我想在java

Question

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class combodemo implements ActionListener {
    JFrame f;
    JPanel p;
    JTextField tf;
    JButton b1;
    JButton b2;
    JRadioButton rb1;
    JRadioButton rb2;
    JLabel l;
    JComboBox cb;
    JCheckBox c1, c2, c3;
    ButtonGroup bg;

    combodemo() {
        String[] h = {
            "red",
            "yellow",
            "green"
        };
        cb = new JComboBox(h);
        f = new JFrame();
        p = new JPanel();
        tf = new JTextField(30);
        b1 = new JButton("OK");
        b2 = new JButton("Clear");
        rb1 = new JRadioButton("male");
        rb2 = new JRadioButton("Female");
        l = new JLabel("Enter Text");
        c1 = new JCheckBox("java");
        c2 = new JCheckBox("C++");
        c3 = new JCheckBox("Microsoft");
        bg = new ButtonGroup();

        f.add(p);
        p.add(l);
        p.add(tf);
        b1.addActionListener(this);
        b2.addActionListener(this);
        p.add(b1);
        p.add(b2);
        bg.add(rb1);
        bg.add(rb2);
        p.add(rb1);
        p.add(rb2);
        p.add(cb);
        p.add(c1);
        p.add(c2);
        p.add(c3);

        f.setVisible(true);
        f.pack();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public void actionPerformed(ActionEvent ae)

    {
        String str = (String) cb.getSelectedItem();
        '
        if (str.equals("red"))
            p.setBackground(Color.red);

        if (str.equals("green"))
            p.setBackground(Color.green);

        if (str.equals("yellow"))
            p.setBackground(Color.yellow);

        if (ae.getActionCommand() == "OK") {
            tf.setText("This is example of swing");
        }
        if (ae.getActionCommand() == "Clear") {
            tf.setText("");
        }
    }
    public static void main(String[] args)

    {
        combodemo cd = new combodemo();
    }
}

实际上当我运行此代码并在点击“RED”，“GREEN”或“YELLOW”时更改面板的颜色时，需要我点击“确定”才能更改面板的颜色。我想点击“RED”，“GREEN”或“Yellow”上的名字来改变颜色，请帮我摆脱这个问题。

我在今天的演讲中从NIIT学习了这段代码，当我编写代码时，发生了很多错误。但是现在我已经完成了代码但是我现在面临的问题我已经在上面写过了。

帮助将不胜感激。

Answer 1

你需要做两件事......

首先将actionlistner添加到jcombobox

cb.addActionListener(this);

第二，实施处理事件的逻辑。

public void actionPerformed(ActionEvent ae)

{
    if(ae.getSource() instanceof JComboBox) {
            String str = (String)cb.getSelectedItem();
            if(str.equals("red"))
            p.setBackground(Color.red);

            if(str.equals("green"))
            p.setBackground(Color.green);

            if(str.equals("yellow"))
            p.setBackground(Color.yellow);
        }
          /////

完整代码

package test;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class combodemo implements ActionListener
{
JFrame f;
JPanel p;
JTextField tf;
JButton b1;
JButton b2;
JRadioButton rb1;
JRadioButton rb2;
JLabel l;
JComboBox cb;
JCheckBox c1,c2,c3;
ButtonGroup bg;

combodemo()
{
String  []h = {"red","yellow","green"};
cb = new JComboBox(h);
f = new JFrame();
p = new JPanel();
tf = new JTextField(30);
b1 = new JButton("OK");
b2 = new JButton("Clear");
rb1 = new JRadioButton("male");
rb2 = new JRadioButton("Female");
l = new JLabel("Enter Text");
c1 = new JCheckBox("java");
c2 = new JCheckBox("C++");
c3 = new JCheckBox("Microsoft");
bg = new ButtonGroup();

f.add(p);
p.add(l);
p.add(tf);
b1.addActionListener(this);
b2.addActionListener(this);
cb.addActionListener(this);
p.add(b1);
p.add(b2);
bg.add(rb1);
bg.add(rb2);
p.add(rb1);
p.add(rb2);
p.add(cb);
p.add(c1);
p.add(c2);
p.add(c3);

f.setVisible(true);
f.pack();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed(ActionEvent ae)

{
    if(ae.getSource() instanceof JComboBox) {
        String str = (String)cb.getSelectedItem();
        if(str.equals("red"))
        p.setBackground(Color.red);

        if(str.equals("green"))
        p.setBackground(Color.green);

        if(str.equals("yellow"))
        p.setBackground(Color.yellow);
    }


if(ae.getActionCommand()=="OK")
{
tf.setText("This is example of swing");
}
if(ae.getActionCommand()=="Clear")
{
tf.setText("");
}
}
public static void main (String [] args)

{
combodemo cd = new combodemo();
} 
}