Java GridBagLayout不工作

Question

我正在尝试使用GridbagLayout，但没有得到我所期望的结果，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：

黄色是按钮名称，红色是行和列。

谁能解释一下我的代码出了什么问题吗？

Answer 1

问题是，没有任何东西能够说服第二个网格列(Gridx=1)具有任何宽度，因为没有任何组件只需要放入第二列。因此，第二列的宽度为0，所以尽管Button1跨越了前两列，但它看起来并不是那样，因为它的所有宽度需要都由第一列满足；虽然按钮5和按钮7跨在第二列和第三列上，但它们的所有宽度需要由第三列满足。

要修复它，你必须说服按钮应该更宽（1,5,7）占用更多的空间。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。由于我不太理解的原因，当它留在里面时就不起作用了。）：

资料来源：

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：正如评论中指出的那样，上面的方法不适合，因为它阻止了布局的动态调整大小。要使布局扩展以填充其容器的大小，需要weightx和weighty约束，但第二列没有任何宽度。

这里有一个替代解决方案的尝试。这是一个肮脏的黑客，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);