JTextField 可以在网格布局中调整大小吗？

Question

下面是我测试BorderLayout和GridLayout的代码，但是我发现JPanel中的JTextField使用GridLayout是不可调整大小的，不管我改了多少次JTextField.setPreferredSize，它仍然保持不变。

public class Boderlayout implements ActionListener {
    JButton bCalculate;
    JLabel lPrinAmount,lInterestRate,lPayPerYear,lResult;
    JTextField tPrinAmount,tInterestRate,tPayPerYear,tResult;
    
    public static void main (String[] args) {
        new Boderlayout();
    }

    public Boderlayout() {
        JFrame frame = new JFrame();
        frame.setLayout(new BorderLayout());
        
        JPanel p2 = new JPanel();
        p2.setBackground(Color.BLUE);
        p2.setPreferredSize(new Dimension(600,100));
        frame.add(p2,BorderLayout.SOUTH);
        
        bCalculate = new JButton("Calculate");
        bCalculate.setPreferredSize(new Dimension(550,85));
        p2.add(bCalculate);
        bCalculate.addActionListener(this);
        
        JPanel p3 = new JPanel();
        p3.setBackground(Color.GREEN);
        p3.setLayout(new GridLayout(6,1));
        p3.setPreferredSize(new Dimension(300,300));
        frame.add(p3,BorderLayout.CENTER);
            
        lPrinAmount = new JLabel("Principle Amount: ");
        lPrinAmount.setPreferredSize(new Dimension(200,40));
        p3.add(lPrinAmount);
            
        tPrinAmount = new JTextField(20);
        tPrinAmount.setPreferredSize(new Dimension(170,40));
        p3.add(tPrinAmount);
            
        tPrinAmount.addActionListener(this);
            
        lInterestRate = new JLabel("Interest Rate: ");
        lInterestRate.setPreferredSize(new Dimension(200,40));
        p3.add(lInterestRate);
            
        tInterestRate = new JTextField(20);
        tInterestRate.setPreferredSize(new Dimension(100,40));
        p3.add(tInterestRate);
            
        tInterestRate.addActionListener(this);
            
        lPayPerYear = new JLabel("Payment Period (Year): ");
        lPayPerYear.setPreferredSize(new Dimension(200,40));
        p3.add(lPayPerYear);
            
        tPayPerYear = new JTextField(20);
        tPayPerYear.setPreferredSize(new Dimension(170,40));
        p3.add(tPayPerYear);
            
        tPayPerYear.addActionListener(this);
        
        JPanel p5 = new JPanel();
        p5.setLayout(new GridLayout(2,1));
        p5.setBackground(Color.WHITE);
        p5.setPreferredSize(new Dimension(300,300));
        frame.add(p5,BorderLayout.EAST);
        
        lResult = new JLabel("Result");
        lResult.setPreferredSize(new Dimension(170,40));
        p5.add(lResult);
            
        tResult = new JTextField(50);
        tResult.setPreferredSize(new Dimension(170,200));
        tResult.setEditable(false);
        p5.add(tResult);
        
        frame.pack();
        frame.setVisible(true);
    }
    
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
        if (e.getSource() == bCalculate) {
            double prinAmount = Double.parseDouble(tPrinAmount.getText());
            double interestRate = Integer.parseInt(tInterestRate.getText());
            double paymentYear = Integer.parseInt(tPayPerYear.getText());
            
            double interestRatePercentage = interestRate / 100;
            double loanInterest = prinAmount * interestRatePercentage;
            double year = 12 * paymentYear;
            double mortgageResult = (loanInterest * (Math.pow((1 + (interestRatePercentage / 12)), year)) / (Math.pow((1 + (interestRatePercentage) / 12), year) - 1)) / 12;
            
            String stringmortgageResult = Double.toString(mortgageResult);
            String newline = System.getProperty("line.separator");
            String finalResult = "Principle Amount: " + tPrinAmount.getText() + newline + "Interest Rate: " + tInterestRate.getText() + "%" + newline + "Payment Period: " + tPayPerYear.getText()
            + newline + "Mortgage: " + stringmortgageResult;
            tResult.setText(finalResult);
        }
    }
}

Answer 1

请参阅How to Use GridLayout。
这是该网页的引述：

GridLayout 对象将组件放置在单元格网格中。每个组件占用其单元格内的所有可用空间，并且每个单元格的大小完全相同。

换句话说，GridLayout不考虑它所包含的组件的首选大小。

一个布局管理器会考虑其包含的组件的首选大小是GridBagLayout。

BorderLayout 仅考虑其包含的组件的部分首选大小。对于EAST 组件，BorderLayout 使用其首选宽度但不使用其首选高度。 BorderLayout 最初将使用其 CENTER 组件的首选宽度和高度。

