Matrix Model
Here we describe how to implement a matrix model
(
By default, ZK does not provide a built-in model implementation class for MatrixModel because Biglistbox is designed to handle unlimited data set, therefore, there is no need to handle model data in memory. This usage is application-dependent and varies from case to case. However, you can extend your own implementation from the
skeleton class.
To implement a MatrixModel, one needs to consider the performance issue that handles a huge data set in memory with Java Collection Framework. The issue is when using the default implementation of Java Collection Framework as it goes through every entry to gather the value of hashCode when searching the key in Map/Set or to check every entry for equals and toString functions. This implementation method greatly reduces the performance of Biglistbox. Therefore, to use the Biglistbox component with MatrixModel, we need to implement a clever and simple List for traversing huge data sets.
FakerKeyList
In this example, we create a FakerKeyList to implement the List interface for MatrixModel to handle the partial big data in memory.
private class FakerKeyList<T> extends AbstractList<T> {
final int _size;
Map<String, T> _updateCache = new HashMap<String,T> ();
final Fun<?> _fn;
final String _key;
public FakerKeyList(int size, int key, Fun<?> fn) {
_size = size;
_key = key + "_" + size;
_fn = fn;
}
@Override
public T get(int index) {
// if changed, returns the changed value
Object val = _updateCache.get(String.valueOf(index));
if (val != null)
return (T) val;
return (T) _fn.apply(index);
}
@Override
public int hashCode() {
return _key.hashCode();
}
@Override
public boolean equals(Object obj) {
if (obj == this)
return true;
if (obj instanceof FakerKeyList) {
return _key.equals(((FakerKeyList)(obj))._key);
}
return false;
}
@Override
public String toString() {
return _key;
}
// omitted...
}
As you can see, we use a key string as the key for toString, hashCode, and equals methods to speed up searching time. Fun class on the other hand, is a handy class to render the model data for this example.
FakerMatrixModel
In this example, we create a FakerMatrixModel to implement MatrixModel. Following is the fragment code:
public class FakerMatrixModel<Head extends List, Row extends List, Cell, Header> extends
AbstractListModel<Row> implements MatrixModel<Row, Head, Cell, Header>, Sortable {
// omitted...
private boolean _sortDir = true;
@Override
public Row getElementAt(int index) {
final int rowIndex = _sortDir ? index : getSize() - index - 1; // handle the sorting
final String key = String.valueOf(rowIndex);
List<String> value = _rowCache.get(key);
if (value == null) {
value = new FakerKeyList<String>(_colSize, rowIndex, new Fun() {
@Override
public Object apply(int index) {
return "y = " + rowIndex;
}});
_rowCache.put(key, value);
}
return (Row) value;
}
// omitted...
}
MatrixModel is extended from the ListModel interface and uses the getElementAt(int) method to receive row data from the FakerKeyList object that implements the List interface.
Sortable Model
The MatrixModel can also support
interface. In your implementor class you can just implement the
interface and provide
and
methods.
For example,
public void sort(Comparator cmpr, boolean ascending) {
_sorting = cmpr;
_sortDir = ascending;
fireEvent(ListDataEvent.STRUCTURE_CHANGED, -1, -1);
}
@Override
public String getSortDirection(Comparator cmpr) {
if (Objects.equals(_sorting, cmpr))
return _sortDir ? "ascending" : "descending";
return "natural";
}
As you can see, we fire a data change event with ListDataEvent.STRUCTURE_CHANGED attribute to notify the component that model data has been changed.
Notify for Data Updates
MatrixModel is the same as ListModel when notify for data updates, please refer to ListMode#Notify_for_Data_Updates
Resource
All of the examples above can be found here - Github’s FakerMatrixModel source code
Version History
| Version | Date | Content |
|---|---|---|
| 6.0.1 | March 2012 | The Biglistbox and MatrixModel were introduced |