java.lang.Object | |
↳ | android.support.v7.widget.RecyclerView.Adapter<VH extends android.support.v7.widget.RecyclerView.ViewHolder> |
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Base class for an Adapter
Adapters provide a binding from an app-specific data set to views that are displayed
within a RecyclerView
.
Public Constructors | |||||||||||
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Public Methods | |||||||||||
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This method internally calls
onBindViewHolder(ViewHolder, int) to update the
RecyclerView.ViewHolder contents with the item at the given position and also sets up some
private fields to be used by RecyclerView.
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This method calls
onCreateViewHolder(ViewGroup, int) to create a new
RecyclerView.ViewHolder and initializes some private fields to be used by RecyclerView.
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Returns the total number of items in the data set hold by the adapter.
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Return the stable ID for the item at
position .
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Return the view type of the item at
position for the purposes
of view recycling.
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Returns true if one or more observers are attached to this adapter.
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Returns true if this adapter publishes a unique
long value that can
act as a key for the item at a given position in the data set.
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Notify any registered observers that the data set has changed.
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Notify any registered observers that the item at
position has changed.
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Notify any registered observers that the item reflected at
position
has been newly inserted.
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Notify any registered observers that the item reflected at
fromPosition
has been moved to toPosition .
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Notify any registered observers that the
itemCount items starting at
position positionStart have changed.
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Notify any registered observers that the currently reflected
itemCount
items starting at positionStart have been newly inserted.
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Notify any registered observers that the
itemCount items previously
located at positionStart have been removed from the data set.
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Notify any registered observers that the item previously located at
position
has been removed from the data set.
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Called by RecyclerView to display the data at the specified position.
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Called when RecyclerView needs a new
RecyclerView.ViewHolder of the given type to represent
an item.
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Called when a view created by this adapter has been attached to a window.
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Called when a view created by this adapter has been detached from its window.
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Called when a view created by this adapter has been recycled.
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Register a new observer to listen for data changes.
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Indicates whether each item in the data set can be represented with a unique identifier
of type
Long .
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Unregister an observer currently listening for data changes.
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[Expand]
Inherited Methods | |||||||||||
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This method internally calls onBindViewHolder(ViewHolder, int)
to update the
RecyclerView.ViewHolder
contents with the item at the given position and also sets up some
private fields to be used by RecyclerView.
This method calls onCreateViewHolder(ViewGroup, int)
to create a new
RecyclerView.ViewHolder
and initializes some private fields to be used by RecyclerView.
Returns the total number of items in the data set hold by the adapter.
Return the stable ID for the item at position
. If hasStableIds()
would return false this method should return NO_ID
. The default implementation
of this method returns NO_ID
.
position | Adapter position to query |
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Return the view type of the item at position
for the purposes
of view recycling.
The default implementation of this method returns 0, making the assumption of a single view type for the adapter. Unlike ListView adapters, types need not be contiguous. Consider using id resources to uniquely identify item view types.
position | position to query |
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position
. Type codes need not be contiguous.
Returns true if one or more observers are attached to this adapter.
Returns true if this adapter publishes a unique long
value that can
act as a key for the item at a given position in the data set. If that item is relocated
in the data set, the ID returned for that item should be the same.
Notify any registered observers that the data set has changed.
There are two different classes of data change events, item changes and structural changes. Item changes are when a single item has its data updated but no positional changes have occurred. Structural changes are when items are inserted, removed or moved within the data set.
This event does not specify what about the data set has changed, forcing any observers to assume that all existing items and structure may no longer be valid. LayoutManagers will be forced to fully rebind and relayout all visible views.
RecyclerView
will attempt to synthesize visible structural change events
for adapters that report that they have stable IDs
when
this method is used. This can help for the purposes of animation and visual
object persistence but individual item views will still need to be rebound
and relaid out.
If you are writing an adapter it will always be more efficient to use the more
specific change events if you can. Rely on notifyDataSetChanged()
as a last resort.
Notify any registered observers that the item at position
has changed.
This is an item change event, not a structural change event. It indicates that any
reflection of the data at position
is out of date and should be updated.
