java.lang.Object | |
↳ | android.support.v7.widget.RecyclerView.ViewHolder |
Known Direct Subclasses |
A ViewHolder describes an item view and metadata about its place within the RecyclerView.
RecyclerView.Adapter
implementations should subclass ViewHolder and add fields for caching
potentially expensive findViewById(int)
results.
While RecyclerView.LayoutParams
belong to the RecyclerView.LayoutManager
,
ViewHolders
belong to the adapter. Adapters should feel free to use
their own custom ViewHolder implementations to store data that makes binding view contents
easier. Implementations should assume that individual item views will hold strong references
to ViewHolder
objects and that RecyclerView
instances may hold
strong references to extra off-screen item views for caching purposes
Fields | |||||||||||
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itemView |
Public Constructors | |||||||||||
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Public Methods | |||||||||||
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Returns the Adapter position of the item represented by this ViewHolder.
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Returns The itemId represented by this ViewHolder.
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Returns the position of the ViewHolder in terms of the latest layout pass.
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When LayoutManager supports animations, RecyclerView tracks 3 positions for ViewHolders
to perform animations.
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This method is deprecated.
This method is deprecated because its meaning is ambiguous due to the async
handling of adapter updates. Please use
getLayoutPosition() or
getAdapterPosition() depending on your use case.
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Informs the recycler whether this item can be recycled.
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Returns a string containing a concise, human-readable description of this
object.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
|
Returns the Adapter position of the item represented by this ViewHolder.
Note that this might be different than the getLayoutPosition()
if there are
pending adapter updates but a new layout pass has not happened yet.
RecyclerView does not handle any adapter updates until the next layout traversal. This may create temporary inconsistencies between what user sees on the screen and what adapter contents have. This inconsistency is not important since it will be less than 16ms but it might be a problem if you want to use ViewHolder position to access the adapter. Sometimes, you may need to get the exact adapter position to do some actions in response to user events. In that case, you should use this method which will calculate the Adapter position of the ViewHolder.
Note that if you've called notifyDataSetChanged()
, until the
next layout pass, the return value of this method will be NO_POSITION
.
NO_POSITION
if item has been removed from the adapter,
notifyDataSetChanged()
has been called after the last
layout pass or the ViewHolder has already been recycled.
Returns The itemId represented by this ViewHolder.
NO_ID
otherwise
Returns the position of the ViewHolder in terms of the latest layout pass.
This position is mostly used by RecyclerView components to be consistent while RecyclerView lazily processes adapter updates.
For performance and animation reasons, RecyclerView batches all adapter updates until the next layout pass. This may cause mismatches between the Adapter position of the item and the position it had in the latest layout calculations.
LayoutManagers should always call this method while doing calculations based on item
positions. All methods in RecyclerView.LayoutManager
, RecyclerView.State
,
RecyclerView.Recycler
that receive a position expect it to be the layout position
of the item.
If LayoutManager needs to call an external method that requires the adapter position of
the item, it can use getAdapterPosition()
or
convertPreLayoutPositionToPostLayout(int)
.
When LayoutManager supports animations, RecyclerView tracks 3 positions for ViewHolders to perform animations.
If a ViewHolder was laid out in the previous onLayout call, old position will keep its adapter index in the previous layout.
NO_POSITION
if old position does not exists or cleared (pre-layout is
complete).
This method is deprecated.
This method is deprecated because its meaning is ambiguous due to the async
handling of adapter updates. Please use getLayoutPosition()
or
getAdapterPosition()
depending on your use case.
Informs the recycler whether this item can be recycled. Views which are not recyclable will not be reused for other items until setIsRecyclable() is later set to true. Calls to setIsRecyclable() should always be paired (one call to setIsRecyclabe(false) should always be matched with a later call to setIsRecyclable(true)). Pairs of calls may be nested, as the state is internally reference-counted.
recyclable | Whether this item is available to be recycled. Default value is true. |
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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.