Added in API level 3

AlphabetIndexer

open class AlphabetIndexer : DataSetObserver, SectionIndexer
kotlin.Any
   ↳ android.database.DataSetObserver
   ↳ android.widget.AlphabetIndexer

A helper class for adapters that implement the SectionIndexer interface. If the items in the adapter are sorted by simple alphabet-based sorting, then this class provides a way to do fast indexing of large lists using binary search. It caches the indices that have been determined through the binary search and also invalidates the cache if changes occur in the cursor.

Your adapter is responsible for updating the cursor by calling setCursor if the cursor changes. getPositionForSection method does the binary search for the starting index of a given section (alphabet).

Summary

Public constructors
AlphabetIndexer(cursor: Cursor!, sortedColumnIndex: Int, alphabet: CharSequence!)

Constructs the indexer.
Public methods
open Int
getPositionForSection(sectionIndex: Int)

Performs a binary search or cache lookup to find the first row that matches a given section's starting letter.
open Int

Returns the section index for a given position in the list by querying the item and comparing it with all items in the section array.
open Array<Any!>!

Returns the section array constructed from the alphabet provided in the constructor.
open Unit

open Unit

open Unit
setCursor(cursor: Cursor!)

Sets a new cursor as the data set and resets the cache of indices.
Protected methods
open Int
compare(word: String!, letter: String!)

Default implementation compares the first character of word with letter.
Properties
CharSequence!

The string of characters that make up the indexing sections.
Int

The index of the cursor column that this list is sorted on.
Cursor!

Cursor that is used by the adapter of the list view.

Public constructors

AlphabetIndexer

Added in API level 3
AlphabetIndexer(
    cursor: Cursor!, 
    sortedColumnIndex: Int, 
    alphabet: CharSequence!)

Constructs the indexer.

Parameters
cursor Cursor!: the cursor containing the data set
sortedColumnIndex Int: the column number in the cursor that is sorted alphabetically
alphabet CharSequence!: string containing the alphabet, with space as the first character. For example, use the string " ABCDEFGHIJKLMNOPQRSTUVWXYZ" for English indexing. The characters must be uppercase and be sorted in ascii/unicode order. Basically characters in the alphabet will show up as preview letters.

Public methods

getPositionForSection

Added in API level 3
open fun getPositionForSection(sectionIndex: Int): Int

Performs a binary search or cache lookup to find the first row that matches a given section's starting letter.

Parameters
sectionIndex Int: the section to search for
Return
Int the row index of the first occurrence, or the nearest next letter. For instance, if searching for "T" and no "T" is found, then the first row starting with "U" or any higher letter is returned. If there is no data following "T" at all, then the list size is returned.

getSectionForPosition

Added in API level 3
open fun getSectionForPosition(position: Int): Int

Returns the section index for a given position in the list by querying the item and comparing it with all items in the section array.

Parameters
position Int: the position within the adapter for which to return the corresponding section index
Return
Int the index of the corresponding section within the array of section objects, constrained to fall within the array bounds

getSections

Added in API level 3
open fun getSections(): Array<Any!>!

Returns the section array constructed from the alphabet provided in the constructor.

Return
Array<Any!>! the section array

onChanged

Added in API level 3
open fun onChanged(): Unit

onInvalidated

Added in API level 3
open fun onInvalidated(): Unit

setCursor

Added in API level 3
open fun setCursor(cursor: Cursor!): Unit

Sets a new cursor as the data set and resets the cache of indices.

Parameters
cursor Cursor!: the new cursor to use as the data set

Protected methods

compare

Added in API level 3
protected open fun compare(
    word: String!, 
    letter: String!
): Int

Default implementation compares the first character of word with letter.

Properties

mAlphabet

Added in API level 3
protected var mAlphabet: CharSequence!

The string of characters that make up the indexing sections.

mColumnIndex

Added in API level 3
protected var mColumnIndex: Int

The index of the cursor column that this list is sorted on.

mDataCursor

Added in API level 3
protected var mDataCursor: Cursor!

Cursor that is used by the adapter of the list view.