Android ROOM - 如何在 RecyclerView 中显示来自 3 个相关实体的数据？
Android ROOM- How can I display data from 3 related entities in a RecyclerView?
基本上，我有 3 个相关实体需要从中获取数据：练习、exercise_workout_junction 和 exercise_workout_goals。
我需要在 RecyclerView 中显示以下内容：
1. exercise_Name (from exercises entity)
2. number_Of_Sets (from workout_goals entity)
3. min_Reps (from workout_goals entity)
4. max_reps (from workout_goals entity)
（其中 workout_id 是 1、2、3 或 4，具体取决于所选的锻炼，显示的锻炼由 workout_id 决定。）
实现这个的最佳方法是什么？
练习实体
@Entity(tableName = "exercises_table")
public class Exercises {
@PrimaryKey(autoGenerate = true)
int exercises_id;
private String exercise_name;
@ForeignKey(entity = ExerciseType.class, parentColumns = "exercise_type_id", childColumns = "exercise_type_id")
private int exercise_type_id;
@ForeignKey(entity = ExerciseEquipment.class, parentColumns = "exercise_equipment_id", childColumns = "exercise_equipment_id")
private int exercise_equipment_id;
public Exercises(String exercise_name, int exercise_type_id, int exercise_equipment_id ) {
this.exercise_name = exercise_name;
this.exercise_type_id = exercise_type_id;
this.exercise_equipment_id = exercise_equipment_id;
}
public int getExercise_equipment_id() {
return exercise_equipment_id;
}
public void setExercises_id(int exercise_equipment_id) {
this.exercises_id = exercises_id;
}
public int getExercises_id() {
return exercises_id;
}
public String getExercise_name() {
return exercise_name;
}
public int getExercise_type_id() {
return exercise_type_id;
}
}
运动目标实体
@Entity(tableName = "exercise_workout_goals_table")
public class Exercise_Workout_Goals {
@PrimaryKey(autoGenerate = true)
private int exercise_workout_goal_id;
@ForeignKey(entity = Junction.class, parentColumns = "exercise_workout_id", childColumns = "junction_id")
private int junction_id;
private int set_number;
private int min_reps;
private int max_reps;
public Exercise_Workout_Goals(int junction_id, int set_number, int min_reps, int max_reps ) {
this.junction_id = junction_id;
this.set_number = set_number;
this.min_reps = min_reps;
this.max_reps = max_reps;
}
public int getExercise_workout_goal_id() {
return exercise_workout_goal_id;
}
public void setExercise_workout_goal_id(int exercise_workout_goal_id) {
this.exercise_workout_goal_id = exercise_workout_goal_id;
}
public int getJunction_id() {
return junction_id;
}
public int getSet_number() {
return set_number;
}
public int getMin_reps() {
return min_reps;
}
public int getMax_reps() {
return max_reps;
}
}
连接实体
@Entity(tableName = "exercise_workout_junction_table")
public class Junction {
@PrimaryKey(autoGenerate = true)
private int exercise_workout_id;
@ForeignKey(entity = Exercises.class, parentColumns = "exercises_id", childColumns = "exercise_id")
int exercise_id;
@ForeignKey(entity = Workouts.class, parentColumns = "workout_id", childColumns = "workout_id")
private int workout_id;
public Junction(int exercise_id, int workout_id) {
this.exercise_id = exercise_id;
this.workout_id = workout_id;
}
public void setExercise_workout_id(int exercise_workout_id) {
this.exercise_workout_id = exercise_workout_id;
}
public int getExercise_workout_id() {
return exercise_workout_id;
}
public int getExercise_id() {
return exercise_id;
}
public int getWorkout_id() {
return workout_id;
}
}
数据库
@Database(entities = {Junction.class, Exercise_Workout_Goals.class, ExerciseEquipment.class,
Exercises.class, ExerciseType.class, Workouts.class, WorkoutType.class}, version = 4, exportSchema = false)
public abstract class ExerciseDatabase extends RoomDatabase {
private static ExerciseDatabase instance;
public abstract JunctionDao junctionDao();
public abstract ExerciseEquipmentDao exerciseEquipmentDao();
public abstract WorkoutTypeDao workoutTypeDao();
public abstract ExercisesDao exercisesDao();
public abstract WorkoutsDao workoutsDao();
public abstract ExerciseWorkoutGoalsDao exerciseWorkoutGoalsDao();
public abstract ExerciseTypeDao exerciseTypeDao();
//create instance of database
