Swing Hacks

Let Your JTables Do the Sorting #23

Chapter 3, Tables and Trees

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115

HACK

This caches the comparators, but only one is used for sorting at any given

time. In

setSortColumn( ), you cache the index of the sort column, but then

you need to pull up the corresponding

Comparator

. Set the

comparator

—the

one that will be used to perform the sort—to

null

, and then check the com-

parators list to see if there is a

Comparator

at the given index. If so, it will

become the new

comparator

.

Now, you’re ready to handle the sorting. When you need to sort, either

because the sort index has changed or because the underlying model has

changed, you call the

resort( )

method, shown in Example 3-7.

This starts by resetting the size of the

sortedIndicies array, which will be

wrong if the number of rows in the

delegatedModel has changed. Next, build

up an array list of

SortingDelegates, an inner class containing a value from

the

delegatedModel (in the column to be sorted) and a mapped row number.

This class is shown in Example 3-8.

Example 3-7. Resorting based on the current comparator

protected void resort( ) {

// does sortedIndicies need to grow or shrink?

if (sortedIndicies.length != delegatedModel.getRowCount( )) {

sortedIndicies = new int [delegatedModel.getRowCount( )];

}

// build up a list of SortingDelegates

ArrayList sortMe = new ArrayList( );

for (int i=0; i<delegatedModel.getRowCount( ); i++) {

SortingDelegate sd =

new SortingDelegate ...