What is the width of a "column" for a JTextField?

Question

Per the JTextField doc, you can set the width of the field delineated in “columns”, but cannot find a definition for “columns”.

Moreover, doing something like this:

new JTextField("abc", 3);

Results in a text field of width populated with the string abc and then extra whitespace afterwards.

Can someone clarify the the definition of columns as used in the JTextField constructor?

score 4 · Answer 1 · answered Dec 13 '17 at 00:53

If you are using a standard JTextField, the columns specifies the preferred width of the component as some multiple of getColumnWidth().

The method getColumnWidth() defines the width in pixels of each column. The documentation states: "By default this is defined to be the width of the character 'm' for the font used."

The text field may display at a different size if the layout manager modifies it.

score 1 · Answer 2 · answered Aug 22 '16 at 17:28

1

The columns property of JTextField is used to determine the preferred width of the object. If an initial String is provided as in your example new JTextField("abc", 3); then the field is painted to match the text size. Otherwise, the columns allow parallel stacking of text within the JTextField itself. Therefore, the reason you get whitespace after the "abc" in your example is because it defaults to place the string in the first column, then two columns of whitespace.

answered Aug 22 '16 at 17:28

g_haxor

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3

OK, but if you simply do: new JTextField(5); Then the width of the resulting object accomodates more than 5 characters. For instance, I can fit about 8 underscore '_' characters in this text field that is noted as 5 columns. So I'm not clear on *what* column width is. E.g. what is the pixel width of a column and how does that relate to text that will be placed in it? – user3092671 Aug 22 '16 at 17:41
The columns are autosized to fit the necessary information. I'm not sure about Swing's methods, but in FX you can force column width in pixels, percentages of total space, or equal space for all the columns. – g_haxor Aug 22 '16 at 17:53
i dont understand what this column bs is. is there a use case where we can see how it affects the ui? – hariszhr Jan 02 '17 at 20:48
does it affect when we are using some specific layout? – hariszhr Jan 02 '17 at 20:55
This statement is simply false "the columns allow parallel stacking of text within the JTextField itself" A JTextField is a single line of text. The "columns" setting influences the preferred width of that line. – Enwired Dec 13 '17 at 00:55

score 0 · Answer 3 · answered Aug 14 '23 at 23:15

Thanks for the Enwired's answer. This bugged me for some time. To further elaborate Enwired's answer, it is the number of m's that the JTextField can display on the screen (panel or window).

Observations

new JTextField("mmm", 3);   // this 3 is number of 'm' that we allow to fit in, please note that 'mmm' and 'abc' widths are different even though they are same character count, that is 3

For the above code it will display a JTextField with 3 m's width. (we can type more m's on this JTextField, but on the TextField it shows only 3m's)

If we type "abc" on this, there is still remaining space on the text field where we can accommodate another character like shown below,

new JTextField("mmm", 3);

so, the conclusion seems to be it (argument value 3) is not the number of characters that we can fit into JTextField, but the number of 'm' that we can fit in.

What is the width of a "column" for a JTextField?

3 Answers3