我正在尝试将ActionListener添加到JButton，它在另一个* .java文件中定义，但它不起作用。如果我从Main公共类中调用这个JButton它可以正常工作，我错过了什么？
我正在使用Java Swing构建一个简单的Paint应用程序。我已将代码分成几个* .java文件，以使其更具可读性。 JButton在SideBar.java文件中定义，我想添加ActionController.java文件，该文件将调用JButtons的所有actionListener。但是，当我添加.addActionListener（）的代码（在ActionController.java文件中）时，按下按钮时没有任何反应。但是，当我在Main.java文件中添加相同的代码时，按下的按钮工作正常。有人能告诉我我错过了什么吗？
我还有另一个关于代码可读性的问题。我是Java的新手，所以我的问题是在这么多类中划分代码的逻辑是否良好？我创建了一个Main类，它将定义应用程序的框架，SideBar.java将包含侧边栏的所有布局，TopMenu.java，它将包含应用程序的Menu，DrawingArea.java，它将是空白的图形应用程序的论文，Draw.java，它将包含绘图的所有函数（调整大小铅笔，选择颜色），以及AcionController.java，它将所有函数（在Draw.java文件中定义）分配给按钮，滑块这是创建应用程序的好方法还是建议以其他方式划分？
下面你可以找到我迄今为止编写的应用程序的代码：
main.Java
package sample;
import sample.applicationLayout.ActionController;
import sample.applicationLayout.DrawingArea;
import sample.applicationLayout.TopMenu;
import sample.applicationLayout.SideBar;
import javax.swing.*;
import java.awt.*;
public class Main {
Main() {
//creating Frame for the application
JFrame frame = new JFrame("Paint Application");
//creating menu
TopMenu menu = new TopMenu();
frame.setJMenuBar(menu);
//END OF MENU
SideBar sideBar = new SideBar();
DrawingArea drawingArea = new DrawingArea();
ActionController actionController = new ActionController();
actionController.clickOnButtons();
frame.add(sideBar, BorderLayout.WEST);
frame.add(drawingArea, BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1200, 800);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}//end of Main()
public static void main(String[] args) {
new Main();
}//end of public static void main(String[] args)
}//end of Main class
action controller.Java
package sample.applicationLayout;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ActionController {
SideBar sideBar = new SideBar();
ListenForButton listenForButton = new ListenForButton();
public ActionController() {
}
public void clickOnButtons() {
sideBar.getButton_pencil().addActionListener(listenForButton);
}
//listener for the buttons
public class ListenForButton implements ActionListener {
public void actionPerformed(ActionEvent e) {
System.out.println("button 1");
}//end of public void actionPerformed
}//end of public class ListenForButton
}//end of ActionController class
draw.Java
package sample;
public class Draw {
}
top menu.Java
package sample.applicationLayout;
import javax.swing.*;
public class TopMenu extends JMenuBar {
public TopMenu() {
JMenu fileMenu = new JMenu("File");
JMenu infoMenu = new JMenu("Info");
JMenuItem newMenuItem = new JMenuItem("New");
JMenuItem openMenuItem = new JMenuItem("Open");
JMenuItem saveMenuItem = new JMenuItem("Save");
JMenuItem clearMenuItem = new JMenuItem("Clear");
JMenuItem exitMenuItem = new JMenuItem("Exit");
JMenuItem aboutmeMenuItem = new JMenuItem("About");
this.add(fileMenu);
this.add(infoMenu);
fileMenu.add(newMenuItem);
fileMenu.add(openMenuItem);
fileMenu.add(saveMenuItem);
fileMenu.add(clearMenuItem);
fileMenu.add(exitMenuItem);
infoMenu.add(aboutmeMenuItem);
}//end of TopMenu()
}//end of TopMenu extends JMenuBar
drawing area.Java
package sample.applicationLayout;
import javax.swing.*;
import java.awt.*;
public class DrawingArea extends JPanel {
public DrawingArea() {
this.setPreferredSize(new Dimension(1100, 800));
this.setBackground(Color.WHITE);
}//end of DrawingArea()
}//end of DrawingArea extends JPanel
sidebar.Java
package sample.applicationLayout;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
public class SideBar extends JPanel {
private JButton button_pencil, button_brush, button_line, button_oval, button_rectangle,
button_filled_oval, button_filled_rectangle, button_text, button_eraser, button_bucket;
//===========================================
public JButton getButton_pencil() {
return button_pencil;
}
//===========================================
public SideBar() {
this.setPreferredSize(new Dimension(120, 800));
BoxLayout boxLayout = new BoxLayout(this, BoxLayout.Y_AXIS);
//fist JPanel with buttons
JPanel panelA = new JPanel();
// panelA.setBackground(Color.WHITE);
panelA.setPreferredSize(new Dimension(120, 250));
Border panelAborder = BorderFactory.createTitledBorder("Paint:");
panelA.setBorder(panelAborder);
panelA.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
//icons for buttons
ImageIcon icon_pencil = new ImageIcon("graphics/icon_pencil.png");
ImageIcon icon_brush = new ImageIcon("graphics/icon_brush.png");
ImageIcon icon_line = new ImageIcon("graphics/icon_line.png");
