编译代码后出现两个错误。
错误是:
1。
local variable input is accessed within inner class;
needs to be declared final
String name = input.getText();
2。
local variable c_age is accessed within inner class;
needs to be declared final
Object child_age = c_age.getSelectedItem();
这是我的代码:
import javax.swing.*;
import java.awt.event.*;
public class GUI
{
public static void main(String[] args)
{
JFrame frame = new JFrame("Try GUI");
JLabel l1 = new JLabel("Please Enter Your Child's Name");
JTextField input = new JTextField("",10);
JLabel l2 = new JLabel("Choose Your Child's Age");
String[] age = {"Age","1","2","3","4","5","6"};
JComboBox c_age = new JComboBox(age);
JButton button = new JButton("Search");
JTextArea result = new JTextArea();
JScrollPane extend_area = new JScrollPane(result);
button.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent ae)
{
String name = input.getText();
Object child_age = c_age.getSelectedItem();
}
});
JPanel panel = new JPanel();
panel.add(l1);
panel.add(input);
panel.add(l2);
panel.add(c_age);
panel.add(button);
panel.add(extend_area);
frame.add(panel);
frame.setSize(350,350);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
我该如何解决这个错误?
您需要声明
JTextField input = new JTextField("",10);
和
JComboBox c_age = new JComboBox(age);
像这样:
final JTextField input = new JTextField("",10);
final JComboBox c_age = new JComboBox(age);
这意味着input
并且c_age
不能更改:
必须在内部类的主体之前明确分配在内部类中使用但未声明的任何局部变量。
摘自Java语言规范的部分-8.1.3内部类和封闭实例
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