SparseArrayCompat
public
class
SparseArrayCompat
extends Object
implements
Cloneable
java.lang.Object | |
↳ | android.support.v4.util.SparseArrayCompat<E> |
SparseArrays map integers to Objects. Unlike a normal array of Objects, there can be gaps in the indices. It is intended to be more memory efficient than using a HashMap to map Integers to Objects, both because it avoids auto-boxing keys and its data structure doesn't rely on an extra entry object for each mapping.
Note that this container keeps its mappings in an array data structure, using a binary search to find keys. The implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.
To help with performance, the container includes an optimization when removing keys: instead of compacting its array immediately, it leaves the removed entry marked as deleted. The entry can then be re-used for the same key, or compacted later in a single garbage collection step of all removed entries. This garbage collection will need to be performed at any time the array needs to be grown or the the map size or entry values are retrieved.
It is possible to iterate over the items in this container using
keyAt(int)
and valueAt(int)
. Iterating over the keys using
keyAt(int)
with ascending values of the index will return the
keys in ascending order, or the values corresponding to the keys in ascending
order in the case of valueAt(int)
.
Summary
Public constructors | |
---|---|
SparseArrayCompat()
Creates a new SparseArray containing no mappings. |
|
SparseArrayCompat(int initialCapacity)
Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. |
Public methods | |
---|---|
void
|
append(int key, E value)
Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array. |
void
|
clear()
Removes all key-value mappings from this SparseArray. |
SparseArrayCompat<E>
|
clone()
|
void
|
delete(int key)
Removes the mapping from the specified key, if there was any. |
E
|
get(int key)
Gets the Object mapped from the specified key, or |
E
|
get(int key, E valueIfKeyNotFound)
Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made. |
int
|
indexOfKey(int key)
Returns the index for which |
int
|
indexOfValue(E value)
Returns an index for which |
boolean
|
isEmpty()
Return true if size() is 0. |
int
|
keyAt(int index)
Given an index in the range |
void
|
put(int key, E value)
Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one. |
void
|
remove(int key)
Alias for |
void
|
removeAt(int index)
Removes the mapping at the specified index. |
void
|
removeAtRange(int index, int size)
Remove a range of mappings as a batch. |
void
|
setValueAt(int index, E value)
Given an index in the range |
int
|
size()
Returns the number of key-value mappings that this SparseArray currently stores. |
String
|
toString()
This implementation composes a string by iterating over its mappings. |
E
|
valueAt(int index)
Given an index in the range |
Inherited methods | |
---|---|
From
class
java.lang.Object
|
Public constructors
SparseArrayCompat
SparseArrayCompat ()
Creates a new SparseArray containing no mappings.
SparseArrayCompat
SparseArrayCompat (int initialCapacity)
Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings. If you supply an initial capacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations.
Parameters | |
---|---|
initialCapacity |
int |
Public methods
append
void append (int key, E value)
Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.
Parameters | |
---|---|
key |
int |
value |
E |
delete
void delete (int key)
Removes the mapping from the specified key, if there was any.
Parameters | |
---|---|
key |
int |
get
E get (int key)
Gets the Object mapped from the specified key, or null
if no such mapping has been made.
Parameters | |
---|---|
key |
int |
Returns | |
---|---|
E |
get
E get (int key, E valueIfKeyNotFound)
Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made.
Parameters | |
---|---|
key |
int |
valueIfKeyNotFound |
E |
Returns | |
---|---|
E |
indexOfKey
int indexOfKey (int key)
Returns the index for which keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.
Parameters | |
---|---|
key |
int |
Returns | |
---|---|
int |
indexOfValue
int indexOfValue (E value)
Returns an index for which valueAt(int)
would return the
specified key, or a negative number if no keys map to the
specified value.
Beware that this is a linear search, unlike lookups by key, and that multiple keys can map to the same value and this will find only one of them.
Note also that unlike most collections' indexOf
methods,
this method compares values using ==
rather than equals
.
Parameters | |
---|---|
value |
E |
Returns | |
---|---|
int |
isEmpty
boolean isEmpty ()
Return true if size() is 0.
Returns | |
---|---|
boolean |
true if size() is 0. |
keyAt
int keyAt (int index)
Given an index in the range 0...size()-1
, returns
the key from the index
th key-value mapping that this
SparseArray stores.
Parameters | |
---|---|
index |
int |
Returns | |
---|---|
int |
put
void put (int key, E value)
Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.
Parameters | |
---|---|
key |
int |
value |
E |
removeAt
void removeAt (int index)
Removes the mapping at the specified index.
Parameters | |
---|---|
index |
int |
removeAtRange
void removeAtRange (int index, int size)
Remove a range of mappings as a batch.
Parameters | |
---|---|
index |
int : Index to begin at |
size |
int : Number of mappings to remove
|
setValueAt
void setValueAt (int index, E value)
Given an index in the range 0...size()-1
, sets a new
value for the index
th key-value mapping that this
SparseArray stores.
Parameters | |
---|---|
index |
int |
value |
E |
size
int size ()
Returns the number of key-value mappings that this SparseArray currently stores.
Returns | |
---|---|
int |
toString
String toString ()
This implementation composes a string by iterating over its mappings. If this map contains itself as a value, the string "(this Map)" will appear in its place.
Returns | |
---|---|
String |
valueAt
E valueAt (int index)
Given an index in the range 0...size()-1
, returns
the value from the index
th key-value mapping that this
SparseArray stores.
Parameters | |
---|---|
index |
int |
Returns | |
---|---|
E |