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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 null if no such mapping has been made.

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 keyAt(int) would return the specified key, or a negative number if the specified key is not mapped.

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.

boolean isEmpty()

Return true if size() is 0.

int keyAt(int index)

Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseArray stores.

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 delete(int).

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 0...size()-1, sets a new value for the indexth key-value mapping that this SparseArray stores.

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 0...size()-1, returns the value from the indexth key-value mapping that this SparseArray stores.

Inherited methods

From class java.lang.Object

Public constructors

SparseArrayCompat

added in version 22.1.0
SparseArrayCompat ()

Creates a new SparseArray containing no mappings.

SparseArrayCompat

added in version 22.1.0
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

added in version 22.1.0
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

clear

added in version 22.1.0
void clear ()

Removes all key-value mappings from this SparseArray.

clone

added in version 22.1.0
SparseArrayCompat<E> clone ()

Returns
SparseArrayCompat<E>

delete

added in version 22.1.0
void delete (int key)

Removes the mapping from the specified key, if there was any.

Parameters
key int

get

added in version 22.1.0
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

added in version 22.1.0
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

added in version 22.1.0
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

added in version 22.1.0
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

added in version 22.1.0
int keyAt (int index)

Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseArray stores.

Parameters
index int

Returns
int

put

added in version 22.1.0
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

remove

added in version 22.1.0
void remove (int key)

Alias for delete(int).

Parameters
key int

removeAt

added in version 22.1.0
void removeAt (int index)

Removes the mapping at the specified index.

Parameters
index int

removeAtRange

added in version 22.1.0
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

added in version 22.1.0
void setValueAt (int index, 
                E value)

Given an index in the range 0...size()-1, sets a new value for the indexth key-value mapping that this SparseArray stores.

Parameters
index int

value E

size

added in version 22.1.0
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

added in version 22.1.0
E valueAt (int index)

Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseArray stores.

Parameters
index int

Returns
E