我目前有一个包含三个不同类的项目。我有一个驱动程序类（main），一个GUI面板，其中包含所有按钮侦听器和gui组件，然后是第三个类，其中包含Graphics Panel所遵循的方法。
我想知道如何让我的JMenuItem“new”来调用我的GraphicsPanel类中的clear方法。
主要方法：
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
public class guiDriver {
public static void main(String[] args) {
JFrame frame = new JFrame("Pen Simulator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
GUIPanel panel = new GUIPanel();
frame.add(panel);
// there is a method to set minimum size
frame.setMinimumSize(new Dimension(600, 400));
JMenuBar menuBar = new JMenuBar();
// File Menu
JMenu fileMenu = new JMenu("File");
JMenu helpMenu = new JMenu("Help");
menuBar.add(fileMenu);
menuBar.add(helpMenu);
JMenuItem item1 = new JMenuItem("New");
JMenuItem item2 = new JMenuItem("Load");
JMenuItem item3 = new JMenuItem("Save");
JMenuItem item4 = new JMenuItem("Exit");
fileMenu.add(item1);
fileMenu.add(item2);
fileMenu.add(item3);
fileMenu.add(item4);
// Help Menu
JMenuItem about = new JMenuItem("About");
helpMenu.add(about);
frame.setJMenuBar(menuBar); // setting the Frames menubar as the newly
// created menubar
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
GUIPANEL：
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class GUIPanel extends JPanel {
private JTextField userCommand;
private JLabel instruction1;
private JButton instruct, clear;
private GraphicsPanel graphics;
private int penX, penY, angle;
private int currentDirection = 0;
private boolean penIsUp = false;
private Color penColour;
public GUIPanel() {
graphics = new GraphicsPanel();
setLayout(new BorderLayout());
// SOUTH PANEL CONSTRUCTOR
JPanel command = new JPanel();
command.setLayout(new BoxLayout(command, BoxLayout.LINE_AXIS));
instruction1 = new JLabel("Enter Command:");
// BUTTO
instruct = new JButton("Execute");
instruct.addActionListener(new ButtonListener());
clear = new JButton("Clear Graphics");
// TEXT FIELD
userCommand = new JTextField(10);
command.add(instruction1);
command.add(Box.createRigidArea(new Dimension(4, 0)));
command.add(userCommand);
command.add(Box.createRigidArea(new Dimension(2, 0)));
command.add(instruct);
command.add(Box.createRigidArea(new Dimension(2, 0)));
command.add(clear);
add(command, BorderLayout.SOUTH);
add(graphics, BorderLayout.CENTER);
init();
}
public void init() {
penX = graphics.getWidth() / 2;
penY = graphics.getHeight() / 2;
}
public void moveForward() {
String command = userCommand.getText().toLowerCase();
int distance = Integer.parseInt(command.replace("forward ", ""));
userCommand.setText("");
if (penIsUp == false) {
if (currentDirection == 0) {
graphics.drawLine(penColour, penX, penY, penX, (penY - distance));
penY = penY - distance;
}
if (currentDirection == 1) {
graphics.drawLine(penColour, penX, penY, penX + distance, penY);
penX = penX + distance;
}
if (currentDirection == 2) {
graphics.drawLine(penColour, penX, penY, penX, (penY + distance));
penY = penY + distance;
}
if (currentDirection == 3) {
graphics.drawLine(penColour, penX, penY, penX - distance, penY);
penX = penX - distance;
}
graphics.repaint();
} else if (penIsUp == true) {
penY = penY - distance;
}
}
public void moveBackward() {
String command = userCommand.getText().toLowerCase();
int distance = Integer.parseInt(command.replace("backward ", ""));
userCommand.setText("");
if (penIsUp == false) {
graphics.drawLine(penColour, penX, penY, penX, (penY + distance));
graphics.repaint();
penY = penY + distance;
} else if (penIsUp == true) {
penX = penX + distance;
}
}
public void penUp() {
penIsUp = true;
userCommand.setText("");
}
public void penDown() {
penIsUp = false;
userCommand.setText("");
}
class ButtonListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
if (userCommand.getText().equalsIgnoreCase("something")) {
System.out.println("you typed something");
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("turnleft")) {
currentDirection = currentDirection - 1;
if (currentDirection == -1) {
currentDirection = 3;
}
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("turnright")) {
currentDirection = currentDirection + 1;
if (currentDirection == 4) {
currentDirection = 0;
}
userCommand.setText("");
}
else if (userCommand.getText().startsWith("forward ")) {
try {
moveForward();
} catch (NumberFormatException e1) {
System.out.println("Invalid command");
}
}
else if (userCommand.getText().startsWith("backward ")) {
try {
moveBackward();
}
catch (NumberFormatException e1) {
System.out.println("Invalid command");
}
}
else if (userCommand.getText().equalsIgnoreCase("black")) {
penColour = Color.BLACK;
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("green")) {
penColour = Color.GREEN;
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("red")) {
penColour = Color.RED;
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("reset")) {
graphics.clear();
penX = 0;
penY = 0;
userCommand.setText("");
graphics.repaint();
}
else if (userCommand.getText().equalsIgnoreCase("penUp")) {
penUp();
userCommand.setText("");
}
else if (userCommand.getText().equalsIgnoreCase("penDown")) {
penDown();
userCommand.setText("");
}
}
}
}
GraphicsPanel：
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.swing.JPanel;
@SuppressWarnings("serial")
public class GraphicsPanel extends JPanel {
/**
* The default BG colour of the image.
*/
private final static Color BACKGROUND_COL = Color.DARK_GRAY;
/**
* The underlying image used for drawing. This is required so any previous
* drawing activity is persistent on the panel.
*/
private BufferedImage image;
public GraphicsPanel() {
Dimension resolution = Toolkit.getDefaultToolkit().getScreenSize();
int width = (int) resolution.getWidth(); // casting the screen width to
// integer
int height = (int) resolution.getHeight(); // casting the scren height
// to integer
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// Set max size of the panel, so that is matches the max size of the
// image.
setMaximumSize(new Dimension(image.getWidth(), image.getHeight()));
clear();
}
public void drawLine(Color color, int x1, int y1, int x2, int y2) {
Graphics g = image.getGraphics();
g.setColor(color);
g.translate(getWidth() / 2, getHeight() / 2);
g.drawLine(x1, y1, x2, y2);
}
/**
* Clears the image contents.
*/
public void clear() {
Graphics g = image.getGraphics();
g.setColor(BACKGROUND_COL);
g.fillRect(0, 0, image.getWidth(), image.getHeight());
}
@Override
public void paint(Graphics g) {
// render the image on the panel.
g.drawImage(image, 0, 0, null);
}
}
在可能的情况下，我还希望能够添加一个滚动条，这样当我的绘图超出图形面板时，它会创建一个滚动条，但添加一个滚动条似乎不适合。
感谢任何帮助和指导。
编辑：
item1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
clear();
}
});
答案 0 :(得分：1)
添加ActionListener（或使用lambda表达式，如果您使用的是Java 8或更高版本）到新按钮，然后调用clear()方法。
除此之外，您不应该覆盖paint()，而应覆盖paintComponent()。
要使JScrollPane正常工作，您需要设置面板的首选尺寸，方法是在内容大小发生变化时调用setPreferredSize()，或者重写getPreferredSize()。此外，您需要让JScrollPane重新计算在更改面板首选尺寸后是否需要滚动条，因此您需要在首选尺寸更改后调用面板上的revalidate()。