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Builder

open class Builder<T : RoomDatabase!>
kotlin.Any
   ↳ androidx.room.RoomDatabase.Builder

Builder for RoomDatabase.

Summary

Public methods

open RoomDatabase.Builder<T>
addCallback(@NonNull callback: RoomDatabase.Callback)

Adds a Callback to this database.

open RoomDatabase.Builder<T>
addMigrations(@NonNull vararg migrations: Migration!)

Adds a migration to the builder.

open RoomDatabase.Builder<T>

Disables the main thread query check for Room.

open T

Creates the databases and initializes it.

open RoomDatabase.Builder<T>
createFromAsset(@NonNull databaseFilePath: String)

Configures Room to create and open the database using a pre-packaged database located in the application 'assets/' folder.

open RoomDatabase.Builder<T>
createFromFile(@NonNull databaseFile: File)

Configures Room to create and open the database using a pre-packaged database file.

open RoomDatabase.Builder<T>

Sets whether table invalidation in this instance of RoomDatabase should be broadcast and synchronized with other instances of the same RoomDatabase, including those in a separate process.

open RoomDatabase.Builder<T>

Allows Room to destructively recreate database tables if Migrations that would migrate old database schemas to the latest schema version are not found.

open RoomDatabase.Builder<T>
fallbackToDestructiveMigrationFrom(vararg startVersions: Int)

Informs Room that it is allowed to destructively recreate database tables from specific starting schema versions.

open RoomDatabase.Builder<T>

Allows Room to destructively recreate database tables if Migrations are not available when downgrading to old schema versions.

open RoomDatabase.Builder<T>

Sets the database factory.

open RoomDatabase.Builder<T>

Sets the journal mode for this database.

open RoomDatabase.Builder<T>
setQueryExecutor(@NonNull executor: Executor)

Sets the Executor that will be used to execute all non-blocking asynchronous queries and tasks, including LiveData invalidation, Flowable scheduling and ListenableFuture tasks.

open RoomDatabase.Builder<T>
setTransactionExecutor(@NonNull executor: Executor)

Sets the Executor that will be used to execute all non-blocking asynchronous transaction queries and tasks, including LiveData invalidation, Flowable scheduling and ListenableFuture tasks.

Public methods

addCallback

@NonNull open fun addCallback(@NonNull callback: RoomDatabase.Callback): RoomDatabase.Builder<T>

Adds a Callback to this database.

Parameters
callback RoomDatabase.Callback: The callback.
Return
RoomDatabase.Builder<T>: This Builder instance.

addMigrations

@NonNull open fun addMigrations(@NonNull vararg migrations: Migration!): RoomDatabase.Builder<T>

Adds a migration to the builder.

Each Migration has a start and end versions and Room runs these migrations to bring the database to the latest version.

If a migration item is missing between current version and the latest version, Room will clear the database and recreate so even if you have no changes between 2 versions, you should still provide a Migration object to the builder.

A migration can handle more than 1 version (e.g. if you have a faster path to choose when going version 3 to 5 without going to version 4). If Room opens a database at version 3 and latest version is >= 5, Room will use the migration object that can migrate from 3 to 5 instead of 3 to 4 and 4 to 5.

Parameters
migrations Migration!: The migration object that can modify the database and to the necessary changes.
Return
RoomDatabase.Builder<T>: This Builder instance.

allowMainThreadQueries

@NonNull open fun allowMainThreadQueries(): RoomDatabase.Builder<T>

Disables the main thread query check for Room.

Room ensures that Database is never accessed on the main thread because it may lock the main thread and trigger an ANR. If you need to access the database from the main thread, you should always use async alternatives or manually move the call to a background thread.

You may want to turn this check off for testing.

Return
RoomDatabase.Builder<T>: This Builder instance.

build

@NonNull open fun build(): T

Creates the databases and initializes it.

By default, all RoomDatabases use in memory storage for TEMP tables and enables recursive triggers.

Return
T: A new database instance.

createFromAsset

@NonNull open fun createFromAsset(@NonNull databaseFilePath: String): RoomDatabase.Builder<T>

Configures Room to create and open the database using a pre-packaged database located in the application 'assets/' folder.

Room does not open the pre-packaged database, instead it copies it into the internal app database folder and then opens it. The pre-packaged database file must be located in the "assets/" folder of your application. For example, the path for a file located in "assets/databases/products.db" would be "databases/products.db".

The pre-packaged database schema will be validated. It might be best to create your pre-packaged database schema utilizing the exported schema files generated when Database#exportSchema() is enabled.

This method is not supported for an in memory database Builder.

Parameters
databaseFilePath String: The file path within the 'assets/' directory of where the database file is located.
Return
RoomDatabase.Builder<T>: This Builder instance.

createFromFile

@NonNull open fun createFromFile(@NonNull databaseFile: File): RoomDatabase.Builder<T>

Configures Room to create and open the database using a pre-packaged database file.

Room does not open the pre-packaged database, instead it copies it into the internal app database folder and then opens it. The given file must be accessible and the right permissions must be granted for Room to copy the file.

The pre-packaged database schema will be validated. It might be best to create your pre-packaged database schema utilizing the exported schema files generated when Database#exportSchema() is enabled.

