Java ActionListener将变量返回到包含ActionListener的方法 [英] Java ActionListener Return Variable To Method That Contains ActionListener
问题描述
我有一个像这样的方法,该方法被赋予一个JButton
数组,并在每次按下它们时返回其文本:
I have a method like so, which is given an array of JButton
and returns their text whenever they are pressed:
public static String foo(JButton[] buttons) {
for (JButton i : buttons) {
i.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
return i.getText();
}
});
}
}
但是,当然,由于我将变量返回给null方法,因此该代码将无法编译.那么,我如何让i.getText()
以及foo()
方法也返回其输出?
But, of course, this code will not compile because I am returning a variable to a null method. So, how would I have i.getText()
return its output too the foo()
method?
编辑,所有代码:
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class JCustomFrame {
public static void showMessageFrame(String title, String message,
String[] textOnButtons, ImageIcon icon) {
final JFrame frame = new JFrame();
JPanel panel = new JPanel();
panel.setLayout(new GridBagLayout());
panel.setBackground(Color.WHITE);
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
c.fill = GridBagConstraints.RELATIVE;
c.gridx = 0;
c.gridy = 0;
c.insets = new Insets(5, 5, 5, 5);
JLabel messageLabel = new JLabel(message);
messageLabel.setFont(messageLabel.getFont().deriveFont(16.0f));
panel.add(messageLabel, c);
c.gridy = 1;
c.gridx = 0;
for (int i = 0; i < textOnButtons.length; i++) {
JButton button = new JButton(textOnButtons[i]);
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
return ((JButton) arg0.getSource()).getText();
frame.dispose();
}
});
button.setFont(button.getFont().deriveFont(16.0f));
panel.add(button, c);
c.gridx++;
}
if (icon == null) {
frame.setIconImage(new BufferedImage(1, 1,
BufferedImage.TYPE_INT_ARGB_PRE));
} else {
frame.setIconImage(icon.getImage());
}
frame.add(panel);
frame.setTitle(title);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.pack();
}
public static void main(String[] args) {
JCustomFrame.showMessageFrame("Test Frame",
"Do you really want to do this?", new String[] { "Hell No",
"Sure, Why Not" }, null);
}
}
推荐答案
此语句没有道理:
那么,我如何让i.getText()也通过foo()方法返回其输出?
So, how would I have i.getText() return its output too the foo() method?
在将ActionListeners添加到按钮之后,方法foo()
不再运行,并且根据事件驱动编程的规则,肯定会在用户按下按钮时结束.相反,尽管您可以让ActionListeners更改类的状态,但是任何类都足够了.例如:
The method foo()
is no longer running after the ActionListeners have been added to the buttons, and certainly will have ended by the time a user pushes a button, as per the rules of event-driven programming. Instead, though you could have the ActionListeners change the state of a class, any class, and that should suffice. For instance:
class FooClass {
private String text;
public void foo(JButton[] buttons) {
for (JButton i : buttons) {
i.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
text = e.getActionCommand();
}
});
}
}
}
如果您需要有关可行解决方案的更多详细信息,请告诉我们有关您的实际程序和特定问题的更多详细信息.
If you need greater detail on a viable solution, please tell us more details about your actual program and your specific problem.
现在,如果您实际上需要一种方法来返回按下的按钮的值,则需要通过通知机制和回调方法来执行此操作,但是解决方案的详细信息将取决于实际的详细信息.问题和代码.
Now if you actually needed a method to return the value of the button pressed, you would need to do this via notification mechanisms and a call-back method, but again the details of a solution will depend on the details of the actual problem and code.
修改
您正在尝试模拟JOptionPane.您的解决方案是使用JOptionPane,向其中添加JPanel或使用模式JDialog创建自己的JPanel:
You're trying to emulate a JOptionPane. Your solution is to either use a JOptionPane, adding a JPanel to it, or create your own using a modal JDialog:
import java.awt.Color;
import java.awt.Component;
import java.awt.Dialog.ModalityType;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JCustomFrame2 {
public static String showMessageFrame(Window owner, String title,
String message, String[] textOnButtons, ImageIcon icon) {
final JDialog dialog = new JDialog(owner);
StringBuilder sb = new StringBuilder();
// make it application modal!
dialog.setModalityType(ModalityType.APPLICATION_MODAL);
JPanel panel = new JPanel();
panel.setLayout(new GridBagLayout());
panel.setBackground(Color.WHITE);
GridBagConstraints c = new GridBagConstraints();
c.anchor = GridBagConstraints.EAST;
c.fill = GridBagConstraints.RELATIVE;
c.gridx = 0;
c.gridy = 0;
c.insets = new Insets(5, 5, 5, 5);
JLabel messageLabel = new JLabel(message);
messageLabel.setFont(messageLabel.getFont().deriveFont(16.0f));
panel.add(messageLabel, c);
c.gridy = 1;
c.gridx = 0;
for (int i = 0; i < textOnButtons.length; i++) {
JButton button = new JButton(textOnButtons[i]);
button.addActionListener(new ButtonListener(sb));
button.setFont(button.getFont().deriveFont(16.0f));
panel.add(button, c);
c.gridx++;
}
if (icon == null) {
dialog.setIconImage(new BufferedImage(1, 1,
BufferedImage.TYPE_INT_ARGB_PRE));
} else {
dialog.setIconImage(icon.getImage());
}
dialog.add(panel);
dialog.setTitle(title);
dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
dialog.pack();
dialog.setVisible(true);
return sb.toString();
}
private static class ButtonListener implements ActionListener {
private StringBuilder sb;
public ButtonListener(StringBuilder sb) {
this.sb = sb;
}
@Override
public void actionPerformed(ActionEvent e) {
sb.append(e.getActionCommand());
Component component = (Component) e.getSource();
Window win = SwingUtilities.getWindowAncestor(component);
if (win != null) {
win.dispose();
}
}
}
public static String showMessageFrame(String title,
String message, String[] textOnButtons, ImageIcon icon) {
return showMessageFrame(null, title, message, textOnButtons, icon);
}
public static void main(String[] args) {
String result = JCustomFrame2.showMessageFrame("Test Frame",
"Do you really want to do this?", new String[] { "Hell No",
"Sure, Why Not" }, null);
System.out.println(result);
}
}
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