我正在尝试实现一组使用 3 个 ItemListener 检测到的 3 个 JRadiobutton 以及由 2 个 ActionListener 选择的一组 2 个 JButton 。
当按下“OK”JButton
时,应检测到当前的 JRadioButton
选择。
我尝试通过将 ActionEvent
和 ItemEvent
组合到一个方法中来实现此目的,其中 if 语句可用于验证按下“OK”时选择了哪个 JRadioButton
。
产生的错误消息是方法不是抽象的,并且不会覆盖actionListener中的抽象方法actionPerformed(ActionEvent)
。
当主方法被抽象时,它不会实例化。
我尝试在 public void actionPerformed
方法之前放置 @Override
并使用 alt+ins 插入覆盖,但这不起作用。
代码如下:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
class MainMenu extends JFrame implements ActionListener, ItemListener {
JPanel pnl = new JPanel();
JPanel grid = new JPanel(new GridLayout(3, 1));
JRadioButton input1 = new JRadioButton("Enter New Information", true);
JRadioButton input2 = new JRadioButton("Load from a CSV file");
JRadioButton input3 = new JRadioButton("Save to a CSV file");
ButtonGroup inputs = new ButtonGroup();
JButton b1 = new JButton("OK");
JButton b2 = new JButton("Cancel");
JTextArea txtArea = new JTextArea(5, 25);
public void actionPerformed(ActionEvent event2, ItemEvent event1) {
txtArea.setText(event2.getActionCommand() + " Clicked");
if (event2.getSource() == b1 && event1.getItemSelectable() == input1) {
System.exit(0);
}
if (event2.getSource() == b1 && event1.getItemSelectable() == input2) {
final JFileChooser fc = new JFileChooser();
int returnVal = fc.showOpenDialog(null);
System.exit(0);
}
if (event2.getSource() == b1 && event1.getItemSelectable() == input3) {
System.exit(0);
}
if (event2.getSource() == b2) {
System.exit(0);
}
}
public MainMenu() {
super("Main Menu");
setSize(300, 200);
Container contentPane = getContentPane();
ButtonGroup buttonGroup = new javax.swing.ButtonGroup();
inputs.add(input1);
inputs.add(input2);
inputs.add(input3);
setDefaultCloseOperation(EXIT_ON_CLOSE);
add(grid);
add(pnl);
grid.add(input1);
grid.add(input2);
grid.add(input3);
grid.setBorder(BorderFactory.createLineBorder(Color.BLACK));
pnl.add(b1);
pnl.add(b2);
pnl.add(txtArea);
b1.addActionListener(this);
b2.addActionListener(this);
input1.addItemListener(this);
input2.addItemListener(this);
input3.addItemListener(this);
contentPane.add("North", grid);
contentPane.add("South", pnl);
setVisible(true);
}
}
最佳答案
基本上,您违反了 ActionListener
和 JRadioButton
的契约(Contract)要求(因为它们希望您向它们传递对实现 ItemListener
接口(interface)的类的引用)...
你不能简单地以这种方式“组成”回调,你必须满足你实现的接口(interface)的要求。
事实上,您并不真正关心 JRadioButton
何时发生变化,您只关心按下 Ok
或 Cancel
按钮时的变化,因此您可以完全摆脱 ItemListener
要求,只需检查您感兴趣的 JRadioButton
的 selected
状态,例如...
@Override
public void actionPerformed(ActionEvent event2) {
txtArea.setText(event2.getActionCommand() + " Clicked");
Object source = event2.getSource();
if (source == b1 && input1.isSelected()) {
System.exit(0);
}
if (source == b1 && input2.isSelected()) {
final JFileChooser fc = new JFileChooser();
int returnVal = fc.showOpenDialog(null);
System.exit(0);
}
if (event2.getSource() == b1 && input3.isSelected()) {
System.exit(0);
}
if (event2.getSource() == b2) {
System.exit(0);
}
}
作为一个可运行的示例......
import java.awt.Color;
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
class MainMenu extends JFrame implements ActionListener {
JPanel pnl = new JPanel();
JPanel grid = new JPanel(new GridLayout(3, 1));
JRadioButton input1 = new JRadioButton("Enter New Information", true);
JRadioButton input2 = new JRadioButton("Load from a CSV file");
JRadioButton input3 = new JRadioButton("Save to a CSV file");
ButtonGroup inputs = new ButtonGroup();
JButton b1 = new JButton("OK");
JButton b2 = new JButton("Cancel");
JTextArea txtArea = new JTextArea(5, 25);
@Override
public void actionPerformed(ActionEvent event2) {
txtArea.setText(event2.getActionCommand() + " Clicked");
Object source = event2.getSource();
if (source == b1 && input1.isSelected()) {
System.exit(0);
}
if (source == b1 && input2.isSelected()) {
final JFileChooser fc = new JFileChooser();
int returnVal = fc.showOpenDialog(null);
System.exit(0);
}
if (event2.getSource() == b1 && input3.isSelected()) {
System.exit(0);
}
if (event2.getSource() == b2) {
System.exit(0);
}
}
public MainMenu() {
super("Main Menu");
setSize(300, 200);
Container contentPane = getContentPane();
ButtonGroup buttonGroup = new javax.swing.ButtonGroup();
inputs.add(input1);
inputs.add(input2);
inputs.add(input3);
setDefaultCloseOperation(EXIT_ON_CLOSE);
add(grid);
add(pnl);
grid.add(input1);
grid.add(input2);
grid.add(input3);
grid.setBorder(BorderFactory.createLineBorder(Color.BLACK));
pnl.add(b1);
pnl.add(b2);
pnl.add(txtArea);
b1.addActionListener(this);
b2.addActionListener(this);
input1.addActionListener(this);
input2.addActionListener(this);
input3.addActionListener(this);
contentPane.add("North", grid);
contentPane.add("South", pnl);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
ex.printStackTrace();
}
MainMenu frame = new MainMenu();
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
您可能想仔细看看 the Interfaces trail和How to Use Buttons, Check Boxes, and Radio Buttons
关于java - JRadiobutton 结合 JButtons 实现。错误方法不是抽象的并且不会覆盖抽象方法,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25117214/