Swing/Java: How to use the getText and setText str

问题:

I'm trying to make input nameField appear in a Label called label1 after a Button called button1 is clicked. Right now it says: 'txt' and I understand why. But I don't know how I can use the string! Can anyone explain me what I'm doing wrong and how to use this string properly?

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class thisismytest2 {
    public static void main(String[] args) {

        final JFrame frame = new JFrame();  
        JPanel panel = new JPanel();    
        JTextField nameField = new JTextField("...", 2);    
        JButton button1 = new JButton();
        final JLabel label1 = new JLabel();
        label1.setText("txt");
        label1.setVisible(false);
        String txt = nameField.getText();

        frame.add(panel);
        panel.add(button1);
        panel.add(label1);
        frame.setSize(200,200);
        frame.setVisible(true);
        panel.add(nameField);
        frame.setSize(600,400); 
        nameField.setBounds(400, 40, 400, 30);

        button1.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent arg0) {

                label1.setVisible(true);
            }
        });
        }
        }

回答1:

You are setting the label text before the button is clicked to "txt". Instead when the button is clicked call setText() on the label and pass it the text from the text field.

Example:

label1.setText(nameField.getText()); 

回答2:

in your action performed method, call:

label1.setText(nameField.getText());

This way, when the button is clicked, label will be updated to the nameField text.

回答3:

the getText method returns a String, while the setText receives a String, so you can write it like label1.setText(nameField.getText()); in your listener.

回答4:

Setup a DocumentListener on nameField. When nameField is updated, update your label.

http://download.oracle.com/javase/1.5.0/docs/api/javax/swing/JTextField.html