//synchronised means only one thread at a time can access this method so you don't accidentally create 2 instances of this database
public static synchronized ExerciseDatabase getInstance(Context context){
//we only want to instantiate this database if we don't already have an instance
if(instance == null){
//if there is no existing database we want to create one
instance = Room.databaseBuilder(context.getApplicationContext(),
ExerciseDatabase.class, "exercise_database")
//this tells room how to migrate to new schema when database version updated to avoid app crashing
.fallbackToDestructiveMigration()
//this adds the pre-populated database values
.addCallback(roomCallback)
.build();
}
return instance;
}
private static RoomDatabase.Callback roomCallback = new RoomDatabase.Callback(){
@Override
public void onCreate(@NonNull SupportSQLiteDatabase db) {
super.onCreate(db);
new PopulateDbAsyncTask(instance).execute();
}
};
private static class PopulateDbAsyncTask extends AsyncTask<Void,Void,Void> {
private JunctionDao junctionDao;
private ExerciseEquipmentDao exerciseEquipmentDao;
private ExerciseTypeDao exerciseTypeDao;
private WorkoutTypeDao workoutTypeDao;
private ExercisesDao exercisesDao;
private WorkoutsDao workoutsDao;
private ExerciseWorkoutGoalsDao exerciseWorkoutGoalsDao;
private PopulateDbAsyncTask(ExerciseDatabase db){
junctionDao = db.junctionDao();
exerciseEquipmentDao = db.exerciseEquipmentDao();
exerciseTypeDao = db.exerciseTypeDao();
workoutTypeDao = db.workoutTypeDao();
exercisesDao = db.exercisesDao();
workoutsDao = db.workoutsDao();
exerciseWorkoutGoalsDao = db.exerciseWorkoutGoalsDao();
}
@Override
protected Void doInBackground(Void... voids) {
// auto inc id
junctionDao.insert(new Junction(1,1));
junctionDao.insert(new Junction(2,1));
junctionDao.insert(new Junction(3,1));
junctionDao.insert(new Junction(4,1));
junctionDao.insert(new Junction(5,1));
junctionDao.insert(new Junction(6,1));
junctionDao.insert(new Junction(7,1));
junctionDao.insert(new Junction(8,1));
junctionDao.insert(new Junction(11,2));
junctionDao.insert(new Junction(9,2));
junctionDao.insert(new Junction(1,2));
junctionDao.insert(new Junction(2,2));
junctionDao.insert(new Junction(12,2));
junctionDao.insert(new Junction(13,2));
junctionDao.insert(new Junction(15,2));
junctionDao.insert(new Junction(16,2));
junctionDao.insert(new Junction(9,3));
junctionDao.insert(new Junction(2,3));
junctionDao.insert(new Junction(1,3));
junctionDao.insert(new Junction(5,3));
junctionDao.insert(new Junction(10,3));
junctionDao.insert(new Junction(6,3));
junctionDao.insert(new Junction(7,3));
junctionDao.insert(new Junction(8,3));
junctionDao.insert(new Junction(2,4));
junctionDao.insert(new Junction(1,4));
junctionDao.insert(new Junction(11,4));
junctionDao.insert(new Junction(3,4));
junctionDao.insert(new Junction(12,4));
junctionDao.insert(new Junction(13,4));
junctionDao.insert(new Junction(14,4));
junctionDao.insert(new Junction(15,4));
junctionDao.insert(new Junction(16,4));
// Auto inc id
exerciseEquipmentDao.insert(new ExerciseEquipment("A Person / Something Heavy"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Pull Up Bar"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Chair"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Bands"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Body-Weight"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Something heavy you can wedge your legs under/ A training partner\n"));
exerciseEquipmentDao.insert(new ExerciseEquipment("A form of weight\n"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Backpack / Other form of weight\n"));
exerciseTypeDao.insert(new ExerciseType("Shoulders")); // auto inc ID
exerciseTypeDao.insert(new ExerciseType("Triceps"));
exerciseTypeDao.insert(new ExerciseType("Biceps"));
exerciseTypeDao.insert(new ExerciseType("Chest"));
exerciseTypeDao.insert(new ExerciseType("Back"));
exerciseTypeDao.insert(new ExerciseType("Legs"));
//auto inc id (pk)
workoutTypeDao.insert(new WorkoutType(" Full-Body"));
