Added in API level 1

SparseArray

open class SparseArray<E : Any!> : Cloneable
kotlin.Any
   ↳ android.util.SparseArray

SparseArray maps integers to Objects and, unlike a normal array of Objects, its indices can contain gaps. SparseArray is intended to be more memory-efficient than a HashMap, 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 HashMap because 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 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 of all removed entries. This garbage collection must be performed whenever the array needs to be grown, or when 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 returns the keys in ascending order. In the case of valueAt(int), the values corresponding to the keys are returned in ascending order.

Summary

Public constructors

Creates a new SparseArray containing no mappings.

SparseArray(initialCapacity: Int)

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

Public methods
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.

open Unit

Removes all key-value mappings from this SparseArray.

open SparseArray<E>

open Boolean
contains(key: Int)

Returns true if the key exists in the array.

open Boolean

Compares the contents of this SparseArray to the specified SparseArray.

open Int

Returns a hash code value for the contents of this SparseArray, combining the Objects#hashCode(Object) result of all its keys and values.

open Unit
delete(key: Int)

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

open E
get(key: Int)

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

open E
get(key: Int, valueIfKeyNotFound: E)

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

open Int

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

open Int
indexOfValue(value: E)

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

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.

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.

open Unit
remove(key: Int)

Alias for delete(int).

open Unit
removeAt(index: Int)

Removes the mapping at the specified index.

open Unit
removeAtRange(index: Int, size: Int)

Remove a range of mappings as a batch.

open Unit
set(key: Int, value: E)

Alias for put(int,java.lang.Object) to support Kotlin [index]= operator.

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.

open Int

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

open String

Returns a string representation of the object.

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.

Public constructors

SparseArray

Added in API level 1
SparseArray()

Creates a new SparseArray containing no mappings.

SparseArray

Added in API level 1
SparseArray(initialCapacity: Int)

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.

Public methods

append

Added in API level 1
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

Added in API level 1
open fun clear(): Unit

Removes all key-value mappings from this SparseArray.

clone

Added in API level 1
open fun clone(): SparseArray<E>
Return
SparseArray<E> a clone of this instance.
Exceptions
java.lang.CloneNotSupportedException if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.

contains

Added in API level 30
open fun contains(key: Int): Boolean

Returns true if the key exists in the array. This is equivalent to indexOfKey(int) >= 0.

Parameters
key Int: Potential key in the mapping
Return
Boolean true if the key is defined in the mapping

contentEquals

Added in API level 31
open fun contentEquals(other: SparseArray<*>?): Boolean

Compares the contents of this SparseArray to the specified SparseArray. For backwards compatibility reasons, Object#equals(Object) cannot be implemented, so this serves as a manually invoked alternative.

Parameters
other SparseArray<*>?: This value may be null.

contentHashCode

Added in API level 31
open fun contentHashCode(): Int

Returns a hash code value for the contents of this SparseArray, combining the Objects#hashCode(Object) result of all its keys and values. For backwards compatibility, Object#hashCode() cannot be implemented, so this serves as a manually invoked alternative.

delete

Added in API level 1
open fun delete(key: Int): Unit

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

get

Added in API level 1
open fun get(key: Int): E

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

get

Added in API level 1
open fun get(
    key: Int,
    valueIfKeyNotFound: E
): E

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

indexOfKey

Added in API level 1
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.

indexOfValue

Added in API level 1
open fun indexOfValue(value: E): Int

Returns an index for which valueAt would return the specified value, 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.

keyAt

Added in API level 1
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.

The keys corresponding to indices in ascending order are guaranteed to be in ascending order, e.g., keyAt(0) will return the smallest key and keyAt(size()-1) will return the largest key.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting android.os.Build.VERSION_CODES#P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting android.os.Build.VERSION_CODES#Q and later.

put

Added in API level 1
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.

remove

Added in API level 1
open fun remove(key: Int): Unit

Alias for delete(int).

removeAt

Added in API level 11
open fun removeAt(index: Int): Unit

Removes the mapping at the specified index.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting android.os.Build.VERSION_CODES#P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting android.os.Build.VERSION_CODES#Q and later.

removeAtRange

Added in API level 19
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

For indices outside of the range 0...size()-1, the behavior is undefined.

set

Added in API level 31
open fun set(
    key: Int,
    value: E
): Unit

Alias for put(int,java.lang.Object) to support Kotlin [index]= operator.

setValueAt

Added in API level 1
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.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting android.os.Build.VERSION_CODES#P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting android.os.Build.VERSION_CODES#Q and later.

size

Added in API level 1
open fun size(): Int

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

toString

Added in API level 1
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.

Return
String a string representation of the object.

valueAt

Added in API level 1
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.

The values corresponding to indices in ascending order are guaranteed to be associated with keys in ascending order, e.g., valueAt(0) will return the value associated with the smallest key and valueAt(size()-1) will return the value associated with the largest key.

For indices outside of the range 0...size()-1, the behavior is undefined for apps targeting android.os.Build.VERSION_CODES#P and earlier, and an ArrayIndexOutOfBoundsException is thrown for apps targeting android.os.Build.VERSION_CODES#Q and later.