在java小程序中按下按钮后绘制线

当我试着这样做时，出现了以下错误 令牌上的语法错误；预期 令牌上的语法错误；期望

在ButtonTest.actionPerformedButtonTest.java:58

import java.awt.*;
import java.awt.event.*;//step-1
import java.applet.Applet;

public class ButtonTest extends Applet implements ActionListener//step-2
{
    Button b1,b2,b3;
    Font f;
    Graphics gc;
    public void init()
    {
            b1=new Button("Request");
            b2=new Button("Grant");
            b3=new Button("Accept");

            f=new Font("Arial",Font.BOLD,12);

            b1.setFont(f);
            b2.setFont(f);
            b3.setFont(f);

            b1.addActionListener(this);
            b2.addActionListener(this);
            b3.addActionListener(this);

            add(b1);
            add(b2);
            add(b3);
    }

    public void paint(Graphics gc) 
    {
        gc.drawLine(100, 150, 100, 400); 
        gc.drawLine(300, 150, 300, 400); 
        gc.drawOval(95, 155, 10, 10);  //1.1
        gc.drawOval(95, 225, 10, 10);  //1.2
        gc.drawOval(95, 295, 10, 10);  //1.3
        gc.drawOval(95, 365, 10, 10);  //1.4
        gc.drawOval(295, 155, 10, 10);  //2.1
        gc.drawOval(295, 225, 10, 10);  //2.2
        gc.drawOval(295, 295, 10, 10);  //2.3
        gc.drawOval(295, 365, 10, 10);  //2.4

    }
    public void myPaint(Graphics gc)  // this line is not working*******???????
                {
                    gc.drawLine(95, 155, 295, 225);  //1.1 to 2.2
                    gc.drawLine(95, 295, 295, 225);  //1.3 to 2.2
                    gc.drawLine(95, 295, 295, 365);  //1.3 to 2.4
                    gc.drawString(">>>", 260, 220); 
                    gc.drawString(">>>", 218, 255);
                    gc.drawString(">>>", 267, 365);
                } 
    public void actionPerformed(ActionEvent ae)
    {
            if(ae.getSource()==b1)
            {
                    myPaint(gc);     //this line is not working
                    setBackground(Color.red);

             }
            else if(ae.getSource()==b2)
            {
                 setBackground(Color.green);
            }
            else{
                 setBackground(Color.blue);
            }

     }
}
/*<applet code="ButtonTest" width=300 height=300>

*/ 错误是 令牌上的语法错误；预期 令牌上的语法错误；期望

---

在ButtonTest.actionPerformedButtonTest.java:58中，代码中有一些错误。编辑完代码后，请单击该行

import java.awt.*;
import java.awt.event.*;//step-1
import java.applet.Applet;

public class ButtonTest extends Applet implements ActionListener//step-2
{
    Button b1,b2,b3;
    Font f;
    Graphics gc;
    public void init()
    {
            b1=new Button("Request");
            b2=new Button("Grant");
            b3=new Button("Accept");

            f=new Font("Arial",Font.BOLD,12);

            b1.setFont(f);
            b2.setFont(f);
            b3.setFont(f);

            b1.addActionListener(this);
            b2.addActionListener(this);
            b3.addActionListener(this);

            add(b1);
            add(b2);
            add(b3);
    }

    public void paint(Graphics gc) 
    {
        gc.drawLine(100, 150, 100, 400); 
        gc.drawLine(300, 150, 300, 400); 
        gc.drawOval(95, 155, 10, 10);  //1.1
        gc.drawOval(95, 225, 10, 10);  //1.2
        gc.drawOval(95, 295, 10, 10);  //1.3
        gc.drawOval(95, 365, 10, 10);  //1.4
        gc.drawOval(295, 155, 10, 10);  //2.1
        gc.drawOval(295, 225, 10, 10);  //2.2
        gc.drawOval(295, 295, 10, 10);  //2.3
        gc.drawOval(295, 365, 10, 10);  //2.4

    }
    public void myPaint(Graphics gc)  // this line is not working*******???????
                {
                    gc.drawLine(95, 155, 295, 225);  //1.1 to 2.2
                    gc.drawLine(95, 295, 295, 225);  //1.3 to 2.2
                    gc.drawLine(95, 295, 295, 365);  //1.3 to 2.4
                    gc.drawString(">>>", 260, 220); 
                    gc.drawString(">>>", 218, 255);
                    gc.drawString(">>>", 267, 365);
                } 
    public void actionPerformed(ActionEvent ae)
    {
            if(ae.getSource()==b1)
            {
                    myPaint(gc);     //this line is not working
                    setBackground(Color.red);

             }
            else if(ae.getSource()==b2)
            {
                 setBackground(Color.green);
            }
            else{
                 setBackground(Color.blue);
            }

     }
}
/*<applet code="ButtonTest" width=300 height=300>

public void myPaint(Graphics gc)

工作。线路

myPaint();

不起作用，因为myPaint需要图形类型的参数。方法调用应该如下所示

myPaint(gc);

我不知道您真正想做什么，但是您可以通过调用

this.getGraphics()

在myPaint中不需要使用gc作为参数，也不需要将图形作为成员存储在类中

---

希望这有助于您使用哪种Java。在actionPerformedActionEvent ae方法中，定义另一个方法public void paintGraphics gc。这是不可能的1为什么要编写小程序？如果是老师指定的，请参考。2为什么使用AWT？请参阅，了解放弃AWT使用组件而支持Swing的许多好理由。