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 |
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 |
clear()Removes all key-value mappings from this SparseArray. |
| open SparseArray<E> |
clone() |
| open Boolean |
Returns true if the key exists in the array. |
| open Boolean |
contentEquals(other: SparseArray<*>?)Compares the contents of this |
| open Int |
Returns a hash code value for the contents of this |
| open Unit |
Removes the mapping from the specified key, if there was any. |
| open E |
Gets the Object mapped from the specified key, or |
| open E |
Gets the Object mapped from the specified key, or the specified Object if no such mapping has been made. |
| open Int |
indexOfKey(key: Int)Returns the index for which |
| open Int |
indexOfValue(value: E)Returns an index for which |
| open Int |
Given an index in the range |
| open Unit |
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 |
Alias for |
| open Unit |
Removes the mapping at the specified index. |
| open Unit |
removeAtRange(index: Int, size: Int)Remove a range of mappings as a batch. |
| open Unit |
Alias for |
| open Unit |
setValueAt(index: Int, value: E)Given an index in the range |
| open Int |
size()Returns the number of key-value mappings that this SparseArray currently stores. |
| open String |
toString()Returns a string representation of the object. |
| open E |
Given an index in the range |
Public constructors
SparseArray
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
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
open fun clear(): Unit
Removes all key-value mappings from this SparseArray.
clone
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
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
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
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
open fun delete(key: Int): Unit
Removes the mapping from the specified key, if there was any.
get
open fun get(key: Int): E
Gets the Object mapped from the specified key, or null if no such mapping has been made.
get
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
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
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
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
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.
removeAt
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
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 |
set
open fun set(
key: Int,
value: E
): Unit
Alias for put(int,java.lang.Object) to support Kotlin [index]= operator.
See Also
setValueAt
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
open fun size(): Int
Returns the number of key-value mappings that this SparseArray currently stores.
toString
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
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.