Question

我正在尝试为我的JFrame添加一个标题，因此它显示为“CBallMaze Ball Maze Application”，但每当我在创建JFrame时输入它时，它会在标题中给出错误消息。

如果我不尝试添加标题并且使用这样的公共静态void表示

，则此代码运行正常

CBallMaze JFrame = new CBallMaze();
JFrame.setSize(775, 650);
JFrame.createGUI();
JFrame.setVisible(true);

当前代码=

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

public class CBallMaze extends JFrame implements ActionListener 
{
//Below is where I have declared all the different objects I have used throughout my program

private JButton buttonRight, buttonLeft, buttonUp, buttonDown, buttonTL, buttonTR, buttonBL, buttonBR, buttonCenter, optionOne, optionTwo, optionThree, optionExit, scenarioAct, scenarioRun, scenarioReset;
private JPanel panelCentre, panelRight, panelBottom, buttonPanel, compassPanel, optionsPanel, selectionPanel, panelAct, panelRun, panelReset;
private JTextField optionTF, squareTF, directionTF;
private JLabel option, square, direction;
private Icon iconAct, iconRun, iconReset;

public static void main(String[] args)
{
    JFrame CBallMaze = new JFrame("Title");
    CBallMaze.setSize(775, 650);
    CBallMaze.createGUI();
    CBallMaze.setVisible(true);
}
private void createGUI()
{   
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    Container window = getContentPane();
    window.setLayout(new BorderLayout() );

    //Panels

    panelCentre = new JPanel();
    panelCentre.setPreferredSize(new Dimension(625, 450));
    panelCentre.setBackground(Color.RED);
    window.add(panelCentre);
    panelCentre.setLayout(new GridLayout(21, 30));

    panelRight = new JPanel();
    panelRight.setPreferredSize(new Dimension(180, 450));
    panelRight.setBackground(Color.WHITE);
    window.add(panelRight, BorderLayout.EAST);

    optionsPanel = new JPanel();
    optionsPanel.setPreferredSize(new Dimension(150, 100));
    optionsPanel.setBackground(Color.WHITE);
    panelRight.add(optionsPanel, BorderLayout.EAST);

    buttonPanel = new JPanel();
    buttonPanel.setPreferredSize(new Dimension(175, 100));
    buttonPanel.setBackground(Color.WHITE);
    panelRight.add(buttonPanel, BorderLayout.EAST);

    selectionPanel = new JPanel();
    selectionPanel.setPreferredSize(new Dimension(175, 150));
    selectionPanel.setBackground(Color.WHITE);
    panelRight.add(selectionPanel, BorderLayout.EAST);

    compassPanel = new JPanel();
    compassPanel.setPreferredSize(new Dimension(175, 300));
    compassPanel.setBackground(Color.BLUE);
    panelRight.add(compassPanel, BorderLayout.EAST);

    panelBottom = new JPanel();
    panelBottom.setPreferredSize(new Dimension(875, 50));
    panelBottom.setBackground(Color.WHITE);
    window.add(panelBottom, BorderLayout.SOUTH);

    panelAct = new JPanel();
    panelAct.setPreferredSize(new Dimension(200, 40));
    panelAct.setBackground(Color.WHITE);
    panelBottom.add(panelAct, BorderLayout.SOUTH);

    panelRun = new JPanel();
    panelRun.setPreferredSize(new Dimension(200, 40));
    panelRun.setBackground(Color.WHITE);
    panelBottom.add(panelRun, BorderLayout.SOUTH);

    panelReset = new JPanel();
    panelReset.setPreferredSize(new Dimension(200, 40));
    panelReset.setBackground(Color.WHITE);
    panelBottom.add(panelReset, BorderLayout.SOUTH);

    //Displays

    option = new JLabel("Option:    ");
    optionsPanel.add(option, BorderLayout.LINE_START);
    option.setEnabled(true);
    option.setForeground(Color.BLACK);
    option.setHorizontalAlignment(JLabel.LEFT);

    optionTF = new JTextField("");
    optionsPanel.add(optionTF, BorderLayout.LINE_END);
    optionTF.setEnabled(true);
    optionTF.setPreferredSize(new Dimension(50, 25));
    optionTF.setHorizontalAlignment(JTextField.CENTER);

    square = new JLabel("Square:   ");
    optionsPanel.add(square, BorderLayout.LINE_START);
    square.setEnabled(true);
    square.setForeground(Color.BLACK);
    square.setHorizontalAlignment(JLabel.LEFT);

    squareTF = new JTextField("");
    optionsPanel.add(squareTF, BorderLayout.LINE_END);
    squareTF.setEnabled(true);
    squareTF.setPreferredSize(new Dimension(50, 25));
    squareTF.setHorizontalAlignment(JTextField.CENTER);

    direction = new JLabel("Direction:  ");
    optionsPanel.add(direction, BorderLayout.LINE_START);
    direction.setEnabled(true);
    direction.setForeground(Color.BLACK);
    direction.setHorizontalAlignment(JLabel.LEFT);

    directionTF = new JTextField("");
    optionsPanel.add(directionTF, BorderLayout.LINE_END);
    directionTF.setEnabled(true);
    directionTF.setPreferredSize(new Dimension(50, 25));
    directionTF.setHorizontalAlignment(JTextField.CENTER);

