Question

修

现在，导入在此处显示为下划线

import javax.swing.event.ChangeListener;

并且下面的行显示带下划线

slider.addChangeListener（的ChangeListener（））;

我对此并不清楚

完整代码

package areaofrectangleslider;

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;
import javax.swing.event.ChangeListener;


public class Areaofrectangleslider extends JFrame implements 
        ActionListener, ChangeListener {

    private JPanel panel;
    private Random random;
    private javax.swing.Timer timer;
    private JSlider slider;
    private JTextField gapField;
    private JLabel gapLabel;



    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        EventQueue.invokeLater(new Runnable() {
        public void run(){
        Areaofrectangleslider frame = new Areaofrectangleslider();
        frame.setSize(250,300);
        frame.createGUI();
        frame.setVisible(true);

        }


    });
    }

    public void actionPerformed(ActionEvent e) {
     //   throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    int x, y, size;
    Graphics paper = panel.getGraphics();
    x = random.nextInt(200);
    y = random.nextInt(200);
    size = random.nextInt(20);
    paper.fillOval(x, y, size, size);

    }

    @Override
    public void changed(ObservableValue observable, Object oldValue, Object newValue) {
       // throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    int timeGap = slider.getValue();
    gapField.setText(Integer.toString(timeGap));
    timer.setDelay(timeGap);

    }

    private void createGUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Container window = getContentPane();
        window.setLayout(new FlowLayout());
        random = new Random();

        panel = new JPanel();
        panel.setPreferredSize(new Dimension(200,200));
        panel.setBackground(Color.white);
        window.add(panel);

        gapLabel = new JLabel("TIme Gap: ");
        window.add(gapLabel);
        gapField = new JTextField(10);
        window.add(gapField);

        slider = new JSlider(JSlider.HORIZONTAL,200,2000,1000);
        window.add(slider);
        slider.addChangeListener(ChangeListener());
        gapField.setText(Integer.toString(slider.getValue()));
        timer = new javax.swing.Timer(1000, this);
        timer.start();



//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

}

旧

我似乎无法解决为什么我在这里得到错误

slider.addChangeListener(this);

（this）以红色下划线标出

我得到的控制台读数是：

Exception in thread "main" java.lang.ClassCastException: areaofrectangleslider.Areaofrectangleslider cannot be cast to javax.swing.event.ChangeListener
    at areaofrectangleslider.Areaofrectangleslider.createGUI(Areaofrectangleslider.java:91)
    at areaofrectangleslider.Areaofrectangleslider.main(Areaofrectangleslider.java:46)
Java Result:

以下完整代码

package areaofrectangleslider;

import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;


public class Areaofrectangleslider extends JFrame implements 
        ActionListener, ChangeListener {

    private JPanel panel;
    private Random random;
    private javax.swing.Timer timer;
    private JSlider slider;
    private JTextField gapField;
    private JLabel gapLabel;



    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        Areaofrectangleslider frame = new Areaofrectangleslider();
        frame.setSize(250,300);
        frame.createGUI();
        frame.setVisible(true);


    }

    @Override
    public void actionPerformed(ActionEvent e) {
     //   throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    int x, y, size;
    Graphics paper = panel.getGraphics();
    x = random.nextInt(200);
    y = random.nextInt(200);
    size = random.nextInt(20);
    paper.fillOval(x, y, size, size);

    }

    @Override
    public void changed(ObservableValue observable, Object oldValue, Object newValue) {
       // throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    int timeGap = slider.getValue();
    gapField.setText(Integer.toString(timeGap));
    timer.setDelay(timeGap);

    }

    private void createGUI() {
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        Container window = getContentPane();
        window.setLayout(new FlowLayout());
        random = new Random();

        panel = new JPanel();
        panel.setPreferredSize(new Dimension(200,200));
        panel.setBackground(Color.white);
        window.add(panel);

        gapLabel = new JLabel("TIme Gap: ");
        window.add(gapLabel);
        gapField = new JTextField(10);
        window.add(gapField);

        slider = new JSlider(JSlider.HORIZONTAL,200,2000,1000);
        window.add(slider);
        slider.addChangeListener(this);
        gapField.setText(Integer.toString(slider.getValue()));
        timer = new javax.swing.Timer(1000, this);
        timer.start();



//        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

}

Answer 1

javafx.beans.value.ChangeListener;与javax.swing.event.ChangeListener

不同

永远不要使用getGraphics来尝试和执行自定义绘画，这不是绘画在Swing中的工作原理。有关自定义绘画如何工作的详细信息，请参阅Painting in AWT and Swing和Performing Custom Painting

另外（如下所述），所有UI创作和修改都应在事件调度线程的上下文中执行...

public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            Areaofrectangleslider frame = new Areaofrectangleslider();
            frame.setSize(250,300);
            frame.createGUI();
            frame.setVisible(true);
        }
    });
}

有关详细信息，请参阅Initial Threads

Answer 2

JSlider中addChangeListner的方法签名是 public void addChangeListener(ChangeListener l) 其中ChangeListner为javax.swing.event.ChangeListener。因此，在您的代码中，您传递的javafx.beans.value.ChangeListener类型错误且无法投放。

这似乎用红色加下划线

2 个答案: