通过Jpanel

Question

我有一个Jpanel类，每个类代表3个面板，用于自己的选项卡。它决定在面板上添加什么，以及什么不是。然后我有一个类，我存储程序使用的数据。但是当我创建3个实例时，每个选项卡一个，我必须确保每个实例的数据类相同，即使修改后仍然保持不变。

这里我实例化了标签，并传递了标签和数据的编号（Mensola）

    Mensola m = new Mensola(20);

    JTabbedPane tabbedPane = new JTabbedPane();

    JComponent panel1 = new MyPanel1(1,m);
    tabbedPane.addTab("Aggiungi",null ,panel1,"Aggiungi");

    JComponent panel2 = new MyPanel1(2,m);
    tabbedPane.addTab("Cerca",null, panel2,"Cerca");

    JComponent panel3 = new MyPanel1(3,m);
    tabbedPane.addTab("Togli",null, panel3,"Togli");

    add(tabbedPane);

    tabbedPane.setTabLayoutPolicy(JTabbedPane.SCROLL_TAB_LAYOUT);

小组类：

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;

public class MyPanel1 extends JPanel implements ActionListener, ListSelectionListener{

    private Libro temp;

    ActionEvent Event;

    Mensola m = new Mensola(20);

    private String sTemp = "Non conosiuto";

    private JLabel title;
    private JLabel author;
    private JLabel editor;
    private JLabel pages;
    private JLabel price;
    private JLabel type;
    private JLabel inProduzione;
    private JLabel message;
    private JLabel nummeroLibri;

    private JRadioButton si;
    private JRadioButton no;

    private ButtonGroup group;

    private JList list;

    private String[] generi = {"Horror", "Commedia", "Thriller", "Comic"}; 

    private JTextField titleField;
    private JTextField authorField;
    private JTextField editorField;
    private JTextField pagesField;
    private JTextField priceField;

    private JButton aggiungi;
    private JButton cerca;
    private JButton togli;  

    public MyPanel1(int sheet,Mensola x){

        m = x;

        this.setLayout(new FlowLayout());

        m = new Mensola(20);

        title = new JLabel("Titolo:  ");
        author = new JLabel("autore: ");
        editor = new JLabel("editore: ");
        pages = new JLabel("pagine: ");
        price = new JLabel("prezzo: ");

        type = new JLabel("genere: ");
        type.setPreferredSize(new Dimension(280,20));

        inProduzione = new JLabel("In porduzione: ");

        message = new JLabel("");
        message.setPreferredSize(new Dimension(280,170));

        nummeroLibri = new JLabel("Nummero di liberi: 0");

        list = new JList(generi);
        list.addListSelectionListener(this); 
        list.setPreferredSize(new Dimension(280,70));

        titleField = new JTextField("",20);
        authorField = new JTextField("",20);
        editorField = new JTextField("",20);
        pagesField = new JTextField("",20);
        priceField = new JTextField("",20);

        aggiungi = new JButton("Aggiungi Libro");
        aggiungi.addActionListener(this);
        aggiungi.setPreferredSize(new Dimension(280,30));

        cerca = new JButton("Cerca Libro In Base Al Titolo");
        cerca.addActionListener(this);
        cerca.setPreferredSize(new Dimension(280,30));

        togli = new JButton("Togli Libro In Base Al Titolo");
        togli.addActionListener(this);
        togli.setPreferredSize(new Dimension(280,30));

        si = new JRadioButton("Si");
        si.addActionListener(this); 
        no = new JRadioButton("No");
        no.addActionListener(this); 
        group = new ButtonGroup();
        group.add(si);
        group.add(no); 

        if(sheet == 1){
            this.add(title);
            this.add(titleField);
            this.add(author);
            this.add(authorField);
            this.add(editor);
            this.add(editorField);
            this.add(pages);
            this.add(pagesField);
            this.add(price);
            this.add(priceField);
            this.add(inProduzione);
            this.add(si);
            this.add(no);
            this.add(type);
            this.add(list);
            this.add(aggiungi);
            this.add(nummeroLibri);
            this.add(message);

        }else if (sheet == 2){
            this.add(title);
            this.add(titleField);
            this.add(cerca);
            this.add(nummeroLibri);
            this.add(message);

        }else {
            this.add(title);
            this.add(titleField);
            this.add(togli);
            this.add(nummeroLibri);
            this.add(message);  
        }
    }
}

Answer 1

如果我正确理解您的问题，您可能需要使用Singleton Design Pattern。

因此，不是每次都创建新对象，而是创建一个方法getInstance()，它创建一个新的Object（如果还没有现有的）或返回当前实例。因此，确保您始终使用对象的相同实例。

另一种方法是每次都使用构造函数变量，但是你不能创建一个新的Object，否则你将使用不同的实例。

编辑：澄清我的回答：

将方法getInstance()添加到Mensola类。简化为：

private static Mensola mensolaInstance;
[...]
public static Mensola getInstance() { 
     if (mensolaInstance == null)
         mensolaInstance = new Mensola(20); // or whatever
     return mensolaInstance;
}

您想要访问Mensola对象的任何时间和地点，只需使用Mensola.getInstance()即可。您不再需要将其作为参数传递。

所以A级需要Mensola，你可以从那里打电话给getInstance()。之后，B级需要与Mensola合作，您只需拨打getInstance()。