GridLayoutManager.SpanSizeLookup

fun getSpanGroupIndex(adapterPosition: Int, spanCount: Int): Int

Returns the index of the group this position belongs.

If getOrientation is VERTICAL, this is a row value. If getOrientation is HORIZONTAL, this is a column value.

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.

fun getSpanIndex(position: Int, spanCount: Int): Int

Returns the final span index of the provided position.

If getOrientation is VERTICAL, this is a column value. If getOrientation is HORIZONTAL, this is a row value.

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) 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. 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.

abstract fun getSpanSize(position: Int): Int

Returns the number of span occupied by the item at position.

fun invalidateSpanGroupIndexCache(): Unit

Clears the span group index cache. GridLayoutManager automatically calls this method when adapter changes occur.

fun invalidateSpanIndexCache(): Unit

Clears the span index cache. GridLayoutManager automatically calls this method when adapter changes occur.

fun isSpanGroupIndexCacheEnabled(): Boolean

Returns whether results of getSpanGroupIndex method are cached or not.

fun isSpanIndexCacheEnabled(): Boolean

Returns whether results of getSpanIndex method are cached or not.

fun setSpanGroupIndexCacheEnabled(cacheSpanGroupIndices: Boolean): Unit

Sets whether the results of getSpanGroupIndex method should be cached or not. By default these values are not cached. If you are not overriding getSpanGroupIndex with something highly performant, and you are using spans to calculate scrollbar offset and range, you should set this to true for better performance.

fun setSpanIndexCacheEnabled(cacheSpanIndices: Boolean): Unit

Sets whether the results of getSpanIndex method should be cached or not. By default these values are not cached. If you are not overriding getSpanIndex with something highly performant, you should set this to true for better performance.