如何从其他类访问 jFrame 的组件？

Question

我有两个类，第一个是NewJFrame.java。它的代码是-

package javaapplication10;
import java.awt.Label;
public class NewJFrame extends javax.swing.JFrame {

    public NewJFrame() {
        initComponents();
    }



    private void initComponents() {

        jButton1 = new javax.swing.JButton();
        f = new javax.swing.JTextField();
        l = new java.awt.Label();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jButton1.setText("jButton1");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });

        l.setText("label1");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(139, 139, 139)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(f, javax.swing.GroupLayout.PREFERRED_SIZE, 76, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addComponent(l, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jButton1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)))
                .addContainerGap(185, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(f, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addComponent(jButton1)
                .addGap(22, 22, 22)
                .addComponent(l, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(186, Short.MAX_VALUE))
        );

        pack();
    }

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        System.out.println("Calling");
        NewClass1 n = new NewClass1();
        n.st();

    }                                        



    public static void main(String args[]) {

        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }



        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
            }
        });
    }

    protected javax.swing.JTextField f;
    protected javax.swing.JButton jButton1;
    protected java.awt.Label l;

}

我正在使用 netbeans。 主要代码行是 -

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
            System.out.println("Calling");
            NewClass1 n = new NewClass1();
            n.st();

        } 

和变量声明

protected javax.swing.JTextField f;
protected javax.swing.JButton jButton1;
protected java.awt.Label l;

我的第二个类是 NewClass.java，它的代码是 - 包javaapplication10;

import java.awt.Label;
public class NewClass1 extends NewJFrame{

    public void st()

    {
        l.setText(f.getText());
    }

}

我要做的是单击按钮（jbutton1），并且必须在Label（l）中设置写在textfield（f）中的文本。 当我单击按钮时，控制台上打印了“呼叫”，但标签上的文本没有改变。问题是什么？请帮忙。

Answer 1

为什么不直接改JLabell的文字呢？通过以下方式：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) 
{                                         
  System.out.println("Calling");
  //NewClass1 n = new NewClass1();
  //n.st();
   l.setText(f.getText());   
}    

更新
好的，你去吧，如果你想通过子类来做：

把jButton1ActionPerformed改成这样：

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) 
{                                         
  System.out.println("Calling");
  NewClass1 n = new NewClass1(this);
  n.st();
}

并将NewClass的构造函数更改如下：

NewJFrame njf;
public NewClass(NewJFrame jf)
{
  this.nfj = jf;
}
public void st()
{
  nfj.l.setText(nfj.f.getText());
}