android-room

问题 Suppose there is a Dao class with the following two methods: 1) delete(items: List<Item>): Completable 2) insert(items: List< Item >): Single<List<Long>> How can I chain them into a @transaction method in Dao class starting with ‘delete method’ and then returning ‘insert method’ result? I want to have a method with a signature like this: @Transaction fun deleteAndInsert(): Single<List<Long> > { ... } 回答1: I'm assuming your main goal is to have the return type of deleteAndInsert() as Single .

问题 Suppose there is a Dao class with the following two methods: 1) delete(items: List<Item>): Completable 2) insert(items: List< Item >): Single<List<Long>> How can I chain them into a @transaction method in Dao class starting with ‘delete method’ and then returning ‘insert method’ result? I want to have a method with a signature like this: @Transaction fun deleteAndInsert(): Single<List<Long> > { ... } 回答1: I'm assuming your main goal is to have the return type of deleteAndInsert() as Single .

问题 I have a Component which contains a foreign key coming from Component_category My purpose is that a component list will be filtered by the selected component category. Both classes are as followed: Component @Entity(tableName = "component_table", foreignKeys = { @ForeignKey( entity = Rack.class, parentColumns = "rack_id", childColumns = "component_id", onDelete = ForeignKey.CASCADE, onUpdate = ForeignKey.CASCADE ), @ForeignKey( entity = ComponentCat.class, parentColumns = "component_cat_id",

问题 I have a Component which contains a foreign key coming from Component_category My purpose is that a component list will be filtered by the selected component category. Both classes are as followed: Component @Entity(tableName = "component_table", foreignKeys = { @ForeignKey( entity = Rack.class, parentColumns = "rack_id", childColumns = "component_id", onDelete = ForeignKey.CASCADE, onUpdate = ForeignKey.CASCADE ), @ForeignKey( entity = ComponentCat.class, parentColumns = "component_cat_id",

问题 I have implemented a room database which is distributed from a resource file using SQLiteAssetHelper the first time the app is started. The database contains game status data so if the Player wants to start all over again, I want to copy again the database file from the resource and overwrite the "local/internal" file. So my idea was to delete the interal db-file so that SQLiteAssetHelper will copy the Initial database from the resource again. Thank you! Kev 回答1: Here's a working example:

问题 i am storing user information in a local room database. In activities and fragments I use AndroidViewModel and LiveData to listen to changes made to the database and update the UI. Now I want to analyze all of the past user data to give recommendations for future decisions. My recommendations change on every change to the database made by the user so I need to update my reommendations frequently while doing the same calculations over and over again. I was thinking about starting a service on

问题 i am storing user information in a local room database. In activities and fragments I use AndroidViewModel and LiveData to listen to changes made to the database and update the UI. Now I want to analyze all of the past user data to give recommendations for future decisions. My recommendations change on every change to the database made by the user so I need to update my reommendations frequently while doing the same calculations over and over again. I was thinking about starting a service on

问题 I'm have a method annotated with @Transaction in my DAO class, which is causing the following error: A DAO method can be annotated with only one of the following:Insert,Delete,Query,Update Here's my class: @Dao interface Dao { @Insert(onConflict = REPLACE) fun insertList(chacaras: List<String>) @Query("SELECT * FROM chacara WHERE cityId = :cityId") fun getListOfCity(cityId: String): LiveData<List<String>> @Delete fun deleteList(chacaraList: List<String>) @Transaction fun updateList(list: List

问题 I am making an app and I am using Android Room Persistence Library to handle my database layer. Room Library works like charm and everything is fine with it. But I want the database that room creates to be removed when the user uninstall the app. I tried uninstalling the app and then installed again, but somehow the database was still there and app was able to get the old data from it. I thought maybe because my app data backup is set to auto in the settings and android is backing it up on

问题 NOTE: I cannot use relation as we had performance issue which is not reproduced on direct join query. Until I added target user and from group user and corresponding LEFT JOIN chat_user ON chat_user.chat_user_id = message_item.messages_target_user LEFT JOIN chat_user ON chat_user.chat_user_id = message_item.messages_from_group_user It worked well. But after addition, I can not figure out how to make those prefixes map in the query. class ReadMessageEntity( @Embedded var message: MessageEntity