使用一个按钮更改多个JPanel的颜色

Question

所以我有三个面板，我有三种不同的按钮，可以将它们分别更改为各自的颜色。我需要添加第四个按钮，将所有三个面板恢复到它们原来默认的浅灰色。我添加了这个"重置"按钮，它只会将第一个面板改回原位。我做错了什么？

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.FlowLayout;
import java.awt.Color;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class PanelDemo extends JFrame implements ActionListener
{
public static final int WIDTH = 300;
public static final int HEIGHT = 200;
private JPanel redPanel;
private JPanel whitePanel;
private JPanel bluePanel;
public static void main(String[] args)
{
PanelDemo gui = new PanelDemo();
gui.setVisible(true);
}
public PanelDemo()
{
super("Panel Demonstration");
setSize(WIDTH, HEIGHT);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
JPanel biggerPanel = new JPanel();
biggerPanel.setLayout(new GridLayout(1, 3));
redPanel = new JPanel();
redPanel.setBackground(Color.LIGHT_GRAY);
biggerPanel.add(redPanel);
whitePanel = new JPanel();
whitePanel.setBackground(Color.LIGHT_GRAY);
biggerPanel.add(whitePanel);
bluePanel = new JPanel();
bluePanel.setBackground(Color.LIGHT_GRAY);
biggerPanel.add(bluePanel);
add(biggerPanel, BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
buttonPanel.setBackground(Color.LIGHT_GRAY);
buttonPanel.setLayout(new FlowLayout());
JButton redButton = new JButton("Red");
redButton.setBackground(Color.RED);
redButton.addActionListener(this);
buttonPanel.add(redButton);
JButton whiteButton = new JButton("White");
whiteButton.setBackground(Color.WHITE);
whiteButton.addActionListener(this);
buttonPanel.add(whiteButton);
JButton blueButton = new JButton("Blue");
blueButton.setBackground(Color.BLUE);
blueButton.addActionListener(this);
buttonPanel.add(blueButton);
JButton resetButton = new JButton("Reset");
resetButton.setBackground(Color.LIGHT_GRAY);
resetButton.addActionListener(this);
buttonPanel.add(resetButton);
add(buttonPanel, BorderLayout.SOUTH);
}
@Override
public void actionPerformed(ActionEvent e)
{
String buttonString = e.getActionCommand();
if (buttonString.equals("Red"))
redPanel.setBackground(Color.RED);
else if (buttonString.equals("White"))
whitePanel.setBackground(Color.WHITE);
else if (buttonString.equals("Blue"))
bluePanel.setBackground(Color.BLUE);
else if (buttonString.equals("Reset"))
redPanel.setBackground(Color.LIGHT_GRAY);
else if (buttonString.equals("Reset"))
bluePanel.setBackground(Color.LIGHT_GRAY);
else if (buttonString.equals("Reset"))
whitePanel.setBackground(Color.LIGHT_GRAY);
else
System.out.println("Unexpected error.");

}
}

Answer 1

这是您的问题。每个面板上都有重置的if else。将下面的代码与您现有的代码进行比较。这只是一个简单的逻辑问题。

public void actionPerformed(ActionEvent e) {
String buttonString = e.getActionCommand();
if (buttonString.equals("Red"))
redPanel.setBackground(Color.RED);
else if (buttonString.equals("White"))
whitePanel.setBackground(Color.WHITE);
else if (buttonString.equals("Blue"))
bluePanel.setBackground(Color.BLUE);
else if (buttonString.equals("Reset")) {
redPanel.setBackground(Color.LIGHT_GRAY);
bluePanel.setBackground(Color.LIGHT_GRAY);
whitePanel.setBackground(Color.LIGHT_GRAY);
}
else
System.out.println("Unexpected error.");

还有一些建议。

• 不要扩展JFrame。只要用一个例子就可以了。这是更好的技巧
• 将以下内容作为构造函数中的最后一条语句。它将使面板在屏幕上居中

setLocationRelativeTo(null);
// or when using a frame instance.
frame.setLocationRelativeTo(null);