GridLayoutManager.SpanSizeLookup

Artifact: androidx.recyclerview:recyclerview

Added in 1.0.0

Kotlin |Java

public abstract class GridLayoutManager.SpanSizeLookup

Known direct subclasses

GridLayoutManager.DefaultSpanSizeLookup

GridLayoutManager.DefaultSpanSizeLookup

Default implementation for SpanSizeLookup.

A helper class to provide the number of spans each item occupies.

Default implementation sets each item to occupy exactly 1 span.

See also
`setSpanSizeLookup`

Summary

Public constructors
`SpanSizeLookup()`

Public methods
`int`	`getSpanGroupIndex(int adapterPosition, int spanCount)` Returns the index of the group this position belongs.
`int`	`getSpanIndex(int position, int spanCount)` Returns the final span index of the provided position.
`abstract int`	`getSpanSize(int position)` Returns the number of span occupied by the item at `position`.
`void`	`invalidateSpanGroupIndexCache()` Clears the span group index cache.
`void`	`invalidateSpanIndexCache()` Clears the span index cache.
`boolean`	`isSpanGroupIndexCacheEnabled()` Returns whether results of `getSpanGroupIndex` method are cached or not.
`boolean`	`isSpanIndexCacheEnabled()` Returns whether results of `getSpanIndex` method are cached or not.
`void`	`setSpanGroupIndexCacheEnabled(boolean cacheSpanGroupIndices)` Sets whether the results of `getSpanGroupIndex` method should be cached or not.
`void`	`setSpanIndexCacheEnabled(boolean cacheSpanIndices)` Sets whether the results of `getSpanIndex` method should be cached or not.

Public constructors

SpanSizeLookup

Added in 1.0.0

public SpanSizeLookup()

Public methods

getSpanGroupIndex

Added in 1.0.0

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.

Parameters
`int adapterPosition`	The position in adapter
`int spanCount`	The total number of spans in the grid

Returns
`int`	The index of the span group including the item at the given adapter position

getSpanIndex

Added in 1.0.0

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.

Parameters
`int position`	The position of the item
`int spanCount`	The total number of spans in the grid

Returns
`int`	The final span position of the item. Should be between 0 (inclusive) and `spanCount`(exclusive)

getSpanSize

Added in 1.0.0

public abstract int getSpanSize(int position)

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

Parameters
`int position`	The adapter position of the item

Returns
`int`	The number of spans occupied by the item at the provided position

invalidateSpanGroupIndexCache

Added in 1.1.0

public void invalidateSpanGroupIndexCache()

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

invalidateSpanIndexCache

Added in 1.0.0

public void invalidateSpanIndexCache()

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

isSpanGroupIndexCacheEnabled

Added in 1.1.0

public boolean isSpanGroupIndexCacheEnabled()

Returns whether results of getSpanGroupIndex method are cached or not.

Returns
`boolean`	True if results of `getSpanGroupIndex` are cached.

isSpanIndexCacheEnabled

Added in 1.0.0

public boolean isSpanIndexCacheEnabled()

Returns whether results of getSpanIndex method are cached or not.

Returns
`boolean`	True if results of `getSpanIndex` are cached.

setSpanGroupIndexCacheEnabled

Added in 1.1.0

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.

Parameters
`boolean cacheSpanGroupIndices`	Whether results of getGroupSpanIndex should be cached or not.

setSpanIndexCacheEnabled

Added in 1.0.0

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.

Parameters
`boolean cacheSpanIndices`	Whether results of getSpanIndex should be cached or not.