java - 需要 Action 监听者的建议

我试图获取我的jslider的值并输入它，以便它是在我的第一段代码中创建的if语句中创建的每个形状的边界长度和面积的值，然后用答案更新我的2个jtextfields边界长度和面积，如何做到这一点的任何提示？

public class MyFrame extends javax.swing.JFrame {
    public MyFrame() {
        // Create the menu
        JMenuBar topMenu = new JMenuBar();
        this.setJMenuBar(topMenu);

        //create the menu button "shapes"
        JMenu shapes = new JMenu("Shapes");
        topMenu.add(shapes);
        //Create the 3 shapes for the menu
        JMenuItem square = new JMenuItem("Square");
        square.addActionListener(new ShapeAction());

        JMenuItem circle = new JMenuItem("Circle");
        circle.addActionListener(new ShapeAction());

        JMenuItem triangle = new JMenuItem("Triangle");
        triangle.addActionListener(new ShapeAction());

        //add shapes to menu
        shapes.add(circle);
        shapes.add(triangle);
        shapes.add(square);

        //add the menu
        setJMenuBar(topMenu);


        MyControlPanel pane = new MyControlPanel();
        getContentPane().add(pane);

        this.add(pane);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        // <snip>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                new MyFrame().setVisible(true);
                }
                });
}
        class ShapeAction implements ActionListener{
            public void actionPerformed(ActionEvent e){
                JMenuItem clickedMenu = (JMenuItem)e.getSource();

                if (clickedMenu.getText().equals("Square")){
                    //implement abstract methods
                    MyShape aSquare = new ASquare();

                }
                else if (clickedMenu.getText().equals("Circle")){
                    //implement abstract methods
                    MyShape ACircle = new ACircle();

                }
                else if (clickedMenu.getText().equals("Triangle")){
                    //implement abstract methods
                    MyShape ATriangle = new ATriangle();

                }
            }
        }
    }

package assignment;

//import java.awt.FlowLayout;
import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;


public class MyControlPanel extends javax.swing.JPanel {

JSlider slider;
JLabel sliderLabel;
JLabel sliderdimension;
JLabel blank;
JLabel dl;
JLabel area1;

/**
 * Creates new form MyControlPanel
 */
public MyControlPanel() {


    slider = new JSlider();
    slider.setValue(50);
    slider.addChangeListener(new MyChangeAction());
    slider.setMajorTickSpacing(10);
    slider.setPaintLabels(true);
    slider.setPaintTicks(true);
    slider.setBounds(300, 50, 100, 50);

    sliderLabel = new JLabel("50");
    blank = new JLabel("     ");
    sliderdimension = new JLabel("Shape Dimension:");

    JTextField boundary_length = new JTextField("Boundary Length");
    JTextField area = new JTextField("Area");

    dl = new JLabel("Boundary Length =");
    area1 = new JLabel("Area =");

    setLayout(new BorderLayout());


    JPanel sliderPanel = new JPanel();
    sliderPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 10, 0));


    sliderPanel.add(sliderdimension);
    sliderPanel.add(sliderLabel);
    sliderPanel.add(slider);
    sliderPanel.add(dl);
    sliderPanel.add(boundary_length);
    sliderPanel.add(area1);
    sliderPanel.add(area);
    this.add(sliderPanel, BorderLayout.PAGE_END);



}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
    this.setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 400, Short.MAX_VALUE)
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 300, Short.MAX_VALUE)
    );
}// </editor-fold>
// Variables declaration - do not modify
// End of variables declaration

public class MyChangeAction implements ChangeListener {

    //complete code here
    public void stateChanged(ChangeEvent ce) {
        int value = slider.getValue();
        String str = Integer.toString(value);
        sliderLabel.setText(str);


    }
} // end class




    }

package assignment;

public abstract class MyShape
 {

double thelength;
double thearea;



public abstract double computeBoundaryLength(double Length);

public abstract double computeArea (double Length);
 }

package assignment;


public class ACircle extends MyShape {

@Override
public double computeBoundaryLength(double Length)
{
    thelength=(2*Length*Math.PI);
return thelength;
}

