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 | |
|---|---|
<init>()A helper class to provide the number of spans each item occupies. |
|
| Public methods | |
|---|---|
| open Unit |
Clears the span index cache. |
| open Boolean |
Returns whether results of |
| open Int |
getSpanIndex(position: Int, spanCount: Int)Returns the final span index of the provided position. |
| open Unit |
setSpanIndexCacheEnabled(cacheSpanIndices: Boolean)Sets whether the results of |
| open Int |
getSpanGroupIndex(adapterPosition: Int, spanCount: Int)Returns the index of the group this position belongs. |
| abstract Int |
getSpanSize(position: Int)Returns the number of span occupied by the item at |
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
invalidateSpanIndexCache
open fun invalidateSpanIndexCache(): Unit
Clears the span index cache. GridLayoutManager automatically calls this method when adapter changes occur.
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. |
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) |
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), you should set this to true for better performance.
| Parameters | |
|---|---|
cacheSpanIndices |
Boolean: Whether results of getSpanIndex should be cached or not. |
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 |