问题描述
我正在尝试使用 GridBagLayout ，但我没有得到我期望的结果，我在这段代码中找不到错误：
I'm trying to use GridBagLayout, but I don't get what I expect and I can't find the error in this code:
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);
}
}
此图片说明了我的需求：
This picture illustrate what I need:
黄色是按钮名称，红色是行和列。
Yellow are button name, red are row and columns.
这是真正发生的事情：
This is what really happens:
有人能解释我代码中的错误吗？
Can anyone explain what is wrong in my code?
推荐答案
问题是没有任何东西说服第二个网格列（gridx = 1）有任何宽度，因为没有需要的组件在第二列中仅适用 。因此第二列的宽度为0，所以尽管Button1跨越前两列，但它看起来并不那样，因为第一列满足了它的所有宽度需求;虽然Button5和Button7跨在第二列和第三列，但第三列都满足了它们的所有宽度需求。
The problem is that nothing is persuading the second grid column (gridx=1) to have any width, because there is no component that needs to fit only in the second column. The second column thus has 0 width, so although Button1 does straddle the first two columns, it doesn't look that way because all of its width need is satisfied by the first column; and although Button5 and Button7 straddle the second and third columns, all of their width need is satisfied by the third column.
要修复它，你必须说服应该按下的按钮。更宽（1,5,7）以占用更多空间。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，当它留在时，它不起作用。）：
To fix it you must persuade the buttons which should to be wider (1, 5, 7) to take up more space. Here I added padding to those buttons by setting c.ipadx = 35;. (I also removed the weightx = 1.0 constraint. For reasons I don't quite understand, it didn't work when that was left in.):
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，上述方法并不合适，因为它会阻止布局动态调整大小。要扩展布局以填充其容器的大小，需要 weightx 和 weighty 约束，但是第二列没有任何宽度。
As pointed out in the comments, the above approach is not suitable because it prevents the layout being resized dynamically. To have the layout expand to fill the size of its container, the weightx and weighty constraints are needed, but then the second column does not get any width.
这是对替代解决方案的尝试。这是一个肮脏的黑客，在第二列的底部插入一个不可见的组件，以强制列具有宽度：
Here is an attempt at an alternative solution. It's a dirty hack that inserts an invisible component at the bottom of the second column to force the column to have width:
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);
在调整窗口大小时这很好用，因为尽管组件的初始大小是固定的，但GridBagLayout按比例放大它与其他组件。但它仍然不完美。也许有一个更好的解决方案，但我找不到它。
This copes fairly well when the window is resized because although the component is given a fixed initial size, GridBagLayout scales up it proportionally with the other components. It is still not perfect, though. Maybe there is a better solution but I can't find it.
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