@Override
public double computeArea(double Length)
{
    thearea=(Length*Length*Math.PI);
    return thearea;
}

}

最佳答案

创建您的textfields类变量，并将这两行放在您的stateChanged方法中：

boundary_length.setText(str);
area.setText(str);

另外，请确保创建具有固定列数的文本字段，以使它们不会根据显示的文本而改变长度。

更新

我对您的代码进行了一些更改，以将滑块的值传递给您的自定义形状：


MyControlPanel成为MyFrame的内部类
文本字段成为MyControlPanel的类变量
滑块成为MyFrame的类变量，因此可以在ShapeAction中访问其值。


样例代码：

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class MyFrame extends javax.swing.JFrame {

    JSlider slider;

    public MyFrame() {
        // Create the menu
        JMenuBar topMenu = new JMenuBar();
        this.setJMenuBar(topMenu);

        //create the menu button "shapes"
        JMenu shapes = new JMenu("Shapes");
        topMenu.add(shapes);
        //Create the 3 shapes for the menu
        JMenuItem square = new JMenuItem("Square");
        square.addActionListener(new ShapeAction());

        JMenuItem circle = new JMenuItem("Circle");
        circle.addActionListener(new ShapeAction());

        JMenuItem triangle = new JMenuItem("Triangle");
        triangle.addActionListener(new ShapeAction());

        //add shapes to menu
        shapes.add(circle);
        shapes.add(triangle);
        shapes.add(square);

        //add the menu
        setJMenuBar(topMenu);


        MyControlPanel pane = new MyControlPanel();
        getContentPane().add(pane);

        this.add(pane);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        // <snip>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                new MyFrame().setVisible(true);
                }
                });
}
        class ShapeAction implements ActionListener{
            public void actionPerformed(ActionEvent e){
                JMenuItem clickedMenu = (JMenuItem)e.getSource();
                if (clickedMenu.getText().equals("Circle")){
                    int value = slider.getValue();
                    MyShape ACircle = new ACircle(value);
                }
            }
        }

        public class MyControlPanel extends javax.swing.JPanel {

            JLabel sliderLabel;
            JLabel sliderdimension;
            JLabel blank;
            JLabel dl;
            JLabel area1;
            JTextField boundary_length = new JTextField("Boundary Length");
            JTextField area = new JTextField("Area");

            public MyControlPanel() {
                slider = new JSlider();
                slider.setValue(50);
                slider.addChangeListener(new MyChangeAction());
                slider.setMajorTickSpacing(10);
                slider.setPaintLabels(true);
                slider.setPaintTicks(true);
                slider.setBounds(300, 50, 100, 50);

                sliderLabel = new JLabel("50");
                blank = new JLabel("     ");
                sliderdimension = new JLabel("Shape Dimension:");

                dl = new JLabel("Boundary Length =");
                area1 = new JLabel("Area =");

                setLayout(new BorderLayout());

                JPanel sliderPanel = new JPanel();
                sliderPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 10, 0));
                sliderPanel.add(sliderdimension);
                sliderPanel.add(sliderLabel);
                sliderPanel.add(slider);
                sliderPanel.add(dl);
                sliderPanel.add(boundary_length);
                sliderPanel.add(area1);
                sliderPanel.add(area);
                this.add(sliderPanel, BorderLayout.PAGE_END);
            }

            public class MyChangeAction implements ChangeListener {
                public void stateChanged(ChangeEvent ce) {
                    int value = slider.getValue();
                    String str = Integer.toString(value);
                    sliderLabel.setText(str);
                    boundary_length.setText(str);
                    area.setText(str);
                }
            }
        }
}

您还应该在形状类（例如ACircle）中添加一个构造器，该构造器将滑块的值作为输入（在其他方法中随意使用）

public class ACircle extends MyShape {

    int value;

    public ACircle(int value) {
        this.value = value;
    }

    // other methods
}