Android架构组件：使用枚举

Question

@Entity(tableName = "tasks")
public class Task extends SyncEntity {

    @PrimaryKey(autoGenerate = true)
    String taskId;

    String title;

    /** Status of the given task.
     * Enumerated Values: 0 (Active), 1 (Inactive), 2 (Completed)
     */
    @Embedded
    Status status;

    @TypeConverters(DateConverter.class)
    Date startDate;

    @TypeConverters(StatusConverter.class)
    public enum Status {
        ACTIVE(0),
        INACTIVE(1),
        COMPLETED(2);

        private int code;

        Status(int code) {
            this.code = code;
        }

        public int getCode() {
            return code;
        }
    }
}

public class StatusConverter {

    @TypeConverter
    public static Task.Status toStatus(int status) {
        if (status == ACTIVE.getCode()) {
            return ACTIVE;
        } else if (status == INACTIVE.getCode()) {
            return INACTIVE;
        } else if (status == COMPLETED.getCode()) {
            return COMPLETED;
        } else {
            throw new IllegalArgumentException("Could not recognize status");
        }
    }

    @TypeConverter
    public static Integer toInteger(Task.Status status) {
        return status.getCode();
    }
}

/**
 * Base class for all Room entities that are synchronized.
 */
@Entity
public class SyncEntity {

    @ColumnInfo(name = "created_at")
    Long createdAt;

    @ColumnInfo(name = "updated_at")
    Long updatedAt;
}

Answer 1

我可以在房间和typeConverters一起使用枚举值。在您的代码中有一些部分需要更改：

1）您必须声明实体的字段是公共的，或者它们必须有公共的getter/setter。否则您将得到以下错误：

yourField在您的实体中不是公共的；无法从外部包访问

您可以定义一个空构造函数来跳过此错误。

5）在TypeConverter中使用int而不是Integer。

总和；以下工作符合预期：

@Entity(tableName = "tasks")
public class Task extends SyncEntity {

    @PrimaryKey(autoGenerate = true)
    public String taskId;

    public String title;

    /** Status of the given task.
     * Enumerated Values: 0 (Active), 1 (Inactive), 2 (Completed)
     */
    @TypeConverters(StatusConverter.class)
    public Status status;

    @TypeConverters(DateConverter.class)
    public Date startDate;

    // empty constructor 
    public Task() {
    }

    public enum Status {
        ACTIVE(0),
        INACTIVE(1),
        COMPLETED(2);

        private int code;

        Status(int code) {
            this.code = code;
        }

        public int getCode() {
            return code;
        }
    }
}