    //buttons

    buttonTL = new JButton("");
    buttonPanel.add(buttonTL);
    buttonTL.setPreferredSize(new Dimension(45, 25));
    buttonTL.setEnabled(false);

    buttonUp = new JButton("^");
    buttonPanel.add(buttonUp);
    buttonUp.setPreferredSize(new Dimension(45, 25));
    buttonUp.addActionListener(this);

    buttonTR = new JButton("");
    buttonPanel.add(buttonTR); 
    buttonTR.setPreferredSize(new Dimension(45, 25));
    buttonTR.setEnabled(false);

    buttonLeft = new JButton("<");
    buttonPanel.add(buttonLeft);
    buttonLeft.setPreferredSize(new Dimension(45, 25));
    buttonLeft.addActionListener(this);

    buttonCenter = new JButton("");
    buttonPanel.add(buttonCenter);
    buttonCenter.setPreferredSize(new Dimension(45, 25));
    buttonCenter.setEnabled(false);

    buttonRight = new JButton(">");
    buttonPanel.add(buttonRight);
    buttonRight.setPreferredSize(new Dimension(45, 25));
    buttonRight.addActionListener(this);

    buttonBL = new JButton("");
    buttonPanel.add(buttonBL);
    buttonBL.setPreferredSize(new Dimension(45, 25));
    buttonBL.setEnabled(false);

    buttonDown = new JButton("v");
    buttonPanel.add(buttonDown);
    buttonDown.setPreferredSize(new Dimension(45, 25));
    buttonDown.addActionListener(this);

    buttonBR = new JButton("");
    buttonPanel.add(buttonBR);
    buttonBR.setPreferredSize(new Dimension(45, 25));
    buttonBR.setEnabled(false);

    optionOne = new JButton("Option One");
    selectionPanel.add(optionOne);
    optionOne.setPreferredSize(new Dimension(125, 25));

    optionTwo = new JButton("Option Two");
    selectionPanel.add(optionTwo);
    optionTwo.setPreferredSize(new Dimension(125, 25));

    optionThree = new JButton("Option Three");
    selectionPanel.add(optionThree);
    optionThree.setPreferredSize(new Dimension(125, 25));

    optionExit = new JButton("Exit");
    selectionPanel.add(optionExit);
    optionExit.setPreferredSize(new Dimension(125, 25));

    try
    {
        //iconAct = new ImageIcon(Toolkit.getDefaultToolkit().createImage(CBallMaze.class.getResource("Act.jpg")));
        iconAct = new ImageIcon("Act.jpg");
    }
    catch (Exception e)
    {
        System.err.println("Act Icon ImageIcon "+e);    
    }

    scenarioAct = new JButton("Act");
    scenarioAct.setIcon(iconAct);
    panelAct.add(scenarioAct);
    scenarioAct.addActionListener(this);
    scenarioAct.setPreferredSize(new Dimension(75, 30));

    try
    {
        //iconRun = new ImageIcon(Toolkit.getDefaultToolkit().createImage(CBallMaze.class.getResource("Run.jpg")));
        iconRun = new ImageIcon("Run.jpg");
    }
    catch (Exception e)
    {
        System.err.println("Run Icon ImageIcon "+e);    
    }

    scenarioRun = new JButton("Run");
    scenarioRun.setIcon(iconRun);
    panelRun.add(scenarioRun);
    scenarioRun.addActionListener(this);
    scenarioRun.setPreferredSize(new Dimension(75, 30));

    try
    {
        //iconReset = new ImageIcon(Toolkit.getDefaultToolkit().createImage(CBallMaze.class.getResource("Reset.jpg")));
        iconReset = new ImageIcon("Reset.jpg");
    }
    catch (Exception e)
    {
        System.err.println("Reset Icon ImageIcon "+e);  
    }

    scenarioReset = new JButton("Reset");
    scenarioReset.setIcon(iconReset);
    panelReset.add(scenarioReset);
    scenarioReset.addActionListener(this);
    scenarioReset.setPreferredSize(new Dimension(75, 30));

}
}

Answer 1

使用此JFrame CBallMaze = new JFrame("Title");，您可以创建一个JFrame变量并为其分配一个JFrame对象，然后期望它具有CBallMaze行为，这是不会发生的。相反，您需要创建一个CBallMaze对象并将其分配给CBallMaze变量。

所以改变这个：

JFrame CBallMaze = new JFrame("Title");
CBallMaze.setSize(775, 650);
CBallMaze.createGUI();
CBallMaze.setVisible(true);

到此：

CBallMaze cBallMaze = new CBallMaze("Title"); // different variable type and object
cBallMaze.setSize(775, 650); // note the variable begins with lower case letter
cBallMaze.createGUI();
cBallMaze.setVisible(true);

侧面建议：

摆脱所有这些setPreferredSize(...)调用，而是使用布局管理器和智能创建组件（即，为JTextFields提供列属性）来帮助创建一个简单而令人愉悦的GUI。
如果您打算调用带有String参数的构造函数，那么 make make 一个String参数的构造函数。第一行应该调用super(...)构造函数并将该String参数传递给。

对于类型JFrame，方法createGUI（）未定义

1 个答案: