java - 如何调整 GridLayout 中 JComponent 的大小？

Question

我是 Java 编程新手。您能帮我设计第一个应用程序(这是一个简单的计算器)吗？这是我写的代码:

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

class InputPad extends JFrame {

    private JLabel statusLabel;
    private JTextArea expTextArea;

    InputPad() {
        prepareGUI();
    }

    private void prepareGUI(){
        JFrame mainFrame = new JFrame("My Calculator");
        mainFrame.setSize(450,450);
        mainFrame.setLayout(new GridLayout(3,2));
        mainFrame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent){
                System.exit(0);
            }
        });

        JLabel headerLabel = new JLabel("Put your expression here:", JLabel.CENTER);
        statusLabel = new JLabel("",JLabel.CENTER);
        expTextArea = new JTextArea("1+(2^3*4)");

        //Digits Panel
        JPanel digitPanel = new JPanel();
        GroupLayout layoutDigits = new GroupLayout(digitPanel);
        digitPanel.setLayout(layoutDigits);
        layoutDigits.setAutoCreateGaps(true);
        layoutDigits.setAutoCreateContainerGaps(true);

        //Operators Panel
        JPanel operatorPanel = new JPanel();
        GroupLayout layoutOperators = new GroupLayout(operatorPanel);
        operatorPanel.setLayout(layoutOperators);
        layoutOperators.setAutoCreateGaps(true);
        layoutOperators.setAutoCreateContainerGaps(true);


        JButton[] numButtons= new JButton[10];

        int i;
        for (i=0;i<10;i++){
            numButtons[i] = new JButton(Integer.toString(i));
            numButtons[i].addActionListener(e -> {
//            TODO
            });
        }

        JButton bEquals = new JButton("=");
        bEquals.addActionListener(e -> {
//            TODO
        });

        JButton bPlus = new JButton("+");
        bPlus.addActionListener(e -> {
//            TODO
        });
        JButton bMinus = new JButton("-");
        bMinus.addActionListener(e -> {
//            TODO
        });
        JButton bMultiply = new JButton("*");
        bMultiply.addActionListener(e -> {
//            TODO
        });
        JButton bDivide = new JButton("/");
        bDivide.addActionListener(e -> {
//            TODO
        });
        JButton bLeftParenthesis = new JButton("(");
        bLeftParenthesis.addActionListener(e -> {
//            TODO
        });
        JButton bRightParenthesis = new JButton(")");
        bRightParenthesis.addActionListener(e -> {
//            TODO
        });
        JButton bPower = new JButton("^");
        bPower.addActionListener(e -> {
//            TODO
        });
        JButton bDel = new JButton("←");
        bDel.addActionListener(e -> {
//            TODO
        });


        layoutDigits.setHorizontalGroup(
                layoutDigits.createSequentialGroup()
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.LEADING)
                                .addComponent(numButtons[7])
                                .addComponent(numButtons[4])
                                .addComponent(numButtons[1])
                                .addComponent(numButtons[0]))
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.LEADING)
                                .addComponent(numButtons[8])
                                .addComponent(numButtons[5])
                                .addComponent(numButtons[2])
                                .addComponent(bEquals))
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.LEADING)
                                .addComponent(numButtons[9])
                                .addComponent(numButtons[6])
                                .addComponent(numButtons[3]))
        );
        layoutDigits.setVerticalGroup(
                layoutDigits.createSequentialGroup()
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(numButtons[7])
                                .addComponent(numButtons[8])
                                .addComponent(numButtons[9]))
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(numButtons[4])
                                .addComponent(numButtons[5])
                                .addComponent(numButtons[6]))
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(numButtons[1])
                                .addComponent(numButtons[2])
                                .addComponent(numButtons[3]))
                        .addGroup(layoutDigits.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(numButtons[0])
                                .addComponent(bEquals))
        );

        layoutOperators.setHorizontalGroup(
                layoutOperators.createSequentialGroup()
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.LEADING)
                                .addComponent(bPlus)
                                .addComponent(bMinus)
                                .addComponent(bLeftParenthesis)
                                .addComponent(bPower))
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.LEADING)
                                .addComponent(bMultiply)
                                .addComponent(bDivide)
                                .addComponent(bRightParenthesis)
                                .addComponent(bDel))
        );
        layoutOperators.setVerticalGroup(
                layoutOperators.createSequentialGroup()
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(bPlus)
                                .addComponent(bMultiply))
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(bMinus)
                                .addComponent(bDivide))
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(bLeftParenthesis)
                                .addComponent(bRightParenthesis))
                        .addGroup(layoutOperators.createParallelGroup(GroupLayout.Alignment.BASELINE)
                                .addComponent(bPower)
                                .addComponent(bDel))
        );


        mainFrame.add(headerLabel);
        mainFrame.add(expTextArea);
        mainFrame.add(digitPanel);
        mainFrame.add(operatorPanel);
        mainFrame.add(statusLabel);
        mainFrame.setVisible(true);
    }