//auto inc primary key
exercisesDao.insert(new Exercises("Squat",6,1));
exercisesDao.insert(new Exercises("Pike Push-up",1,6));
exercisesDao.insert(new Exercises("Weighted Chin-up",5,5));
exercisesDao.insert(new Exercises("Nordic Hamstring Curls",6,7));
exercisesDao.insert(new Exercises("Dips",2,8));
exercisesDao.insert(new Exercises("Lateral Banded Side Raises",1,4));
exercisesDao.insert(new Exercises("Face Pulls with bands",1,4));
exercisesDao.insert(new Exercises("Band Bicep Curls",3,4));
exercisesDao.insert(new Exercises("Weighted Pull-ups",5,5));
exercisesDao.insert(new Exercises("Bulgarian Split Squats",6,9));
exercisesDao.insert(new Exercises("Push-ups",4,6));
exercisesDao.insert(new Exercises("Diamond Push-ups",2,6));
exercisesDao.insert(new Exercises("Seated Rows with Bands",5,4));
exercisesDao.insert(new Exercises("Resistance Band Chest Flyes",4,4));
exercisesDao.insert(new Exercises("Band Tricep Extensions",2,4));
exercisesDao.insert(new Exercises("Band Shrugs",5,4));
workoutsDao.insert(new Workouts("A",1));
workoutsDao.insert(new Workouts("B",1));
workoutsDao.insert(new Workouts("C",1));
workoutsDao.insert(new Workouts("D",1));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(1,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(2,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(3,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(4,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(5,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(6,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(7,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(8,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(9,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(10,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(11,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(12,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(13,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(14,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(15,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(16,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(17,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(18,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(19,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(20,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(21,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(22,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(23,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(24,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(25,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(26,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(27,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(28,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(29,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(30,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(31,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(32,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(33,3,4,50));
return null;
}
}
}
所以你想执行一个连接操作，然后将数据填充到 recyclerview。 SQL 查询是
SELECT exercises_table.exercise_Name, exercise_workout_goals_table.set_number, exercise_workout_goals_table.min_reps, exercise_workout_goals_table.max_reps FROM exercises_table LEFT JOIN exercise_workout_junction_table ON exercises_table.exercises_id = exercise_workout_junction_table.exercise_workout_id LEFT JOIN exercise_workout_goals_table ON exercise_workout_junction_table.workout_id = exercise_workout_goals_table.exercise_workout_goal_id;
首先，您创建一个新的 class（比如 ExerciseAndGoal），其中包含连接操作的结果字段。然后在任何 DAO 中，你创建一个 return 类型的 ExerciseAndGoal 列表的新函数。对该 SQL 查询使用注解 @Query("")。
查看教程
https://medium.com/@gokulbalakrishnan/join-queries-room-persistence-library-f0527e7b0da1
现在您可以在后台线程中访问 DAO。假设你使用AsyncTask，你在doInBackground()中这样写。
见
在 onPostExecute() 中，您会将列表填充到 recycerview。假设您遵循教程并实现了适配器 class。现在您在适配器 class 中有了一个列表。更新列表并调用 notifyDataSetChanged()。
见
