如何在android房间实体内注释默认值? [英] How to annotate a default value inside a android room entity?

问题描述

在查看 @ColumnInfo 新 Android 持久性库的文档.

I couldn't find any information how to annotate a SQL - "DEFAULT" value while looking into the @ColumnInfo docs for the new Android Persistence Library.

Room 甚至提供默认值的注释吗?

Does Room even provide an annotation for default values?

我目前的解决方案是手动创建相应的表...

My current solution would be to manually create the corresponding Table ...

CREATE TABLE MyTable (
  ...
  MyDefaultValuedCol  TEXT DEFAULT 'Default Value',
  MyDefaultFlagCol    INT  DEFAULT 1
)

...然后将 Room 放在最上面.

... and put Room on top.

@Entity(tableName = "MyTable")
class MyClass {
    ...

    public String MyDefaultValuedCol;

    public boolean MyDefaultFlagCol;

}

推荐答案

随着房间持久性 2.2.0 的发布，@ColumnInfo 注释中添加了一个新属性，可用于指定列的默认值.请参阅文档.

With the release of room persistence 2.2.0, there's a new property added to @ColumnInfo annotation which can be used to specify the default value of a column. See documentation.

@Entity(tableName = "users")
data class User(
    @PrimaryKey val id: Long,
    @ColumnInfo(name = "user_name", defaultValue = "temp") val name: String
    @ColumnInfo(name = "last_modified", defaultValue = "CURRENT_TIMESTAMP" ) val lastModified: String
)

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