ImageIcon icon_oval = new ImageIcon("graphics/icon_oval.png");
ImageIcon icon_rectangle = new ImageIcon("graphics/icon_rectangle.png");
ImageIcon icon_filled_oval = new ImageIcon("graphics/icon_filled_oval.png");
ImageIcon icon_filled_rectangle = new ImageIcon("graphics/icon_filled_rectangle.png");
ImageIcon icon_text = new ImageIcon("graphics/icon_text.png");
ImageIcon icon_eraser = new ImageIcon("graphics/icon_eraser.png");
ImageIcon icon_bucket = new ImageIcon("graphics/icon_bucket.png");
//creating JButtons for basic paint drawing functions
button_pencil = new JButton();
button_brush = new JButton();
button_line = new JButton();
button_oval = new JButton();
button_rectangle = new JButton();
button_filled_oval = new JButton();
button_filled_rectangle = new JButton();
button_text = new JButton();
button_eraser = new JButton();
button_bucket = new JButton();
//set size of the buttons
button_pencil.setPreferredSize(new Dimension(35,35));
button_brush.setPreferredSize(new Dimension(35,35));
button_line.setPreferredSize(new Dimension(35,35));
button_oval.setPreferredSize(new Dimension(35,35));
button_rectangle.setPreferredSize(new Dimension(35,35));
button_filled_oval.setPreferredSize(new Dimension(35,35));
button_filled_rectangle.setPreferredSize(new Dimension(35,35));
button_text.setPreferredSize(new Dimension(35,35));
button_eraser.setPreferredSize(new Dimension(35,35));
button_bucket.setPreferredSize(new Dimension(35,35));
//color picker should be in an individual JPane
//setting icons to buttons
button_pencil.setIcon(icon_pencil);
button_brush.setIcon(icon_brush);
button_line.setIcon(icon_line);
button_oval.setIcon(icon_oval);
button_rectangle.setIcon(icon_rectangle);
button_filled_oval.setIcon(icon_filled_oval);
button_filled_rectangle.setIcon(icon_filled_rectangle);
button_text.setIcon(icon_text);
button_eraser.setIcon(icon_eraser);
button_bucket.setIcon(icon_bucket);
gbc.gridx = 0;
gbc.gridy = 0;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_pencil, gbc);
gbc.gridx = 1;
gbc.gridy = 0;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_brush, gbc);
gbc.gridx = 0;
gbc.gridy = 1;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_line, gbc);
gbc.gridx = 1;
gbc.gridy = 1;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_oval, gbc);
gbc.gridx = 0;
gbc.gridy = 2;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_rectangle, gbc);
gbc.gridx = 1;
gbc.gridy = 2;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_filled_oval, gbc);
gbc.gridx = 0;
gbc.gridy = 3;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_filled_rectangle, gbc);
gbc.gridx = 1;
gbc.gridy = 3;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_text, gbc);
gbc.gridx = 0;
gbc.gridy = 4;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_eraser, gbc);
gbc.gridx = 1;
gbc.gridy = 4;
gbc.insets = new Insets(5,5,5,5);
panelA.add(button_bucket, gbc);
//second JPanel with sliders
JPanel panelB = new JPanel();
// panelB.setBackground(Color.red);
panelB.setPreferredSize(new Dimension(120, 200));
Border panelBborder = BorderFactory.createTitledBorder("Paint:");
panelB.setBorder(panelBborder);
panelB.add(new JButton("button1"));
panelB.add(new JButton("button2"));
//third JPanel with color picker
JPanel panelC = new JPanel();
// panelC.setBackground(Color.blue);
panelC.setPreferredSize(new Dimension(120, 200));
Border panelCborder = BorderFactory.createTitledBorder("Paint:");
panelC.setBorder(panelCborder);
panelC.add(new JButton("button1"));
panelC.add(new JButton("button2"));
//adding JPanels to main JPanel
this.add(panelA, BorderLayout.NORTH);
this.add(panelB, BorderLayout.CENTER);
this.add(panelC, BorderLayout.SOUTH);
}//end of public SideBar()
}//end of public class SideBar extends JPanel
可以在ActionController.java文件中找到JButton（在SideBar.java中定义）动作侦听器的代码。
好！我正在回答我自己的问题:)但我想出了答案，也许它会帮助别人。问题在于将SideBar类初始化两次，一次在Main.java文件中，另一次在ActionController.java文件中。我更改了以下代码：
在Main.java文件中：
actionController.clickOnButtons();
变成：
actionController.clickOnButtons(sideBar);
并在ActionController.java文件中：
SideBar sideBar = new SideBar();
ListenForButton listenForButton = new ListenForButton();
public ActionController() {
}
public void clickOnButtons() {
sideBar.getButton_pencil().addActionListener(listenForButton);
}
变成：
ListenForButton listenForButton = new ListenForButton();
public ActionController() {
}
public void clickOnButtons(SideBar sideBar) {
sideBar.getButton_pencil().addActionListener(listenForButton);
}
也许这将在未来给别人一个暗示。