Android APIs
public static class

RecyclerView.State

extends Object
java.lang.Object
   ↳ android.support.v7.widget.RecyclerView.State

Class Overview

Contains useful information about the current RecyclerView state like target scroll position or view focus. State object can also keep arbitrary data, identified by resource ids.

Often times, RecyclerView components will need to pass information between each other. To provide a well defined data bus between components, RecyclerView passes the same State object to component callbacks and these components can use it to exchange data.

If you implement custom components, you can use State's put/get/remove methods to pass data between your components without needing to manage their lifecycles.

Summary

Public Constructors
RecyclerView.State()
Public Methods
boolean didStructureChange()
<T> T get(int resourceId)
Gets the Object mapped from the specified id, or null if no such data exists.
int getItemCount()
Returns the total number of items that can be laid out.
int getTargetScrollPosition()
If scroll is triggered to make a certain item visible, this value will return the adapter index of that item.
boolean hasTargetScrollPosition()
Returns if current scroll has a target position.
boolean isPreLayout()
void onViewIgnored(RecyclerView.ViewHolder holder)
void put(int resourceId, Object data)
Adds a mapping from the specified id to the specified value, replacing the previous mapping from the specified key if there was one.
void remove(int resourceId)
Removes the mapping from the specified id, if there was any.
String toString()
Returns a string containing a concise, human-readable description of this object.
boolean willRunPredictiveAnimations()
Returns whether RecyclerView will run predictive animations in this layout pass or not.
boolean willRunSimpleAnimations()
Returns whether RecyclerView will run simple animations in this layout pass or not.
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public RecyclerView.State ()

Public Methods

public boolean didStructureChange ()

Returns
  • true if the structure of the data set has changed since the last call to onLayoutChildren, false otherwise

public T get (int resourceId)

Gets the Object mapped from the specified id, or null if no such data exists.

Parameters
resourceId Id of the resource you want to remove. It is suggested to use R.id.* to preserve cross functionality and avoid conflicts.

public int getItemCount ()

Returns the total number of items that can be laid out. Note that this number is not necessarily equal to the number of items in the adapter, so you should always use this number for your position calculations and never access the adapter directly.

RecyclerView listens for Adapter's notify events and calculates the effects of adapter data changes on existing Views. These calculations are used to decide which animations should be run.

To support predictive animations, RecyclerView may rewrite or reorder Adapter changes to present the correct state to LayoutManager in pre-layout pass.

For example, a newly added item is not included in pre-layout item count because pre-layout reflects the contents of the adapter before the item is added. Behind the scenes, RecyclerView offsets getViewForPosition(int) calls such that LayoutManager does not know about the new item's existence in pre-layout. The item will be available in second layout pass and will be included in the item count. Similar adjustments are made for moved and removed items as well.

You can get the adapter's item count via getItemCount() method.

Returns
  • The number of items currently available
See Also

public int getTargetScrollPosition ()

If scroll is triggered to make a certain item visible, this value will return the adapter index of that item.

Returns
  • Adapter index of the target item or NO_POSITION if there is no target position.

public boolean hasTargetScrollPosition ()

Returns if current scroll has a target position.

Returns
  • true if scroll is being triggered to make a certain position visible
See Also

public boolean isPreLayout ()

public void onViewIgnored (RecyclerView.ViewHolder holder)

public void put (int resourceId, Object data)

Adds a mapping from the specified id to the specified value, replacing the previous mapping from the specified key if there was one.

Parameters
resourceId Id of the resource you want to add. It is suggested to use R.id.* to preserve cross functionality and avoid conflicts.
data The data you want to associate with the resourceId.

public void remove (int resourceId)

Removes the mapping from the specified id, if there was any.

Parameters
resourceId Id of the resource you want to remove. It is suggested to use R.id.* to preserve cross functionality and avoid conflicts.

public String toString ()

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression: 

   getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Returns
  • a printable representation of this object.

public boolean willRunPredictiveAnimations ()

Returns whether RecyclerView will run predictive animations in this layout pass or not.

Returns
  • true if RecyclerView is calculating predictive animations to be run at the end of the layout pass.

public boolean willRunSimpleAnimations ()

Returns whether RecyclerView will run simple animations in this layout pass or not.

Returns
  • true if RecyclerView is calculating simple animations to be run at the end of the layout pass.