java - 我应该使用什么布局管理器？

Question

我正在创建一个应用程序来测试系统托盘，但我不知道应该使用什么布局管理器来使其看起来像这样:

我遇到的问题是我无法垂直对齐 textField 中的文本，所以我想:“为什么不使用布局管理器并使其随消息缩放。”对此您有何看法？

Answer 1

简单:使用布局的组合。整体的 BorderLayout，JLabel 位于 PAGE_START 位置，JScrollPane/JTextArea 位于 CENTER 位置。以及在 PAGE_END 位置使用 JPanel 并持有 JButton 的 FlowLayout.RIGHT。

例如，

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import javax.swing.*;

@SuppressWarnings("serial")
public class FooPanel extends JPanel {
    private static final String PROMPT = "This is prompt text:";
    private static final int TA_ROWS = 10;
    private static final int TA_COLS = 30;
    private static final int GAP = 5; 

    private JTextArea textArea = new JTextArea(TA_ROWS, TA_COLS);

    public FooPanel() {
        JPanel bottomPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
        bottomPanel.add(new JButton("Submit"));

        setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setLayout(new BorderLayout(GAP, GAP));
        add(new JLabel(PROMPT), BorderLayout.PAGE_START);
        add(new JScrollPane(textArea), BorderLayout.CENTER);
        add(bottomPanel, BorderLayout.PAGE_END);
    }

    private static void createAndShowGui() {
        FooPanel mainPanel = new FooPanel();

        JFrame frame = new JFrame("FooPanel");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            createAndShowGui();
        });
    }
}

或者，底部 JPanel 可以使用 BoxLayout 并水平粘合将按钮推到上面:

        JPanel bottomPanel = new JPanel();
        bottomPanel.setLayout(new BoxLayout(bottomPanel, BoxLayout.LINE_AXIS));
        bottomPanel.add(Box.createHorizontalGlue());
        bottomPanel.add(new JButton("Submit"));

在模式对话框中使用上述内容的示例，并展示如何在 JTextArea 中换行:

import java.awt.BorderLayout;
import java.awt.Dialog.ModalityType;
import java.awt.FlowLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import javax.swing.*;

@SuppressWarnings("serial")
public class FooPanel extends JPanel {
    private static final int TA_ROWS = 10;
    private static final int TA_COLS = 30;
    private static final int GAP = 5;

    private JTextArea textArea = new JTextArea(TA_ROWS, TA_COLS);

    public FooPanel(String prompt) {
        textArea.setWrapStyleWord(true);
        textArea.setLineWrap(true);

        JPanel bottomPanel = new JPanel();
        bottomPanel.setLayout(new BoxLayout(bottomPanel, BoxLayout.LINE_AXIS));
        bottomPanel.add(Box.createHorizontalGlue());
        bottomPanel.add(new JButton(new SendAction("Send", KeyEvent.VK_S)));

        setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setLayout(new BorderLayout(GAP, GAP));
        add(new JLabel(prompt), BorderLayout.PAGE_START);
        add(new JScrollPane(textArea), BorderLayout.CENTER);
        add(bottomPanel, BorderLayout.PAGE_END);
    }

    public String getText() {
        return textArea.getText();
    }

    private class SendAction extends AbstractAction {
        public SendAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic); // alt-key shortcut mnemonic
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            // simply dispose of this window
            Window win = SwingUtilities.getWindowAncestor(FooPanel.this);
            win.dispose();
        }
    }

    private static void createAndShowGui() {
        String prompt = "Enter the text that is to be displayed in the tray:";
        final FooPanel mainPanel = new FooPanel(prompt);

        final JFrame frame = new JFrame("FooPanel");
        final JTextArea displayArea = new JTextArea(TA_ROWS, TA_COLS);
        displayArea.setFocusable(false);
        displayArea.setEditable(false);
        displayArea.setWrapStyleWord(true);
        displayArea.setLineWrap(true);

        final JDialog dialog = new JDialog(frame, "Enter Text", ModalityType.APPLICATION_MODAL);
        dialog.add(mainPanel);
        dialog.pack();

        JPanel framePanel = new JPanel(new BorderLayout());
        framePanel.add(new JScrollPane(displayArea), BorderLayout.CENTER);
        framePanel.add(new JPanel() {
            {
                add(new JButton(new AbstractAction("Show Dialog") {
                    {
                        putValue(MNEMONIC_KEY, KeyEvent.VK_S);
                    }

                    public void actionPerformed(ActionEvent e) {
                        dialog.setLocationRelativeTo(frame);
                        dialog.setVisible(true);

                        String text = mainPanel.getText();
                        displayArea.setText(text);
                    };
                }));
            }
        }, BorderLayout.PAGE_END);

        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(framePanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> {
            createAndShowGui();
        });
    }
}