SharedPreferencesMigration

public final class SharedPreferencesMigration<T extends Object> implements DataMigration


DataMigration instance for migrating from SharedPreferences to DataStore.

Summary

Public constructors

<T extends Object> SharedPreferencesMigration(
    Function0<SharedPreferences> produceSharedPreferences,
    Set<String> keysToMigrate,
    SuspendFunction1<T, Boolean> shouldRunMigration,
    SuspendFunction2<SharedPreferencesView, T, T> migrate
)

DataMigration from SharedPreferences to DataStore.

<T extends Object> SharedPreferencesMigration(
    Context context,
    String sharedPreferencesName,
    Set<String> keysToMigrate,
    SuspendFunction1<T, Boolean> shouldRunMigration,
    SuspendFunction2<SharedPreferencesView, T, T> migrate
)

DataMigration from SharedPreferences to DataStore.

Public methods

void

Clean up any old state/data that was migrated into the DataStore.

@NonNull T
migrate(T currentData)

Perform the migration.

boolean
shouldMigrate(T currentData)

Return whether this migration needs to be performed.

Public constructors

SharedPreferencesMigration

public final <T extends Object> SharedPreferencesMigration(
    Function0<SharedPreferences> produceSharedPreferences,
    Set<String> keysToMigrate,
    SuspendFunction1<T, Boolean> shouldRunMigration,
    SuspendFunction2<SharedPreferencesView, T, T> migrate
)

DataMigration from SharedPreferences to DataStore.

Note: This migration only supports the basic SharedPreferences types: boolean, float, int, long, string and string set. If the result of getAll contains other types, they will be ignored.

Example usage:

val sharedPrefsMigration = SharedPreferencesMigration(
produceSharedPreferences = { EncryptedSharedPreferences.create(...) }
) { prefs: SharedPreferencesView, myData: MyData ->
myData.toBuilder().setCounter(prefs.getCounter(COUNTER_KEY, default = 0)).build()
}
Parameters
Function0<SharedPreferences> produceSharedPreferences

Should return the instance of SharedPreferences to migrate from.

Set<String> keysToMigrate

The list of keys to migrate. The keys will be mapped to datastore .Preferences with their same values. If the key is already present in the new Preferences, the key will not be migrated again. If the key is not present in the SharedPreferences it will not be migrated. If keysToMigrate is not set, all keys will be migrated from the existing SharedPreferences.

SuspendFunction2<SharedPreferencesView, T, T> migrate

maps SharedPreferences into T. Implementations should be idempotent since this may be called multiple times. See DataMigration.migrate for more information. The lambda accepts a SharedPreferencesView which is the view of the SharedPreferences to migrate from (limited to keysToMigrate and a T which represent the current data. The function must return the migrated data. If SharedPreferences is empty or does not contain any keys which you specified, this callback will not run.

SharedPreferencesMigration

public final <T extends Object> SharedPreferencesMigration(
    Context context,
    String sharedPreferencesName,
    Set<String> keysToMigrate,
    SuspendFunction1<T, Boolean> shouldRunMigration,
    SuspendFunction2<SharedPreferencesView, T, T> migrate
)

DataMigration from SharedPreferences to DataStore.

If the SharedPreferences is empty once the migration completes, this migration will attempt to delete it.

Example usage:

val sharedPrefsMigration = SharedPreferencesMigration(
context,
mySharedPreferencesName
) { prefs: SharedPreferencesView, myData: MyData ->
myData.toBuilder().setCounter(prefs.getCounter(COUNTER_KEY, default = 0)).build()
}
Parameters
Context context

Context used for getting SharedPreferences.

String sharedPreferencesName

The name of the SharedPreferences.

Set<String> keysToMigrate

The list of keys to migrate. The keys will be mapped to datastore .Preferences with their same values. If the key is already present in the new Preferences, the key will not be migrated again. If the key is not present in the SharedPreferences it will not be migrated. If keysToMigrate is not set, all keys will be migrated from the existing SharedPreferences.

SuspendFunction2<SharedPreferencesView, T, T> migrate

maps SharedPreferences into T. Implementations should be idempotent since this may be called multiple times. See DataMigration.migrate for more information. The lambda accepts a SharedPreferencesView which is the view of the SharedPreferences to migrate from (limited to keysToMigrate and a T which represent the current data. The function must return the migrated data. If SharedPreferences is empty or does not contain any keys which you specified, this callback will not run.

Public methods

cleanUp

public void cleanUp()

Clean up any old state/data that was migrated into the DataStore. This will not be called if the migration fails. If cleanUp throws an exception, the exception will be propagated back to the DataStore call that triggered the migration and future calls to DataStore will result in DataMigrations being attempted again. This method may be run multiple times when any failure is encountered.

This is useful for cleaning up files or data outside of DataStore and accessing any data from DataStore directly from inside this function will result in deadlock, since DataStore doesn't return data until all migrations complete.

migrate

public @NonNullmigrate(T currentData)

Perform the migration. Implementations should be idempotent since this may be called multiple times. If migrate fails, DataStore will not commit any data to disk, cleanUp will not be called, and the exception will be propagated back to the DataStore call that triggered the migration. Future calls to DataStore will result in DataMigrations being attempted again. This method may be run multiple times when any failure is encountered.

Note that this will always be called before a call to cleanUp.

Note that accessing any data from DataStore directly from inside this function will result in deadlock, since DataStore doesn't return data until all migrations complete.

Parameters
T currentData

the current data (it might be populated from other migrations or from manual changes before this migration was added to the app)

Returns
@NonNull T

The migrated data.

shouldMigrate

public boolean shouldMigrate(T currentData)

Return whether this migration needs to be performed. If this returns false, no migration or cleanup will occur. Apps should do the cheapest possible check to determine if this migration should run, since this will be called every time the DataStore is initialized. This method may be run multiple times when any failure is encountered.

Note that this will always be called before each call to migrate.

Note that accessing any data from DataStore directly from inside this function will result in deadlock, since DataStore doesn't return data until all migrations complete.

Parameters
T currentData

the current data (which might already populated from previous runs of this or other migrations)