Graphical User Interfaces - Java - page 614

Nothing complicated about it. The last JLabel (“Monkey wrench in works”) is commented
out because, as noted, the LayoutManager throws an exception if the number of components
is not evenly divisible by the number of columns. It was put in during testing and then com-
mented out, but was left in place for further consideration. Note that this layout operates cor-
rectly with more than two columns, but it does assume that all columns are approximately
the same height (relaxing this requirement has been left as an exercise for the reader).

Finally, let's look at the code for the layout manager itself, shown in Example 14-13 . After
some constants and fields and two constructors, the methods are listed in about the same or-
der as the discussion earlier in this recipe: the dummy add/remove component methods; then
the preferredSize() and minimumLayoutSize() methods (which delegate to com-
puteLayoutSize ); and, finally, layoutContainer , which does the actual laying out of the
components within the container. As you can see, the entire EntryLayout layout manager
class is only about 140 lines, including a lot of comments.

Example 14-13. EntryLayout.java
// package com.darwinsys.swingui.layout;
public public class implements LayoutManager {

/** The array of widths, as decimal fractions (0.4 == 40%, etc.). */
protected

class EntryLayout EntryLayout implements

protected final final double double [] widthPercentages ;

/** The number of columns. */
protected

protected final final int int COLUMNS ;

/** The default padding */
protected protected final int HPAD = 5 , VPAD = 5 ;

/** The actual padding */
protected

final static static int

protected final final int int hpad , vpad ;

/** True if the list of widths was valid. */
protected

protected boolean boolean validWidths = false false ;

/** Construct an EntryLayout with widths and padding specified.
* @param relWidths Array of doubles specifying relative column widths.
* @param h Horizontal padding between items
* @param v Vertical padding between items
*/
public

public EntryLayout ( double double [] relWidths , int int h , int int v ) {

COLUMNS = relWidths . length ;
widthPercentages = new

new double double [ COLUMNS ];

for for ( int int i = 0 ; i < relWidths . length ; i ++) {

iif ( relWidths [ i ] >= 1.0 )
throw throw new new IllegalArgumentException (