这是我在运行您的代码时得到的窗口。

这是您使用GridBagLayout 而不是GridLayout 修改后的代码。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BorderFactory;
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.JTextField;

public class Boderlayout implements ActionListener {
    JButton bCalculate;
    JLabel lPrinAmount, lInterestRate, lPayPerYear, lResult;
    JTextArea tResult;
    JTextField tPrinAmount, tInterestRate, tPayPerYear;

    public static void main(String[] args) {
        new Boderlayout();
    }

    public Boderlayout() {
        JFrame frame = new JFrame();

        JPanel p2 = new JPanel();
        p2.setBackground(Color.BLUE);
        p2.setPreferredSize(new Dimension(600, 100));
        frame.add(p2, BorderLayout.SOUTH);

        bCalculate = new JButton("Calculate");
        bCalculate.setPreferredSize(new Dimension(550, 85));
        p2.add(bCalculate);
        bCalculate.addActionListener(this);

        JPanel p3 = new JPanel();
        p3.setBackground(Color.GREEN);
        p3.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        p3.setPreferredSize(new Dimension(300, 300));
        frame.add(p3, BorderLayout.CENTER);

        lPrinAmount = new JLabel("Principle Amount: ");
        lPrinAmount.setPreferredSize(new Dimension(200, 40));
        gbc.gridx = 0;
        gbc.gridy = 0;
        p3.add(lPrinAmount, gbc);

        tPrinAmount = new JTextField(20);
        tPrinAmount.setPreferredSize(new Dimension(170, 40));
        gbc.gridy = 1;
        p3.add(tPrinAmount, gbc);

        tPrinAmount.addActionListener(this);

        lInterestRate = new JLabel("Interest Rate: ");
        lInterestRate.setPreferredSize(new Dimension(200, 40));
        gbc.gridy = 2;
        p3.add(lInterestRate, gbc);

        tInterestRate = new JTextField(20);
        tInterestRate.setPreferredSize(new Dimension(100, 40));
        gbc.gridy = 3;
        p3.add(tInterestRate, gbc);

        tInterestRate.addActionListener(this);

        lPayPerYear = new JLabel("Payment Period (Year): ");
        lPayPerYear.setPreferredSize(new Dimension(200, 40));
        gbc.gridy = 4;
        p3.add(lPayPerYear, gbc);

        tPayPerYear = new JTextField(20);
        tPayPerYear.setPreferredSize(new Dimension(170, 40));
        gbc.gridy = 5;
        p3.add(tPayPerYear, gbc);

        tPayPerYear.addActionListener(this);

        JPanel p5 = new JPanel();
        p5.setLayout(new BoxLayout(p5, BoxLayout.PAGE_AXIS));
        p5.setBackground(Color.WHITE);
        p5.setPreferredSize(new Dimension(300, 300));
        frame.add(p5, BorderLayout.EAST);

        lResult = new JLabel("Result");
        lResult.setPreferredSize(new Dimension(170, 40));
        p5.add(lResult);

        tResult = new JTextArea();
        tResult.setPreferredSize(new Dimension(170, 200));
        tResult.setEditable(false);
        tResult.setBorder(BorderFactory.createLineBorder(Color.darkGray));
        p5.add(tResult);

        frame.pack();
        frame.setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == bCalculate) {
            double prinAmount = Double.parseDouble(tPrinAmount.getText());
            double interestRate = Integer.parseInt(tInterestRate.getText());
            double paymentYear = Integer.parseInt(tPayPerYear.getText());

            double interestRatePercentage = interestRate / 100;
            double loanInterest = prinAmount * interestRatePercentage;
            double year = 12 * paymentYear;
            double mortgageResult = (loanInterest
                    * (Math.pow((1 + (interestRatePercentage / 12)), year))
                    / (Math.pow((1 + (interestRatePercentage) / 12), year) - 1)) / 12;

            String stringmortgageResult = Double.toString(mortgageResult);
            String newline = System.getProperty("line.separator");
            String finalResult = "Principle Amount: " + tPrinAmount.getText() + newline
                    + "Interest Rate: " + tInterestRate.getText() + "%" + newline
                    + "Payment Period: " + tPayPerYear.getText() + newline + "Mortgage: "
                    + stringmortgageResult;
            tResult.setText(finalResult);
        }
    }
}

这是我运行上述代码时得到的窗口。

请注意，我将tResult 更改为JTextArea 而不是JTextField。