# LeanbackSpanSizeLookup

Artifact: [androidx.leanback:leanback-grid](https://developer.android.com/jetpack/androidx/releases/leanback) [View Source](https://cs.android.com/search?q=file:androidx/leanback/widget/LeanbackSpanSizeLookup.java+class:androidx.leanback.widget.LeanbackSpanSizeLookup) Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

*** ** * ** ***


```
public abstract class LeanbackSpanSizeLookup
```

<br />

*** ** * ** ***

A helper class to provide the number of spans each item occupies. `https://developer.android.com/reference/androidx/leanback/widget/BaseGridView` retrieves the object from `https://developer.android.com/reference/androidx/recyclerview/widget/RecyclerView.Adapter` via `https://developer.android.com/reference/androidx/leanback/widget/FacetProvider` interface implemented by the adapter. The class is similar to `https://developer.android.com/reference/androidx/recyclerview/widget/GridLayoutManager.SpanSizeLookup`. It supports two special span size: `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()` and `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS()`.

## Summary

| ### Constants |
|---|---|
| `static final int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS() = -2` Value returned by `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)`: fill all spans. |
| `static final int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS() = -1` Value returned by `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)`: fill all spans and padding area, it takes full width of a vertical grid view or full height of a horizontal grid view. |

| ### Public constructors |
|---|
| `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#LeanbackSpanSizeLookup()()` |

| ### Public methods |
|---|---|
| `static @https://jspecify.dev/docs/api/org/jspecify/annotations/NonNull.html https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getDefault()()` Return the default LeanbackSpanSizeLookup that each item has a span size of 1. |
| `int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)(int adapterPosition, int spanCount)` Returns the index of the group this position belongs. |
| `int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)(int position, int spanCount)` Returns the final span index of the provided position. |
| `abstract int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)(int position)` Returns the number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`, `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS()`. |
| `int` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int,int)(int position, int spanCount)` Returns the number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`. |
| `void` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#invalidateSpanGroupIndexCache()()` Clears the span group index cache. |
| `void` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#invalidateSpanIndexCache()()` Clears the span index cache. |
| `boolean` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#isSpanGroupIndexCacheEnabled()()` Returns whether results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)` method are cached or not. |
| `boolean` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#isSpanIndexCacheEnabled()()` Returns whether results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` method are cached or not. |
| `void` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#setSpanGroupIndexCacheEnabled(boolean)(boolean cacheSpanGroupIndices)` Sets whether the results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)` method should be cached or not. |
| `void` | `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#setSpanIndexCacheEnabled(boolean)(boolean cacheSpanIndices)` Sets whether the results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` method should be cached or not. |

## Constants

### FILL_ALL_SPANS

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public static final int FILL_ALL_SPANS = -2
```

Value returned by `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)`: fill all spans. It's equivalent of returning the spanCount.

### FILL_ALL_SPANS_AND_PADDINGS

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public static final int FILL_ALL_SPANS_AND_PADDINGS = -1
```

Value returned by `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)`: fill all spans and padding area, it takes full width of a vertical grid view or full height of a horizontal grid view.

## Public constructors

### LeanbackSpanSizeLookup

Added in 1.1.0-alpha02

```
public LeanbackSpanSizeLookup()
```

## Public methods

### getDefault

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public static @NonNull LeanbackSpanSizeLookup getDefault()
```

Return the default LeanbackSpanSizeLookup that each item has a span size of 1.

### getSpanGroupIndex

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public int getSpanGroupIndex(int adapterPosition, int spanCount)
```

Returns the index of the group this position belongs.

If `https://developer.android.com/reference/androidx/leanback/widget/VerticalGridView`, this is a row value. If `https://developer.android.com/reference/androidx/leanback/widget/HorizontalGridView`, 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 [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public int getSpanIndex(int position, int spanCount)
```

Returns the final span index of the provided position.

If `https://developer.android.com/reference/androidx/leanback/widget/VerticalGridView`, this is a column value. If `https://developer.android.com/reference/androidx/leanback/widget/HorizontalGridView`, 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 (`https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#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 `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#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 |
|---|---|
| `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 [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public abstract int getSpanSize(int position)
```

Returns the number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`, `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS()`.

| Parameters |
|---|---|
| `int position` | The adapter position of the item. |

| Returns |
|---|---|
| `int` | The number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`, `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS()`. |

### getSpanSize

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public int getSpanSize(int position, int spanCount)
```

Returns the number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`. Default implementation calls `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanSize(int)` without spanCount. Subclass may override this method to return span size based on spanCount.

| Parameters |
|---|---|
| `int position` | The adapter position of the item. |
| `int spanCount` | The total available spans of the grid. |

| Returns |
|---|---|
| `int` | The number of spans this item will take, or `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#FILL_ALL_SPANS_AND_PADDINGS()`. |

### invalidateSpanGroupIndexCache

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public void invalidateSpanGroupIndexCache()
```

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

### invalidateSpanIndexCache

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public void invalidateSpanIndexCache()
```

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

### isSpanGroupIndexCacheEnabled

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public boolean isSpanGroupIndexCacheEnabled()
```

Returns whether results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)` method are cached or not.

| Returns |
|---|---|
| `boolean` | True if results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)` are cached. |

### isSpanIndexCacheEnabled

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public boolean isSpanIndexCacheEnabled()
```

Returns whether results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` method are cached or not.

| Returns |
|---|---|
| `boolean` | True if results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` are cached. |

### setSpanGroupIndexCacheEnabled

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public void setSpanGroupIndexCacheEnabled(boolean cacheSpanGroupIndices)
```

Sets whether the results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanGroupIndex(int,int)` method should be cached or not. By default these values are not cached. If you are not overriding `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#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 |
|---|---|
| `boolean cacheSpanGroupIndices` | Whether results of getGroupSpanIndex should be cached or not. |

### setSpanIndexCacheEnabled

Added in [1.1.0-alpha02](https://developer.android.com/jetpack/androidx/releases/leanback#1.1.0-alpha02)

```
public void setSpanIndexCacheEnabled(boolean cacheSpanIndices)
```

Sets whether the results of `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` method should be cached or not. By default these values are not cached. If you are not overriding `https://developer.android.com/reference/androidx/leanback/widget/LeanbackSpanSizeLookup#getSpanIndex(int,int)` 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. |