SavedStateHandle
class SavedStateHandle
| kotlin.Any | |
| ↳ | androidx.lifecycle.SavedStateHandle |
A handle to saved state passed down to androidx.lifecycle.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 androidx.lifecycle.LiveData returned by getLiveData(String).
You can write a value to it via set(String, Object) or setting a value to androidx.lifecycle.MutableLiveData returned by getLiveData(String).
Summary
Public constructors |
|
|---|---|
<init>(@NonNull initialState: MutableMap<String!, Any!>)Creates a handle with the given initial arguments. |
|
<init>()Creates a handle with the empty state. |
|
Public methods |
|
|---|---|
| Boolean | |
| T? |
Returns a value associated with the given key. |
| MutableLiveData<T> |
getLiveData(@NonNull key: String)Returns a |
| MutableLiveData<T> |
getLiveData(@NonNull key: String, initialValue: T)Returns a |
| MutableSet<String!> |
keys()Returns all keys contained in this |
| T? |
Removes a value associated with the given key. |
| Unit |
Associate the given value with the key. |
Public constructors
<init>
SavedStateHandle(@NonNull initialState: MutableMap<String!, Any!>)
Creates a handle with the given initial arguments.
<init>
SavedStateHandle()
Creates a handle with the empty state.
Public methods
contains
@MainThread fun contains(@NonNull key: String): Boolean
| Return | |
|---|---|
Boolean |
true if there is value associated with the given key. |
get
@MainThread @Nullable fun <T : Any!> get(@NonNull key: String): T?
Returns a value associated with the given key.
getLiveData
@MainThread @NonNull fun <T : Any!> getLiveData(@NonNull key: String): MutableLiveData<T>
Returns a androidx.lifecycle.LiveData that access data associated with the given key.
See Also
getLiveData
@MainThread @NonNull fun <T : Any!> getLiveData(
@NonNull key: String,
initialValue: T
): MutableLiveData<T>
Returns a androidx.lifecycle.LiveData that access data associated with the given key.
<code>LiveData<String> liveData = savedStateHandle.get(KEY, "defaultValue");
</code>
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.
<code>String defaultValue = ...; // nullable
LiveData<String> liveData;
if (defaultValue != null) {
liveData = savedStateHandle.get(KEY, defaultValue);
} else {
liveData = savedStateHandle.get(KEY);
}
</code>
| 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. |
keys
@MainThread @NonNull fun keys(): MutableSet<String!>
Returns all keys contained in this SavedStateHandle
remove
@MainThread @Nullable fun <T : Any!> remove(@NonNull key: String): T?
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 androidx.lifecycle.LiveData previously returned by SavedStateHandle#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 |
| Return | |
|---|---|
T? |
a value that was previously associated with the given key. |
set
@MainThread fun <T : Any!> set(
@NonNull key: String,
@Nullable value: T?
): Unit
Associate the given value with the key. The value must have a type that could be stored in android.os.Bundle
| Parameters | |
|---|---|
<T> |
any type that can be accepted by Bundle. |