}

我尝试了 JFrame 的 GridLayout，但除了主 JFrame 之外，我无法调整 JComponent 的大小。即使我无法将两个 JPanel(并排)放置在 GridLayout 的一个单元格中，也无法将 JLabel 扩展到 GridLayout 的两个单元格。

这就是我得到的:

这就是我想要的:

Answer 1

让我们从 Layout Managers 的使用开始，来自 GridLayout 的链接

GridLayout simply makes a bunch of components equal in size and displays them in the requested number of rows and columns

所以，这不是您想要的，但如果您阅读 GridBagLayout它说的部分:

GridBagLayout is a sophisticated, flexible layout manager. It aligns components by placing them within a grid of cells, allowing components to span more than one cell. The rows in the grid can have different heights, and grid columns can have different widths.

我们可以将它们两者结合起来，以及 BoxLayout您将得到与您想要实现的类似的输出:

<小时/>

请注意:

在发布代码之前，请注意以下提示:

1. 您正在扩展 JFrame 并同时创建 JFrame 对象，不鼓励这样做，请删除其中一个，在本例中当您使用该对象并且这是建议执行的操作时，只需从类中删除 extends JFrame 即可。如果您确实需要扩展某些内容，请不要扩展 JFrame，而是扩展 JPanel。

2. 将程序放入 EDT 中，就像我在 main() 方法中所做的那样

3. 不要使用 System.exit(0);，而是调用 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)，如上面的代码所示

<小时/>

现在是代码

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class CalculatorExample {
    private JFrame frame;
    private JTextArea area;
    private JButton[][] digitsButtons, symbolsButtons;
    private String[][] digitsText = {{"7", "8", "9"}, {"4", "5", "6"}, {"1", "2", "3"}, {"0", "="}}; //Looks strange but this will make the button adding easier
    private String[][] symbolsText = {{"+", "*"}, {"-", "/"}, {"(", ")"}, {"^", "←"}};
    private JPanel buttonsPane, areaAndResultsPane, digitsPane, symbolsPane;
    private JLabel label;
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new CalculatorExample().createAndShowGui();
            }
        });
    }
    
    public void createAndShowGui() {
        frame = new JFrame("Calculator Example");
        area = new JTextArea();
        area.setRows(5);
        area.setColumns(20);
        label = new JLabel("Results go here");
        digitsButtons = new JButton [4][3];
        symbolsButtons= new JButton [4][2];
        areaAndResultsPane = new JPanel();
        areaAndResultsPane.setLayout(new BoxLayout(areaAndResultsPane, BoxLayout.PAGE_AXIS));
        
        buttonsPane = new JPanel();
        buttonsPane.setLayout(new GridLayout(1, 2, 10, 10));
        
        digitsPane = new JPanel();
        digitsPane.setLayout(new GridBagLayout());
        
        symbolsPane = new JPanel();
        symbolsPane.setLayout(new GridLayout(4, 2));
        
        GridBagConstraints c = new GridBagConstraints();
        
        for (int i = 0; i < digitsText.length; i++) {
            for (int j = 0; j < digitsText[i].length; j++) {
                digitsButtons[i][j] = new JButton(digitsText[i][j]);
            }
        }
        
        for (int i = 0; i < symbolsText.length; i++) {
            for (int j = 0; j < symbolsText[i].length; j++) {
                symbolsButtons[i][j] = new JButton(symbolsText[i][j]);
            }
        }
        
        areaAndResultsPane.add(area);
        areaAndResultsPane.add(label);
        
        boolean shouldBreak = false;
        for (int i = 0; i < digitsButtons.length; i++) {
            for (int j = 0; j < digitsButtons[i].length; j++) {
                c.gridx = j;
                c.gridy = i;
                c.fill = GridBagConstraints.HORIZONTAL;
                c.weightx = 0.5;
                if (i == 3) {
                    if (j == 1) {
                        c.gridwidth = 2; //This makes the "=" button larger
                        shouldBreak = true;
                    }
                }
                digitsPane.add(digitsButtons[i][j], c);
                if (shouldBreak) {
                    break;
                }
            }
        }
        
        for (int i = 0; i < symbolsButtons.length; i++) {
            for (int j = 0; j < symbolsButtons[i].length; j++) {
                symbolsPane.add(symbolsButtons[i][j]);
            }
        }
        
        frame.add(areaAndResultsPane, BorderLayout.NORTH);
        buttonsPane.add(digitsPane);
        buttonsPane.add(symbolsPane);
        
        frame.add(buttonsPane, BorderLayout.CENTER);
        
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}

这是嵌套 JPanel 完成的，每个面板都有不同的布局，我希望它可以帮助您从这里继续。