SparseArrayCompat

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 map size or entry values are retrieved.

It is possible to iterate over the items in this container using keyAt and valueAt. Iterating over the keys using keyAt 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.

Summary

Public constructors
<E : Any?> SparseArrayCompat(initialCapacity: Int)

Creates a new SparseArray containing no mappings that will not require any additional memory allocation to store the specified number of mappings.
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android
N

Public functions
open Unit
append(key: Int, value: E)

Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.
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N
open Unit

Removes all key-value mappings from this SparseArray.
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open SparseArrayCompat<E>
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open Boolean

Returns true if the specified key is mapped.
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N
open Boolean
containsValue(value: E)

Returns true if the specified value is mapped from any key.
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N
open Unit
delete(key: Int)

This function is deprecated. Alias for remove(int).
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open operator E?
get(key: Int)

Gets the Object mapped from the specified key, or null if no such mapping has been made.
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N
open E
get(key: Int, defaultValue: E)

Gets the Object mapped from the specified key, or defaultValue if no such mapping has been made.
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open Int

Returns the index for which keyAt would return the specified key, or a negative number if the specified key is not mapped.
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open Int
indexOfValue(value: E)

Returns an index for which valueAt would return the specified key, or a negative number if no keys map to the specified value.
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open Boolean

Return true if size is 0.
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open Int
keyAt(index: Int)

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

Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.
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open Unit

Copies all of the mappings from the other to this map.
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open E?
putIfAbsent(key: Int, value: E)

Add a new value to the array map only if the key does not already have a value or it is mapped to null.
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open Unit
remove(key: Int)

Removes the mapping from the specified key, if there was any.
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open Boolean
remove(key: Int, value: Any?)

Remove an existing key from the array map only if it is currently mapped to value.
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open Unit
removeAt(index: Int)

Removes the mapping at the specified index.
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open Unit
removeAtRange(index: Int, size: Int)

Remove a range of mappings as a batch.
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open E?
replace(key: Int, value: E)

Replace the mapping for key only if it is already mapped to a value.
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open Boolean
replace(key: Int, oldValue: E, newValue: E)

Replace the mapping for key only if it is already mapped to a value.
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open Unit
setValueAt(index: Int, value: E)

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

Returns the number of key-value mappings that this SparseArray currently stores.
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open String

Returns a string representation of the object.
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open E
valueAt(index: Int)

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

Public properties
Boolean

Return true if size is 0.
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Extension functions
inline operator Boolean
<T : Any?> SparseArrayCompat<T>.contains(key: Int)

Returns true if the collection contains key.
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inline Unit
<T : Any?> SparseArrayCompat<T>.forEach(action: (key: Int, value) -> Unit)

Performs the given action for each key/value entry.
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inline T
<T : Any?> SparseArrayCompat<T>.getOrDefault(key: Int, defaultValue: T)

Return the value corresponding to key, or defaultValue when not present.
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inline T
<T : Any?> SparseArrayCompat<T>.getOrElse(key: Int, defaultValue: () -> T)

Return the value corresponding to key, or from defaultValue when not present.
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inline Boolean

Return true when the collection contains elements.
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IntIterator

Return an iterator over the collection's keys.
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operator SparseArrayCompat<T>

Creates a new collection by adding or replacing entries from other.
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inline operator Unit
<T : Any?> SparseArrayCompat<T>.set(key: Int, value: T)

Allows the use of the index operator for storing values in the collection.
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Iterator<T>

Return an iterator over the collection's values.
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Extension properties
Int

Returns the number of key/value pairs in the collection.
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Public constructors

SparseArrayCompat

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<E : Any?> SparseArrayCompat(initialCapacity: Int = 10)

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 = 10

initial capacity of the array. The array will not require any additional memory allocation to store the specified number of mappings. If you supply an initialCapacity of 0, the sparse array will be initialized with a light-weight representation not requiring any additional array allocations. Default initialCapacity is 10.

Public functions

append

Cmn android N
Added in 1.0.0
open fun append(key: Int, value: E): Unit

Puts a key/value pair into the array, optimizing for the case where the key is greater than all existing keys in the array.

clear

Cmn android N
Added in 1.0.0
open fun clear(): Unit

Removes all key-value mappings from this SparseArray.

clone

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Added in 1.0.0
open fun clone(): SparseArrayCompat<E>

containsKey

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Added in 1.0.0
open fun containsKey(key: Int): Boolean

Returns true if the specified key is mapped.

containsValue

Cmn android N
Added in 1.0.0
open fun containsValue(value: E): Boolean

Returns true if the specified value is mapped from any key.

delete

android
Added in 1.0.0
Deprecated in 1.1.0
open fun delete(key: Int): Unit

get

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Added in 1.0.0
open operator fun get(key: Int): E?

Gets the Object mapped from the specified key, or null if no such mapping has been made.

get

Cmn android N
Added in 1.0.0
open fun get(key: Int, defaultValue: E): E

Gets the Object mapped from the specified key, or defaultValue if no such mapping has been made.

indexOfKey

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Added in 1.0.0
open fun indexOfKey(key: Int): Int

Returns the index for which keyAt would return the specified key, or a negative number if the specified key is not mapped.

