Android Guides | Samples

Android.Util.SparseArray Class

SparseArrays map integers to Objects.

See Also: SparseArray

Syntax

[Android.Runtime.Register("android/util/SparseArray", DoNotGenerateAcw=true)]
public class SparseArray : Object, ICloneable, IDisposable

Remarks

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 SparseArray`1.keyAt(int) and SparseArray`1.ValueAt(Int32). 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).

[Android Documentation]

Requirements

Namespace: Android.Util
Assembly: Mono.Android (in Mono.Android.dll)
Assembly Versions: 0.0.0.0
Since: Added in API level 1

The members of Android.Util.SparseArray are listed below.

See Also: Object

Public Constructors

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

Protected Constructors

A constructor used when creating managed representations of JNI objects; called by the runtime.

Protected Properties

[read-only]
override
ThresholdClassIntPtr. This API supports the Mono for Android infrastructure and is not intended to be used directly from your code.
[read-only]
override
ThresholdTypeType. This API supports the Mono for Android infrastructure and is not intended to be used directly from your code.

Public Methods

Append(Int32, Object)
Clear()
Removes all key-value mappings from this SparseArray.
Clone() : SparseArray
Creates and returns a copy of this Object.
Delete(Int32)
Removes the mapping from the specified key, if there was any.
Get(Int32) : Object
Gets the Object mapped from the specified key, or null if no such mapping has been made.
Get(Int32, Object) : Object
IndexOfKey(Int32) : Int32
Returns the index for which SparseArray`1.keyAt(int) would return the specified key, or a negative number if the specified key is not mapped.
IndexOfValue(Object) : Int32
KeyAt(Int32) : Int32
Given an index in the range 0...size()-1, returns the key from the indexth key-value mapping that this SparseArray stores.
Put(Int32, Object)
Remove(Int32)
Alias for SparseArray`1.delete(int).
RemoveAt(Int32)
Removes the mapping at the specified index.
RemoveAtRange(Int32, Int32)
Remove a range of mappings as a batch.
SetValueAt(Int32, Object)
Size() : Int32
Returns the number of key-value mappings that this SparseArray currently stores.
ValueAt(Int32) : Object
Given an index in the range 0...size()-1, returns the value from the indexth key-value mapping that this SparseArray stores.