GridLayoutManager.SpanSizeLookup

public int getSpanGroupIndex(int adapterPosition, int spanCount)

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.

public int getSpanIndex(int position, int spanCount)

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.

public abstract int getSpanSize(int position)

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

public void invalidateSpanGroupIndexCache()

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

public void invalidateSpanIndexCache()

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

public boolean isSpanGroupIndexCacheEnabled()

Returns whether results of getSpanGroupIndex method are cached or not.

public boolean isSpanIndexCacheEnabled()

Returns whether results of getSpanIndex method are cached or not.

public void setSpanGroupIndexCacheEnabled(boolean cacheSpanGroupIndices)

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.

public void setSpanIndexCacheEnabled(boolean cacheSpanIndices)

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.