英文:
Android Room Type Converter for Custom Object
问题
错误信息指出无法将自定义对象列表保存到数据库中，建议考虑添加类型转换器。您的数据类定义如下：
@Entity(tableName = "calorie_daily_table")data class CalorieDaily(@PrimaryKeyvar date: String,var breakfast: List<Meal>)data class Meal(var foodItem: String,var foodQuantity: String,var calorie: Int)
要处理这种情况，您可以编写一个类型转换器（TypeConverter）。以下是一个示例类型转换器的代码：
class Converter {var gson = Gson()@TypeConverterfun mealListToString(meals: List<Meal>): String {return gson.toJson(meals)}@TypeConverterfun stringToMealList(data: String): List<Meal> {val listType = object : TypeToken<List<Meal>>() {}.typereturn gson.fromJson(data, listType)}}
请确保在数据库配置中使用此类型转换器，以便Room知道如何将List<Meal>转换为字符串并存储到数据库中。这应该解决您遇到的错误。
英文:
I'm getting an error while using a list of custom object with Room.
error: Cannot figure out how to save this field into database. You can consider adding a type converter for it.
So my data class is like this:
@Entity(tableName = "calorie_daily_table")data class CalorieDaily(@PrimaryKeyvar date: String,var breakfast: List<Meal>)data class Meal(var foodItem: String,var foodQuantity: String,var calorie: Int)
How can i write a TypeConverter to handle this?
So, I've something like this:
class Converter {var gson = Gson()@TypeConverterfun foodItemToString(foodItems: List<FoodItem>): String {return gson.toJson(foodItems)}@TypeConverterfun stringToFoodItem(data: String): List<FoodItem> {val listType = object : TypeToken<List<FoodItem>>() {}.typereturn gson.fromJson(data, listType)}}
But, still getting the same error.
答案1
得分: 1
你需要将注解@Embedded添加到你的第二个数据类Meal中。
英文:
You have to add the annotation @Embedded to your second data class Meal
答案2
得分: 0
尝试在早餐之前添加@TypeConverters。
@TypeConverters(Converter::class)var breakfast: List<Meal>
英文:
Try adding @TypeConverters before breakfast.
@TypeConverters(Converter::class)var breakfast: List<Meal>
答案3
得分: 0
更新的工作代码：
@Entity(tableName = "calorie_daily_table")data class CalorieDaily(@PrimaryKeyvar date: String,@TypeConverters(Converters::class)var breakfast: List<Meal>)data class Meal(var foodItem: String,var foodQuantity: String,var calorie: Int)class Converter {var gson = Gson()@TypeConverterfun fromBreakfast(mealItems: List<Meal>): String {return gson.toJson(mealItems)}@TypeConverterfun toBreakfast(data: String): List<Meal> {val listType = object : TypeToken<List<Meal>>() {}.typereturn gson.fromJson(data, listType)}}
英文:
Updated working code:
@Entity(tableName = "calorie_daily_table")data class CalorieDaily(@PrimaryKeyvar date: String,@TypeConverters(Converters::class)var breakfast: List<Meal>)data class Meal(var foodItem: String,var foodQuantity: String,var calorie: Int)class Converter {var gson = Gson()@TypeConverterfun fromBreakfast(mealItems: List<Meal>): String {return gson.toJson(mealItems)}@TypeConverterfun toBreakfast(data: String): List<Meal> {val listType = object : TypeToken<List<Meal>>() {}.typereturn gson.fromJson(data, listType)}}
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