javafx.collections

Class ListChangeListener.Change<E>

java.lang.Object

javafx.collections.ListChangeListener.Change<E>

Type Parameters:

E - the list element type

Enclosing interface:

public abstract static class ListChangeListener.Change<E>
extends Object

Represents a report of a changes done to an Observablelist. The Change may consist of one or more actual changes and must be iterated by next() method. Each change must be one of the following:

Permutation change : wasPermutated() returns true in this case. The permutation happened at range between from(inclusive) and to(exclusive) and can be queried by calling getPermutation(int) method.
Add or remove change : In this case, at least one of the wasAdded(), wasRemoved() returns true. If both methods return true, wasReplaced() will also return true.
The getRemoved() method returns a list of elements that have been replaced or removed from the list.

The range between from(inclusive) and to(exclusive) denotes the sublist of the list that contain new elements. Note that this is a half-open interval, so if no elements were added, getFrom() is equal to getTo().

It is possible to get a list of added elements by calling getAddedSubList().

Note that in order to maintain correct indexes of the separate add/remove changes, these changes must be sorted by their from index.
Update change : wasUpdated() return true on an update change. All elements between from(inclusive) and to(exclusive) were updated.

Important: It's necessary to call next() method before calling any other method of Change. The same applies after calling reset(). The only methods that works at any time is getList().

Typical usage is to observe changes on an ObservableList in order to hook or unhook (or add or remove a listener) or in order to maintain some invariant on every element in that ObservableList. A common code pattern for doing this looks something like the following:

ObservableList theList = ...;

 theList.addListener(new ListChangeListener<Item>() {
     public void onChanged(Change<tem> c) {
         while (c.next()) {
             if (c.wasPermutated()) {
                     for (int i = c.getFrom(); i < c.getTo(); ++i) {
                          //permutate
                     }
                 } else if (c.wasUpdated()) {
                          //update item
                 } else {
                     for (Item remitem : c.getRemoved()) {
                         remitem.remove(Outer.this);
                     }
                     for (Item additem : c.getAddedSubList()) {
                         additem.add(Outer.this);
                     }
                 }
             }
         }
     });

 }

Warning: This class directly accesses the source list to acquire information about the changes.
This effectively makes the Change object invalid when another change occurs on the list.
For this reason it is not safe to use this class on a different thread.
It also means the source list cannot be modified inside the listener since that would invalidate this Change object for all subsequent listeners.

Note: in case the change contains multiple changes of different type, these changes must be in the following order: permutation change(s), add or remove changes, update changes This is because permutation changes cannot go after add/remove changes as they would change the position of added elements. And on the other hand, update changes must go after add/remove changes because they refer with their indexes to the current state of the list, which means with all add/remove changes applied.

Since:

JavaFX 2.0

Constructor Summary

Constructors
Constructor and Description

Change(ObservableList<E> list)
Constructs a new change done to a list.

Constructors
Constructor and Description
`Change(ObservableList<E> list)` Constructs a new change done to a list.

Method Summary

All MethodsInstance MethodsAbstract MethodsConcrete Methods
Modifier and Type	Method and Description
`int`	`getAddedSize()` Size of the interval that was added.
`List<E>`	`getAddedSubList()` To get a subList view of the list that contains only the elements added, use getAddedSubList() method.
`abstract int`	`getFrom()` If wasAdded is true, the interval contains all the values that were added.
`ObservableList<E>`	`getList()` The source list of the change.
`protected abstract int[]`	`getPermutation()` If this change is an permutation, it returns an integer array that describes the permutation.
`int`	`getPermutation(int i)` By calling these method, you can observe the permutation that happened.
`abstract List<E>`	`getRemoved()` An immutable list of removed/replaced elements.
`int`	`getRemovedSize()` Size of getRemoved() list.
`abstract int`	`getTo()` The end of the change interval.
`abstract boolean`	`next()` Go to the next change.
`abstract void`	`reset()` Reset to the initial stage.
`boolean`	`wasAdded()` Indicates if elements were added during this change
`boolean`	`wasPermutated()` Indicates if the change was only a permutation.
`boolean`	`wasRemoved()` Indicates if elements were removed during this change.
`boolean`	`wasReplaced()` Indicates if elements were replaced during this change.
`boolean`	`wasUpdated()` Indicates that the elements between getFrom() (inclusive) to getTo() exclusive has changed.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Change
```
public Change(ObservableList<E> list)
```
  Constructs a new change done to a list.
  
