如何在Java中的switch语句中使用带有组合框的Jbuttons

Question

这是我第一次发帖，请善待并知道我会记得解决任何建议！

我正在尝试创建一个绘制形状的程序。我需要我的程序一次只显示一个选择，圆形，方形或三角形。当我单击“绘制...”选项时，它应该仅绘制相应的形状，并在侧面标记高度或半径。形状是固定大小，但标签需要反映用户输入的内容。

但是，我正在使用switch语句在它们之间切换。我的开关立即显示所有内容！我该如何解决？

这是我的代码：

import java.awt.event.ActionEvent;
import java.awt.Graphics;
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.event.ActionListener;
import javax.swing.JComboBox;

public class MainPanel extends JPanel implements ActionListener{ 


            JTextField num1;
            JTextField num2;
            JTextField num3;
            JTextField num4;
            JLabel equals;
            JTextField answer;
            JLabel labelTxt;
            JComboBox shapeList;
            JButton drawAThing;
            JLabel radiusLabel;
            JLabel base;
            JLabel lengthLabel;
            JLabel height;
            JButton drawACircle;
            JButton drawASquare;
            JButton drawATriangle;

    MainPanel(){

        String [] shapes = {"circle", "square", "triangle"};
        shapeList = new JComboBox(shapes);
        shapeList.setSelectedIndex(2);
        shapeList.addActionListener(this); 
        add(shapeList); 


    }

            @Override
    public void actionPerformed(ActionEvent e) {
        Object o = e.getSource();
        Object a = e.getSource();

        if (o == shapeList){
            JComboBox cb = (JComboBox)e.getSource();
            String msg = (String)cb.getSelectedItem();


            switch(msg){
            case "circle": 
                radiusLabel = new JLabel();
                radiusLabel.setText("Radius: ");
                add(radiusLabel);

                num1 = new JTextField(12);
                add(num1);


                drawACircle = new JButton("Draw a circle ");
                drawACircle.addActionListener(this);
                add(drawACircle);

                if (a == drawACircle){

                    drawACircleThing();
                    remove(drawACircle);

                    this.revalidate();
                    this.repaint();
                    }



                break;

            case "square":
                    lengthLabel = new JLabel();
                    lengthLabel.setText("Side Length: ");
                    add(lengthLabel);

                    num2 = new JTextField(12);
                    add(num2);


                    drawASquare = new JButton("Draw a square ");
                    drawASquare.addActionListener(this);
                    add(drawASquare);

                    if (a == drawASquare){

                    drawASquareThing();
                    remove(drawASquare);

                    this.revalidate();
                    this.repaint();
                    }

               break;

            case "triangle":
                    base = new JLabel();
                    base.setText("Base: ");
                    add(base);

                    num3 = new JTextField(12);
                    add(num3);

                    height = new JLabel();
                    base.setText("height: ");
                    add(height);

                    num4 = new JTextField(12);
                    add(num4);


                    drawATriangle = new JButton("Draw a triangle ");
                    drawATriangle.addActionListener(this);
                    add(drawATriangle);

                    if (a == drawATriangle){

                        drawATriangleThing();

                    remove(drawATriangle);

                    this.revalidate();
                    this.repaint();

                    }

                    break;


                 default:
                    break;

        }
    }
    }

            @Override
public void paintComponent(Graphics g) 
{
    g.setColor(Color.BLUE ); 
    g.fillRect(50, 50, 200, 200);
    g.fillOval(100,100,200,200);

}
private void drawASquareThing()
{
    Graphics g = getGraphics();
    g.setColor(Color.green);
    g.fillRect(150,100,330,200);    
    g.drawString("My square", 50, 10); 

}
private void drawATriangleThing()
{
    Graphics g = getGraphics();
    g.setColor(Color.yellow);
    g.fillRect(150,100,330,200);    
        g.drawString("My Triangle", 50, 10); 

}

public void drawACircleThing()
{
    Graphics g = getGraphics();
    g.setColor(Color.ORANGE);

    int [] xPoints = {50, 50, 100};
    int [] yPoints = {50, 100, 100};

    g.drawPolygon(xPoints, yPoints, 3);
    g.fillPolygon(yPoints, xPoints, 3);

}


}

我的新代码：

import java.awt.event.ActionEvent;
import java.awt.Graphics;
import java.awt.Color;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.event.ActionListener;
import javax.swing.JComboBox;

public class MainPanel extends JPanel implements ActionListener{ 


            JTextField num1;
            JTextField num2;
            JTextField num3;
            JTextField num4;

