另一個JLabel的setText class. Java

Question

所以，我見過很多類似的問題，但它們都有點不同，似乎不適合我的問題。

因此，我有一個“主”class、一個“面板”class 和一個“日”class。在我的面板 class 中，我創建了一個 JFrame 對象，並在我的面板 class 中創建了一個 JTextFiton 當文本字段的內容是“星期一”時，我想顯示當天的名稱，而我在這一天上學。 為此，我想使用 JLabel。 由於顯示日期名稱等的方法在日期 class 內，我必須在面板 class 內創建 JLabel object，但在日期 class 內對其進行編輯。

但是，當我使用 text.setText("Test"); 它不編譯。 在Eclipse，報如下錯誤：text cannot be resolved (text is my JLabel object)。 我認為 Day class 根本不知道文本 object（即使我制作文本 object static，這在類似情況下有所幫助）。

編輯：根據 DevilsHnd 的提議進行了調整。 還是不行

Class 日：

package basicsPack;

import java.awt.Color;
import basicsPack.Panel.*;
import javax.swing.JLabel;

public class Day{
    
    boolean isSchool;
    String[] stunden;
    String name;
    
    
    public Day(boolean isSchool, String[] stunden, String name) {
        
        this.isSchool = isSchool;  
        this.stunden = stunden;
        this.name = name;
        
    }
    
    public void sagName() {
        
        System.out.println(this.isSchool);
        System.out.println(this.name);
        text.setText("Label Text"); //This is what gives an error.
    }
}

面板 Class：

package basicsPack;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Scanner;

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Panel extends JPanel implements ActionListener {
    
    //Screen Settings
    final int originalTileSize = 16;
    final int scale = 3;
    final int tileSize = originalTileSize * scale;
    final int maxScreenCol = 16;
    final int maxScreenRow = 12;
    final int screenWidth = tileSize * maxScreenCol;
    final int screenHeight = tileSize * maxScreenRow;
    
    JLabel text;
    JButton knopf;
    JTextField field;
    Tage days; 
    String textInhalt;
    
        public Panel(){
        
        this.setPreferredSize(new Dimension(screenWidth, screenHeight));
        this.setBackground(Color.black);
        this.setDoubleBuffered(true);
        this.setFocusable(true);
        
        //Initialize Button 
        knopf = new JButton("klick");
        knopf.addActionListener(this);
        knopf.setPreferredSize(new Dimension (100, 35));
        
        //Initialize Text field 
        field = new JTextField();
        field.setFont(new Font("Serif",Font.BOLD,30));
        field.setPreferredSize(new Dimension (200, 50));
        
        text = new JLabel("asd");
        text.setForeground(Color.red);
        
        this.add(field);
        this.add(knopf);
        this.add(text);

        }
    
    public void loop() {
        
        try (Scanner input = new Scanner(System.in))
        {

                System.out.println("welchen Tag? ");
            
                switch(textInhalt) 
                {
                
                case "Montag":
                    Montag.sagName();
                    break;
                    
                case "Dienstag":
                    Dienstag.sagName();
                    break;
                    
                case "Mittwoch":
                    Mittwoch.sagName();
                    break;
                    
                case "Donnerstag":
                    Donnerstag.sagName();
                    break;  
        
                case "Freitag":
                    Freitag.sagName();
                    break;
                
                case "Samstag":
                    Samstag.sagName();
                    break;
                    
                case "Sonntag":
                    Sonntag.sagName();
                    break;  
                }
            }   
        }
    
        static String[] monHours = {"Bio", "Bio", "Mathe", "Mathe", "Chemie", "Chemie", "frei", "Musik", "Musik"};
        static String[] dinHours = {"", "", "", "", "", "", "", "", ""};
        static String[] mitHours = {"", "", "", "", "", "", "", "", ""};
        static String[] donHours = {"", "", "", "", "", "", "", "", ""};
        static String[] freHours = {"", "", "", "", "", "", "", "", ""};
        static String[] samHours = {"", "", "", "", "", "", "", "", ""};
        static String[] sonHours = {"", "", "", "", "", "", "", "", ""};
        
        static Day Montag = new Tage(true, monHours, "Montag");
        static Day Dienstag = new Tage(true, dinHours, "Dinestag")  ;
        static Day Mittwoch = new Tage(true, mitHours, "Mittwoch")  ;
        static Day Donnerstag = new Tage(true, donHours, "Donnerstag")  ;
        static Day Freitag = new Tage(true, freHours, "Freitag")  ;
        static Day Samstag = new Tage(false, samHours, "Samstag")  ;
        static Day Sonntag = new Tage(false, sonHours, "Sonntag")  ;        
        
        
        @Override
        public void actionPerformed(ActionEvent e) {
            if(e.getSource()==knopf) {
    
                textInhalt = field.getText();
                loop();
            }
        }
}

Answer 1

您尚未將 JLabel 聲明為 class 成員以使其 class 成為全局成員，例如：

public class Panel extends JPanel implements ActionListener {

//Screen Settings
final int originalTileSize = 16;
final int scale = 3;
final int tileSize = originalTileSize * scale;
final int maxScreenCol = 16;
final int maxScreenRow = 12;
final int screenWidth = tileSize * maxScreenCol;
final int screenHeight = tileSize * maxScreenRow;

JButton knopf;
JTextField field;
JLabel text;        // <-- Added!!
Tage days; 
String textInhalt;

    public Panel(){
    
    this.setPreferredSize(new Dimension(screenWidth, screenHeight));
    this.setBackground(Color.black);
    this.setDoubleBuffered(true);
    this.setFocusable(true);
    
    //Initialize Button 
    knopf = new JButton("klick");
    knopf.addActionListener(this);
    knopf.setPreferredSize(new Dimension (100, 35));
    
    //Initialize Text field 
    field = new JTextField();
    field.setFont(new Font("Serif",Font.BOLD,30));
    field.setPreferredSize(new Dimension (200, 50));
    
    text = new JLabel("asd");       // <-- Modified!!
    text.setForeground(Color.red);
    
    this.add(field);
    this.add(knopf);

    // ......  The rest of you Panel class here  ......

當天class：

package basicsPack;

import java.awt.Color;
import basicsPack.Panel.*;
import javax.swing.JLabel;

public class Day {
    
    boolean isSchool;
    String[] stunden;
    String name;
    
    
    public Day(boolean isSchool, String[] stunden, String name) {
        this.isSchool = isSchool;  
        this.stunden = stunden;
        this.name = name;
    }
    
    public void sagName() {
        System.out.println(this.isSchool);
        System.out.println(this.name);
        Panel.text.setText("Label Text");  //  <---
    }
}

Answer 2

你的Day class 是一個數據 class。它根本不應該有任何對JPanel的引用。

這是Day class 的樣子：

package basicspack;

public class Day {

    boolean isSchool;
    String[] stunden;
    String name;

    public Day(boolean isSchool, String[] stunden, String name) {
        this.isSchool = isSchool;
        this.stunden = stunden;
        this.name = name;
    }

    public boolean isSchool() {
        return isSchool;
    }

    public void setSchool(boolean isSchool) {
        this.isSchool = isSchool;
    }

    public String[] getStunden() {
        return stunden;
    }

    public void setStunden(String[] stunden) {
        this.stunden = stunden;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

您可以通過調用Day getter 方法來更改ActionListener中JLabel的文本。

不要將您的類 ( Panel ) 命名為與 Java 標准類 ( java.awt.Panel ) 相同的名稱。