Question

I want to print a String in a JLabel

我为此使用了此代码，但它没有打印，请问哪里出错了代码是通过JLabel在JFrame中显示日期首先我为一天制作了一个字符串然后我得到了日历并用它来获得 DAY_OF_WEEK 并通过 usind 如果我不打印日期但它没有打印为什么我不知道请更正它

package com.lalankumar.widget;

import javax.swing.*;

import java.awt.Color;
import java.io.*;
import java.awt.Font;
import java.util.*;

    public class RWidget extends JFrame{
    
        String wday;
        int d;
        public RWidget() {
            
             Calendar c = Calendar.getInstance();
            d= c.get(Calendar.DAY_OF_WEEK);
          Font dayFont = new Font("Courier", Font.BOLD, 25);        
           Font routine = new Font("Courier", Font.ITALIC, 15);                
            setUndecorated(true);
            setLocation(1168,0);
            setSize(200,200);
            setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
             setVisible(true);
            setBackground(new Color(1.0f,1.0f,1.0f,0.1f));
                
                if(d==2) {
                    wday="Monday";                       
                } else if(d==3) {
                     wday="Tuesday";                         
                } else if(d==4) {
                    wday="Wednesday";                       
                } else if(d==5) {
                    wday="Thursday";                        
                } else if(d==6) {
                    wday="Friday";                      
                } else if(d==7) {
                    wday="Saturday";                        
                } else {
                    wday="Sunday";                      
                }
                JLabel dayl= new JLabel(wday);                  
                dayl.setFont(dayFont);                  
                
        }           
        
        public static void main(String[] args) {
            new RWidget();   
        }
          }

请快点帮忙

上面给出了完整的代码请检查哪里出错或为什么它不工作。

Answer 1

您正在创建一个新的 JLabel，您正在为其设置文本，但您没有将其添加到您的 JFrame。

我将逐步简化您的代码，并对更改的作用添加一些注释：

package com.lalankumar.widget;

import javax.swing.*;

import java.awt.Color;
import java.io.*;
import java.awt.Font;
import java.util.*;

    public class RWidget extends JFrame{
    
        // String wday; we don't need this variable
        // int d; this can be a local variable
        public RWidget() {
            
            Calendar c = Calendar.getInstance();
            int d= c.get(Calendar.DAY_OF_WEEK);
            Font dayFont = new Font("Courier", Font.BOLD, 25);        
            Font routine = new Font("Courier", Font.ITALIC, 15);
            JLabel text = new JLabel(""); // create a new JLabel, and set the font
            text.setFont(dayFont);
            this.add(text); // add the new Label to the JFrame
            // if you add a String to the constructor, you'll see that immediately on the JFrame
            
            setUndecorated(true);
            setLocation(1168,0);
            setSize(200,200);
            setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
            setVisible(true);
            // comment this, to make the jFrame easier to see
            // setBackground(new Color(1.0f,1.0f,1.0f,0.1f));
                // replace the conditions by a switch to improve readability
                switch(d) {
                   case 2: text.setText("Monday"); break;
                   case 3: text.setText("Tuesday"); break;
                   case 4: text.setText("Wednesday"); break;
                   case 5: text.setText("Thursday"); break;
                   case 6: text.setText("Friday"); break;
                   case 7: text.setText("Saturday"); break;
                   default: text.setText("Sunday");
                }
                // don't create a new JLabel
                // JLabel dayl= new JLabel(wday);                  
                // dayl.setFont(dayFont);                  
                
        }           
        
        public static void main(String[] args) {
            new RWidget();   
        }
          }

你还可以做什么，而不是开关：

String[] days = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
text.setText(days[d-1]);

使用 JLabel 在 JFrame 中打印的问题

1 个答案: