java - jTextField 和 Jpanel 颜色输出

Question

创建一个程序，您可以在文本字段中输入颜色名称，然后使用该颜色将面板背景颜色设置为文本字段中指定的颜色 我无法获取输出

import javax.swing.*;

import java.awt.Color;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.SwingUtilities;

public class textfield implements  ActionListener{

    JTextField Input;
    JPanel color;
    JButton Button;

    public JPanel createContentPane (){

        // We create a bottom JPanel to place everything on.
        JPanel totalGUI = new JPanel();
        totalGUI.setLayout(null);

        // Creation of a Panel to contain the JLabels
        Input = new JTextField ("color", 35);
        Input.setBackground (Color.white);
        Input.setLocation(50,50);
        Input.setSize(100, 30);
        Input.addActionListener (this);
        totalGUI.add(Input);

        color = new JPanel();
        color.setBackground (Color.white);
        color.setLocation(200, 50);
        color.setSize(200, 100);
        totalGUI.add(color);


        totalGUI.setOpaque(true);
        return totalGUI;
    }

    public void actionPerformed(ActionEvent e) {

        String text = Input.getText();
        { if (text == "green")
            color.setBackground(color.green);
        }
    }

    private static void createAndShowGUI() {

        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("Assignment");

        textfield demo = new textfield();
        frame.setContentPane(demo.createContentPane());

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 300);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Answer 1

有一些问题。

1. 您应该使用 equals 方法而不是 == 来比较字符串的相等性。

2. 将 color.green 更改为 Color.GREEN

   public void actionPerformed(ActionEvent e) {
   
       String text = Input.getText();
       if (text.equals("green"))
       {
           color.setBackground(Color.GREEN);
       }
   }
   

对于多种颜色，您可以使用if-else或切换大小写

使用if-else:

   public void actionPerformed(ActionEvent e) {

        String text = Input.getText();
        if (text.equals("green"))
        {
            color.setBackground(Color.GREEN);
        }
        else if(text.equals("red"))
        {
            color.setBackground(Color.RED);
        }
        else if(text.equals("yellow"))
        {
            color.setBackground(Color.YELLOW);
        }
        else
        {
            color.setBackground(Color.BLUE);
        }

    }

使用开关盒:

public void actionPerformed(ActionEvent e) {

    String text = Input.getText();

    switch (text) {
        case "green":
            color.setBackground(Color.GREEN);
            break;
        case "red":
            color.setBackground(Color.RED);
            break;
        case "yellow":
            color.setBackground(Color.YELLOW);
            break;
        case "blue":
            color.setBackground(Color.BLUE);
            break;

    }

}