ConcatAdapter
public
final
class
ConcatAdapter
extends Adapter<RecyclerView.ViewHolder>
java.lang.Object | ||
↳ | androidx.recyclerview.widget.RecyclerView.Adapter<androidx.recyclerview.widget.RecyclerView.ViewHolder> | |
↳ | androidx.recyclerview.widget.ConcatAdapter |
An RecyclerView.Adapter
implementation that presents the contents of multiple adapters in sequence.
MyAdapter adapter1 = ...; AnotherAdapter adapter2 = ...; ConcatAdapter concatenated = new ConcatAdapter(adapter1, adapter2); recyclerView.setAdapter(concatenated);
By default, ConcatAdapter
isolates view types of nested adapters from each other such
that
it will change the view type before reporting it back to the RecyclerView
to avoid any
conflicts between the view types of added adapters. This also means each added adapter will have
its own isolated pool of RecyclerView.ViewHolder
s, with no re-use in between added adapters.
If your RecyclerView.Adapter
s share the same view types, and can support sharing RecyclerView.ViewHolder
s between added adapters, provide an instance of ConcatAdapter.Config
where you set
ConcatAdapter.Config.isolateViewTypes
to false
. A common usage pattern for this is to return
the R.layout.<layout_name>
from the RecyclerView.Adapter.getItemViewType(int)
method.
When an added adapter calls one of the notify
methods, ConcatAdapter
properly
offsets values before reporting it back to the RecyclerView
.
If an adapter calls RecyclerView.Adapter.notifyDataSetChanged()
, ConcatAdapter
also calls
RecyclerView.Adapter.notifyDataSetChanged()
as calling
RecyclerView.Adapter.notifyItemRangeChanged(int, int)
will confuse the RecyclerView
.
You are highly encouraged to to use SortedList
or ListAdapter
to avoid
calling RecyclerView.Adapter.notifyDataSetChanged()
.
Whether ConcatAdapter
should support stable ids is defined in the ConcatAdapter.Config
object. Calling RecyclerView.Adapter.setHasStableIds(boolean)
has no effect. See documentation
for ConcatAdapter.Config.StableIdMode
for details on how to configure ConcatAdapter
to use
stable ids. By default, it will not use stable ids and sub adapter stable ids will be ignored.
Similar to the case above, you are highly encouraged to use ListAdapter
, which will
automatically calculate the changes in the data set for you so you won't need stable ids.
It is common to find the adapter position of a RecyclerView.ViewHolder
to handle user action on the
RecyclerView.ViewHolder
. For those cases, instead of calling RecyclerView.ViewHolder.getAdapterPosition()
,
use RecyclerView.ViewHolder.getBindingAdapterPosition()
. If your adapters share RecyclerView.ViewHolder
s,
you can use the RecyclerView.ViewHolder.getBindingAdapter()
method to find the adapter which last
bound that RecyclerView.ViewHolder
.
Summary
Nested classes | |
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class |
ConcatAdapter.Config
The configuration object for a |
Public constructors | |
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ConcatAdapter(Adapter...<? extends RecyclerView.ViewHolder> adapters)
Creates a ConcatAdapter with |
|
ConcatAdapter(ConcatAdapter.Config config, Adapter...<? extends RecyclerView.ViewHolder> adapters)
Creates a ConcatAdapter with the given config and the given adapters in the given order. |
|
ConcatAdapter(List<? extends Adapter<? extends RecyclerView.ViewHolder>> adapters)
Creates a ConcatAdapter with |
|
ConcatAdapter(ConcatAdapter.Config config, List<? extends Adapter<? extends RecyclerView.ViewHolder>> adapters)
Creates a ConcatAdapter with the given config and the given adapters in the given order. |
Public methods | |
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boolean
|
addAdapter(Adapter<? extends RecyclerView.ViewHolder> adapter)
Appends the given adapter to the existing list of adapters and notifies the observers of
this |
boolean
|
addAdapter(int index, Adapter<? extends RecyclerView.ViewHolder> adapter)
Adds the given adapter to the given index among other adapters that are already added. |
int
|
findRelativeAdapterPositionIn(Adapter<? extends RecyclerView.ViewHolder> adapter, RecyclerView.ViewHolder viewHolder, int localPosition)
Returns the position of the given |
List<? extends Adapter<? extends RecyclerView.ViewHolder>>
|
getAdapters()
Returns an unmodifiable copy of the list of adapters in this |
int
|
getItemCount()
Returns the total number of items in the data set held by the adapter. |
long
|
getItemId(int position)
Return the stable ID for the item at |
int
|
getItemViewType(int position)
Return the view type of the item at |
void
|
onAttachedToRecyclerView(RecyclerView recyclerView)
Called by RecyclerView when it starts observing this Adapter. |
void
|
onBindViewHolder(RecyclerView.ViewHolder holder, int position)
Called by RecyclerView to display the data at the specified position. |
RecyclerView.ViewHolder
|
onCreateViewHolder(ViewGroup parent, int viewType)
Called when RecyclerView needs a new |
void
|
onDetachedFromRecyclerView(RecyclerView recyclerView)
Called by RecyclerView when it stops observing this Adapter. |
boolean
|
onFailedToRecycleView(RecyclerView.ViewHolder holder)
Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled due to its transient state. |
void
|
onViewAttachedToWindow(RecyclerView.ViewHolder holder)
Called when a view created by this adapter has been attached to a window. |
void
|
onViewDetachedFromWindow(RecyclerView.ViewHolder holder)
Called when a view created by this adapter has been detached from its window. |
void
|
onViewRecycled(RecyclerView.ViewHolder holder)
Called when a view created by this adapter has been recycled. |
boolean
|
removeAdapter(Adapter<? extends RecyclerView.ViewHolder> adapter)
Removes the given adapter from the adapters list if it exists |
void
|
setHasStableIds(boolean hasStableIds)
Calling this method is an error and will result in an |
void
|
setStateRestorationPolicy(RecyclerView.Adapter.StateRestorationPolicy strategy)
Calling this method is an error and will result in an |
Inherited methods | |
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Public constructors
ConcatAdapter
public ConcatAdapter (Adapter...<? extends RecyclerView.ViewHolder> adapters)
Creates a ConcatAdapter with ConcatAdapter.Config.DEFAULT
and the given adapters in the given
order.
Parameters | |
---|---|
adapters |
Adapter : The list of adapters to add
|
ConcatAdapter
public ConcatAdapter (ConcatAdapter.Config config, Adapter...<? extends RecyclerView.ViewHolder> adapters)
Creates a ConcatAdapter with the given config and the given adapters in the given order.
Parameters | |
---|---|
config |
ConcatAdapter.Config : The configuration for this ConcatAdapter |
adapters |
Adapter : The list of adapters to add |
See also:
ConcatAdapter
public ConcatAdapter (List<? extends Adapter<? extends RecyclerView.ViewHolder>> adapters)
Creates a ConcatAdapter with ConcatAdapter.Config.DEFAULT
and the given adapters in the given
order.
Parameters | |
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adapters |
List : The list of adapters to add
|
ConcatAdapter
public ConcatAdapter (ConcatAdapter.Config config, List<? extends Adapter<? extends RecyclerView.ViewHolder>> adapters)
Creates a ConcatAdapter with the given config and the given adapters in the given order.
Parameters | |
---|---|
config |
ConcatAdapter.Config : The configuration for this ConcatAdapter |
adapters |
List : The list of adapters to add |
See also:
Public methods
addAdapter
public boolean addAdapter (Adapter<? extends RecyclerView.ViewHolder> adapter)
Appends the given adapter to the existing list of adapters and notifies the observers of
this ConcatAdapter
.
Parameters | |
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adapter |
Adapter : The new adapter to add |
Returns | |
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boolean |
true if the adapter is successfully added because it did not already exist,
false otherwise. |
addAdapter
public boolean addAdapter (int index, Adapter<? extends RecyclerView.ViewHolder> adapter)
Adds the given adapter to the given index among other adapters that are already added.
Parameters | |
---|---|
index |
int : The index into which to insert the adapter. ConcatAdapter will throw an
IndexOutOfBoundsException if the index is not between 0 and current
adapter count (inclusive). |
adapter |
Adapter : The new adapter to add to the adapters list. |
Returns | |
---|---|
boolean |
true if the adapter is successfully added because it did not already exist,
false otherwise. |
findRelativeAdapterPositionIn
public int findRelativeAdapterPositionIn (Adapter<? extends RecyclerView.ViewHolder> adapter, RecyclerView.ViewHolder viewHolder, int localPosition)
Returns the position of the given RecyclerView.ViewHolder
in the given RecyclerView.Adapter
.
If the given RecyclerView.Adapter
is not part of this ConcatAdapter
,
RecyclerView.NO_POSITION
is returned.
Parameters | |
---|---|
adapter |
Adapter : The adapter which is a sub adapter of this ConcatAdapter or itself. |
viewHolder |
RecyclerView.ViewHolder : The view holder whose local position in the given adapter will be returned. |
localPosition |
int : The position of the given RecyclerView.ViewHolder in this RecyclerView.Adapter . |
Returns | |
---|---|
int |
The local position of the given RecyclerView.ViewHolder in the given RecyclerView.Adapter or
RecyclerView.NO_POSITION if the RecyclerView.ViewHolder is not bound to an item or the
given RecyclerView.Adapter is not part of this ConcatAdapter.
|
getAdapters
public List<? extends Adapter<? extends RecyclerView.ViewHolder>> getAdapters ()
Returns an unmodifiable copy of the list of adapters in this ConcatAdapter
.
Note that this is a copy hence future changes in the ConcatAdapter are not reflected in
this list.
Returns | |
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List<? extends Adapter<? extends RecyclerView.ViewHolder>> |
A copy of the list of adapters in this ConcatAdapter. |
getItemCount
public int getItemCount ()
Returns the total number of items in the data set held by the adapter.
Returns | |
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int |
The total number of items in this adapter. |
getItemId
public long getItemId (int position)
Return the stable ID for the item at position
. If hasStableIds()
would return false this method should return RecyclerView.NO_ID
. The default implementation
of this method returns RecyclerView.NO_ID
.
Parameters | |
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position |
int : Adapter position to query |
Returns | |
---|---|
long |
the stable ID of the item at position |
getItemViewType
public int getItemViewType (int position)
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.
Parameters | |
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position |
int : position to query |
Returns | |
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int |
integer value identifying the type of the view needed to represent the item at
position . Type codes need not be contiguous.
|
onAttachedToRecyclerView
public void onAttachedToRecyclerView (RecyclerView recyclerView)
Called by RecyclerView when it starts observing this Adapter.
Keep in mind that same adapter may be observed by multiple RecyclerViews.
Parameters | |
---|---|
recyclerView |
RecyclerView : The RecyclerView instance which started observing this adapter. |
onBindViewHolder
public void onBindViewHolder (RecyclerView.ViewHolder holder, int position)
Called by RecyclerView to display the data at the specified position. This method should
update the contents of the RecyclerView.ViewHolder.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 RecyclerView.ViewHolder.getBindingAdapterPosition()
which
will have the updated adapter position.
Override onBindViewHolder(ViewHolder, int, List)
instead if Adapter can
handle efficient partial bind.
Parameters | |
---|---|
holder |
RecyclerView.ViewHolder : The ViewHolder which should be updated to represent the contents of the
item at the given position in the data set. |
position |
int : The position of the item within the adapter's data set.
|
onCreateViewHolder
public RecyclerView.ViewHolder onCreateViewHolder (ViewGroup parent, int viewType)
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, List)
. 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 View.findViewById(int)
calls.
Parameters | |
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parent |
ViewGroup : The ViewGroup into which the new View will be added after it is bound to
an adapter position. |
viewType |
int : The view type of the new View. |
Returns | |
---|---|
RecyclerView.ViewHolder |
A new ViewHolder that holds a View of the given view type. |
onDetachedFromRecyclerView
public void onDetachedFromRecyclerView (RecyclerView recyclerView)
Called by RecyclerView when it stops observing this Adapter.
Parameters | |
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recyclerView |
RecyclerView : The RecyclerView instance which stopped observing this adapter. |
onFailedToRecycleView
public boolean onFailedToRecycleView (RecyclerView.ViewHolder holder)
Called by the RecyclerView if a ViewHolder created by this Adapter cannot be recycled
due to its transient state. Upon receiving this callback, Adapter can clear the
animation(s) that effect the View's transient state and return true
so that
the View can be recycled. Keep in mind that the View in question is already removed from
the RecyclerView.
In some cases, it is acceptable to recycle a View although it has transient state. Most
of the time, this is a case where the transient state will be cleared in
onBindViewHolder(ViewHolder, int)
call when View is rebound to a new position.
For this reason, RecyclerView leaves the decision to the Adapter and uses the return
value of this method to decide whether the View should be recycled or not.
Note that when all animations are created by RecyclerView.ItemAnimator
, you
should never receive this callback because RecyclerView keeps those Views as children
until their animations are complete. This callback is useful when children of the item
views create animations which may not be easy to implement using an RecyclerView.ItemAnimator
.
You should never fix this issue by calling
holder.itemView.setHasTransientState(false);
unless you've previously called
holder.itemView.setHasTransientState(true);
. Each
View.setHasTransientState(true)
call must be matched by a
View.setHasTransientState(false)
call, otherwise, the state of the View
may become inconsistent. You should always prefer to end or cancel animations that are
triggering the transient state instead of handling it manually.
Parameters | |
---|---|
holder |
RecyclerView.ViewHolder : The ViewHolder containing the View that could not be recycled due to its
transient state. |
Returns | |
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boolean |
True if the View should be recycled, false otherwise. Note that if this method
returns true , RecyclerView will ignore the transient state of
the View and recycle it regardless. If this method returns false ,
RecyclerView will check the View's transient state again before giving a final decision.
Default implementation returns false.
|
onViewAttachedToWindow
public void onViewAttachedToWindow (RecyclerView.ViewHolder holder)
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.
Parameters | |
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holder |
RecyclerView.ViewHolder : Holder of the view being attached
|
onViewDetachedFromWindow
public void onViewDetachedFromWindow (RecyclerView.ViewHolder holder)
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 and detaching them as appropriate.
Parameters | |
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holder |
RecyclerView.ViewHolder : Holder of the view being detached
|
onViewRecycled
public void onViewRecycled (RecyclerView.ViewHolder holder)
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.
RecyclerView calls this method right before clearing ViewHolder's internal data and
sending it to RecycledViewPool. This way, if ViewHolder was holding valid information
before being recycled, you can call RecyclerView.ViewHolder.getBindingAdapterPosition()
to get
its adapter position.
Parameters | |
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holder |
RecyclerView.ViewHolder : The ViewHolder for the view being recycled
|
removeAdapter
public boolean removeAdapter (Adapter<? extends RecyclerView.ViewHolder> adapter)
Removes the given adapter from the adapters list if it exists
Parameters | |
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adapter |
Adapter : The adapter to remove |
Returns | |
---|---|
boolean |
true if the adapter was previously added to this ConcatAdapter and
now removed or false if it couldn't be found.
|
setHasStableIds
public void setHasStableIds (boolean hasStableIds)
Calling this method is an error and will result in an UnsupportedOperationException
.
You should use the ConcatAdapter.Config
object passed into the ConcatAdapter to configure this
behavior.
Parameters | |
---|---|
hasStableIds |
boolean : Whether items in data set have unique identifiers or not.
|
setStateRestorationPolicy
public void setStateRestorationPolicy (RecyclerView.Adapter.StateRestorationPolicy strategy)
Calling this method is an error and will result in an UnsupportedOperationException
.
ConcatAdapter infers this value from added RecyclerView.Adapter
s.
Parameters | |
---|---|
strategy |
RecyclerView.Adapter.StateRestorationPolicy : The saved state restoration strategy for this Adapter such that
ConcatAdapter will allow state restoration only if all added
adapters allow it or
there are no adapters.
|
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Last updated 2021-03-24 UTC.