Summary: Ctors | Methods | Inherited Methods

SavedStateHandle

Kotlin |Java

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
`void`	`clearSavedStateProvider(String key)` Clear any `SavedStateRegistry.SavedStateProvider` that was previously set via `setSavedStateProvider(String, SavedStateProvider)`.
`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 `LiveData` that access data associated with the given key.
`<T> MutableLiveData<T>`	`getLiveData(String key, T initialValue)` Returns a `LiveData` that access data associated with the given key.
`Set<String>`	`keys()` Returns all keys contained in this `SavedStateHandle`
`<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.
`void`	`setSavedStateProvider(String key, SavedStateRegistry.SavedStateProvider provider)` Set a `SavedStateRegistry.SavedStateProvider` that will have its state saved into this SavedStateHandle.

Inherited methods

From class


        
          java.lang.Object

`Object`	`clone()`
`boolean`	`equals(Object arg0)`
`void`	`finalize()`
`final Class<?>`	`getClass()`
`int`	`hashCode()`
`final void`	`notify()`
`final void`	`notifyAll()`
`String`	`toString()`
`final void`	`wait(long arg0, int arg1)`
`final void`	`wait(long arg0)`
`final void`	`wait()`

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

clearSavedStateProvider

public void clearSavedStateProvider (String key)

Clear any SavedStateRegistry.SavedStateProvider that was previously set via setSavedStateProvider(String, SavedStateProvider). Note: calling this method within SavedStateRegistry.SavedStateProvider.saveState() is supported, but will only affect future state saving operations.

Parameters
`key`	`String`: a key previously used with `setSavedStateProvider(String, SavedStateRegistry.SavedStateProvider)`

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(String, Object)

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");

LiveData can have 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.getLiveData(KEY, defaultValue);
     } else {
         liveData = savedStateHandle.getLiveData(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`

setSavedStateProvider

public void setSavedStateProvider (String key, 
                SavedStateRegistry.SavedStateProvider provider)

Set a SavedStateRegistry.SavedStateProvider that will have its state saved into this SavedStateHandle. This provides a mechanism to lazily provide the Bundle of saved state for the given key.

Calls to get(String) with this same key will return the previously saved state as a Bundle if it exists.

     Bundle previousState = savedStateHandle.get("custom_object");
     if (previousState != null) {
         // Convert the previousState into your custom object
     }
     savedStateHandle.setSavedStateProvider("custom_object", () -> {
         Bundle savedState = new Bundle();
         // Put your custom object into the Bundle, doing any conversion required
         return savedState;
     });

Note: calling this method within SavedStateRegistry.SavedStateProvider.saveState() is supported, but will only affect future state saving operations.

Parameters
`key`	`String`: a key which will populated with a `Bundle` produced by the provider
`provider`	`SavedStateRegistry.SavedStateProvider`: a SavedStateProvider which will receive a callback to `SavedStateRegistry.SavedStateProvider.saveState()` when the state should be saved