javafx.collections.transformation.TransformationList Maven / Gradle / Ivy
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package javafx.collections.transformation;
import javafx.collections.ListChangeListener.Change;
import java.util.List;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import javafx.collections.ObservableListBase;
import javafx.collections.WeakListChangeListener;
/**
* A base class for all lists that wrap another list in a way that changes
* (transforms) the wrapped list's elements, order, size, or structure.
*
* If the source list is observable, a listener is automatically added to it
* and the events are delegated to {@link #sourceChanged(javafx.collections.ListChangeListener.Change)}.
*
* @param the type parameter of this list
* @param the upper bound of the type of the source list
* @since JavaFX 8.0
*/
public abstract class TransformationList extends ObservableListBase {
/**
* Contains the source list of this transformation list.
* This is never null and should be used to directly access source list content
*/
private ObservableList source;
/**
* This field contains the result of expression "source instanceof {@link javafx.collections.ObservableList}".
* If this is true, it is possible to do transforms online.
*/
private ListChangeListener sourceListener;
/**
* Creates a new Transformation list wrapped around the source list.
* @param source the wrapped list
*/
protected TransformationList(ObservableList source) {
if (source == null) {
throw new NullPointerException();
}
this.source = source;
source.addListener(new WeakListChangeListener<>(getListener()));
}
/**
* The source list specified in the constructor of this transformation list.
* @return The List that is directly wrapped by this TransformationList
*/
public final ObservableList getSource() {
return source;
}
/**
* Checks whether the provided list is in the chain under this
* {@code TransformationList}.
*
* This means the list is either the direct source as returned by
* {@link #getSource()} or the direct source is a {@code TransformationList},
* and the list is in it's transformation chain.
* @param list the list to check
* @return true if the list is in the transformation chain as specified above.
*/
public final boolean isInTransformationChain(ObservableList list) {
if (source == list) {
return true;
}
List currentSource = source;
while (currentSource instanceof TransformationList transformationList) {
currentSource = transformationList.source;
if (currentSource == list) {
return true;
}
}
return false;
}
private ListChangeListener getListener() {
if (sourceListener == null) {
sourceListener = c -> {
TransformationList.this.sourceChanged(c);
};
}
return sourceListener;
}
/**
* Called when a change from the source is triggered.
* @param c the change
*/
protected abstract void sourceChanged(Change c);
/**
* Maps the index of this list's element to an index in the direct source list.
* @param index the index in this list
* @return the index of the element's origin in the source list
* @see #getSource()
*/
public abstract int getSourceIndex(int index);
/**
* Maps the index of this list's element to an index of the provided {@code list}.
*
* The {@code list} must be in the transformation chain.
*
* @param list a list from the transformation chain
* @param index the index of an element in this list
* @return the index of the element's origin in the provided list
* @see #isInTransformationChain(javafx.collections.ObservableList)
*/
public final int getSourceIndexFor(ObservableList list, int index) {
if (!isInTransformationChain(list)) {
throw new IllegalArgumentException("Provided list is not in the transformation chain of this"
+ "transformation list");
}
List currentSource = source;
int idx = getSourceIndex(index);
while (currentSource != list && currentSource instanceof TransformationList tSource) {
idx = tSource.getSourceIndex(idx);
currentSource = tSource.source;
}
return idx;
}
/**
* Maps the index of the direct source list's element to an index in this list.
* @param index the index in the source list
* @return the index of the element in this list if it is contained
* in this list or negative value otherwise
* @see #getSource()
* @see #getSourceIndex(int)
*
* @since 9
*/
public abstract int getViewIndex(int index);
}