https://developer.android.com/guide/topics/ui/layout/recyclerview
基本上，我有 3 个相关实体需要从中获取数据：练习、exercise_workout_junction 和 exercise_workout_goals。
我需要在 RecyclerView 中显示以下内容：
1. exercise_Name (from exercises entity)
2. number_Of_Sets (from workout_goals entity)
3. min_Reps (from workout_goals entity)
4. max_reps (from workout_goals entity)
（其中 workout_id 是 1、2、3 或 4，具体取决于所选的锻炼，显示的锻炼由 workout_id 决定。）
实现这个的最佳方法是什么？
练习实体
@Entity(tableName = "exercises_table")
public class Exercises {
@PrimaryKey(autoGenerate = true)
int exercises_id;
private String exercise_name;
@ForeignKey(entity = ExerciseType.class, parentColumns = "exercise_type_id", childColumns = "exercise_type_id")
private int exercise_type_id;
@ForeignKey(entity = ExerciseEquipment.class, parentColumns = "exercise_equipment_id", childColumns = "exercise_equipment_id")
private int exercise_equipment_id;
public Exercises(String exercise_name, int exercise_type_id, int exercise_equipment_id ) {
this.exercise_name = exercise_name;
this.exercise_type_id = exercise_type_id;
this.exercise_equipment_id = exercise_equipment_id;
}
public int getExercise_equipment_id() {
return exercise_equipment_id;
}
public void setExercises_id(int exercise_equipment_id) {
this.exercises_id = exercises_id;
}
public int getExercises_id() {
return exercises_id;
}
public String getExercise_name() {
return exercise_name;
}
public int getExercise_type_id() {
return exercise_type_id;
}
}
运动目标实体
@Entity(tableName = "exercise_workout_goals_table")
public class Exercise_Workout_Goals {
@PrimaryKey(autoGenerate = true)
private int exercise_workout_goal_id;
@ForeignKey(entity = Junction.class, parentColumns = "exercise_workout_id", childColumns = "junction_id")
private int junction_id;
private int set_number;
private int min_reps;
private int max_reps;
public Exercise_Workout_Goals(int junction_id, int set_number, int min_reps, int max_reps ) {
this.junction_id = junction_id;
this.set_number = set_number;
this.min_reps = min_reps;
this.max_reps = max_reps;
}
public int getExercise_workout_goal_id() {
return exercise_workout_goal_id;
}
public void setExercise_workout_goal_id(int exercise_workout_goal_id) {
this.exercise_workout_goal_id = exercise_workout_goal_id;
}
public int getJunction_id() {
return junction_id;
}
public int getSet_number() {
return set_number;
}
public int getMin_reps() {
return min_reps;
}
public int getMax_reps() {
return max_reps;
}
}
连接实体
@Entity(tableName = "exercise_workout_junction_table")
public class Junction {
@PrimaryKey(autoGenerate = true)
private int exercise_workout_id;
@ForeignKey(entity = Exercises.class, parentColumns = "exercises_id", childColumns = "exercise_id")
int exercise_id;
@ForeignKey(entity = Workouts.class, parentColumns = "workout_id", childColumns = "workout_id")
private int workout_id;
public Junction(int exercise_id, int workout_id) {
this.exercise_id = exercise_id;
this.workout_id = workout_id;
}
public void setExercise_workout_id(int exercise_workout_id) {
this.exercise_workout_id = exercise_workout_id;
}
public int getExercise_workout_id() {
return exercise_workout_id;
}
public int getExercise_id() {
return exercise_id;
}
public int getWorkout_id() {
return workout_id;
}
}
数据库
@Database(entities = {Junction.class, Exercise_Workout_Goals.class, ExerciseEquipment.class,
Exercises.class, ExerciseType.class, Workouts.class, WorkoutType.class}, version = 4, exportSchema = false)
public abstract class ExerciseDatabase extends RoomDatabase {
private static ExerciseDatabase instance;
public abstract JunctionDao junctionDao();
public abstract ExerciseEquipmentDao exerciseEquipmentDao();
public abstract WorkoutTypeDao workoutTypeDao();
public abstract ExercisesDao exercisesDao();
public abstract WorkoutsDao workoutsDao();
public abstract ExerciseWorkoutGoalsDao exerciseWorkoutGoalsDao();
public abstract ExerciseTypeDao exerciseTypeDao();
//create instance of database
//synchronised means only one thread at a time can access this method so you don't accidentally create 2 instances of this database
