Introductory session on Jetpack Datastore that Google has released in Sep 2020, aiming at replacing SharedPreference.

1. Introduction to
Jetpack DataStore
Wonyoung Choi (Toru)
Android Advocate,
Singapore Tourism Board

2. Introduction

3. 1.Data storage solution in Jetpack Library
2.Aiming at replacing SharedPreferences
3.Released in alpha, in Sep 2020
What is DataStore?

4. 1.Supporting Key-Value pair / typed object
2.Backed by Kotlin Coroutines, and Flow
3.Storing data in asynchronous way
What is DataStore?

5. Components of DataStore
DataStore
Preference Proto

6. 1.Preference:Key-Value Pair to store data
2.Proto:custom data type with specified
Schema using Protocol Buffers
Components of DataStore

7. Comparison to SharedPreference

9. 1.Safe to use in UI Thread
2.Robust to RuntimeException when parsing
3.Providing migration
4.Type safety
Highlights on DataStore

10. Using DataStore

11. dependencies {
// Preferences DataStore
implementation “androidx.datastore:datastore-preferences:1.0.0-alpha01"
}
For Preference DataStore

12. plugins {
...
id "com.google.protobuf" version "0.8.12"
}
dependencies {
implementation "androidx.datastore:datastore-core:1.0.0-alpha01"
implementation "com.google.protobuf:protobuf-javalite:3.10.0"
...
}
For ProtoDataStore

13. protobuf {
protoc {
artifact = "com.google.protobuf:protoc:3.10.0"
}
generateProtoTasks {
all().each { task ->
task.builtins {
java {
option 'lite'
}
}
}
}
}
For ProtoDataStore

14. syntax = "proto3";
option java_package = "<your package name here>";
option java_multiple_files = true;
message Settings {
int my_counter = 1;
}
For ProtoDataStore
app/src/main/proto/
filename.proto

15. Create DataStore

16. // with Preferences DataStore
val dataStore: DataStore<Preferences> = context.createDataStore(
name = "settings"
)
For Preference DataStore

17. object SettingsSerializer : Serializer<Settings> {
override fun readFrom(input: InputStream): Settings {
try {
return Settings.parseFrom(input)
} catch (exception: InvalidProtocolBufferException) {
throw CorruptionException("Cannot read proto.", exception)
}
}
override fun writeTo(t: Settings, output: OutputStream) = t.writeTo(output)
}
For ProtoDataStore

18. // with Proto DataStore
val settingsDataStore: DataStore<Settings> = context.createDataStore(
fileName = "settings.pb",
serializer = SettingsSerializer
)
For ProtoDataStore

19. Read from DataStore

20. 1.Loading stored data in Flow
2.Retrieving data on Dispatchers.IO
3.Ensuring non-blocking UI thread
What is under the hood of reading DataStore

21. val MY_COUNTER = preferencesKey<Int>("my_counter")
val myCounterFlow: Flow<Int> = dataStore.data
.map { currentPreferences ->
// Unlike Proto DataStore, there's no type safety here.
currentPreferences[MY_COUNTER] ?: 0
}
For Preference DataStore

22. val myCounterFlow: Flow<Int> = settingsDataStore.data
.map { settings ->
// The myCounter property is generated for you from your proto schema!
settings.myCounter
}
For ProtoDataStore

23. Write to DataStore

24. 1.Loading stored data in Flow
2.Retrieving data on Dispatchers.IO
3.Ensuring non-blocking UI thread
Writing to DataStore

25. suspend fun incrementCounter() {
dataStore.edit { settings ->
// We can safely increment our counter without losing data due to races!
val currentCounterValue = settings[MY_COUNTER] ?: 0
settings[MY_COUNTER] = currentCounterValue + 1
}
}
For Preference DataStore

26. suspend fun incrementCounter() {
settingsDataStore.updateData { currentSettings ->
// We can safely increment our counter without losing data due to races!
currentSettings.toBuilder()
.setMyCounter(currentSettings.myCounter + 1)
.build()
}
}
For ProtoDataStore

27. Migration

28. 1.Defining SharedPreferencesMigration
2.Telling DataStore to use migration obj
Migration SharedPreferences to DataStore

29. val migration = SharedPreferencesMigration(context, "settings_preferences")
val dataStore: DataStore<Preferences> = context.createDataStore(
name = "settings",
migrations = listOf(migration)
)
For Preference DataStore

30. val migration = SharedPreferencesMigration(
context,
"settings_preferences"
) { sharedPrefs: SharedPreferencesView, currentData: UserPreferences ->
// Map your sharedPrefs to your type here
}
val settingsDataStore: DataStore<Settings> = context.createDataStore(
produceFile = { File(context.filesDir, "settings.preferences_pb") },
serializer = SettingsSerializer,
migrations = listOf(migration)
)
For ProtoDataStore

31. Furthermore

32. 1.Alpha stage
2.learning curve on what Datastore uses
3.Possibilities of changes in future
Furthermore

33. Thank you!
TORU0239
TORU_0239