排列计算器界面

Question

在这段代码中，前三个按钮出现在文本区域，我怎样才能让这些按钮从标题下方开始？在添加按钮之前，按钮区域从标题下方开始，但是一旦我添加了按钮，它就会出现在标题上

   public Design ()
   {

    header = new JPanel ();
    header.setBounds(0, 0, 300, 100);
    header.setBackground(Color.WHITE);
    header.setLayout (null);

    buttonarea = new JPanel ();
    buttonarea.setBounds (0,0, 300, 300);
    buttonarea.setBackground(Color.BLACK);
    buttonarea.setLayout(new GridLayout (6,3));

    add (header);
    add (buttonarea);

    zero = new JButton ("0");
    zero.setBackground(Color.PINK);
    one = new JButton ("1");
    one.setBackground(Color.PINK);
    two = new JButton ("2");
    two.setBackground(Color.PINK);
    three = new JButton ("3");
    three.setBackground(Color.PINK);
    four = new JButton ("4");
    four.setBackground(Color.PINK);
    five = new JButton ("5");
    five.setBackground(Color.PINK);
    six = new JButton ("6");
    six.setBackground(Color.PINK);
    seven = new JButton ("7");
    seven.setBackground(Color.PINK);
    eight = new JButton ("8");
    eight.setBackground(Color.PINK);
    nine = new JButton ("9");
    nine.setBackground(Color.PINK);
    add = new JButton ("+");
    add.setBackground(Color.PINK);
    subtract = new JButton ("-");
    subtract.setBackground(Color.PINK);
    divide = new JButton ("*");
    divide.setBackground(Color.PINK);
    multiply = new JButton ("/");
    multiply.setBackground(Color.PINK);
    square = new JButton ("x^2");
    square.setBackground(Color.PINK);
    equal = new JButton ("=");
    equal.setBackground(Color.PINK);
    c = new JButton ("C");
    c.setBackground(Color.PINK);
    clear = new JButton ("delete");
    clear.setBackground(Color.PINK);
    dot = new JButton (".");
    dot.setBackground(Color.PINK);

    written = new JTextArea ();
    written.setBackground(Color.WHITE);

   header.add (written);

    buttonarea.add (c);
    buttonarea.add (clear);
    buttonarea.add (equal);
    buttonarea.add (zero);
    buttonarea.add (one);
    buttonarea.add (add);
    buttonarea.add (two);   
    buttonarea.add (three);
    buttonarea.add (subtract);
    buttonarea.add (four);
    buttonarea.add (five);
    buttonarea.add (multiply);
    buttonarea.add (six);
    buttonarea.add (seven);
    buttonarea.add (square);
    buttonarea.add (eight); 
    buttonarea.add (nine);    
    buttonarea.add (dot);  
   }  

Answer 1

虽然空布局和setBounds() 在 Swing 新手看来是创建复杂 GUI 的最简单和最好的方法，但创建的 Swing GUI 越多，使用它们时遇到的困难就越严重。当 GUI 调整大小时，它们不会调整您的组件大小，它们是增强或维护的皇家女巫，放置在滚动窗格中时它们完全失败，在与原始不同的所有平台或屏幕分辨率上查看时它们看起来很糟糕.

对主 GUI 使用 BorderLayout，放置 JTextField BorderLayout.PAGE_START。使用 JPanel 将 JButtons 放置在 GridLayout 中，并将此 JPanel 放置在主 GUI 的 BorderLayout.CENTER 位置。

例如这个图形用户界面：

可以用这个 GUI 制作：

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;

@SuppressWarnings("serial")
public class SimpleCalc extends JPanel {
    private static final String[][] BTN_TEXTS = {
        {"C", "Del", "X^2", "+"},
        {"7", "8", "9", "-"},
        {"4", "5", "6", "*"},
        {"1", "2", "3", "/"},
        {"0", ".", "", "="}
    };
    private static final int COLS = 12;
    private static final int GAP = 3;
    private static final char[] NUMBER_ARRAY = "0123456789".toCharArray();
    private static final List<Character> NUMBER_LIST = new ArrayList<>();
    private static final float FONT_SIZE = 36f;
    private JTextField display = new JTextField(COLS);

    static {
        for (char c : NUMBER_ARRAY) {
            NUMBER_LIST.add(c);
        }
    }

    public SimpleCalc() {
        display.setFont(display.getFont().deriveFont(FONT_SIZE));
        display.setFocusable(false);

        int rows = BTN_TEXTS.length;
        int cols = BTN_TEXTS[0].length;
        JPanel buttonPanel = new JPanel(new GridLayout(rows, cols, GAP, GAP));
        for (String[] btnTextRow : BTN_TEXTS) {
            for (String btnText : btnTextRow) {
                if (btnText.isEmpty()) {
                    buttonPanel.add(new JLabel());
                } else {
                    Action action = null;
                    if (NUMBER_LIST.contains(btnText.charAt(0))) {
                        action = new NumericAction(btnText);
                    } else if (".".equals(btnText)) {
                        action = new DotAction(btnText);
                    } else {
                        action = new OperationAction(btnText);
                    }
                    JButton button = new JButton(action);
                    button.setFont(button.getFont().deriveFont(Font.BOLD, FONT_SIZE));
                    buttonPanel.add(button);
                }
            }
        }

        setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
        setLayout(new BorderLayout(GAP, GAP));
        add(display, BorderLayout.PAGE_START);
        add(buttonPanel, BorderLayout.CENTER);
    }

    private class NumericAction extends AbstractAction {
        public NumericAction(String name) {
            super(name);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            String text = display.getText();
            text += e.getActionCommand();
            display.setText(text);
        }
    }

    private class DotAction extends AbstractAction {
        public DotAction(String name) {
            super(name);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            String text = display.getText();
            if (text.contains(".")) {
                return; // only one dot allowed
            }
            text += e.getActionCommand();
            display.setText(text);
        }
    }

    private class OperationAction extends AbstractAction {
        public OperationAction(String name) {
            super(name);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO write code for operations buttons
        }
    }

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

        JFrame frame = new JFrame("SimpleCalc");
        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(new Runnable() {
            public void run() {
                createAndShowGui();
            }
        });
    }
}

Answer 2

add (header);
add (buttonarea);

我猜你正在使用一个使用 BorderLayout 的 JFrame。上面的代码在 BorderLayout 的 CENTER 中添加了两个组件，这是不允许的。

相反，您应该指定适当的约束：

add (header, BorderLayout.PAGE_NORTH);
add (buttonarea, BorderLayout.CENTER);

如果您没有在框架上使用 BorderLayout，那么您应该这样做。阅读 How to Use BorderLayout 上的 Swing 教程部分，了解更多信息和示例。

另外，在创建 JTextAra 时，您应该使用：

written = new JTextArea (row, columns);

给文本区域一个合适的大小。在这种情况下，您可以直接将文本区域添加到框架中：

//add (header, BorderLayout.PAGE_NORTH);
add (written, BorderLayout.PAGE_NORTH);

不需要包装面板。