如何将 ActionListener 添加到添加到 JPanel 的 JButton？
我的目标是制作油漆类型的应用程序。
谢谢你的建议.. 但代码中仍然存在错误。
在 netbeans IDE 中，button1.addActionListener(panel); 行中出现错误：“类中的方法 addActionListener 无法应用于给定类型”
所以我使用它的建议将其转换为 ActionListener。所以该行是button1.addActionListener((ActionListener) panel); 但仍然在下面的 'if 语句' 中出现错误：找不到符号变量 'button1'
再次感谢您的帮助。 这是更改后的代码。我更改了变量名称并使用适配器类来使代码更简单。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class r extends JPanel
{
public int x1,x2,y1,y2;
public static double SWITCH;
public r()
{
setBackground(Color.WHITE);
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent m)
{
x1=m.getX();
y1=m.getY();
repaint();
}
public void mouseReleased(MouseEvent m)
{
x1=x2=y1=y2=0;
repaint();
}
});
addMouseMotionListener(new MouseMotionAdapter()
{
public void mouseDragged(MouseEvent m)
{
x2=m.getX();
y2=m.getY();
repaint();
}
});
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
if(SWITCH == 2)
{
g.drawRect(x1, y1, x2, y2);
}
else if (SWITCH == 3)
{
g.drawOval(x1,y1,x2,y2);
}
else
{
g.drawString("qwe", x1, y1);
}
}
}
public class q extends JFrame implements ActionListener
{
public static void main(String[] args)
{
q window = new q();
window.setVisible(true);
window.setSize(1024, 800);
window.setDefaultCloseOperation(EXIT_ON_CLOSE);
Container cont = window.getContentPane();
cont.setLayout(new GridLayout(2,2));
r panel = new r();
JPanel BPanel = new JPanel();
cont.add(panel);
cont.add(BPanel);
BPanel.setBackground(Color.blue);
JButton button1,button2;
button1 = new JButton("Rect");
button2 = new JButton("Oval");
BPanel.add(button1);
BPanel.add(button2);
button1.addActionListener((ActionListener) panel);
button2.addActionListener((ActionListener) panel);
}
public void actionPerformed(ActionEvent a)
{
Object obj;
obj=a.getSource();
if (obj== button1)
{
SWITCH = 2;
repaint();
}
else
{
SWITCH = 3;
repaint();
}
}
}
My aim is to make a paint type application.
Thank you for your suggestions..
but there is still error in the code.
In netbeans IDE error : 'method addActionListener in class cannot be applied to given types' occurs in the line button1.addActionListener(panel);
so i used it suggestion to cast it to ActionListener. so the line is button1.addActionListener((ActionListener) panel);
but still in the below 'if statement' error occurs : cannot find symbol variable 'button1'
Thanks again for your help.
here is changed code. i changed the variable names and used adapter class to make code simpler.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class r extends JPanel
{
public int x1,x2,y1,y2;
public static double SWITCH;
public r()
{
setBackground(Color.WHITE);
addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent m)
{
x1=m.getX();
y1=m.getY();
repaint();
}
public void mouseReleased(MouseEvent m)
{
x1=x2=y1=y2=0;
repaint();
}
});
addMouseMotionListener(new MouseMotionAdapter()
{
public void mouseDragged(MouseEvent m)
{
x2=m.getX();
y2=m.getY();
repaint();
}
});
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
if(SWITCH == 2)
{
g.drawRect(x1, y1, x2, y2);
}
else if (SWITCH == 3)
{
g.drawOval(x1,y1,x2,y2);
}
else
{
g.drawString("qwe", x1, y1);
}
}
}
public class q extends JFrame implements ActionListener
{
public static void main(String[] args)
{
q window = new q();
window.setVisible(true);
window.setSize(1024, 800);
window.setDefaultCloseOperation(EXIT_ON_CLOSE);
Container cont = window.getContentPane();
cont.setLayout(new GridLayout(2,2));
r panel = new r();
JPanel BPanel = new JPanel();
cont.add(panel);
cont.add(BPanel);
BPanel.setBackground(Color.blue);
JButton button1,button2;
button1 = new JButton("Rect");
button2 = new JButton("Oval");
BPanel.add(button1);
BPanel.add(button2);
button1.addActionListener((ActionListener) panel);
button2.addActionListener((ActionListener) panel);
}
public void actionPerformed(ActionEvent a)
{
Object obj;
obj=a.getSource();
if (obj== button1)
{
SWITCH = 2;
repaint();
}
else
{
SWITCH = 3;
repaint();
}
}
}
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评论（1）
我认为你缺乏基本的Java概念。
在任何静态上下文中都没有“this”引用，即 static void main。
将“this”替换为“r”、“z3”的实例。
除此之外，你的 UI 代码确实到处都是，但这是另一个问题的讨论。
I think your basic Java concepts are lacking.
There is no "this" reference in any static context, i.e. static void main.
Replace "this" with your instance of "r", "z3".
Other than that, your UI code is really all over the place, but that's a discussion for another question.