相关疑难解决方法(0)

在Android房间持久化库中如何将整个Model对象插入到本身具有另一个列表的表中.

让我告诉你我的意思:

@Entity(tableName = TABLE_NAME)
public class CountryModel {

    public static final String TABLE_NAME = "Countries";

    @PrimaryKey
    private int idCountry;

    private List<CountryLang> countryLang = null;

    public int getIdCountry() {
        return idCountry;
    }

    public void setIdCountry(int idCountry) {
        this.idCountry = idCountry;
    }

    public String getIsoCode() {
        return isoCode;
    }

    public void setIsoCode(String isoCode) {
        this.isoCode = isoCode;
    }

    /** 
        here i am providing a list of coutry information how to insert 
        this into db along with CountryModel at same …

我很难将列表项目放到房间里.列表项称为测量值,其类型为Measurement.列表项没有与数据库相关的主键.但如果有必要,我可以为ProductModel添加相同的主键.

这是我到目前为止:

@Entity(tableName = TABLE_NAME)
public class ProductModel {

    public static final String TABLE_NAME = "product";

    @PrimaryKey
    private int idProduct;

    private int idCategoryDefault;

    @Relation(parentColumn = "idProduct", entityColumn = "idProduct", entity = SortedAttribute.class)
    private List<SortedAttribute> sortedAttributes = null;
}

@Entity
public class SortedAttribute {

    @PrimaryKey
    private int idProduct;

    private String reference;

    @Embedded
    private List<Measurement> measurements = null; //****how do i get this into room ? its a LIST of measurements, not a measurement so calling Embedded i think wont work as …

我有一个名为Chacara的类,它有各种属性,包括thumbList,它是一个List <String>

将它保存到ROOM时,我使用类型转换器:

class DbTypeConverter {

    @TypeConverter
    fun listToString(list: List<String>): String = Gson().toJson(list)

    @TypeConverter
    fun stringToList(string: String): List<String> {
        return Gson().fromJson<List<String>>(string, object: TypeToken<List<String>>() {}.type)
    }

}

当我获取整个对象并访问thumbList属性时,它按预期工作:

@Query("SELECT * FROM chacara WHERE id = :id LIMIT 1")
abstract fun getChacaraWithId(id: String): LiveData<Chacara>

但是,当我尝试仅获取thumbList属性时,结果不会转换:

@Query("SELECT thumbUrlList FROM chacara WHERE id = :id")
abstract fun getChacaraThumbList(id: String): LiveData<List<String>>

我还在TypeConverter中添加了一个日志,以确保它没有被调用.

TL; DR:ROOM不调用TypeConverter而不将String转换回List(SELECT'column_name'),但在请求整个对象时工作(SELECT*)

详细日志

error: Cannot figure out how to save this field into database. You can consider adding a type converter for it. private final java.util.Date mTime = null;

我有一个字段为的实体 var mStartTime : Date = Date() // java.util.Date

为什么cant Room持久化Date对象？什么可以是日期最好的转换器？

实体和Pojos必须具有可用的公共构造函数.您可以拥有一个空构造函数或其参数与字段匹配的构造函数(按名称和类型)

我将房间整合到我现有的项目中.在使用@Entity标记注释实现Parcelable的POJO并进行必要的更改时,会收到此错误.我已经有一个空的构造函数.任何帮助,将不胜感激.

@Entity(tableName = "Departments")
public class Department implements Parcelable {

    @PrimaryKey(autoGenerate = true)
    private Integer primaryId;
    private Integer id;
    private String departmentName;
    private String logoUrl;
    @Embedded
    private ArrayList<Template> templateList;

    public Department() {
    }

    protected Department(Parcel in) {
        this.primaryId = (Integer) in.readSerializable();
        this.departmentName = in.readString();
        this.logoUrl = in.readString();
        this.id = (Integer) in.readSerializable();
        this.templateList = in.createTypedArrayList(Template.CREATOR);
    }

    public static final Creator<Department> CREATOR = new Creator<Department>() {
        @Override
        public Department createFromParcel(Parcel in) {
            return new Department(in);
        }

        @Override
        public Department[] newArray(int size) …

App Database的Items表的价格为Long数据类型为Long。Db版本= 1

CREATE TABLE items (_id INTEGER PRIMARY KEY AUTOINCREMENT,item_id 
INTEGER,title TEXT,price LONG, UNIQUE (item_id) ON CONFLICT IGNORE)

尝试迁移到Room时遇到以下问题

java.lang.IllegalStateException: Migration didn't properly handle items(moka.pos.test.data.entity.Item).

Expected : price=Column{name='price', type='INTEGER', affinity='3', notNull=false, primaryKeyPosition=0}
Found : price=Column{name='price', type='LONG', affinity='1', notNull=false, primaryKeyPosition=0}

这是我的实体类

@Entity(tableName = "items")
public class Item {

@PrimaryKey(autoGenerate = true)
@ColumnInfo(name = "_id")
private Integer _ID;

@ColumnInfo(name = "item_id")
private Integer id;

@ColumnInfo(name = "title")
private String title;

@ColumnInfo(name = "price") …