Parameters
key: Int

the key to search for
Returns
Int

the index for which keyAt would return the specified key, or a negative number if the specified key is not mapped

indexOfValue

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Added in 1.0.0
open fun indexOfValue(value: E): Int

Returns an index for which valueAt 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.

isEmpty

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Added in 1.0.0
open fun isEmpty(): Boolean

Return true if size is 0.

Returns
Boolean

true if size is 0.

keyAt

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Added in 1.0.0
open fun keyAt(index: Int): Int

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

put

Cmn android N
Added in 1.0.0
open fun put(key: Int, value: E): Unit

Adds a mapping from the specified key to the specified value, replacing the previous mapping from the specified key if there was one.

putAll

Cmn android N
Added in 1.0.0
open fun putAll(other: SparseArrayCompat<E>): Unit

Copies all of the mappings from the other to this map. The effect of this call is equivalent to that of calling put on this map once for each mapping from key to value in other.

putIfAbsent

Cmn android N
Added in 1.1.0
open fun putIfAbsent(key: Int, value: E): E?

Add a new value to the array map only if the key does not already have a value or it is mapped to null.

Parameters
key: Int

The key under which to store the value.
value: E

The value to store for the given key.
Returns
E?

Returns the value that was stored for the given key, or null if there was no such key.

remove

Cmn android N
Added in 1.0.0
open fun remove(key: Int): Unit

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

remove

Cmn android N
Added in 1.1.0
open fun remove(key: Int, value: Any?): Boolean

Remove an existing key from the array map only if it is currently mapped to value.

Parameters
key: Int

The key of the mapping to remove.
value: Any?

The value expected to be mapped to the key.
Returns
Boolean

Returns true if the mapping was removed.

removeAt

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Added in 1.0.0
open fun removeAt(index: Int): Unit

Removes the mapping at the specified index.

removeAtRange

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Added in 1.0.0
open fun removeAtRange(index: Int, size: Int): Unit

Remove a range of mappings as a batch.

Parameters
index: Int

Index to begin at
size: Int

Number of mappings to remove

replace

Cmn android N
Added in 1.1.0
open fun replace(key: Int, value: E): E?

Replace the mapping for key only if it is already mapped to a value.

Parameters
key: Int

The key of the mapping to replace.
value: E

The value to store for the given key.
Returns
E?

Returns the previous mapped value or null.

replace

Cmn android N
Added in 1.1.0
open fun replace(key: Int, oldValue: E, newValue: E): Boolean

Replace the mapping for key only if it is already mapped to a value.

Parameters
key: Int

The key of the mapping to replace.
oldValue: E

The value expected to be mapped to the key.
newValue: E

The value to store for the given key.
Returns
Boolean

Returns true if the value was replaced.

setValueAt

Cmn android N
Added in 1.0.0
open fun setValueAt(index: Int, value: E): Unit

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

size

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Added in 1.0.0
open fun size(): Int

Returns the number of key-value mappings that this SparseArray currently stores.

toString

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open fun toString(): String

Returns a string representation of the object.

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.

valueAt

Cmn android N
Added in 1.0.0
open fun valueAt(index: Int): E

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

Public properties

isEmpty

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Added in 1.3.0
val isEmpty: Boolean

Return true if size is 0.

Returns
Boolean

true if size is 0.

Extension functions

contains

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inline operator fun <T : Any?> SparseArrayCompat<T>.contains(key: Int): Boolean

Returns true if the collection contains key.

forEach

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inline fun <T : Any?> SparseArrayCompat<T>.forEach(action: (key: Int, value) -> Unit): Unit

Performs the given action for each key/value entry.

getOrDefault

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inline fun <T : Any?> SparseArrayCompat<T>.getOrDefault(key: Int, defaultValue: T): T

Return the value corresponding to key, or defaultValue when not present.

getOrElse

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inline fun <T : Any?> SparseArrayCompat<T>.getOrElse(key: Int, defaultValue: () -> T): T

Return the value corresponding to key, or from defaultValue when not present.

isNotEmpty

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inline fun <T : Any?> SparseArrayCompat<T>.isNotEmpty(): Boolean

Return true when the collection contains elements.

keyIterator

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fun <T : Any?> SparseArrayCompat<T>.keyIterator(): IntIterator

Return an iterator over the collection's keys.

plus

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operator fun <T : Any?> SparseArrayCompat<T>.plus(other: SparseArrayCompat<T>): SparseArrayCompat<T>

Creates a new collection by adding or replacing entries from other.

set

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inline operator fun <T : Any?> SparseArrayCompat<T>.set(key: Int, value: T): Unit

Allows the use of the index operator for storing values in the collection.

valueIterator

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fun <T : Any?> SparseArrayCompat<T>.valueIterator(): Iterator<T>

Return an iterator over the collection's values.

Extension properties

size

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val SparseArrayCompat<T>.size: Int

Returns the number of key/value pairs in the collection.