Java GridBagLayout 不起作用答案

【问题标题】：Java GridBagLayout not workingJava GridBagLayout 不起作用
【发布时间】：2014-11-23 04:24:10
【问题描述】：

我正在尝试使用GridBagLayout，但我没有得到预期的结果，并且在此代码中找不到错误：

public class GridBagEx1 extends JPanel {

    private static final long serialVersionUID = 1L;

    protected void makebutton(String name, GridBagLayout gridbag, GridBagConstraints c) {
        JButton button = new JButton(name);
        gridbag.setConstraints(button, c);
        add(button);
    }

    public void init() {
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints c = new GridBagConstraints();
        setLayout(gridbag);

        c.fill = BOTH;

        c.weightx = 1.0;
        c.weighty = 1.0;

        c.anchor = CENTER;

        c.insets.top = 5;
        c.insets.bottom = 5;
        c.insets.left = 5;
        c.insets.right = 5;

        c.gridx = 0;
        c.gridy = 0;
        c.gridheight = 1;
        c.gridwidth = 2;
        makebutton("Button1", gridbag, c);      

        c.gridx = 2;
        c.gridy = 0;
        c.gridheight = 1;
        c.gridwidth = 1;
        makebutton("Button2", gridbag, c);

        c.gridx = 3;
        c.gridy = 0;
        c.gridheight = 2;
        c.gridwidth = 2;
        makebutton("Button3", gridbag, c);

        c.gridx = 0;
        c.gridy = 1;
        c.gridheight = 1;
        c.gridwidth = 1;
        makebutton("Button4", gridbag, c);

        c.gridx = 1;
        c.gridy = 1;
        c.gridheight = 1;
        c.gridwidth = 2;
        makebutton("Button5", gridbag, c);

        c.gridx = 0;
        c.gridy = 2;
        c.gridheight = 1;
        c.gridwidth = 1;
        makebutton("Button6", gridbag, c);

        c.gridx = 1;
        c.gridy = 2;
        c.gridheight = 1;
        c.gridwidth = 2;
        makebutton("Button7", gridbag, c);

        c.gridx = 3;
        c.gridy = 2;
        c.gridheight = 1;
        c.gridwidth = 1;
        makebutton("Button8", gridbag, c);

        c.gridx = 4;
        c.gridy = 2;
        c.gridheight = 1;
        c.gridwidth = 1;
        makebutton("Button9", gridbag, c);
    }

    public static void main(String args[]) {
        JFrame frame = new JFrame();
        GridBagEx1 ex1 = new GridBagEx1();

        ex1.init();

        frame.add(ex1);
        frame.pack();
        frame.setVisible(true);
    }
}

这张图说明了我需要什么：

黄色为按钮名称，红色为行列。

这是真正发生的事情：

谁能解释我的代码有什么问题？

【问题讨论】：

我还不能解释这个问题，但必须说明你的问题很好地提出了，谢谢你和 1+。
@HovercraftFullOfEels 谢谢
c.fill = BOTH; 应该是 c.fill = GridBagConstraints.BOTH; 和 c.anchor = CENTER; 相同，以便编译代码。
@user1803551 如果你不是 import static java.awt.GridBagConstraints.*; :-)
@GeroldBroser 真...真...

标签： java swing gridbaglayout

【解决方案1】：

问题是没有什么可以说服第二个网格列 (gridx=1) 具有任何宽度，因为没有组件需要仅适合第二列。因此，第二列的宽度为 0，因此尽管 Button1 确实跨越了前两列，但它看起来并不那样，因为它的所有宽度需求都由第一列满足；虽然 Button5 和 Button7 横跨第二列和第三列，但它们的所有宽度需求都由第三列满足。

要修复它，您必须说服应该更宽（1、5、7）的按钮占用更多空间。在这里，我通过设置c.ipadx = 35; 为这些按钮添加了填充。（我还删除了weightx = 1.0 约束。由于我不太明白的原因，它在保留时不起作用。）：

来源：

public void init() {
    GridBagLayout gridbag = new GridBagLayout();
    GridBagConstraints c = new GridBagConstraints();
    setLayout(gridbag);

    c.fill = c.BOTH;

    //c.weightx = 1.0;
    //c.weighty = 1.0;

    c.anchor = c.CENTER;

    c.insets.top = 5;
    c.insets.bottom = 5;
    c.insets.left = 5;
    c.insets.right = 5;

    c.gridx = 0;
    c.gridy = 0;
    c.gridheight = 1;
    c.gridwidth = 2;
    c.ipadx = 35;
    makebutton("Button1", gridbag, c);

    c.gridx = 2;
    c.gridy = 0;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.ipadx = 0;
    makebutton("Button2", gridbag, c);

    c.gridx = 3;
    c.gridy = 0;
    c.gridheight = 2;
    c.gridwidth = 2;
    c.ipadx = 0;
    makebutton("Button3", gridbag, c);

