ActionListener 缺少什么?
我需要先说明一下,我们不允许在课堂上使用 IDE。我显然错过了一些重要的事情。我正在编写一个程序,应该允许用户单击单选按钮,然后将“光”更改为该颜色。我以为我正确连接了听众,但显然我忘记了一些事情。有人可以帮我解决这个问题吗?
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
public class Lab4Frame extends JFrame {
//public boolean red, yellow, green;
Lab4Frame(){
this.setLayout(new BorderLayout());
setTitle("Lab 4 - Application #1");
Lab4Panel p = new Lab4Panel();
Lab4RadioButtonPanel p2 = new Lab4RadioButtonPanel();
add(p, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);
}
public static void main(String[] args){
Lab4Frame frame = new Lab4Frame();
frame.setTitle("Lab4 Application # 1");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(600, 600);
frame.setVisible(true);
}
}
class Lab4RadioButtonPanel extends JPanel {
Lab4Panel canvas = new Lab4Panel();
//Lab4RadioButtonPanel canvas2 = new Lab4RadioButtonPanel();
public Lab4RadioButtonPanel() {
boolean red, green, yellow;
this.setLayout(new FlowLayout());
JRadioButton jrbRed = new JRadioButton("Red", true);
JRadioButton jrbYellow = new JRadioButton("Yellow");
JRadioButton jrbGreen = new JRadioButton("Green");
this.setBorder(BorderFactory.createLineBorder(Color.black));
ButtonGroup group = new ButtonGroup();
group.add(jrbRed);
group.add(jrbYellow);
group.add(jrbGreen);
this.add(jrbRed);
this.add(jrbYellow);
this.add(jrbGreen);
jrbRed.addActionListener(new RedListener(canvas));
jrbYellow.addActionListener(new YellowListener(canvas));
jrbGreen.addActionListener(new GreenListener(canvas));
}
}
class Lab4Panel extends JPanel{
public Lab4Panel(){}
boolean red, green, yellow;
int radius = 5;
int x = -1;
int y = -1;
public void setRed(){
red = true;
repaint();
}
public void setYellow(){
yellow = true;
repaint();
}
public void setGreen(){
green = true;
repaint();
}
protected void paintComponent(Graphics g){
if (x<0 || y<0) {
x = getWidth() / 2 - radius;
y = getHeight() / 2 - radius;
}
super.paintComponent(g);
g.drawRect(x - 10,y - 90, 40, 120);
g.drawRect(x - 5,y - 90, 40, 120);
g.setColor(Color.RED);
g.drawOval(x,y - 80, 4 * radius, 4 * radius);
g.setColor(Color.YELLOW);
g.drawOval(x,y - 40, 4 * radius, 4 * radius);
g.setColor(Color.GREEN);
g.drawOval(x,y, 4 * radius, 4 * radius);
if(red){
g.setColor(Color.RED);
g.fillOval(x,y - 80, 4 * radius, 4 * radius);
repaint();
}
else if (yellow){
g.setColor(Color.YELLOW);
g.fillOval(x,y - 40, 4 * radius, 4 * radius);
repaint();
}
if(green){
g.setColor(Color.GREEN);
g.fillOval(x,y, 4 * radius, 4 * radius);
repaint();
}
}
}
class RedListener implements ActionListener{
//private Lab4RadioButtonPanel canvas;
private Lab4Panel canvas;
RedListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setRed();
}
}
class YellowListener implements ActionListener{
private Lab4Panel canvas;
YellowListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setYellow();
}
}
class GreenListener implements ActionListener{
//private Lab4RadioButtonPanel canvas;
private Lab4Panel canvas;
GreenListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setGreen();
}
}
I need to preface this with we are not allowed to use IDE's in class. I am obviously missing something important. I am writing a program that should allow a user to click a radio button then change the "light" to that color. I thought I connected the listeners correctly but obviously I am forgetting something. Can someone help me with this?
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
public class Lab4Frame extends JFrame {
//public boolean red, yellow, green;
Lab4Frame(){
this.setLayout(new BorderLayout());
setTitle("Lab 4 - Application #1");
Lab4Panel p = new Lab4Panel();
Lab4RadioButtonPanel p2 = new Lab4RadioButtonPanel();
add(p, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);
}
public static void main(String[] args){
Lab4Frame frame = new Lab4Frame();
frame.setTitle("Lab4 Application # 1");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(600, 600);
frame.setVisible(true);
}
}
class Lab4RadioButtonPanel extends JPanel {
Lab4Panel canvas = new Lab4Panel();
//Lab4RadioButtonPanel canvas2 = new Lab4RadioButtonPanel();
public Lab4RadioButtonPanel() {
boolean red, green, yellow;
this.setLayout(new FlowLayout());
JRadioButton jrbRed = new JRadioButton("Red", true);
JRadioButton jrbYellow = new JRadioButton("Yellow");
JRadioButton jrbGreen = new JRadioButton("Green");
this.setBorder(BorderFactory.createLineBorder(Color.black));
ButtonGroup group = new ButtonGroup();
group.add(jrbRed);
group.add(jrbYellow);
group.add(jrbGreen);
this.add(jrbRed);
this.add(jrbYellow);
this.add(jrbGreen);
jrbRed.addActionListener(new RedListener(canvas));
jrbYellow.addActionListener(new YellowListener(canvas));
jrbGreen.addActionListener(new GreenListener(canvas));
}
}
class Lab4Panel extends JPanel{
public Lab4Panel(){}
boolean red, green, yellow;
int radius = 5;
int x = -1;
int y = -1;
public void setRed(){
red = true;
repaint();
}
public void setYellow(){
yellow = true;
repaint();
}
public void setGreen(){
green = true;
repaint();
}
protected void paintComponent(Graphics g){
if (x<0 || y<0) {
x = getWidth() / 2 - radius;
y = getHeight() / 2 - radius;
}
super.paintComponent(g);
g.drawRect(x - 10,y - 90, 40, 120);
g.drawRect(x - 5,y - 90, 40, 120);
g.setColor(Color.RED);
g.drawOval(x,y - 80, 4 * radius, 4 * radius);
g.setColor(Color.YELLOW);
g.drawOval(x,y - 40, 4 * radius, 4 * radius);
g.setColor(Color.GREEN);
g.drawOval(x,y, 4 * radius, 4 * radius);
if(red){
g.setColor(Color.RED);
g.fillOval(x,y - 80, 4 * radius, 4 * radius);
repaint();
}
else if (yellow){
g.setColor(Color.YELLOW);
g.fillOval(x,y - 40, 4 * radius, 4 * radius);
repaint();
}
if(green){
g.setColor(Color.GREEN);
g.fillOval(x,y, 4 * radius, 4 * radius);
repaint();
}
}
}
class RedListener implements ActionListener{
//private Lab4RadioButtonPanel canvas;
private Lab4Panel canvas;
RedListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setRed();
}
}
class YellowListener implements ActionListener{
private Lab4Panel canvas;
YellowListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setYellow();
}
}
class GreenListener implements ActionListener{
//private Lab4RadioButtonPanel canvas;
private Lab4Panel canvas;
GreenListener(Lab4Panel canvas) {
this.canvas = canvas;
}
public void actionPerformed(ActionEvent e){
canvas.setGreen();
}
}
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将下面的代码更改为:
并将
下面的代码更改
为:
我得到如下图所示的结果,我想您会明白您的程序出了什么问题:
Bug 很明显:您显示的面板是在 main 函数中构造的,但是您根据单击单选按钮是在 Lab4RadioButtonPanel 类中构造的,它们不指向同一个对象,这就是问题所在。
Change the code below:
to
and change the code below:
to:
I get the result like figure below, I think you'll get what's wrong with your program:
The bug is clear: the panel you display is constructed in main function, but the panel you change according to clicking a radio button is constructed in class Lab4RadioButtonPanel, they don't point to the same object, this is the problem.
在
repaint()
之后,不会调用paintComponent
调用。有两个Lab4Panel
。您设置听众的那个不是您正在绘制的那个。The
paintComponent
call is not being called after yourrepaint()
s. There are twoLab4Panels
. The one you set the listeners on is not the one you are drawing.