Функция «Действие» Actionization в JAVA

Question

Цель моей программы - ввести текст в текстовое поле. После нажатия кнопки кнопка ActionEvent должна загладить текст и печатать его в текстовой области под кнопкой. Я разместил свой код ниже, но я не уверен, почему он не делает то, что я описал. Это дает мне ошибку: "

Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation  problems: 
field1 cannot be resolved 
area1 cannot be resolved 

at SecondLab.actionPerformed(SecondLab.java:24) 
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) 
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) 
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) 
at javax.swing.DefaultButtonModel.setPressed(Unknown Source) 
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source) 
at java.awt.Component.processMouseEvent(Unknown Source) 
at javax.swing.JComponent.processMouseEvent(Unknown Source) 
at java.awt.Component.processEvent(Unknown Source) 
at java.awt.Container.processEvent(Unknown Source) 
at java.awt.Component.dispatchEventImpl(Unknown Source) 
at java.awt.Container.dispatchEventImpl(Unknown Source) 
at java.awt.Component.dispatchEvent(Unknown Source) 
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) 
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) 
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) 
at java.awt.Container.dispatchEventImpl(Unknown Source) 
at java.awt.Window.dispatchEventImpl(Unknown Source) 
at java.awt.Component.dispatchEvent(Unknown Source) 
at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
at java.awt.EventQueue.access$200(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
at java.awt.EventQueue$4.run(Unknown Source) 
at java.awt.EventQueue$4.run(Unknown Source) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) 
at java.awt.EventQueue.dispatchEvent(Unknown Source) 
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
at java.awt.EventDispatchThread.run(Unknown Source) 

И код:.

import javax.swing.*; 

import java.awt.event.*; 
import java.awt.*; 
import java.io.*; 

public class SecondLab extends JFrame implements ActionListener{ 
public SecondLab() { 
    setLayout(new GridLayout(3, 1, 5, 5)); 

    JTextField field1 = new JTextField(); 
    JTextArea area1 = new JTextArea(); 
    area1.setEditable(false); 
    JButton jbtSubmit = new JButton("Submit"); 
    jbtSubmit.addActionListener(this); 
    add(field1); 
    add(jbtSubmit); 
    add(area1); 


} 

public void actionPerformed(ActionEvent a) { 
String text = field1.getText(); 
String upper = text.toUpperCase(); 
area1.setText(upper); 


} 

public static void main(String[] args) { 
    SecondLab frame = new SecondLab(); 
    frame.setTitle("Lab #2"); //Sets the window title 
    frame.setSize(500, 400); //Starts with a default size 
    frame.setLocationRelativeTo(null); //Starts in center of screen 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Tells the program to end after closing 
    frame.setVisible(true); //Tells the frame to show up 
} 

} 

Answer 1

Переменные field1 и area1 определяются только в пределах объема SecondLab конструктора Объявите это в качестве экземпляра класса переменных

private JTextField field1; 
private JTextArea area1; 

, чтобы сделать их видимыми с помощью метода actionPerformed. Также не забудьте удалить начальные ключевые слова в th е задания

field1 = new JTextField(); 
area1 = new JTextArea(); 

Read: Understanding Class Members