public static synchronized ExerciseDatabase getInstance(Context context){
//we only want to instantiate this database if we don't already have an instance
if(instance == null){
//if there is no existing database we want to create one
instance = Room.databaseBuilder(context.getApplicationContext(),
ExerciseDatabase.class, "exercise_database")
//this tells room how to migrate to new schema when database version updated to avoid app crashing
.fallbackToDestructiveMigration()
//this adds the pre-populated database values
.addCallback(roomCallback)
.build();
}
return instance;
}
private static RoomDatabase.Callback roomCallback = new RoomDatabase.Callback(){
@Override
public void onCreate(@NonNull SupportSQLiteDatabase db) {
super.onCreate(db);
new PopulateDbAsyncTask(instance).execute();
}
};
private static class PopulateDbAsyncTask extends AsyncTask<Void,Void,Void> {
private JunctionDao junctionDao;
private ExerciseEquipmentDao exerciseEquipmentDao;
private ExerciseTypeDao exerciseTypeDao;
private WorkoutTypeDao workoutTypeDao;
private ExercisesDao exercisesDao;
private WorkoutsDao workoutsDao;
private ExerciseWorkoutGoalsDao exerciseWorkoutGoalsDao;
private PopulateDbAsyncTask(ExerciseDatabase db){
junctionDao = db.junctionDao();
exerciseEquipmentDao = db.exerciseEquipmentDao();
exerciseTypeDao = db.exerciseTypeDao();
workoutTypeDao = db.workoutTypeDao();
exercisesDao = db.exercisesDao();
workoutsDao = db.workoutsDao();
exerciseWorkoutGoalsDao = db.exerciseWorkoutGoalsDao();
}
@Override
protected Void doInBackground(Void... voids) {
// auto inc id
junctionDao.insert(new Junction(1,1));
junctionDao.insert(new Junction(2,1));
junctionDao.insert(new Junction(3,1));
junctionDao.insert(new Junction(4,1));
junctionDao.insert(new Junction(5,1));
junctionDao.insert(new Junction(6,1));
junctionDao.insert(new Junction(7,1));
junctionDao.insert(new Junction(8,1));
junctionDao.insert(new Junction(11,2));
junctionDao.insert(new Junction(9,2));
junctionDao.insert(new Junction(1,2));
junctionDao.insert(new Junction(2,2));
junctionDao.insert(new Junction(12,2));
junctionDao.insert(new Junction(13,2));
junctionDao.insert(new Junction(15,2));
junctionDao.insert(new Junction(16,2));
junctionDao.insert(new Junction(9,3));
junctionDao.insert(new Junction(2,3));
junctionDao.insert(new Junction(1,3));
junctionDao.insert(new Junction(5,3));
junctionDao.insert(new Junction(10,3));
junctionDao.insert(new Junction(6,3));
junctionDao.insert(new Junction(7,3));
junctionDao.insert(new Junction(8,3));
junctionDao.insert(new Junction(2,4));
junctionDao.insert(new Junction(1,4));
junctionDao.insert(new Junction(11,4));
junctionDao.insert(new Junction(3,4));
junctionDao.insert(new Junction(12,4));
junctionDao.insert(new Junction(13,4));
junctionDao.insert(new Junction(14,4));
junctionDao.insert(new Junction(15,4));
junctionDao.insert(new Junction(16,4));
// Auto inc id
exerciseEquipmentDao.insert(new ExerciseEquipment("A Person / Something Heavy"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Pull Up Bar"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Chair"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Bands"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Body-Weight"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Something heavy you can wedge your legs under/ A training partner\n"));
exerciseEquipmentDao.insert(new ExerciseEquipment("A form of weight\n"));
exerciseEquipmentDao.insert(new ExerciseEquipment("Backpack / Other form of weight\n"));
exerciseTypeDao.insert(new ExerciseType("Shoulders")); // auto inc ID
exerciseTypeDao.insert(new ExerciseType("Triceps"));
exerciseTypeDao.insert(new ExerciseType("Biceps"));
exerciseTypeDao.insert(new ExerciseType("Chest"));
exerciseTypeDao.insert(new ExerciseType("Back"));
exerciseTypeDao.insert(new ExerciseType("Legs"));
//auto inc id (pk)
workoutTypeDao.insert(new WorkoutType(" Full-Body"));
//auto inc primary key
