android-room

问题 I want to update a member variable of an object inside my Repository on a LiveData- Object. The problem is, that if I call the getValue() Method, I keep getting an NullPointerException, although the value does exist inside my Room- Library. My question now is, how do I get the value from the LiveData Object without calling the observe() Method? (I am not able to call the observe method inside my repository, cause that method wants me to enter a LifeCycleOwner- reference, which is not present

问题 I want to update a member variable of an object inside my Repository on a LiveData- Object. The problem is, that if I call the getValue() Method, I keep getting an NullPointerException, although the value does exist inside my Room- Library. My question now is, how do I get the value from the LiveData Object without calling the observe() Method? (I am not able to call the observe method inside my repository, cause that method wants me to enter a LifeCycleOwner- reference, which is not present

问题 How can I implement created_at and updated_at columns using Room Persistence ORM tools in Android, that can update the timestamp automatically when creating or updating a row in a table? 回答1: I've research many sites, but still not found any results can handle middleware or something like callbacks when we Query , Insert , Update , or Delete ,... methods from DAO s. As @selvin said, RoomDatabase.Callback interface only call when database created in first time. So, use that interface is

问题 I am trying to insert user record in Room database using Kotlin and It's working perfectly. And now I want to return newly inserted record id to check if a record is successfully inserted or not in Room database. But when I am applying Long return type in the insert method and run the code that time I get the following error. error: Method returns long but it should return one of the following: void, long[], java.lang.Long[], java.util.List<java.lang.Long> . If you want to return the list of

问题 I am trying to insert user record in Room database using Kotlin and It's working perfectly. And now I want to return newly inserted record id to check if a record is successfully inserted or not in Room database. But when I am applying Long return type in the insert method and run the code that time I get the following error. error: Method returns long but it should return one of the following: void, long[], java.lang.Long[], java.util.List<java.lang.Long> . If you want to return the list of

问题 how can i filter Recycler View using SearchView i try all the video tuturial but all of them get thier item Recycler View from a list but i get my item from db and dont know how should i do this this is my adapter Code public class AthleteAdapter extends RecyclerView.Adapter<AthleteAdapter.AthleteHolder> { private List<Athlete> athletes = new ArrayList<>(); private OnItemClickListener listener; @NonNull @Override public AthleteHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)

问题 DAO.class: @Dao public interface VisitorDAO { @Query("Select * from visitor") Flowable<List<Visitor>> getAll(); @Insert Completable Insert(Visitor visitor); //Using Single or Maybe tells the Database and the mainthread that this operation will be performed on Rxjava. @Update public void Update(Visitor visitor); @Delete public void Delete(Visitor visitor); } Code: @Override public void onComplete() { visitorFlowable = database.visitorDAO().getAll(); t.setText(visitorFlowable.); //is this the

问题 I have a table called games that has a column called platforms , which contains a list of platform abbreviations. This is a list of all the platforms that specific game came out on. Here's an example of one of the cells in platforms : AMI,GG,SNES,CPC,AST,C64,SPEC,MAC,PS2,NES,3DO,ARC,XBGS,PS3N,PC,IPHN,DSI,HALC,PSPN,ANDR, The user can choose any number of platforms they wish to view games for. For example, they may choose to see games for the following platforms: SNES, MAC, PC So I need a way

问题 I have a table called games that has a column called platforms , which contains a list of platform abbreviations. This is a list of all the platforms that specific game came out on. Here's an example of one of the cells in platforms : AMI,GG,SNES,CPC,AST,C64,SPEC,MAC,PS2,NES,3DO,ARC,XBGS,PS3N,PC,IPHN,DSI,HALC,PSPN,ANDR, The user can choose any number of platforms they wish to view games for. For example, they may choose to see games for the following platforms: SNES, MAC, PC So I need a way

问题 I am trying to change my sqlite database with room library. I am little confuse with left join query. I have implemented it with sqlite, but don't know how can I achieve same withh room? Here is my table creation: first table: Notification db.execSQL("CREATE TABLE IF NOT EXISTS $TABLE_NAME ($COLUMN_ID INTEGER PRIMARY KEY, $ICON TEXT, $TITLE INTEGER," + " $DATE INTEGER, $TYPE INTEGER,$URL TEXT, $MESSAGE INTEGER, FOREIGN KEY($TITLE) REFERENCES ${TableNotificationsTrans.getTableName(this)}(id),"