问题

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class RecallStudy extends JFrame implements KeyListener, ActionListener {

    // CREATION OF ELEMENTS
    JLabel recallLabel;
    JTextField enterText;
    String enterTex;  // Note: It seems like there's a typo here, it should be "enterText" instead of "enterTex"
    JTextField recieveText;  // Typo: It should be "receiveText" instead of "recieveText"
    JPanel displayInfo;
    GridBagConstraints constraints = new GridBagConstraints();

    public static void main(String[] args) {
        // MAKING THE WINDOW
        JFrame frame = new JFrame("RecallStudy");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);
        frame.setLocation(200, 200);
        frame.setContentPane(new RecallStudy());
        frame.pack();
        frame.setVisible(true);
    }

    // GRIDLAYOUT CONSTRUCTION
    public RecallStudy() {
        setLayout(new GridBagLayout());
        constraints.weightx = 3.0;
        constraints.weighty = 3.0;
        constraints.fill = GridBagConstraints.BOTH;
        int x, y; // for clarity
        constraints.gridheight = 2; // span two rows
        addGB(recieveText, x = 2, y = 1);
        constraints.gridheight = 2; // set it back
        addGB(enterText, x = 0, y = 1);
        constraints.gridwidth = 1; // span two columns
        addGB(new JLabel("Recall"), x = 1, y = 0);
        constraints.gridwidth = 2; // set it back
        addGB(new JLabel(""), x = 0, y = 0);
        constraints.gridwidth = 1;
        addGB(new JLabel(""), x = 2, y = 0);
        constraints.gridwidth = 1;
        addGB(new JLabel(""), x = 2, y = 2);
        constraints.gridwidth = 1;
        addGB(new JLabel(""), x = 0, y = 2);
        constraints.gridwidth = 1;

        // Set the proper restrictions on the listeners
        enterText.addKeyListener(this);
        recieveText.setEditable(false);
    }

    void addGB(Component component, int x, int y) {
        constraints.gridx = x;
        constraints.gridy = y;
        add(component, constraints);
    }

    public void keyTyped(KeyEvent e) {
        displayInfo(e, "KEY TYPED: ");
    }

    /** Handle the key pressed event from the text field. */
    public void keyPressed(KeyEvent e) {
        displayInfo(e, "KEY PRESSED: ");
    }

    /** Handle the key released event from the text field. */
    public void keyReleased(KeyEvent e) {
        displayInfo(e, "KEY RELEASED: ");
    }

    /** Handle the button click. */
    public void actionPerformed(ActionEvent e) {
        // Clear the text components.
        enterText.setText("");
        recieveText.setText(enterTex);

        // Return the focus to the typing area.
        enterText.requestFocusInWindow();
    }

    private void displayInfo(KeyEvent e, String keyStatus) {
        // Your implementation for displayInfo should be added here
    }
}

Note: The provided code seems to have some typographical errors, particularly in variable names ("enterTex" should be "enterText" and "recieveText" should be "receiveText"). Also, the displayInfo method is not implemented in the given code. If the code is still not working after correcting these issues, there might be other external factors causing the problem.

 import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class RecallStudy extends JFrame
implements KeyListener, 
ActionListener
{
//CREATION OF ELEMENTS
JLabel recallLabel;
JTextField enterText;
String enterTex;
JTextField recieveText;
JPanel displayInfo;
GridBagConstraints constraints = new GridBagConstraints();
public static void main (String [] args) {
//MAKING THE WINDOW
JFrame frame = new JFrame("RecallStudy");
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
frame.setSize(500, 500);
frame.setLocation(200, 200);
frame.setContentPane(new RecallStudy());
frame.pack();
frame.setVisible(true);
}
//GRIDLAYOUT CONSTRUCTION
public RecallStudy() {
setLayout(new GridBagLayout());
constraints.weightx = 3.0;
constraints.weighty = 3.0;
constraints.fill = GridBagConstraints.BOTH;
int x, y; // for clarity
constraints.gridheight = 2; // span two rows
addGB(recieveText,   x =2, y = 1);
constraints.gridheight = 2; // set it back
addGB(enterText,   x = 0, y = 1);
constraints.gridwidth = 1; // span two columns
addGB(new JLabel("Recall"),  x = 1, y = 0);
constraints.gridwidth = 2; // set it back
addGB(new JLabel(""), x = 0, y = 0);
constraints.gridwidth = 1;
addGB(new JLabel(""), x = 2, y =0);
constraints.gridwidth = 1;
addGB(new JLabel(""), x = 2, y = 2);
constraints.gridwidth = 1;
addGB (new JLabel(""), x = 0, y =2);
constraints.gridwidth = 1;
//Set the proper restrictions on the listeners
enterText.addKeyListener(this);
recieveText.setEditable(false);
}
void addGB(Component component, int x, int y) {
constraints.gridx = x;
constraints.gridy = y;
add(component, constraints);
}
public RecallStudy(String name) {
super (name);
}
public void keyTyped(KeyEvent e) {
displayInfo(e, "KEY TYPED: ");
}
/** Handle the key pressed event from the text field. */
public void keyPressed(KeyEvent e) {
displayInfo(e, "KEY PRESSED: ");
}
/** Handle the key released event from the text field. */
public void keyReleased(KeyEvent e) {
displayInfo(e, "KEY RELEASED: ");
}
/** Handle the button click. */
public void actionPerformed(ActionEvent e) {
//Clear the text components.
enterText.setText("");
recieveText.setText(enterTex);
//Return the focus to the typing area.
enterText.requestFocusInWindow();
}
private void displayInfo (KeyEvent e, String keyStatus) {
}
}

答案1

得分: 1

对于入门：

JTextField recieveText; // 声明字段，但不创建它！

所以应该是：

JTextField recieveText = new JTextField("没有空指针异常！");

然后：

JFrame frame = new JFrame("RecallStudy");
// ..
frame.setContentPane(new RecallStudy());

应该类似于：

JFrame frame = new RecallStudy();
// ..
frame.setTitle("RecallStudy");

但老实说，那段代码充满了 '错误'。最好是将其丢弃，在完成 Swing 教程的基础上重新开始。

> 但这似乎不是它无法运行的原因

始终复制/粘贴错误和异常输出！

JTextField recieveText; // declares the field, but does not create it!

JTextField recieveText = new JTextField("No NullPointerException!");

JFrame frame = new JFrame("RecallStudy");
// ..
frame.setContentPane(new RecallStudy());

JFrame frame = new RecallStudy();
// ..
frame.setTitle("RecallStudy");