如何在JFrame中排列多个面板

Question

我正在尝试制作一个简单的计算器来练习图形界面（我是完全的GUI新手）。 我在Polyashenko的计算器后面以及文本区域和文本区域与按钮之间存在一些不必要的空格问题。另外，我该如何保持布局但消除这些空格，并使底部的三个按钮更小？如果对我正在做的事情有任何提示或者如何更好地实现它，请告诉我。谢谢。

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

public class calculator {

    public static void main(String[] args) {
        // creates the JFrame(a window with decorations)
        JFrame frame = new JFrame("Calculator"); 
        // stops the program when window is closed
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        frame.setSize(377, 350);

        // the main panel of the JFrame, 
        // remembet you cant add content directly to JFrame
        JPanel content = new JPanel(new GridLayout(4, 0)); 
        // panel for the text field
        JPanel textarea = new JPanel(new GridLayout(4, 0)); 
        // panel for the buttons, 
        // GridLayout(int rows, int cols, int horiz_gap, int vert_gap)
        JPanel buttonarea = new JPanel(new GridLayout(4, 5, 2, 2)); 

        //  the panel for the bigger bottom buttons
        JPanel secondbuttonarea = new JPanel(new GridLayout(1, 1, 2, 2)); 
        // the panel for the text on top
        JPanel label = new JPanel(); 
        content.add(label);
        content.add(textarea);
        content.add(buttonarea);
        content.add(secondbuttonarea);

        JLabel words = new JLabel("Polyashenko's Calculator", JLabel.CENTER);
        label.add(words);

        JTextField enterhere = new JTextField("0.", JTextField.CENTER);
        // will set the curser of the text bar on right side
        enterhere.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT); 
        textarea.add(enterhere);

        // makes a button called b1 with text in it
        JButton b1 = new JButton("BkSP"); 
        // adds the backspace button to the buttonarea panel
        buttonarea.add(b1); 
        JButton b2 = new JButton("CE");
        buttonarea.add(b2);
        JButton b3 = new JButton("C");
        buttonarea.add(b3);
        JButton b4 = new JButton("/");
        buttonarea.add(b4);
        JButton b5 = new JButton("sqrt");
        buttonarea.add(b5);
        JButton b6 = new JButton("7");
        buttonarea.add(b6);
        JButton b7 = new JButton("8");
        buttonarea.add(b7);
        JButton b8 = new JButton("9");
        buttonarea.add(b8);
        JButton b9 = new JButton("*");
        buttonarea.add(b9);
        JButton b10 = new JButton("%");
        buttonarea.add(b10);
        JButton b11 = new JButton("4");
        buttonarea.add(b11);
        JButton b12 = new JButton("5");
        buttonarea.add(b12);
        JButton b13 = new JButton("6");
        buttonarea.add(b13);
        JButton b14 = new JButton("-");
        buttonarea.add(b14);
        JButton b15 = new JButton("1/x");
        buttonarea.add(b15);
        JButton b16 = new JButton("1");
        buttonarea.add(b16);
        JButton b17 = new JButton("2");
        buttonarea.add(b17);
        JButton b18 = new JButton("3");
        buttonarea.add(b18);
        JButton b19 = new JButton("+");
        buttonarea.add(b19);
        JButton b20 = new JButton("+/-");
        buttonarea.add(b20);

        JButton b21 = new JButton("0");
        secondbuttonarea.add(b21);
        JButton b22 = new JButton(".");
        secondbuttonarea.add(b22);
        JButton b23 = new JButton("=");
        secondbuttonarea.add(b23);

        // adds the buttonarea panel to the main panel
        frame.getContentPane().add(content); 
        // makes the window visible, put at end of program
        frame.setVisible(true); 
    }
}

- konopoly

---

供日后参考：Netbeans 和 MyEclipse 都有一个方便的 Swing GUI WYSIWYG 编辑器，这使得操作变得容易。你真的需要开始做，因为它不能帮助你处理现有程序。 - Lee Meador

@user2146529，请忽略上面的瞎猜和错误建议，你的方法很好，你不是GUI_Builders的囚犯。 - mKorbel

@user2146529 在这里搜索 Java + Swing + 计算器。 - mKorbel

Answer 1

以下是来自 Hovercraft Full Of Eels (-: forums.sun.com :-)

