gridheight似乎不起作用

Question

I am trying to use the GridBagLayout, but I've some trouble with it. I want to make a layout using 12 rows. So first I make two JPanels filling up the first two rows (with gridheight = 1). Then I make 5 other JPanels to fill up the other 10 rows (with gridheight = 2). The bottom 5 JPanels get gridheight = {2,4,6,8,10}, so they won't overlap or anything. The problem I get now is this:
All the JPanels get the same size!

I also fill up BOTH ways and not using any anchors. If I add a JPanel with gridx = 1, gridy = 0 and gridheight = 2, then it will have a doubled height, so what's the deal here? Do I have to tell the layout system the total amount of rows I am going to use beforehand? If so how do I do that?

Answer 1

there are several aspects to GridBagLayout (GBL) that get missed by first time users.

1) components placed inside the GBL will initialize at their "preferred" size. JPanel, iirc, has a preferred size of 1x1.

2) if you want the GBL cells to resize according to the enclosing container, you need to give them a weightx and weighty. what those two attributes do is say, give the cell a percentage of the available area according to the ratio of all the weightx's and weighty's assigned. eg if i have 2 cells and 1 has weightx = 1.0 and the second one is given 2.0, then the first cell will be 1/2 as wide as the second (or the second one will be twice as wide).

3) GBL takes alot of trial and error when you first dive in, BUT it is the most powerful, flexible, and reliable layout (especially compared to nested layouts, blech)

Answer 2

So for the first two rows I say:

 c.fill = GridBagConstraints.HORIZONTAL;
 c.gridwidth = 1;
 c.gridheight = 1;
 c.ipadx = 100;
 c.ipady = h / (2 * columns + 2);
 c.weightx = 1.0;
 c.weighty = 1.0;

And for the next rows I only change c.ipady:

 c.ipady = h / (columns + 1);

So this basically solved my problem, but I still think it could have been a lot easier.

PS The variable h is the hight of my screen.