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ColumnInfo

public abstract @interface ColumnInfo
implements Annotation

androidx.room.ColumnInfo

Allows specific customization about the column associated with this field.

For example, you can specify a column name for the field or change the column's type affinity.

Summary

Nested classes

@interface ColumnInfo.Collate

 

@interface ColumnInfo.SQLiteTypeAffinity

The SQLite column type constants that can be used in ColumnInfo.typeAffinity()  

Constants

int BINARY

Collation sequence for case-sensitive match.

int BLOB

Column affinity constant for binary data.

String INHERIT_FIELD_NAME

Constant to let Room inherit the field name as the column name.

int INTEGER

Column affinity constant for integers or booleans.

int LOCALIZED

Collation sequence that uses system's current locale.

int NOCASE

Collation sequence for case-insensitive match.

int REAL

Column affinity constant for floats or doubles.

int RTRIM

Collation sequence for case-sensitive match except that trailing space characters are ignored.

int TEXT

Column affinity constant for strings.

int UNDEFINED

Undefined type affinity.

int UNICODE

Collation sequence that uses Unicode Collation Algorithm.

int UNSPECIFIED

Collation sequence is not specified.

String VALUE_UNSPECIFIED

A constant for defaultValue() that makes the column to have no default value.

Public methods

int collate()

The collation sequence for the column, which will be used when constructing the database.

String defaultValue()

The default value for this column.

boolean index()

Convenience method to index the field.

String name()

Name of the column in the database.

int typeAffinity()

The type affinity for the column, which will be used when constructing the database.

Inherited methods

Constants

BINARY

public static final int BINARY

Collation sequence for case-sensitive match.

See also:

Constant Value: 2 (0x00000002)

BLOB

public static final int BLOB

Column affinity constant for binary data.

See also:

Constant Value: 5 (0x00000005)

INHERIT_FIELD_NAME

public static final String INHERIT_FIELD_NAME

Constant to let Room inherit the field name as the column name. If used, Room will use the field name as the column name.

Constant Value: "[field-name]"

INTEGER

public static final int INTEGER

Column affinity constant for integers or booleans.

See also:

Constant Value: 3 (0x00000003)

LOCALIZED

public static final int LOCALIZED

Collation sequence that uses system's current locale.

See also:

Constant Value: 5 (0x00000005)

NOCASE

public static final int NOCASE

Collation sequence for case-insensitive match.

See also:

Constant Value: 3 (0x00000003)

REAL

public static final int REAL

Column affinity constant for floats or doubles.

See also:

Constant Value: 4 (0x00000004)

RTRIM

public static final int RTRIM

Collation sequence for case-sensitive match except that trailing space characters are ignored.

See also:

Constant Value: 4 (0x00000004)

TEXT

public static final int TEXT

Column affinity constant for strings.

See also:

Constant Value: 2 (0x00000002)

UNDEFINED

public static final int UNDEFINED

Undefined type affinity. Will be resolved based on the type.

See also:

Constant Value: 1 (0x00000001)

UNICODE

public static final int UNICODE

Collation sequence that uses Unicode Collation Algorithm.

See also:

Constant Value: 6 (0x00000006)

UNSPECIFIED

public static final int UNSPECIFIED

Collation sequence is not specified. The match will behave like BINARY.

See also:

Constant Value: 1 (0x00000001)

VALUE_UNSPECIFIED

public static final String VALUE_UNSPECIFIED

A constant for defaultValue() that makes the column to have no default value.

Constant Value: "[value-unspecified]"

Public methods

collate

public int collate ()

The collation sequence for the column, which will be used when constructing the database.

The default value is UNSPECIFIED. In that case, Room does not add any collation sequence to the column, and SQLite treats it like BINARY.

Returns
int The collation sequence of the column. This is either UNSPECIFIED, BINARY, NOCASE, RTRIM, LOCALIZED or UNICODE.

defaultValue

public String defaultValue ()

The default value for this column. 

   @ColumnInfo(defaultValue = "No name")
   public String name;

  @ColumnInfo(defaultValue = "0")
   public int flag;

Note that the default value you specify here will NOT be used if you simply insert the Entity with @Insert. In that case, any value assigned in Java/Kotlin will be used. Use @Query with an INSERT statement and skip this column there in order to use this default value.

NULL, CURRENT_TIMESTAMP and other SQLite constant values are interpreted as such. If you want to use them as strings for some reason, surround them with single-quotes. 

   @ColumnInfo(defaultValue = "NULL")
   @Nullable
   public String description;

   @ColumnInfo(defaultValue = "'NULL'")
   @NonNull
   public String name;

You can also use constant expressions by surrounding them with parentheses. 

   @CoumnInfo(defaultValue = "('Created at' || CURRENT_TIMESTAMP)")
   public String notice;

Returns
String The default value for this column.

See also:

index

public boolean index ()

Convenience method to index the field.

If you would like to create a composite index instead, see: Index.

Returns
boolean True if this field should be indexed, false otherwise. Defaults to false.

name

public String name ()

Name of the column in the database. Defaults to the field name if not set.

Returns
String Name of the column in the database.

typeAffinity

public int typeAffinity ()

The type affinity for the column, which will be used when constructing the database.

If it is not specified, the value defaults to UNDEFINED and Room resolves it based on the field's type and available TypeConverters.

See SQLite types documentation for details.

Returns
int The type affinity of the column. This is either UNDEFINED, TEXT, INTEGER, REAL, or BLOB.