  Parameters:
  
  list - that was changed

Method Detail
- next
```
public abstract boolean next()
```
  Go to the next change. The Change in the initial state is invalid a requires a call to next() before calling other methods. The first next() call will make this object represent the first change.
  
  Returns:
  
  true if switched to the next change, false if this is the last change.
- reset
```
public abstract void reset()
```
  Reset to the initial stage. After this call, the next() must be called before working with the first change.
- getList
```
public ObservableList<E> getList()
```
  The source list of the change.
  
  Returns:
  
  a list that was changed
- getFrom
```
public abstract int getFrom()
```
  If wasAdded is true, the interval contains all the values that were added. If wasPermutated is true, the interval marks the values that were permutated. If wasRemoved is true and wasAdded is false, getFrom() and getTo() should return the same number - the place where the removed elements were positioned in the list.
  
  Returns:
  
  a beginning (inclusive) of an interval related to the change
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- getTo
```
public abstract int getTo()
```
  The end of the change interval.
  
  Returns:
  
  a end (exclusive) of an interval related to the change.
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
  
  See Also:
  
  getFrom()
- getRemoved
```
public abstract List<E> getRemoved()
```
  An immutable list of removed/replaced elements. If no elements were removed from the list, an empty list is returned.
  
  Returns:
  
  a list with all the removed elements
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- wasPermutated
```
public boolean wasPermutated()
```
  Indicates if the change was only a permutation.
  
  Returns:
  
  true if the change was just a permutation.
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- wasAdded
```
public boolean wasAdded()
```
  Indicates if elements were added during this change
  
  Returns:
  
  true if something was added to the list
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- wasRemoved
```
public boolean wasRemoved()
```
  Indicates if elements were removed during this change. Note that using set will also produce a change with wasRemoved() returning true. See wasReplaced().
  
  Returns:
  
  true if something was removed from the list
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- wasReplaced
```
public boolean wasReplaced()
```
  Indicates if elements were replaced during this change. This is usually true when set is called on the list. Set operation will act like remove and add operation at the same time.
  Usually, it's not necessary to use this method directly. Handling remove operation and then add operation, as in the example above, will effectively handle also set operation.
  
  Returns:
  
  same as wasAdded() && wasRemoved()
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- wasUpdated
```
public boolean wasUpdated()
```
  Indicates that the elements between getFrom() (inclusive) to getTo() exclusive has changed. This is the only optional event type and may not be fired by all ObservableLists.
  
  Returns:
  
  true if the current change is an update change.
  
  Since:
  
  JavaFX 2.1
- getAddedSubList
```
public List<E> getAddedSubList()
```
  To get a subList view of the list that contains only the elements added, use getAddedSubList() method. This is actually a shortcut to c.getList().subList(c.getFrom(), c.getTo());
```
for (Node n : change.getAddedSubList()) {
       // do something
 }
```
  Returns:
  
  the newly created sublist view that contains all the added elements.
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- getRemovedSize
```
public int getRemovedSize()
```
  Size of getRemoved() list.
  
  Returns:
  
  the number of removed items
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- getAddedSize
```
public int getAddedSize()
```
  Size of the interval that was added.
  
  Returns:
  
  the number of added items
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- getPermutation
```
protected abstract int[] getPermutation()
```
  If this change is an permutation, it returns an integer array that describes the permutation. This array maps directly from the previous indexes to the new ones. This method is not publicly accessible and therefore can return an array safely. The 0 index of the array corresponds to index getFrom() of the list. The same applies for the last index and getTo(). The method is used by wasPermutated() and getPermutation(int) methods.
  
  Returns:
  
  empty array if this is not permutation or an integer array containing the permutation
  
  Throws:
  
  IllegalStateException - if this Change is in initial state
- getPermutation
```
public int getPermutation(int i)
```
  By calling these method, you can observe the permutation that happened. In order to get the new position of an element, you must call:
```
change.getPermutation(oldIndex);
```
  Note: default implementation of this method takes the information from getPermutation() method. You don't have to override this method.
  Parameters:
  
  i - the old index that contained the element prior to this change
  
  Returns:
  
  the new index of the same element
  
  Throws:
  
  IndexOutOfBoundsException - if i is out of the bounds of the list

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Documentation extracted from JavaFX API Documentation.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Java, JavaFX and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.

Class ListChangeListener.Change<E>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Change

Method Detail

next

reset

getList

getFrom

getTo

getRemoved

wasPermutated

wasAdded

wasRemoved

wasReplaced

wasUpdated

getAddedSubList

getRemovedSize

getAddedSize

getPermutation

getPermutation