SortedList

public class SortedList<T>

A Sorted list implementation that can keep items in order and also notify for changes in the list such that it can be bound to a RecyclerView.Adapter.

It keeps items ordered using the compare method and uses binary search to retrieve items. If the sorting criteria of your items may change, make sure you call appropriate methods while editing them to avoid data inconsistencies.

You can control the order of items and change notifications via the Callback parameter.

Summary

Nested types

A callback implementation that can batch notify events dispatched by the SortedList.
public abstract class SortedList.Callback<T2> implements Comparator, ListUpdateCallback

The class that controls the behavior of the SortedList.

Constants
static final int

Used by indexOf when the item cannot be found in the list.

Public constructors
SortedList(
    @NonNull Class<T> klass,
    @NonNull SortedList.Callback<T> callback
)

Creates a new SortedList of type T.
SortedList(
    @NonNull Class<T> klass,
    @NonNull SortedList.Callback<T> callback,
    int initialCapacity
)

Creates a new SortedList of type T.

Public methods
int
add(T item)

Adds the given item to the list.
void
addAll(@NonNull T[] items)

Adds the given items to the list.
void

Adds the given items to the list.
void
addAll(@NonNull T[] items, boolean mayModifyInput)

Adds the given items to the list.
void

Batches adapter updates that happen after calling this method and before calling endBatchedUpdates.
void

Removes all items from the SortedList.
void

Ends the update transaction and dispatches any remaining event to the callback.
T
get(int index)

Returns the item at the given index.
int
indexOf(T item)

Returns the position of the provided item.
void

This method can be used to recalculate the position of the item at the given index, without triggering an onChanged callback.
boolean
remove(T item)

Removes the provided item from the list and calls onRemoved.
T
removeItemAt(int index)

Removes the item at the given index and calls onRemoved.
void
replaceAll(@NonNull T[] items)

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate.
void

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate.
void
replaceAll(@NonNull T[] items, boolean mayModifyInput)

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate.
int

The number of items in the list.
void
updateItemAt(int index, T item)

Updates the item at the given index and calls onChanged and/or onMoved if necessary.

Constants

INVALID_POSITION

Added in 1.0.0
public static final int INVALID_POSITION = -1

Used by indexOf when the item cannot be found in the list.

Public constructors

SortedList

Added in 1.0.0
public SortedList(
    @NonNull Class<T> klass,
    @NonNull SortedList.Callback<T> callback
)

Creates a new SortedList of type T.

Parameters
@NonNull Class<T> klass

The class of the contents of the SortedList.
@NonNull SortedList.Callback<T> callback

The callback that controls the behavior of SortedList.

SortedList

Added in 1.0.0
public SortedList(
    @NonNull Class<T> klass,
    @NonNull SortedList.Callback<T> callback,
    int initialCapacity
)

Creates a new SortedList of type T.

Parameters
@NonNull Class<T> klass

The class of the contents of the SortedList.
@NonNull SortedList.Callback<T> callback

The callback that controls the behavior of SortedList.
int initialCapacity

The initial capacity to hold items.

Public methods

add

Added in 1.0.0
public int add(T item)

Adds the given item to the list. If this is a new item, SortedList calls onInserted.

If the item already exists in the list and its sorting criteria is not changed, it is replaced with the existing Item. SortedList uses areItemsTheSame to check if two items are the same item and uses areContentsTheSame to decide whether it should call onChanged or not. In both cases, it always removes the reference to the old item and puts the new item into the backing array even if areContentsTheSame returns false.

If the sorting criteria of the item is changed, SortedList won't be able to find its duplicate in the list which will result in having a duplicate of the Item in the list. If you need to update sorting criteria of an item that already exists in the list, use updateItemAt. You can find the index of the item using indexOf before you update the object.

Parameters
T item

The item to be added into the list.
Returns
int

The index of the newly added item.
See also
compare
areItemsTheSame
areContentsTheSame

}

addAll

public void addAll(@NonNull T[] items)

Adds the given items to the list. Does not modify or retain the input.

Parameters
@NonNull T[] items

Array of items to be added into the list.
See also
addAll

addAll

Added in 1.0.0
public void addAll(@NonNull Collection<T> items)

Adds the given items to the list. Does not modify or retain the input.

Parameters
@NonNull Collection<T> items

Collection of items to be added into the list.
See also
addAll

addAll

Added in 1.0.0
public void addAll(@NonNull T[] items, boolean mayModifyInput)

Adds the given items to the list. Equivalent to calling add in a loop, except the callback events may be in a different order/granularity since addAll can batch them for better performance.

If allowed, will reference the input array during, and possibly after, the operation to avoid extra memory allocation, in which case you should not continue to reference or modify the array yourself.

