问题
I have an example of a error in my program. I created 4 buttons: 1, 2, 3, 4. Button 2 overlaps button 4, and i just added events for 2 and 4.
If I click on Button 2, it will be hidden, and Button 4 will be displayed. And if I click on Button 4, Button 2 will be displayed, and Button 4 will be covered by Button 2 again. As if anything happened, but, when I click on Button 1 or Button 3 after doing the above, Button 4 will be displayed, when I point at it (not click), it will disappear.
public class UI extends JFrame {
public UI(String title) {
Container container = this.getContentPane();
container.setLayout(null);
JButton btn1 = new JButton("1");
btn1.setBounds(10, 10, 50, 50);
btn1.setBackground(Color.RED);
JButton btn2 = new JButton("2");
btn2.setBounds(10, 70, 50, 50);
btn2.setBackground(Color.GREEN);
JButton btn3 = new JButton("3");
btn3.setBounds(10, 130, 50, 50);
btn3.setBackground(Color.BLUE);
JButton btn4 = new JButton("4");
btn4.setBounds(10, 70, 50, 50);
btn4.setBackground(Color.YELLOW);
container.add(btn1);
container.add(btn2);
container.add(btn3);
container.add(btn4);
btn2.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
btn2.setVisible(false);
}
});
btn4.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
btn2.setVisible(true);
}
});
this.setSize(400, 500);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.setVisible(true);
}
}
Single column of colored buttons
回答1:
You simply have an error in the actionPerformed() methods. You need to change the visibility of both JButtons, not just one.
Here is your code. I only added two lines and they are indicated by the comment // ADDED THIS LINE
public class UI extends JFrame {
public UI(String title) {
Container container = this.getContentPane();
container.setLayout(null);
JButton btn1 = new JButton("1");
btn1.setBounds(10, 10, 50, 50);
btn1.setBackground(Color.RED);
JButton btn2 = new JButton("2");
btn2.setBounds(10, 70, 50, 50);
btn2.setBackground(Color.GREEN);
JButton btn3 = new JButton("3");
btn3.setBounds(10, 130, 50, 50);
btn3.setBackground(Color.BLUE);
JButton btn4 = new JButton("4");
btn4.setBounds(10, 70, 50, 50);
btn4.setBackground(Color.YELLOW);
btn4.setVisible(false); // Initially we only want to see 'btn2'.
container.add(btn1);
container.add(btn2);
container.add(btn3);
container.add(btn4);
btn2.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
btn2.setVisible(false);
btn4.setVisible(true); // ADDED THIS LINE
}
});
btn4.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
btn2.setVisible(true);
btn4.setVisible(false); // ADDED THIS LINE
}
});
this.setSize(400, 500);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new UI("UI"));
}
}
Note that although the code works without it, I think you should set the initial visibility of btn4 to false. I have also done this in the above code.
回答2:
Here's a GUI where button 2 changes into button 4.
How did I make this happen? Simple. I only used three JButtons.
I changed the text of the second button and the background color of the second button, just like Andrew Thompson suggested.
Here's the complete runnable code. What do you know, it's a minimal runnable example!
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JButtonExampleGUI implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new JButtonExampleGUI());
}
private Color buttonColor;
private JButton button2;
private String buttonText;
public JButtonExampleGUI() {
this.buttonColor = Color.GREEN;
this.buttonText = "2";
}
@Override
public void run() {
JFrame frame = new JFrame("JButton Example GUI");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createButtonPanel(),BorderLayout.CENTER);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private JPanel createButtonPanel() {
JPanel panel = new JPanel(new GridLayout(0, 1, 10, 10));
panel.setPreferredSize(new Dimension(400, 500));
Font font = panel.getFont().deriveFont(60f);
JButton button1 = new JButton("1");
button1.setBackground(Color.RED);
button1.setForeground(Color.WHITE);
button1.setFont(font);
panel.add(button1);
button2 = new JButton(buttonText);
button2.addActionListener(new Button2Listener());
button2.setBackground(buttonColor);
button2.setFont(font);
panel.add(button2);
JButton button3 = new JButton("3");
button3.setBackground(Color.BLUE);
button3.setForeground(Color.WHITE);
button3.setFont(font);
panel.add(button3);
return panel;
}
public void updateButton2() {
button2.setText(buttonText);
button2.setBackground(buttonColor);
}
public class Button2Listener implements ActionListener {
@Override
public void actionPerformed(ActionEvent event) {
JButton button = (JButton) event.getSource();
String text = button.getText();
if (text.contentEquals("2")) {
buttonText = "4";
buttonColor = Color.YELLOW;
} else {
buttonText = "2";
buttonColor = Color.GREEN;
}
updateButton2();
}
}
}
来源：https://stackoverflow.com/questions/65318746/buttons-overlap-or-disappear