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我有一項任務，要求球根據用戶點擊的按鈕在屏幕上移動，並通過單擊另一個按鈕讓球在紅色和綠色之間切換。這一切都有效，只是顏色的變化。我有一個聽衆和類對按鈕點擊作出反應，但我似乎沒有得到改變。有沒有更好/更簡單的方法來實現這一目標？使用動作監聽器實現顏色更改
在此先感謝您的幫助！
代碼，我有：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Lab2b extends JFrame {
Lab2b(){
setTitle("Lab 2");
Lab2Panel p = new Lab2Panel();
add(p);
}
public static void main(String[] args){
Lab2b frame = new Lab2b();
frame.setTitle("Lab 2 - Ball Mover ");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(600, 400);
frame.setVisible(true);
}
}
class Lab2Panel extends JPanel{
Lab2Button canvas = new Lab2Button();
JPanel panel = new JPanel();
Lab2Panel() {
setLayout(new BorderLayout());
JButton leftButton = new JButton("left");
JButton rightButton = new JButton("right");
JButton upButton = new JButton("up");
JButton downButton = new JButton("down");
JButton colorButton = new JButton("Change Color");
panel.add(leftButton);
panel.add(rightButton);
panel.add(upButton);
panel.add(downButton);
panel.add(colorButton);
this.add(canvas, BorderLayout.CENTER);
this.add(panel, BorderLayout.SOUTH);
leftButton.addActionListener(new LeftListener(canvas));
rightButton.addActionListener(new RightListener(canvas));
upButton.addActionListener(new UpListener(canvas));
downButton.addActionListener(new DownListener(canvas));
colorButton.addActionListener(new ColorChangeListener(canvas));
}
}
class Lab2Button extends JPanel {
int radius = 5;
int x = -1;
int y = -1;
protected void paintComponent(Graphics g){
if (x<0 || y<0) {
x = getWidth()/2 - radius;
y = getHeight()/2 - radius;
}
super.paintComponent(g);
g.setColor(Color.RED);
g.drawOval(x,y, 2 * radius, 2 * radius);
}
public void moveLeft(){
x -= 5;
this.repaint();
}
public void moveRight(){
x += 5;
this.repaint();
}
public void moveUp(){
y -= 5;
this.repaint();
}
public void moveDown(){
y += 5;
this.repaint();
}
public void colorChange(){
this.repaint();
}
}
class LeftListener implements ActionListener{
private Lab2Button canvas;
LeftListener(Lab2Button canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.moveLeft();
}
}
class RightListener implements ActionListener{
private Lab2Button canvas;
RightListener(Lab2Button canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.moveRight();
}
}
class UpListener implements ActionListener{
private Lab2Button canvas;
UpListener(Lab2Button canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.moveUp();
}
}
class DownListener implements ActionListener{
private Lab2Button canvas;
DownListener(Lab2Button canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.moveDown();
}
}
class ColorChangeListener implements ActionListener {
private Lab2Button canvas;
ColorChangeListener(Lab2Button canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.colorChange();
}
}
按鈕動作監聽器類代碼：
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class Lab2MoveBallListener extends Lab2Button implements ActionListener {
public void actionPerformed(ActionEvent e){
this.moveLeft();
}
}
好吧，改變了這種代碼：
public void colorChange(){
this.repaint();
}
爲了這一點，它與編譯錯誤：錯誤：找不到符號 if（g.getColor（）= Color.RED）{
public void colorChange(){
if (g.getColor() = Color.RED){
g.setColor(Color.GREEN);
}
else{
g.setColor(Color.RED);
}
this.repaint();
}