SpanSizeLookup
abstract class SpanSizeLookup
| kotlin.Any | |
| ↳ | androidx.recyclerview.widget.GridLayoutManager.SpanSizeLookup |
A helper class to provide the number of spans each item occupies.
Default implementation sets each item to occupy exactly 1 span.
Summary
Public constructors |
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<init>()A helper class to provide the number of spans each item occupies. |
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Public methods |
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| open Int |
getSpanGroupIndex(adapterPosition: Int, spanCount: Int)Returns the index of the group this position belongs. |
| open Int |
getSpanIndex(position: Int, spanCount: Int)Returns the final span index of the provided position. |
| abstract Int |
getSpanSize(position: Int)Returns the number of span occupied by the item at |
| open Unit |
Clears the span group index cache. |
| open Unit |
Clears the span index cache. |
| open Boolean |
Returns whether results of |
| open Boolean |
Returns whether results of |
| open Unit |
setSpanGroupIndexCacheEnabled(cacheSpanGroupIndices: Boolean)Sets whether the results of |
| open Unit |
setSpanIndexCacheEnabled(cacheSpanIndices: Boolean)Sets whether the results of |
Public constructors
<init>
SpanSizeLookup()
A helper class to provide the number of spans each item occupies.
Default implementation sets each item to occupy exactly 1 span.
Public methods
getSpanGroupIndex
open fun getSpanGroupIndex(adapterPosition: Int, spanCount: Int): Int
Returns the index of the group this position belongs.
For example, if grid has 3 columns and each item occupies 1 span, span group index for item 1 will be 0, item 5 will be 1.
| Parameters | |
|---|---|
adapterPosition |
Int: The position in adapter |
spanCount |
Int: The total number of spans in the grid |
| Return | |
|---|---|
| Int: The index of the span group including the item at the given adapter position |
getSpanIndex
open fun getSpanIndex(position: Int, spanCount: Int): Int
Returns the final span index of the provided position.
If you have a faster way to calculate span index for your items, you should override this method. Otherwise, you should enable span index cache (setSpanIndexCacheEnabled(boolean)) for better performance. When caching is disabled, default implementation traverses all items from 0 to position. When caching is enabled, it calculates from the closest cached value before the position.
If you override this method, you need to make sure it is consistent with getSpanSize(int). GridLayoutManager does not call this method for each item. It is called only for the reference item and rest of the items are assigned to spans based on the reference item. For example, you cannot assign a position to span 2 while span 1 is empty.
Note that span offsets always start with 0 and are not affected by RTL.
| Parameters | |
|---|---|
position |
Int: The position of the item |
spanCount |
Int: The total number of spans in the grid |
| Return | |
|---|---|
Int: The final span position of the item. Should be between 0 (inclusive) and spanCount(exclusive) |
getSpanSize
abstract fun getSpanSize(position: Int): Int
Returns the number of span occupied by the item at position.
| Parameters | |
|---|---|
position |
Int: The adapter position of the item |
| Return | |
|---|---|
| Int: The number of spans occupied by the item at the provided position |
invalidateSpanGroupIndexCache
open fun invalidateSpanGroupIndexCache(): Unit
Clears the span group index cache. GridLayoutManager automatically calls this method when adapter changes occur.
invalidateSpanIndexCache
open fun invalidateSpanIndexCache(): Unit
Clears the span index cache. GridLayoutManager automatically calls this method when adapter changes occur.
isSpanGroupIndexCacheEnabled
open fun isSpanGroupIndexCacheEnabled(): Boolean
Returns whether results of getSpanGroupIndex(int, int) method are cached or not.
| Return | |
|---|---|
Boolean: True if results of getSpanGroupIndex(int, int) are cached. |
isSpanIndexCacheEnabled
open fun isSpanIndexCacheEnabled(): Boolean
Returns whether results of getSpanIndex(int, int) method are cached or not.
| Return | |
|---|---|
Boolean: True if results of getSpanIndex(int, int) are cached. |
setSpanGroupIndexCacheEnabled
open fun setSpanGroupIndexCacheEnabled(cacheSpanGroupIndices: Boolean): Unit
Sets whether the results of getSpanGroupIndex(int, int) method should be cached or not. By default these values are not cached. If you are not overriding getSpanGroupIndex(int, int) with something highly performant, and you are using spans to calculate scrollbar offset and range, you should set this to true for better performance.
| Parameters | |
|---|---|
cacheSpanGroupIndices |
Boolean: Whether results of getGroupSpanIndex should be cached or not. |
setSpanIndexCacheEnabled
open fun setSpanIndexCacheEnabled(cacheSpanIndices: Boolean): Unit
Sets whether the results of getSpanIndex(int, int) method should be cached or not. By default these values are not cached. If you are not overriding getSpanIndex(int, int) with something highly performant, you should set this to true for better performance.
| Parameters | |
|---|---|
cacheSpanIndices |
Boolean: Whether results of getSpanIndex should be cached or not. |