java - 为什么.setColor(,,,)表示无法在该程序中找到符号？

当我运行该程序时，代码g2.setColor（fillColor）出现找不到符号错误。这是一个遗留问题吗？代码不正确？


  
    
      我从Cay Horstmann的“ Big Java”一书的第165页中逐字键入了此代码
    
  

import java.applet.Applet;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JOptionPane;

/**
 * An applet that lets a user choose a color by specifying the fractions of
 * red, green, and blue.
 */
    public class ColorApplet extends Applet
    {
        public ColorApplet()
        {
            String input;

            //Ask user for red, green, blue values
            input = JOptionPane.showInputDialog("red: ");
            float red = Float.parseFloat(input);

            input = JOptionPane.showInputDialog("green: ");
            float green = Float.parseFloat(input);

            input = JOptionPane.showInputDialog("blue :");
            float blue = Float.parseFloat(input);

            //creates the color based on the RGB inputted values
            Color fillColor= new Color(red, green, blue);
        }

        public void paint(Graphics g)
        {
            Graphics2D g2= (Graphics2D)g;

            g2.setColor(fillColor);

            Rectangle square = new Rectangle((getWidth() - SQUARE_LENGTH)/2,
            (getHeight() - SQUARE_LENGTH)/2, SQUARE_LENGTH, SQUARE_LENGTH);

            g2.fill(square);
        }

        private static final int SQUARE_LENGTH = 100;
    }

最佳答案

fillColor在paint方法中未声明。在您的程序中，fillColor仅在构造函数中具有作用域Color fillColor= new Color(red, green, blue);您可以使其实例变量使其可访问，如下所示：

public class ColorApplet extends Applet
{
   Color fillColor;

// now in constructor
public ColorApplet()
{
...
...
 fillColor= new Color(red, green, blue);
}

现在您可以在fillColor方法中使用paint