exercisesDao.insert(new Exercises("Squat",6,1));
exercisesDao.insert(new Exercises("Pike Push-up",1,6));
exercisesDao.insert(new Exercises("Weighted Chin-up",5,5));
exercisesDao.insert(new Exercises("Nordic Hamstring Curls",6,7));
exercisesDao.insert(new Exercises("Dips",2,8));
exercisesDao.insert(new Exercises("Lateral Banded Side Raises",1,4));
exercisesDao.insert(new Exercises("Face Pulls with bands",1,4));
exercisesDao.insert(new Exercises("Band Bicep Curls",3,4));
exercisesDao.insert(new Exercises("Weighted Pull-ups",5,5));
exercisesDao.insert(new Exercises("Bulgarian Split Squats",6,9));
exercisesDao.insert(new Exercises("Push-ups",4,6));
exercisesDao.insert(new Exercises("Diamond Push-ups",2,6));
exercisesDao.insert(new Exercises("Seated Rows with Bands",5,4));
exercisesDao.insert(new Exercises("Resistance Band Chest Flyes",4,4));
exercisesDao.insert(new Exercises("Band Tricep Extensions",2,4));
exercisesDao.insert(new Exercises("Band Shrugs",5,4));
workoutsDao.insert(new Workouts("A",1));
workoutsDao.insert(new Workouts("B",1));
workoutsDao.insert(new Workouts("C",1));
workoutsDao.insert(new Workouts("D",1));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(1,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(2,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(3,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(4,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(5,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(6,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(7,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(8,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(9,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(10,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(11,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(12,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(13,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(14,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(15,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(16,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(17,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(18,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(19,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(20,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(21,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(22,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(23,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(24,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(25,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(26,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(27,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(28,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(29,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(30,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(31,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(32,3,4,50));
exerciseWorkoutGoalsDao.insert(new Exercise_Workout_Goals(33,3,4,50));
return null;
}
}
}
所以你想执行一个连接操作，然后将数据填充到 recyclerview。 SQL 查询是
SELECT exercises_table.exercise_Name, exercise_workout_goals_table.set_number, exercise_workout_goals_table.min_reps, exercise_workout_goals_table.max_reps FROM exercises_table LEFT JOIN exercise_workout_junction_table ON exercises_table.exercises_id = exercise_workout_junction_table.exercise_workout_id LEFT JOIN exercise_workout_goals_table ON exercise_workout_junction_table.workout_id = exercise_workout_goals_table.exercise_workout_goal_id;
首先，您创建一个新的 class（比如 ExerciseAndGoal），其中包含连接操作的结果字段。然后在任何 DAO 中，你创建一个 return 类型的 ExerciseAndGoal 列表的新函数。对该 SQL 查询使用注解 @Query("")。
查看教程 https://medium.com/@gokulbalakrishnan/join-queries-room-persistence-library-f0527e7b0da1
现在您可以在后台线程中访问 DAO。假设你使用AsyncTask，你在doInBackground()中这样写。
见
在 onPostExecute() 中，您会将列表填充到 recycerview。假设您遵循教程并实现了适配器 class。现在您在适配器 class 中有了一个列表。更新列表并调用 notifyDataSetChanged()。
见 https://developer.android.com/guide/topics/ui/layout/recyclerview