DiffUtil.Callback

Artifact: androidx.recyclerview:recyclerview

Added in 1.0.0

Kotlin |Java

public abstract class DiffUtil.Callback

A Callback class used by DiffUtil while calculating the diff between two lists.

Summary

Public constructors
`Callback()`

Public methods
`abstract boolean`	`areContentsTheSame(int oldItemPosition, int newItemPosition)` Called by the DiffUtil when it wants to check whether two items have the same data.
`abstract boolean`	`areItemsTheSame(int oldItemPosition, int newItemPosition)` Called by the DiffUtil to decide whether two object represent the same Item.
`@Nullable Object`	`getChangePayload(int oldItemPosition, int newItemPosition)` When `areItemsTheSame` returns `true` for two items and `areContentsTheSame` returns false for them, DiffUtil calls this method to get a payload about the change.
`abstract int`	`getNewListSize()` Returns the size of the new list.
`abstract int`	`getOldListSize()` Returns the size of the old list.

Public constructors

Callback

Added in 1.0.0

public Callback()

Public methods

areContentsTheSame

Added in 1.0.0

public abstract boolean areContentsTheSame(int oldItemPosition, int newItemPosition)

Called by the DiffUtil when it wants to check whether two items have the same data. DiffUtil uses this information to detect if the contents of an item has changed.

DiffUtil uses this method to check equality instead of equals so that you can change its behavior depending on your UI. For example, if you are using DiffUtil with a RecyclerView.Adapter, you should return whether the items' visual representations are the same.

This method is called only if areItemsTheSame returns true for these items.

Parameters
`int oldItemPosition`	The position of the item in the old list
`int newItemPosition`	The position of the item in the new list which replaces the oldItem

Returns
`boolean`	True if the contents of the items are the same or false if they are different.

areItemsTheSame

Added in 1.0.0

public abstract boolean areItemsTheSame(int oldItemPosition, int newItemPosition)

Called by the DiffUtil to decide whether two object represent the same Item.

For example, if your items have unique ids, this method should check their id equality.

Parameters
`int oldItemPosition`	The position of the item in the old list
`int newItemPosition`	The position of the item in the new list

Returns
`boolean`	True if the two items represent the same object or false if they are different.

getChangePayload

Added in 1.0.0

public @Nullable Object getChangePayload(int oldItemPosition, int newItemPosition)

When areItemsTheSame returns true for two items and areContentsTheSame returns false for them, DiffUtil calls this method to get a payload about the change.

For example, if you are using DiffUtil with RecyclerView, you can return the particular field that changed in the item and your ItemAnimator can use that information to run the correct animation.

Default implementation returns null.

Parameters
`int oldItemPosition`	The position of the item in the old list
`int newItemPosition`	The position of the item in the new list

Returns
`@Nullable Object`	A payload object that represents the change between the two items.

getNewListSize

Added in 1.0.0

public abstract int getNewListSize()

Returns the size of the new list.

Returns
`int`	The size of the new list.

getOldListSize

Added in 1.0.0

public abstract int getOldListSize()

Returns the size of the old list.

Returns
`int`	The size of the old list.