Question

/**
 *  I'd like to achive following layout:
 *   +----------+----------+
 *   | Button 1 |          |
 *   +----------| Button 2 |
 *   | Button 3 |          |
 *   +----------+----------+
 *  with following code:
 */

JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JButton button;

button = new JButton("Button 1");
c.weightx = 0.5;
c.weighty = 0.5;
c.fill = GridBagConstraints.BOTH;
panel.add(button, c);

button = new JButton("Button 2");
c.gridwidth = GridBagConstraints.REMAINDER;
c.gridheight = 2;
panel.add(button, c);

button = new JButton("Button 3");
c.gridwidth = 1;
panel.add(button, c);

/**
 *  but what I achive is:
 *   +----------+----------+
 *   | Button 1 | Button 2 |
 *   +----------+----------+|
 *   | Button 3 |
 *   +----------+
 */

/**
 *  However layout:
 *   +----------+----------+
 *   |          | Button 2 |
 *   + Button 1 +----------+
 *   |          | Button 3 |
 *   +----------+----------+
 *  is easily achieved as:
 */

JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JButton button;

button = new JButton("Button 1");
c.weightx = 0.5;
c.weighty = 0.5;
c.fill = GridBagConstraints.BOTH;
c.gridheight = 2;
panel.add(button, c);

button = new JButton("Button 2");
c.gridwidth = GridBagConstraints.REMAINDER;
c.gridheight = 1;
panel.add(button, c);

button = new JButton("Button 3");
panel.add(button, c);

任何线索？

问候，Francesc

Answer 1

您需要指定gridx和gridy，默认值为0。

    button = new JButton("Button 1");
    c.weightx = 0.5;
    c.weighty = 0.5;
    c.fill = GridBagConstraints.BOTH;
    panel.add(button, c);

    button = new JButton("Button 3");
    c.gridy = 1;
    c.gridwidth = 1;
    panel.add(button, c);

    button = new JButton("Button 2");
    c.gridx = 1; c.gridy = 0;
    c.gridwidth = GridBagConstraints.REMAINDER;
    c.weighty = 1;c.gridheight = 2;
    panel.add(button, c);

Answer 2

您必须为最后一个按钮设置c.gridx。默认情况下，组件相对于彼此放置。如果为按钮3将gridx设置为0，则强制它到第一列。

JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JButton button;

button = new JButton("Button 1");
c.weightx = 1;
c.weighty = 1;
c.fill = GridBagConstraints.BOTH;
panel.add(button, c);

button = new JButton("Button 2");
c.gridwidth = GridBagConstraints.REMAINDER;
c.gridheight = GridBagConstraints.REMAINDER;        
panel.add(button, c);

button = new JButton("Button 3");
c.gridx = 0;
c.gridwidth = 1;
c.gridheight = 1;
panel.add(button, c);

Answer 3

为什么不使用使用GridLayouts的嵌套JPanel，例如：

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

public class GridLayoutEg {
    public static void main(String[] args) {
        JPanel leftPanel = new JPanel(new GridLayout(0, 1));
        leftPanel.add(new JButton("Button 1"));
        leftPanel.add(new JButton("Button 3"));

        JPanel mainPanel = new JPanel(new GridLayout(1, 0));
        mainPanel.add(leftPanel);
        mainPanel.add(new JButton("Button 2"));

        JFrame frame = new JFrame("Foo");
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

或者我们需要知道的故事还有更多吗？

Answer 4

您需要在约束上设置gridx和gridy。查看本教程：http://download.oracle.com/javase/tutorial/uiswing/layout/gridbag.html

Answer 5

您尚未为元素指定gridx和gridy设置。

JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
JButton button;

button = new JButton("Button 1");
c.weightx = 0.5;
c.weighty = 0.5;
c.fill = GridBagConstraints.BOTH;
c.gridx = 0;
c.gridy = 0;
panel.add(button, c);

button = new JButton("Button 2");
c.gridwidth = GridBagConstraints.REMAINDER;
c.gridheight = 2;
c.gridx = 1;
c.gridy = 0;
panel.add(button, c);

button = new JButton("Button 3");
c.gridwidth = 1;
c.gridx = 0;
c.gridy = 1;
panel.add(button, c);

注意：gridx和gridy的默认值为0，但最好始终设置该值。它更清晰，依赖于默认值可能会在复制和粘贴等时出现问题。因此这种方式更清晰，更安全（尽管稍微冗长一点）。

Answer 6

GridBagLayout被认为是有效的（参见http://www.horstmann.com/articles/Taming_the_GridBagLayout.html）：

标准布局管理者 Java SDK，GridBagLayout就是最有用的，但它的复杂性也被称为恐惧程序员的心。的一部分复杂性在于单调乏味设置网格包约束。

我会阅读这些文章并在论坛上提问（例如http://www.java-forums.org/new-java/28857-gridbaglayout-problems-questions.html）

Answer 7

是的，其他人都是对的。您必须手动设置GridX和GridY。

此外，我建议为每个组件使用一个新的GridBagConstraints实例，因为在更复杂的表单中，您可以轻松地忽略在您正在使用的一个实例中实际设置的值。此外，如果您使用具有许多参数的构造函数，则不必关心默认值，因为您必须每次都指定它们。它需要时间来适应它，但它会在以后回报。


    /**
     *   +----------+----------+
     *   | Button 1 |          |
     *   +----------| Button 2 |
     *   | Button 3 |          |
     *   +----------+----------+
     */

    JPanel panel = new JPanel(new GridBagLayout());

    JButton b1 = new JButton("Button 1");
    panel.add(b1, new GridBagConstraints(0, 0, 1, 1, 0.0, 0.0,
        GridBagConstraints.CENTER, GridBagConstraints.BOTH, new Insets(0, 0, 0,
            0), 0, 0));

    JButton b2 = new JButton("Button 2");
    panel.add(b2, new GridBagConstraints(1, 0, 1, 2, 0.0, 0.0,
        GridBagConstraints.CENTER, GridBagConstraints.BOTH, new Insets(0, 0, 0,
            0), 0, 0));

    JButton b3 = new JButton("Button 3");
    panel.add(b3, new GridBagConstraints(0, 1, 1, 1, 0.0, 0.0,
        GridBagConstraints.CENTER, GridBagConstraints.BOTH, new Insets(0, 0, 0,
            0), 0, 0));

无法使GridBagLayout按预期工作

7 个答案: