SavedStateHandle
public
final
class
SavedStateHandle
extends Object
| java.lang.Object | |
| ↳ | androidx.lifecycle.SavedStateHandle |
A handle to saved state passed down to ViewModel. You should use
SavedStateViewModelFactory if you want to receive this object in ViewModel's
constructor.
This is a key-value map that will let you write and retrieve objects to and from the saved state. These values will persist after the process is killed by the system and remain available via the same object.
You can read a value from it via get(String) or observe it via
LiveData returned
by getLiveData(String).
You can write a value to it via set(String, Object) or setting a value to
MutableLiveData returned by getLiveData(String).
Summary
Public constructors | |
|---|---|
SavedStateHandle(Map<String, Object> initialState)
Creates a handle with the given initial arguments. |
|
SavedStateHandle()
Creates a handle with the empty state. |
|
Public methods | |
|---|---|
boolean
|
contains(String key)
|
<T>
T
|
get(String key)
Returns a value associated with the given key. |
<T>
MutableLiveData<T>
|
getLiveData(String key)
Returns a |
<T>
MutableLiveData<T>
|
getLiveData(String key, T initialValue)
Returns a |
Set<String>
|
keys()
Returns all keys contained in this |
<T>
T
|
remove(String key)
Removes a value associated with the given key. |
<T>
void
|
set(String key, T value)
Associate the given value with the key. |
Inherited methods | |
|---|---|
Public constructors
SavedStateHandle
public SavedStateHandle (Map<String, Object> initialState)
Creates a handle with the given initial arguments.
| Parameters | |
|---|---|
initialState |
Map |
SavedStateHandle
public SavedStateHandle ()
Creates a handle with the empty state.
Public methods
contains
public boolean contains (String key)
| Parameters | |
|---|---|
key |
String |
| Returns | |
|---|---|
boolean |
true if there is value associated with the given key. |
get
public T get (String key)
Returns a value associated with the given key.
| Parameters | |
|---|---|
key |
String |
| Returns | |
|---|---|
T |
|
getLiveData
public MutableLiveData<T> getLiveData (String key)
Returns a LiveData that access data associated with the given key.
| Parameters | |
|---|---|
key |
String |
| Returns | |
|---|---|
MutableLiveData<T> |
|
See also:
getLiveData
public MutableLiveData<T> getLiveData (String key, T initialValue)
Returns a LiveData that access data associated with the given key.
LiveData<String> liveData = savedStateHandle.get(KEY, "defaultValue");
null as a valid value. If the
initialValue is null and the data does not already exist in the
SavedStateHandle, the value of the returned LiveData will be set to
null and observers will be notified. You can call getLiveData(String) if
you want to avoid dispatching null to observers.
String defaultValue = ...; // nullable
LiveData<String> liveData;
if (defaultValue != null) {
liveData = savedStateHandle.get(KEY, defaultValue);
} else {
liveData = savedStateHandle.get(KEY);
}
| Parameters | |
|---|---|
key |
String: The identifier for the value |
initialValue |
T: If no value exists with the given key, a new one is created
with the given initialValue. Note that passing null will
create a LiveData with null value.
|
| Returns | |
|---|---|
MutableLiveData<T> |
|
keys
public Set<String> keys ()
Returns all keys contained in this SavedStateHandle
| Returns | |
|---|---|
Set<String> |
|
remove
public T remove (String key)
Removes a value associated with the given key. If there is a LiveData associated
with the given key, it will be removed as well.
All changes to LiveData previously
returned by getLiveData(String) won't be reflected in
the saved state. Also that LiveData won't receive any updates about new values
associated by the given key.
| Parameters | |
|---|---|
key |
String: a key |
| Returns | |
|---|---|
T |
a value that was previously associated with the given key. |
set
public void set (String key,
T value)
Associate the given value with the key. The value must have a type that could be stored in
Bundle
| Parameters | |
|---|---|
key |
String |
value |
T |