当谈到 Java 时，我是一个初学者，我正在按照书中的说明进行操作。我将使用以下代码创建一个 FigurePanel：
import java.awt.*;
import javax.swing.*;
public class TestFigurePanel extends JFrame{
public TestFigurePanel() {
setLayout(new GridLayout(2, 3, 5, 5));
add(new FigurePanel(FigurePanel.LINE));
}
}
但是在“add(new FigurePanel(FigurePanel.LINE));” 我收到以下错误：
“找不到标志：
符号：类 FigurePanel
类：TestFigurePanel"
如果有人告诉我是什么导致了这个问题，我会很高兴。
在你的包中添加这个类：
import java.awt.*;
import javax.swing.JPanel;
public class FigurePanel extends JPanel {
// Define constants
public static final int LINE = 1;
public static final int RECTANGLE = 2;
public static final int ROUND_RECTANGLE = 3;
public static final int OVAL = 4;
private int type = 1;
private boolean filled;
/** Construct a default FigurePanel */
public FigurePanel() {
}
/** Construct a FigurePanel with the specified type */
public FigurePanel(int type) {
this.type = type;
}
/** Construct a FigurePanel with the specified type and filled */
public FigurePanel(int type, boolean filled) {
this.type = type;
this.filled = filled;
}
/** Draw a figure on the panel */
public void paintComponent(Graphics g) {
super.paintComponent(g);
// Get the appropriate size for the figure
int width = getSize().width;
int height = getSize().height;
switch (type) {
case LINE: // Display two cross lines
g.setColor(Color.BLACK);
g.drawLine(10, 10, width - 10, height - 10);
g.drawLine(width - 10, 10, 10, height - 10);
break;
case RECTANGLE: // Display a rectangle
g.setColor(Color.BLUE);
if (filled)
g.fillRect((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height));
else
g.drawRect((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height));
break;
case ROUND_RECTANGLE: // Display a round-cornered rectangle
g.setColor(Color.RED);
if (filled)
g.fillRoundRect((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height), 20, 20);
else
g.drawRoundRect((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height), 20, 20);
break;
case OVAL: // Display an oval
g.setColor(Color.BLACK);
if (filled)
g.fillOval((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height));
else
g.drawOval((int)(0.1 * width), (int)(0.1 * height),
(int)(0.8 * width), (int)(0.8 * height));
}
}
/** Set a new figure type */
public void setType(int type) {
this.type = type;
repaint();
}
/** Return figure type */
public int getType() {
return type;
}
/** Set a new filled property */
public void setFilled(boolean filled) {
this.filled = filled;
repaint();
}
/** Check if the figure is filled */
public boolean isFilled() {
return filled;
}
/** Specify preferred size */
public Dimension getPreferredSize() {
return new Dimension(80, 80);
}
}