Question

我有一个项目要求我创建一个简单的GUI，顶部有一个jTextArea，JButtons从0到9添加。这很简单，但程序要求我将0置于底部。下面的代码完成了，但是我必须使用Grid Layout而不是flowLayout。当我用GridLayout编写它时，除了左侧，我无法将0对齐到任何东西。如何使用GridLayout，并将0？

居中

public class CalculatorProject {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    GUI gui = new GUI();
}

}

public class GUI extends JFrame {

public GUI() {
    JFrame aWindow = new JFrame("Calculator");
    aWindow.setBounds(30, 30, 175, 215); // Size
    aWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JTextField jta = new JTextField(20);
    FlowLayout flow = new FlowLayout(); // Create a layout manager
    flow.setHgap(5);                   // Set the horizontal gap
    flow.setVgap(5);
    flow.setAlignment(FlowLayout.CENTER);
    Container content = aWindow.getContentPane(); // Get the content pane
    content.setLayout(new GridLayout(4,3,5,5));

    content.setLayout(flow); // Set the container layout mgr
    content.add(jta);
    // Now add six button components
    int array[] = {7, 8, 9, 4, 5, 6, 1, 2, 3, 0};
    for (int i = 0; i <= 9; i++) {
        content.add(new JButton("" + array[i])); 

    }
    aWindow.setVisible(true); // Display the window
}
}

Answer 1

通过使用BorderLayout就是这么简单。将TextField添加到North。现在只需将九个按钮添加到JPanel。将该JPanel添加到中心。最后将Zero按钮添加到South。

public class CalculatorProject {

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    GUI gui = new GUI();
                }
            });

    }

    }

    class GUI extends JFrame {

    GUI() {
        super("Calculator");
        setBounds(30, 30, 160, 190); // Size
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JTextField jta = new JTextField(20);
        JPanel panel = new JPanel();
        setLayout(new BorderLayout(5, 5));
        Container content = this.getContentPane(); // Get the content pane
        content.add(jta, BorderLayout.NORTH);
        // Now add six button components
        int array[] = {7, 8, 9, 4, 5, 6, 1, 2, 3};
        for (int i = 0; i < 9; i++) {
            panel.add(new JButton("" + array[i])); 

        }
        content.add(panel, BorderLayout.CENTER);
        content.add(new JButton("0"), BorderLayout.SOUTH);
        setVisible(true); // Display the window
    }
    }

<强>结果

Answer 2

将空的JPanel添加到您想要为空的网格的方块中。

int array[] = {7, 8, 9, 4, 5, 6, 1, 2, 3, 0};
for (int i = 0; i <= 8; i++) {
    content.add(new JButton("" + array[i])); 
}
content.add(new JPanel());
content.add(new JButton("" + array[9]));
content.add(new JPanel());  // not needed, but fills the last square of the grid

编辑：删除了一个额外无意中出现的单词＆＃34;为空。＆＃34;

Answer 3

让布局和简单的2D字符串数组帮助您。例如，如果为按钮文本声明一个2D字符串数组，如下所示：

    private static final String[][] TEXTS = {
        {"7", "8", "9"},
        {"4", "5", "6"},
        {"1", "2", "3"},
        {"", "0", ""}
    };

然后遍历数组，在文本不是""的地方创建按钮，在空的JLabel中创建空白，并使用JPanel将按钮放入GridLayout，你就在那里。我还建议嵌套JPanels，外部使用BorderLayout，将JTextField保持在顶部 - BorderLayout.PAGE_START，另一个JPanel使用GridLayout，按住按钮并使用JPanel放置在外部BorderLayout的BorderLayout.CENTER位置。例如：

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

public class Gui2 extends JPanel {
    private static final String[][] TEXTS = {
        {"7", "8", "9"},
        {"4", "5", "6"},
        {"1", "2", "3"},
        {"", "0", ""}
    };
    private List<JButton> buttons = new ArrayList<>();
    private JTextField textField = new JTextField(5);

    public Gui2() {
        int rows = TEXTS.length;
        int cols = TEXTS[0].length;
        int gap = 2;
        JPanel gridPanel = new JPanel(new GridLayout(rows, cols, gap, gap));
        for (int r = 0; r < TEXTS.length; r++) {
            for (int c = 0; c < TEXTS[r].length; c++) {
                String text = TEXTS[r][c];
                if (!text.trim().isEmpty()) {
                    JButton button = new JButton(text);
                    gridPanel.add(button);
                    buttons.add(button);
                    // add ActionListener here
                } else {
                    // empty String, so add a blank place-holder JLabel
                    gridPanel.add(new JLabel());
                }
            }
        }

        setBorder(BorderFactory.createEmptyBorder(gap, gap, gap, gap));
        setLayout(new BorderLayout(gap, gap));
        add(textField, BorderLayout.PAGE_START);
        add(gridPanel, BorderLayout.CENTER);
    }

    private static void createAndShowGui() {
        Gui2 mainPanel = new Gui2();

        JFrame frame = new JFrame("Gui2");
        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();
            }
        });
    }
}

在容器java的中心按钮

3 个答案: