調用從在另一個的JPanel

Question

的actionPerformed獲得一個實例變量我已經創建與cardLayout和第一個可見的JPanel一個JFrame具有我已經添加的動作偵聽器以執行一個動作一個JButton。該動作創建一個字符串變量'hhhhh'，我想在另一個JPanel中使用它。這是我遇到的問題。你可以這樣做

Class 1 

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

    public class NHome extends JFrame{ 


    JPanel Bucket= new JPanel(), Start= new JPanel(), Cashier = new csView(), Manager = new JPanel(); 
    JButton stbtn= new JButton("Start"), mnbtn= new JButton("Manager"), csbtn= new JButton("Cashier"); 
    CardLayout cl= new CardLayout(); 
    private final JTextField textField = new JTextField(); 
    private JPasswordField passwordField; 



    public NHome() { 
    textField.setBounds(322, 141, 158, 31); 
    textField.setColumns(10); 
    Bucket.setLayout(cl); 
    Bucket.add(Start, "1"); 
    Bucket.add(Cashier, "2"); 
    Bucket.add(Manager, "3"); 

    Start.setLayout(null); 
    stbtn.addActionListener(new ActionListener() { 
    public void actionPerformed(ActionEvent arg0) { 
    cl.show(Bucket, "2"); 

    /* 
    * I want to use this value of this String in the another class (csView) 
    */ 
    String hhhhh=new String("Peter"); 
    System.out.println(hhhhh); 
     } 
    }); 





    stbtn.setBounds(353, 245, 76, 23); 
    Start.add(stbtn); 

    Start.add(textField); 

    passwordField = new JPasswordField(); 
    passwordField.setBounds(322, 183, 158, 31); 
    Start.add(passwordField); 
    Cashier.setLayout(null); 
    csbtn.setBounds(197, 139, 116, 23); 

    Cashier.add(csbtn); 
    Manager.setBackground(Color.BLUE); 
    Manager.add(mnbtn); 

    cl.show(Bucket, "1"); 

    setTitle("NOVA PHARM"); 

    getContentPane().add(Bucket); 
    setBounds(300, 300, 566, 482); 
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    getContentPane().setLayout(new CardLayout(5, 5)); 
    setResizable(true); 


    } 
    /** 
    * Launch the application. 
    */ 
    public static void main(String[] args) { 
    EventQueue.invokeLater(new Runnable() { 
    public void run() { 
    try { 
    NHome window = new NHome(); 
    window.setVisible(true); 
    } catch (Exception e) { 
    e.printStackTrace(); 
    } 
    } 
    }); 
    } 
    } 

    /* 
    *this is the second class where I want to use the variable 
    */ 

2級

import javax.swing.JPanel; 
    import javax.swing.JLabel; 
    import javax.swing.JTextField; 
    import java.awt.Font; 

    public class csView extends JPanel { 

    /** 
    * Create the panel. 
    */ 
    public csView() { 
    setLayout(null); 
    /** 
    * I want to display the String hhhhh in the JLabel Uniqlbl below 
    * 
    */ 
    JLabel Uniqlbl = new JLabel("Cashier Name:"); 
    Uniqlbl.setFont(new Font("Tahoma", Font.PLAIN, 16)); 
    Uniqlbl.setBounds(227, 62, 253, 46); 
    add(Uniqlbl); 

    } 
    } 

Answer 1

嘗試修改csView

import javax.swing.JPanel; 
import javax.swing.JLabel; 
import javax.swing.JTextField; 
import java.awt.Font; 

public class csView extends JPanel { 
    // Declare those variables here 
    String hhhhh; 
    JLabel Uniqlbl; 

    public csView() { 
     setLayout(null); 

     Uniqlbl = new JLabel("Cashier Name:"); 
     Uniqlbl.setFont(new Font("Tahoma", Font.PLAIN, 16)); 
     Uniqlbl.setBounds(227, 62, 253, 46); 
     add(Uniqlbl); 

    } 

    // Add a setter here 
    public void setHhhhh(String hhhhh) { 
     this.hhhhh = hhhhh; 
     // Edit: Add this line to update the Uniqlbl text 
     Uniqlbl.setText(hhhhh); 
    } 
} 

而在ActionListener的調用setHhhhh（）方法

stbtn.addActionListener(new ActionListener() { 

    public void actionPerformed(ActionEvent arg0) { 
     cl.show(Bucket, "2"); 

     String hhhhh=new String("Peter"); 

     // Call the setter here 
     Cashier.setHhhhh(hhhhh); 

     System.out.println(hhhhh); 
    } 
}); 

我建議你不要在csView構造函數中使用「hhhhh」變量，或者你可能會遇到NullPointerException異常。或者，如果你想這樣做，像這樣首先初始化「hhhhh」變量

String hhhhh = ""; 

Answer 2

一種方法是創建一個在您NHome類作爲一個全局變量的靜態變量。這意味着比csView能夠讀取和寫入變量。

這是如何可以實現的示例：

JPanel Bucket = new JPanel(), Start = new JPanel(), Cashier = new csView(), Manager = new JPanel(); 
JButton stbtn = new JButton("Start"), mnbtn = new JButton("Manager"), csbtn = new JButton("Cashier"); 
CardLayout cl = new CardLayout(); 
private final JTextField textField = new JTextField(); 
private JPasswordField passwordField; 
static String hhhhh; //create the variable here 


public NHome() { 
     textField.setBounds(322, 141, 158, 31); 
     textField.setColumns(10); 
     Bucket.setLayout(cl); 
     Bucket.add(Start, "1"); 
     Bucket.add(Cashier, "2"); 
     Bucket.add(Manager, "3"); 

     Start.setLayout(null); 
     stbtn.addActionListener(new ActionListener() { 
      public void actionPerformed(ActionEvent arg0) { 
       cl.show(Bucket, "2"); 

       /* 
       * I want to use this value of this String in the another class (csView) 
       */ 
       hhhhh = new String("Peter"); //set the value here 
       System.out.println(hhhhh); 
      } 
     }); 

，那麼你可以說你csView實現它：

JLabel Uniqlbl = new JLabel(NHome.hhhhh);