    c.gridx = 0;
    c.gridy = 1;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.ipadx = 0;
    makebutton("Button4", gridbag, c);

    c.gridx = 1;
    c.gridy = 1;
    c.gridheight = 1;
    c.gridwidth = 2;
    c.ipadx = 35;
    makebutton("Button5", gridbag, c);

    c.gridx = 0;
    c.gridy = 2;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.ipadx = 0;
    makebutton("Button6", gridbag, c);

    c.gridx = 1;
    c.gridy = 2;
    c.gridheight = 1;
    c.gridwidth = 2;
    c.ipadx = 35;
    makebutton("Button7", gridbag, c);

    c.gridx = 3;
    c.gridy = 2;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.ipadx = 0;
    makebutton("Button8", gridbag, c);

    c.gridx = 4;
    c.gridy = 2;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.ipadx = 0;
    makebutton("Button9", gridbag, c);
}

编辑： 正如 cmets 中所指出的，上述方法不适合，因为它会阻止动态调整布局大小。要使布局扩展以填充其容器的大小，需要 weightx 和 weighty 约束，但是第二列没有得到任何宽度。

这是一个替代解决方案的尝试。这是一个肮脏的 hack，它在第二列的底部插入一个不可见的组件以强制该列具有宽度：

    c.gridx = 1;
    c.gridy = 3;
    c.gridheight = 1;
    c.gridwidth = 1;
    c.insets.set(0, 0, 0, 0);
    c.weighty = 0;
    add(Box.createRigidArea(new Dimension(50, 0)), c);

这在调整窗口大小时可以很好地应对，因为尽管组件具有固定的初始大小，但 GridBagLayout 会与其他组件成比例地放大它。不过，它仍然不完美。也许有更好的解决方案，但我找不到。

【讨论】：

@FilipB.Vondrášek 我不认为 this 一个具有特定（相当复杂）布局管理器的特殊情况总结并证明 Swing 是可憎的。当然 Swing 有其优点和缺点，但这并不是秘密，每个人都知道。
@FilipB.Vondrášek 如果有一个非可恶的替代方案。
JavaFX 怎么样？不过，从来没有用过。
@Boann 删除重量，x 按钮不调整大小，如果您重新添加它们，此代码将不起作用！
@Boann 另一件事，按钮本身没有尺寸，我希望 gridbaglayout 在 jpanel 的底部为它们分配一个尺寸！

【解决方案2】：

我设法设计了 needed 布局，没有任何 hack 并通过使用 JGoodies FormLayout 支持动态调整大小：

import java.awt.Component;

import javax.swing.JButton;
import javax.swing.JPanel;

import com.jgoodies.forms.factories.FormFactory;
import com.jgoodies.forms.layout.ColumnSpec;
import com.jgoodies.forms.layout.FormLayout;
import com.jgoodies.forms.layout.RowSpec;

public class FormLayoutPanel extends JPanel
    {
    public FormLayoutPanel()
        {
        setAlignmentY( Component.BOTTOM_ALIGNMENT );
        setAlignmentX( Component.RIGHT_ALIGNMENT );
        setLayout( new FormLayout( new ColumnSpec[] {
            ColumnSpec.decode( "41px:grow" ),
            FormFactory.LABEL_COMPONENT_GAP_COLSPEC,
            ColumnSpec.decode( "25px:grow" ),
            FormFactory.LABEL_COMPONENT_GAP_COLSPEC,
            ColumnSpec.decode( "41px:grow" ),
            FormFactory.LABEL_COMPONENT_GAP_COLSPEC,
            ColumnSpec.decode( "41px:grow" ),
            FormFactory.LABEL_COMPONENT_GAP_COLSPEC,
            ColumnSpec.decode( "41px:grow" ), },
            new RowSpec[] {
                RowSpec.decode( "25px:grow" ),
                FormFactory.LINE_GAP_ROWSPEC,
                RowSpec.decode( "25px:grow" ),
                FormFactory.LINE_GAP_ROWSPEC,
                RowSpec.decode( "25px:grow" ), } ) );

        JButton button1 = new JButton( "1" );
        add( button1, "1, 1, 3, 1, fill, fill" );
        JButton button2 = new JButton( "2" );
        add( button2, "5, 1, fill, fill" );
        JButton button3 = new JButton( "3" );
        add( button3, "7, 1, 3, 3, fill, fill" );
        JButton button4 = new JButton( "4" );
        add( button4, "1, 3, fill, fill" );
        JButton button5 = new JButton( "5" );
        add( button5, "3, 3, 3, 1, fill, fill" );
        JButton button6 = new JButton( "6" );
        add( button6, "1, 5, fill, fill" );
        JButton button7 = new JButton( "7" );
        add( button7, "3, 5, 3, 1, fill, fill" );
        JButton button8 = new JButton( "8" );
        add( button8, "7, 5, fill, fill" );
        JButton button9 = new JButton( "9" );
        add( button9, "9, 5, fill, fill" );
        }
    }

【讨论】：