1

好的......我的问题相当直截了当，所以我怀疑不需要添加任何代码，但如果需要我会。

每当我创建一个 GUI 框架并向其中添加几个面板并运行我的应用程序时，内容不会显示，直到我重新调整窗口大小或在工具栏上将其最小化然后恢复它。可能是什么原因造成的，我该如何解决？

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingConstants;
public final class Calculator extends JFrame  
{
    //initialise various variables for use within the program
    //BUTTONS
    private final JButton additionButton = new JButton("+"); 
    private final JButton subtractionButton = new JButton("-");
    private final JButton divisionButton = new JButton("/");
    private final JButton multiplicationButton = new JButton("*");    

    //PANELS
    private JPanel operatorPanel;
    private JPanel operandPanel;

    //LABELS
    private JLabel operationLabel;    

    //constructor to initialise the frame and add components into it
    public Calculator()
    {
        super("Clancy's Calculator");
        setLayout(new BorderLayout(5, 10));
        setSize(370, 200);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setVisible(true);

        //create a message label to display the operation that has just taken place
        operationLabel = new JLabel("YOU HAVE PERFORMED SOME OPERATION",SwingConstants.CENTER);

        add(getOperatorPanel(), BorderLayout.NORTH);
        add(getOperandPanel(), BorderLayout.CENTER);
        add(operationLabel, BorderLayout.SOUTH);
    }

    //setter method for the operator panel
    public void setOperatorPanel()
    {
        operatorPanel = new JPanel();
        operatorPanel.setLayout(new FlowLayout());

        operatorPanel.add(additionButton);
        operatorPanel.add(subtractionButton);
        operatorPanel.add(multiplicationButton);
        operatorPanel.add(divisionButton);
    }
    //getter method for the operator panel
    public JPanel getOperatorPanel()
    {
        setOperatorPanel();
        return operatorPanel;
    }

    //setter method for operands panel
    public void setOperandPanel()
    {
        operandPanel = new JPanel();
        operandPanel.setLayout(new GridLayout(3, 2, 5, 5));

        //LABELS
        JLabel operandOneLabel = new JLabel("Enter the first Operand: ");
        JLabel operandTwoLabel = new JLabel("Enter the second Operand: ");
        JLabel answerLabel = new JLabel("ANSWER: ");

        //TEXT FIELDS
        JTextField operandOneText = new JTextField();   //retrieves one operand
        JTextField operandTwoText = new JTextField();   //retrieves another operand
        JTextField answerText = new JTextField();   //displays answer

        answerText.setEditable(false);  //ensure the answer field is not editable

        operandPanel.add(operandOneLabel);
        operandPanel.add(operandOneText);
        operandPanel.add(operandTwoLabel);
        operandPanel.add(operandTwoText);
        operandPanel.add(answerLabel);
        operandPanel.add(answerText);

    }
    //getter method for operand panel
    public JPanel getOperandPanel()
    {
        setOperandPanel();
        return operandPanel;
    }

    /** main method */
    public static void main(String[] args)
    {
        new Calculator();
    }
}
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1 回答 1

0

我注意到您正在以编程方式设置新的布局管理器。每当您添加、删除或更改 java gui 时，您都需要调用invalidate()或revalidate()让 java 重新创建 GUI。在解决问题invalidate()之前查看是否调用setVisible(true)

于 2013-07-19T19:23:37.050 回答