This method is not supported for an in memory database Builder.

Parameters
databaseFile File: The database file.
Return
RoomDatabase.Builder<T>: This Builder instance.

enableMultiInstanceInvalidation

@NonNull open fun enableMultiInstanceInvalidation(): RoomDatabase.Builder<T>

Sets whether table invalidation in this instance of RoomDatabase should be broadcast and synchronized with other instances of the same RoomDatabase, including those in a separate process. In order to enable multi-instance invalidation, this has to be turned on both ends.

This is not enabled by default.

This does not work for in-memory databases. This does not work between database instances targeting different database files.

Return
RoomDatabase.Builder<T>: This Builder instance.

fallbackToDestructiveMigration

@NonNull open fun fallbackToDestructiveMigration(): RoomDatabase.Builder<T>

Allows Room to destructively recreate database tables if Migrations that would migrate old database schemas to the latest schema version are not found.

When the database version on the device does not match the latest schema version, Room runs necessary Migrations on the database.

If it cannot find the set of Migrations that will bring the database to the current version, it will throw an IllegalStateException.

You can call this method to change this behavior to re-create the database instead of crashing.

If the database was create from an asset or a file then Room will try to use the same file to re-create the database, otherwise this will delete all of the data in the database tables managed by Room.

To let Room fallback to destructive migration only during a schema downgrade then use fallbackToDestructiveMigrationOnDowngrade().

Return
RoomDatabase.Builder<T>: This Builder instance.

fallbackToDestructiveMigrationFrom

@NonNull open fun fallbackToDestructiveMigrationFrom(vararg startVersions: Int): RoomDatabase.Builder<T>

Informs Room that it is allowed to destructively recreate database tables from specific starting schema versions.

This functionality is the same as that provided by fallbackToDestructiveMigration(), except that this method allows the specification of a set of schema versions for which destructive recreation is allowed.

Using this method is preferable to fallbackToDestructiveMigration() if you want to allow destructive migrations from some schema versions while still taking advantage of exceptions being thrown due to unintentionally missing migrations.

Note: No versions passed to this method may also exist as either starting or ending versions in the Migrations provided to addMigrations(Migration...). If a version passed to this method is found as a starting or ending version in a Migration, an exception will be thrown.

Parameters
startVersions Int: The set of schema versions from which Room should use a destructive migration.
Return
RoomDatabase.Builder<T>: This Builder instance.

fallbackToDestructiveMigrationOnDowngrade

@NonNull open fun fallbackToDestructiveMigrationOnDowngrade(): RoomDatabase.Builder<T>

Allows Room to destructively recreate database tables if Migrations are not available when downgrading to old schema versions.

Return
RoomDatabase.Builder<T>: This Builder instance.

openHelperFactory

@NonNull open fun openHelperFactory(@Nullable factory: SupportSQLiteOpenHelper.Factory?): RoomDatabase.Builder<T>

Sets the database factory. If not set, it defaults to FrameworkSQLiteOpenHelperFactory.

Parameters
factory SupportSQLiteOpenHelper.Factory?: The factory to use to access the database.
Return
RoomDatabase.Builder<T>: This Builder instance.

setJournalMode

@NonNull open fun setJournalMode(@NonNull journalMode: RoomDatabase.JournalMode): RoomDatabase.Builder<T>

Sets the journal mode for this database.

This value is ignored if the builder is initialized with Room#inMemoryDatabaseBuilder(Context, Class).

The journal mode should be consistent across multiple instances of RoomDatabase for a single SQLite database file.

The default value is JournalMode#AUTOMATIC.

Parameters
journalMode RoomDatabase.JournalMode: The journal mode.
Return
RoomDatabase.Builder<T>: This Builder instance.

setQueryExecutor

@NonNull open fun setQueryExecutor(@NonNull executor: Executor): RoomDatabase.Builder<T>

Sets the Executor that will be used to execute all non-blocking asynchronous queries and tasks, including LiveData invalidation, Flowable scheduling and ListenableFuture tasks.

When both the query executor and transaction executor are unset, then a default Executor will be used. The default Executor allocates and shares threads amongst Architecture Components libraries. If the query executor is unset but a transaction executor was set, then the same Executor will be used for queries.

For best performance the given Executor should be bounded (max number of threads is limited).

The input Executor cannot run tasks on the UI thread.

Return
RoomDatabase.Builder<T>: This Builder instance.

setTransactionExecutor

@NonNull open fun setTransactionExecutor(@NonNull executor: Executor): RoomDatabase.Builder<T>

Sets the Executor that will be used to execute all non-blocking asynchronous transaction queries and tasks, including LiveData invalidation, Flowable scheduling and ListenableFuture tasks.

When both the transaction executor and query executor are unset, then a default Executor will be used. The default Executor allocates and shares threads amongst Architecture Components libraries. If the transaction executor is unset but a query executor was set, then the same Executor will be used for transactions.

If the given Executor is shared then it should be unbounded to avoid the possibility of a deadlock. Room will not use more than one thread at a time from this executor since only one transaction at a time can be executed, other transactions will be queued on a first come, first serve order.

The input Executor cannot run tasks on the UI thread.

Return
RoomDatabase.Builder<T>: This Builder instance.