Java，Swing：如何设置JTextField的最大宽度？

Question

I'm writing a custom file selection component. In my UI, first the user clicks a button, which pops a JFileChooser ; when it is closed, the absolute path of the selected file is written to a JTextField .

The problem is, absolute paths are usually long, which causes the text field to enlarge, making its container too wide.

I've tried this, but it didn't do anything, the text field is still too wide:

fileNameTextField.setMaximumSize(new java.awt.Dimension(450, 2147483647));

Currently, when it is empty, it is already 400px long, because of GridBagConstraints attached to it.

I'd like it to be like text fields in HTML pages, which have a fixed size and do not enlarge when the input is too long.

So, how do I set the max size for a JTextField ?

Answer 1

It may depend on the layout manager your text field is in. Some layout managers expand and some do not. Some expand only in some cases, others always.

I'm assuming you're doing

filedNameTextField = new JTextField(80); // 80 == columns

If so, for most reasonable layouts, the field should not change size (at least, it shouldn't grow). Often layout managers behave badly when put into JScrollPane s.

In my experience, trying to control the sizes via setMaximumSize and setPreferredWidth and so on are precarious at best. Swing decided on its own with the layout manager and there's little you can do about it.

All that being said, I have no had the problem you are experiencing, which leads me to believe that some judicious use of a layout manager will solve the problem.

Answer 2

I solved this by setting the maximum width on the container of the text field, using setMaximumSize .

According to davetron's answer, this is a fragile solution, because the layout manager might disregard that property. In my case, the container is the top-most, and in a first test it worked.

Answer 3

Don't set any of the sizes on the text field. Instead set the column size to a non-zero value via setColumns or using the constructor with the column argument.

What is happening is that the preferred size reported by the JTextComponent when columns is zero is the entire amount of space needed to render the text. When columns is set to a non-zero value the preferred size is the needed size to show that many standard column widths. (for a variable pitch font it is usually close to the size of the lower case 'm'). With columns set to zero the text field is requesting as much space as it can get and stretching out the whole container.

Since you already have it in a GridBagLayout with a fill, you could probably just set the columns to 1 and let the fill stretch it out based on the other components, or some other suitably low number.