Parameters
@NonNull T[] items

Array of items to be added into the list.
boolean mayModifyInput

If true, SortedList is allowed to modify and permanently reference the input array.
See also
addAll

beginBatchedUpdates

Added in 1.0.0
public void beginBatchedUpdates()

Batches adapter updates that happen after calling this method and before calling endBatchedUpdates. For example, if you add multiple items in a loop and they are placed into consecutive indices, SortedList calls onInserted only once with the proper item count. If an event cannot be merged with the previous event, the previous event is dispatched to the callback instantly.

After running your data updates, you must call endBatchedUpdates which will dispatch any deferred data change event to the current callback.

A sample implementation may look like this: 

    mSortedList.beginBatchedUpdates();
    try {
        mSortedList.add(item1)
        mSortedList.add(item2)
        mSortedList.remove(item3)
        ...
    } finally {
        mSortedList.endBatchedUpdates();
    }

Instead of using this method to batch calls, you can use a Callback that extends BatchedCallback. In that case, you must make sure that you are manually calling dispatchLastEvent right after you complete your data changes. Failing to do so may create data inconsistencies with the Callback.

If the current Callback is an instance of BatchedCallback, calling this method has no effect.

clear

Added in 1.0.0
public void clear()

Removes all items from the SortedList.

endBatchedUpdates

Added in 1.0.0
public void endBatchedUpdates()

Ends the update transaction and dispatches any remaining event to the callback.

get

Added in 1.0.0
public T get(int index)

Returns the item at the given index.

Parameters
int index

The index of the item to retrieve.
Returns
T

The item at the given index.
Throws
java.lang.IndexOutOfBoundsException

if provided index is negative or larger than the size of the list.

indexOf

Added in 1.0.0
public int indexOf(T item)

Returns the position of the provided item.

Parameters
T item

The item to query for position.
Returns
int

The position of the provided item or INVALID_POSITION if item is not in the list.

recalculatePositionOfItemAt

Added in 1.0.0
public void recalculatePositionOfItemAt(int index)

This method can be used to recalculate the position of the item at the given index, without triggering an onChanged callback.

If you are editing objects in the list such that their position in the list may change but you don't want to trigger an onChange animation, you can use this method to re-position it. If the item changes position, SortedList will call onMoved without calling onChanged.

A sample usage may look like: 

    final int position = mSortedList.indexOf(item);
    item.incrementPriority(); // assume items are sorted by priority
    mSortedList.recalculatePositionOfItemAt(position);
In the example above, because the sorting criteria of the item has been changed, mSortedList.indexOf(item) will not be able to find the item. This is why the code above first gets the position before editing the item, edits it and informs the SortedList that item should be repositioned.
Parameters
int index

The current index of the Item whose position should be re-calculated.
See also
updateItemAt
add

remove

Added in 1.0.0
public boolean remove(T item)

Removes the provided item from the list and calls onRemoved.

Parameters
T item

The item to be removed from the list.
Returns
boolean

True if item is removed, false if item cannot be found in the list.

removeItemAt

Added in 1.0.0
public T removeItemAt(int index)

Removes the item at the given index and calls onRemoved.

Parameters
int index

The index of the item to be removed.
Returns
T

The removed item.

replaceAll

public void replaceAll(@NonNull T[] items)

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate. Does not modify or retain the input.

Parameters
@NonNull T[] items

Array of items to replace current items.
See also
replaceAll

replaceAll

Added in 1.0.0
public void replaceAll(@NonNull Collection<T> items)

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate. Does not modify or retain the input.

Parameters
@NonNull Collection<T> items

Array of items to replace current items.
See also
replaceAll

replaceAll

Added in 1.0.0
public void replaceAll(@NonNull T[] items, boolean mayModifyInput)

Replaces the current items with the new items, dispatching ListUpdateCallback events for each change detected as appropriate.

If allowed, will reference the input array during, and possibly after, the operation to avoid extra memory allocation, in which case you should not continue to reference or modify the array yourself.

Note: this method does not detect moves or dispatch onMoved events. It instead treats moves as a remove followed by an add and therefore dispatches onRemoved and onRemoved events. See DiffUtil if you want your implementation to dispatch move events.

Parameters
@NonNull T[] items

Array of items to replace current items.
boolean mayModifyInput

If true, SortedList is allowed to modify and permanently reference the input array.
See also
replaceAll

size

Added in 1.0.0
public int size()

The number of items in the list.

Returns
int

The number of items in the list.

updateItemAt

Added in 1.0.0
public void updateItemAt(int index, T item)

Updates the item at the given index and calls onChanged and/or onMoved if necessary.

You can use this method if you need to change an existing Item such that its position in the list may change.

If the new object is a different object (get(index) != item) and areContentsTheSame returns true, SortedList avoids calling onChanged otherwise it calls onChanged.

If the new position of the item is different than the provided index, SortedList calls onMoved.

Parameters
int index

The index of the item to replace
T item

The item to replace the item at the given Index.
See also
add