            JTextField answer;
            JLabel labelTxt;
            JComboBox shapeList;
            JButton drawAThing;
            JLabel radiusLabel;
            JLabel base;
            JLabel lengthLabel;
            JLabel height;
            JButton drawACircle;
            JButton drawASquare;
            JButton drawATriangle;

    MainPanel(){

        String [] shapes = {"circle", "square", "triangle"};
        shapeList = new JComboBox(shapes);
        shapeList.setSelectedIndex(2);
        shapeList.addActionListener(this); 
        add(shapeList); 

    setVisible(true);


    }

            @Override
    public void actionPerformed(ActionEvent e) {
        Object o = e.getSource();
        Object a = e.getSource();

        if (o == shapeList){
            JComboBox cb = (JComboBox)e.getSource();
            String message = (String)cb.getSelectedItem();


            switch(message){
            case "circle": 

                radiusLabel = new JLabel();
                radiusLabel.setText("Radius: ");
                add(radiusLabel);

                num1 = new JTextField(12);
                add(num1);
                int radiusSize = Integer.parseInt(num1.getText());
                this.revalidate();
                drawACircle = new JButton("Draw a circle ");
                drawACircle.addActionListener(this);
                add(drawACircle);

                if (a == drawACircle){

                    drawACircleThing(radiusSize);

                    }

                    this.repaint();

                break;

            case "square":

                    lengthLabel = new JLabel();
                    lengthLabel.setText("Side Length: ");
                    add(lengthLabel);

                    num2 = new JTextField(12);
                    add(num2);
                    int lengthSize = Integer.parseInt(num2.getText());
                    this.revalidate();
                    drawASquare = new JButton("Draw a square ");
                    drawASquare.addActionListener(this);
                    add(drawASquare);


                    if (a == drawASquare){

                    drawASquareThing(lengthSize);


                    }

                    this.repaint();

               break;

            case "triangle":

                    base = new JLabel();
                    base.setText("Base: ");
                    add(base);


                    num3 = new JTextField(12);
                    add(num3);
                    int baseSize = Integer.parseInt(num3.getText());

                    height = new JLabel();
                    base.setText("height: ");
                    add(height);

                    num4 = new JTextField(12);
                    add(num4);
                    int heightSize = Integer.parseInt(num4.getText());
                    this.revalidate();
                    drawATriangle = new JButton("Draw a triangle ");
                    drawATriangle.addActionListener(this);
                    add(drawATriangle);

                    if (a == drawATriangle){

                        drawATriangleThing(baseSize, heightSize);

                    }

                    this.repaint();

                   break;

                 default:
                    break;

        }
    }
 }

@Override
public void paintComponent(Graphics g) //The last thing that is called and passed by java run time environment of Graphics g. It let’s us draw on the screen.
{
g.setColor(Color.BLUE ); // NEED an import. Don’t need to know all the colors.
g.fillRect(50, 50, 200, 200);
g.fillOval(100,100,200,200);

}
private void drawASquareThing(int lengthSize)
{
    Graphics g = getGraphics();
        g.setColor(Color.PINK);
        g.drawRect(lengthSize, 45, 25, 35);
        g.drawString("My Square", 30, 23);        
}
private void drawATriangleThing(int baseSize, int heightSize)
{

    Graphics g = getGraphics();
    g.setColor(Color.GREEN);
    g.fillRect(60,79,809,400); 
        g.drawRect(baseSize, baseSize, heightSize, heightSize);
        g.drawString("My Triangle", baseSize, heightSize); 

}

public void drawACircleThing(int radiusSize)
{
    Graphics g = getGraphics();
    g.setColor(Color.ORANGE);

    int [] xPoints = {50, 50, 100};
    int [] yPoints = {50, 100, 100};

    g.drawPolygon(xPoints, yPoints, radiusSize);
    g.fillPolygon(yPoints, xPoints, 3);

}


}

Answer 1

你应该做更多关于自定义绘画的摇摆教程。但基本上，您应该在paintComponent方法中执行所有操作，而在其他方法中，您应该设置paintComponent中使用的变量/参数。例如（使用您的代码）

            @Override
public void paintComponent(Graphics g) 
{
    g.setColor(Color.BLUE ); 
    if (fillSquareFlag) g.fillRect(50, 50, 200, 200);
    if (fillCircleFlag) g.fillOval(100,100,200,200);

}

有了这个，您可以为按钮设置按钮操作，如

public void actionPerformed(ActionEvent ae) {
  fillSquareFlag = !fillSquareFlag;
  repaint();
}