>'s <code>ActionListener</code>.
*/
protected ActionListener actionListener;
private String actionCommand;
/**
* Constructs a new <code>JPRButton3D</code> with minimum size
*/
public JPRButton3D() {
this(ABSOLUTE_MIN_WIDTH, ABSOLUTE_MIN_HEIGHT, 1);
}
/**
* Constructs a new <code>JPRButton3D</code> with the given dimensions.
* @param wide the width
* @param high the height
*/
public JPRButton3D(int wide, int high) {
this(wide, high, 1);
}
/**
* Constructs a new <code>JPRButton3D</code> with the given dimensions
* and border magnitude.
* @param wide the width
* @param high the height
* @param border_magnitude the border's magnitude
*/
public JPRButton3D(int wide, int high, int border_magnitude) {
super(wide, high, RAISED, border_magnitude);
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
}
public void processMouseEvent(MouseEvent e) {
if (isEnabled() & e.getModifiers() == MouseEvent.BUTTON1_MASK) {
switch(e.getID()) {
case MouseEvent.MOUSE_PRESSED:
pressed = true;
current_appearance = SUNK;
repaint();
break;
case MouseEvent.MOUSE_EXITED:
if (pressed) {
pressed = false;
current_appearance = RAISED;
repaint();
}
break;
case MouseEvent.MOUSE_RELEASED:
if (pressed) {
current_appearance = RAISED;
repaint();
if (actionListener != null) {
actionListener.actionPerformed(new ActionEvent(this,
ActionEvent.ACTION_PERFORMED, actionCommand,
e.getModifiers()));
}
}
break;
}
}
super.processMouseEvent(e);
}
/**
* Adds the specified <code>ActionListener</code>
* @param listener <code>ActionListener</code> to add
*/
public void addActionListener(ActionListener listener) {
actionListener = AWTEventMulticaster.add(actionListener, listener);
}
/**
* Removes the specified <code>ActionListener</code>
* @param listener <code>ActionListener</code> to remove
*/
public void removeActionListener(ActionListener listener) {
actionListener = AWTEventMulticaster.remove(actionListener,
listener);
}
/**
* Sets the action command associated with action events.
* @param command The action command.
*/
public void setActionCommand(String command) {
actionCommand = command;
}
/**
* Gets the action command associated with action events.
* @return the action command
*/
public String getActionCommand() {
return actionCommand;
}
/**
* Enables or disables this <code>JPRButton3D</code>.
* @param b <code>true</code> to enable, <code>false</code> to disable
*/
public void setEnabled(boolean b) {
if (b) current_appearance = RAISED;
else current_appearance = FLAT;
repaint();
super.setEnabled(b);
}
}
这是我的 LabelButton3DTest 代码（扩展 JPRButton3D）：
import java.awt.*;
import java.awt.event.*;
import jpr.lightweight.JPRButton3D;
public class LabelButton3DTest extends GUIFrame {
LabelButton3D[] b;
String s;
public LabelButton3DTest() {
super("LabelButton3D Test");
setLayout(new FlowLayout());
b = new LabelButton3D[1];
b[0] = new LabelButton3D("Favorite Button");
b[0] = new LabelButton3D(75, 35, 1);
add(b[0]);
pack();
setVisible(true);
}
public static void main(String args[]) {
new LabelButton3DTest();
}
}
这是我的 LabelButton3D 代码：
public class LabelButton3D extends JPRButton3D {
public LabelButton3D(String label) {
}
public LabelButton3D(int wide, int high, int border_magnitude) {
super(wide, high, border_magnitude);
}
}