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.*;
import javax.swing.*;

public class SciCalc {

    private static void createAndShowUI() {
        SciCalcGui gui = new SciCalcGui();
        SciCalcMenu menu = new SciCalcMenu(gui);
        JFrame frame = new JFrame("Calculator");
        frame.getContentPane().add(gui.getMainPanel());
        frame.setJMenuBar(menu.getJMenuBar());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowUI();
            }
        });
    }

    private SciCalc() {
    }
}

class SciCalcGui {

    private static final String[][] STANDARD_BTN_TEXTS = {
        {"7", "8", "9", "/"}, {"4", "5", "6", "*"},
        {"1", "2", "3", "-"}, {"0", ".", "=", "+"}};
    private static final String[][] SCIENTIFIC_BTN_TEXTS = {
        {"sqrt", "1/x", "sin"}, {"%", "Exp", "cos"},
        {"x^y", "ln", "tan"}, {"x^2", "n!", "sec"}};
    private static final int GAP = 5;
    private static final Font BTN_FONT = new Font(Font.DIALOG, Font.BOLD, 20);
    private JPanel mainPanel = new JPanel();
    private JPanel sciPanel;
    private JTextField display = new JTextField();

    SciCalcGui() {
        display.setFont(BTN_FONT);
        JPanel standardPanel = createBtnPanel(STANDARD_BTN_TEXTS, "Standard");
        sciPanel = createBtnPanel(SCIENTIFIC_BTN_TEXTS, "Scientific");
        mainPanel.setLayout(new BorderLayout());
        mainPanel.setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        mainPanel.add(standardPanel, BorderLayout.CENTER);
        mainPanel.add(sciPanel, BorderLayout.WEST);
        mainPanel.add(display, BorderLayout.NORTH);
        sciPanel.setVisible(false);
    }

    public void sciPanelSetVisible(boolean visible) {
        sciPanel.setVisible(visible);
        Window win = SwingUtilities.getWindowAncestor(mainPanel);
        win.pack();
    }

    public JPanel getMainPanel() {
        return mainPanel;
    }

    private JPanel createBtnPanel(String[][] texts, String title) {
        JPanel btnPanel = new JPanel();
        int rows = texts.length;
        int cols = texts[0].length;
        btnPanel.setLayout(new GridLayout(rows, cols, GAP, GAP));
        for (int row = 0; row < texts.length; row++) {
            for (int col = 0; col < texts[row].length; col++) {
                JButton btn = new JButton(texts[row][col]);
                btn.setFont(BTN_FONT);
                btnPanel.add(btn);
            }
        }
        btnPanel.setBorder(BorderFactory.createTitledBorder(title));
        return btnPanel;
    }
}

class SciCalcMenu {

    private static final String STANDARD = "Standard";
    private static final String SCIENTIFIC = "Scientific";
    private SciCalcGui gui;
    private JMenuBar menuBar = new JMenuBar();
    private JMenuItem standardView;
    private JMenuItem scientificView;

    SciCalcMenu(SciCalcGui gui) {
        this.gui = gui;
        standardView = new JMenuItem(STANDARD, KeyEvent.VK_T);
        scientificView = new JMenuItem(SCIENTIFIC, KeyEvent.VK_S);
        ViewAction viewAction = new ViewAction();
        standardView.addActionListener(viewAction);
        scientificView.addActionListener(viewAction);
        standardView.setEnabled(false);
        JMenu viewMenu = new JMenu("View");
        viewMenu.setMnemonic(KeyEvent.VK_V);
        viewMenu.add(standardView);
        viewMenu.add(scientificView);
        menuBar.add(new JMenu("Edit"));
        menuBar.add(viewMenu);
        menuBar.add(new JMenu("Help"));
    }

    public JMenuBar getJMenuBar() {
        return menuBar;
    }

    private class ViewAction implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            String command = e.getActionCommand();
            if (command.equals(STANDARD)) {
                gui.sciPanelSetVisible(false);
                standardView.setEnabled(false);
                scientificView.setEnabled(true);
            } else if (command.equals(SCIENTIFIC)) {
                gui.sciPanelSetVisible(true);
                standardView.setEnabled(true);
                scientificView.setEnabled(false);
            }
        }
    }
}

- mKorbel

Answer 2

GridLayout 在这种情况下看起来不是很好。内容会扩展以填充网格中的盒子。您只能对行和列之间的间距进行最小控制。您可能需要更改布局以使其看起来符合您的要求。GridBagLayout 具有所有这些控件，但难以配置。有时，您可以使用 BorderLayout 和 GridLayout 嵌套面板，使其看起来合理。但这是 Swing，这意味着它可用，但变得非常难以使其看起来流畅。我总是喜欢使用 FlowLayout 来设置 OK/Cancel 按钮。它们在我看来看起来最好，您可以将它们全部向左、右或居中推动。您的计算器按钮应该适用于 GridLayout，但您不能轻松地拥有一个高的“Enter”按钮或宽的“0”按钮。例如，尝试使用垂直的 BoxLayout 而不是 4 高 1 宽的网格。

- Lee Meador