Java swing 从 JTextField 获取输入

Question

我看到很多人问过这样的问题，但它没有回答我的问题。我在 Java 方面还很新。我正在尝试从JTextField 获取一些输入并将其作为String 返回，以便我可以使用它在不同的类中进行比较。这就是我认为的答案，我希望能够在课堂的任何其他部分使用str。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;

public class ClassFrame extends JFrame {

    private static final long serialVersionUID = 2451829341034438685L;

    public static JButton inputButton = new JButton("Send");
    public static JTextArea editTextArea = new JTextArea("Type Here!");
    public static JTextArea uneditTextArea = new JTextArea();

    public ClassFrame(String title) {
        //SET LAYOUT MANAGER (How it arranges components)
        setLayout(new BorderLayout());
        //////CREATE SWING COMPONENTS////////////
        //OUTPUT TEXT AREA
        uneditTextArea.setEditable(false);

        //INPUT TEXT AREA
        editTextArea.setBackground(Color.BLUE);
        editTextArea.setForeground(Color.WHITE);

        //SET CONTENT PANE
        Container c = getContentPane();

        //ADD COMPONENTS TO CONTENT PANE        
        c.add(uneditTextArea, BorderLayout.CENTER);
        c.add(editTextArea, BorderLayout.SOUTH);
        c.add(inputButton, BorderLayout.WEST);

        ClassFrame.inputButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                String str = editTextArea.getText();
                editTextArea.setText(" ");
                System.out.println(str);                
            }
        });
    }
}

Answer 1

查看我的 cmets。

package applet;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;


import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;


public class ClassFrame extends JFrame {


    private static final long serialVersionUID = 2451829341034438685L;

    public static JButton inputButton = new JButton("Send");
    public static JTextArea editTextArea = new JTextArea("Type Here!");
    public static JTextArea uneditTextArea = new JTextArea();

    // MA - Your String, defined here and usable throughout the class

    private String myString;

    public ClassFrame(String title) {

        // MA - Indent your code properly so that it's more readable to both you
        // and others

        //SET LAYOUT MANAGER (How it arranges components)
        setLayout(new BorderLayout());
        //////CREATE SWING COMPONENTS////////////
        //OUTPUT TEXT AREA
        uneditTextArea.setEditable(false);

        //INPUT TEXT AREA
        editTextArea.setBackground(Color.BLUE);
        editTextArea.setForeground(Color.WHITE);

        //SET CONTENT PANE
        Container c = getContentPane();

        //ADD COMPONENTS TO CONTENT PANE        
        c.add(uneditTextArea, BorderLayout.CENTER);
        c.add(editTextArea, BorderLayout.SOUTH);
        c.add(inputButton, BorderLayout.WEST);

        ClassFrame.inputButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {

                // MA - Using the class field myString to receive text from text area

                myString = editTextArea.getText();

                // MA - Don't use a space when you actually want an empty string.
                // As it stands, your code will test for a single space character.
                // You really want it to test whether the text area is empty.

                //editTextArea.setText(" ");

                // MA - Do this instead.  An empty string means the text area has
                // no input at all.

                editTextArea.setText("");

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

我建议您阅读 Java 中的变量作用域。你可以谷歌一下。

Answer 2

根据我对问题的理解，这是一个比较字符串并将输出附加到JTextArea 的简单示例。

public class Test
{
    private static String ENTER = "Enter";
    static JButton enterButton;
    public static JTextArea output;
    public static JTextField input;
    static JFrame frame;
    static JPanel panel;
    public static String testString = "test";

    public static void main(String... args)
    {
        try
        {
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
        createFrame();
    }

    public static void createFrame()
    {
        frame = new JFrame("Test");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        panel.setOpaque(true);
        ButtonListener buttonListener = new ButtonListener();
        output = new JTextArea(15, 50);
        output.setWrapStyleWord(true);
        output.setEditable(false);
        JScrollPane scroller = new JScrollPane(output);
        scroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
        scroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        JPanel inputpanel = new JPanel();
        inputpanel.setLayout(new FlowLayout());
        input = new JTextField(20);
        enterButton = new JButton("Enter");
        enterButton.setActionCommand(ENTER);
        enterButton.addActionListener(buttonListener);
        // enterButton.setEnabled(false);
        input.setActionCommand(ENTER);
        input.addActionListener(buttonListener);
        DefaultCaret caret = (DefaultCaret) output.getCaret();
        caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);
        panel.add(scroller);
        inputpanel.add(input);
        inputpanel.add(enterButton);
        panel.add(inputpanel);
        frame.getContentPane().add(BorderLayout.CENTER, panel);
        frame.pack();
        frame.setLocationByPlatform(true);
        // Center of screen
        // frame.setLocationRelativeTo(null);
        frame.setVisible(true);
        frame.setResizable(false);
        input.requestFocus();
    }

    public static class ButtonListener implements ActionListener
    {

        public void actionPerformed(final ActionEvent ev)
        {
            if (!input.getText().trim().equals(""))
            {
                String cmd = ev.getActionCommand();
                if (ENTER.equals(cmd))
                {
                    output.append(input.getText());
                    if (input.getText().trim().equals(testString)) output.append(" = " + testString);
                    else output.append(" != " + testString);
                    output.append("\n");
                }
            }
            input.setText("");
            input.requestFocus();
        }
    }
}