The item at position
retains the same identity.
position | Position of the item that has changed |
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Notify any registered observers that the item reflected at position
has been newly inserted. The item previously at position
is now at
position position + 1
.
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
position | Position of the newly inserted item in the data set |
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Notify any registered observers that the item reflected at fromPosition
has been moved to toPosition
.
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
fromPosition | Previous position of the item. |
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toPosition | New position of the item. |
Notify any registered observers that the itemCount
items starting at
position positionStart
have changed.
This is an item change event, not a structural change event. It indicates that any reflection of the data in the given position range is out of date and should be updated. The items in the given range retain the same identity.
positionStart | Position of the first item that has changed |
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itemCount | Number of items that have changed |
Notify any registered observers that the currently reflected itemCount
items starting at positionStart
have been newly inserted. The items
previously located at positionStart
and beyond can now be found starting
at position positionStart + itemCount
.
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
positionStart | Position of the first item that was inserted |
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itemCount | Number of items inserted |
Notify any registered observers that the itemCount
items previously
located at positionStart
have been removed from the data set. The items
previously located at and after positionStart + itemCount
may now be found
at oldPosition - itemCount
.
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
positionStart | Previous position of the first item that was removed |
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itemCount | Number of items removed from the data set |
Notify any registered observers that the item previously located at position
has been removed from the data set. The items previously located at and after
position
may now be found at oldPosition - 1
.
This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.
position | Position of the item that has now been removed |
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Called by RecyclerView to display the data at the specified position. This method
should update the contents of the itemView
to reflect the item at
the given position.
Note that unlike ListView
, RecyclerView will not call this
method again if the position of the item changes in the data set unless the item itself
is invalidated or the new position cannot be determined. For this reason, you should only
use the position
parameter while acquiring the related data item inside this
method and should not keep a copy of it. If you need the position of an item later on
(e.g. in a click listener), use getPosition()
which will have the
updated position.
holder | The ViewHolder which should be updated to represent the contents of the item at the given position in the data set. |
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position | The position of the item within the adapter's data set. |
Called when RecyclerView needs a new RecyclerView.ViewHolder
of the given type to represent
an item.
This new ViewHolder should be constructed with a new View that can represent the items of the given type. You can either create a new View manually or inflate it from an XML layout file.
The new ViewHolder will be used to display items of the adapter using
onBindViewHolder(ViewHolder, int)
. Since it will be re-used to display different
items in the data set, it is a good idea to cache references to sub views of the View to
avoid unnecessary findViewById(int)
calls.
parent | The ViewGroup into which the new View will be added after it is bound to an adapter position. |
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viewType | The view type of the new View. |
Called when a view created by this adapter has been attached to a window.
This can be used as a reasonable signal that the view is about to be seen
by the user. If the adapter previously freed any resources in
onViewDetachedFromWindow
those resources should be restored here.
holder | Holder of the view being attached |
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Called when a view created by this adapter has been detached from its window.
Becoming detached from the window is not necessarily a permanent condition; the consumer of an Adapter's views may choose to cache views offscreen while they are not visible, attaching an detaching them as appropriate.
holder | Holder of the view being detached |
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Called when a view created by this adapter has been recycled.
A view is recycled when a RecyclerView.LayoutManager
decides that it no longer
needs to be attached to its parent RecyclerView
. This can be because it has
fallen out of visibility or a set of cached views represented by views still
attached to the parent RecyclerView. If an item view has large or expensive data
bound to it such as large bitmaps, this may be a good place to release those
resources.
holder | The ViewHolder for the view being recycled |
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Register a new observer to listen for data changes.
The adapter may publish a variety of events describing specific changes.
Not all adapters may support all change types and some may fall back to a generic
"something changed"
event if more specific data is not available.
Components registering observers with an adapter are responsible for
unregistering
those observers when finished.
observer | Observer to register |
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Indicates whether each item in the data set can be represented with a unique identifier
of type Long
.
hasStableIds | Whether items in data set have unique identifiers or not. |
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Unregister an observer currently listening for data changes.
The unregistered observer will no longer receive events about changes to the adapter.
observer | Observer to unregister |
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