Android本地数据存储之Room详细使用

//room
def room_version="2.4.2"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
//implementation "androidx.room:room-rxjava2:$room_version"
//implementation "androidx.room:room-rxjava3:$room_version"
//implementation "androidx.room:room-guava:$room_version"
//testImplementation "androidx.room:room-testing:$room_version"
//implementation "androidx.room:room-paging:2.5.0-alpha01"

@Entity
public class Person {

    // 主键，自增长
    @PrimaryKey(autoGenerate = true)
    private int id;
    private String name;
    private String sex;
    private int age;
}

@Dao
public interface PersonDao {
    // 插入
    @Insert
    void insertPersons(Person... persons);
    // 修改
    @Update
    void updatePersons(Person... persons);
    // 删除所有
    @Query("delete from Person")
    void deleteAllPersons();
    // 删除指定实体
    @Delete
    void deletePersons(Person... persons);
    // 根据id删除
    @Query("delete from Person where id in (:ids)")
    void deleteByIds(int ...ids);
    // 根据id查询
    @Query("select * from Person where id in (:ids)")
    List<Person> selectByIds(int ...ids);
    // 查询所有
    @Query("select * from Person order by id desc")
    List<Person> selectAllPersons();
}

@Database(entities = {Person.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    public abstract PersonDao personDao();

    private volatile static AppDatabase instance;

    public static AppDatabase getInstance(Context context){
        if (instance == null) {
            synchronized (DBHelper.class) {
                if (instance == null) {
                    instance = Room.databaseBuilder(context, AppDatabase.class, "person.db").build();
                }
            }
        }
        return instance;
    }
}

ExecutorService pool = Executors.newCachedThreadPool();

// 插入数据
public void insertRoom(View view){
    AppDatabase db = AppDatabase.getInstance(getApplicationContext());

    pool.execute(() -> {
        PersonDao dao = db.personDao();
        Person p1 = new Person("用户1", "男", 18);
        Person p2 = new Person("用户2", "男", 28);
        Person p3 = new Person("用户3", "男", 38);
        dao.insertPersons(p1, p2, p3);
    });

}

// 查询数据
public void queryRoom(View view){

    AppDatabase db = AppDatabase.getInstance(getApplicationContext());

    pool.execute(() -> {

        PersonDao dao = db.personDao();
        List<Person> list = dao.selectAllPersons();
        list.forEach(p-> Log.d("test", p.toString()));

    });
}

// 根据id查询
public void queryRoomById(View view){

    AppDatabase db = AppDatabase.getInstance(getApplicationContext());

    pool.execute(() -> {

        PersonDao dao = db.personDao();
        List<Person> list = dao.selectByIds(3,4);
        list.forEach(p-> Log.d("test", p.toString()));

    });
}

// 删除
public void deleteRoom(View view){

    AppDatabase db = AppDatabase.getInstance(getApplicationContext());

    pool.execute(() -> {

        PersonDao dao = db.personDao();
        dao.deleteByIds(1,2);
    });
}

public class DateConverter {

    @TypeConverter
    public static Date toDate(Long dateLong){
        return dateLong == null ? null : new Date(dateLong);
    }

    @TypeConverter
    public static Long fromDate(Date date){
        return date == null ? null : date.getTime();
    }
}

@Entity
@TypeConverters({DateConverter.class})
public class BsGoods {
    private static final long serialVersionUID = 1122172437556010779L;
    // 主键
    @PrimaryKey
    private Long id;
    private Date createdDate;
    private Date updatedDate;

    ...
}

public class BigDecimalConverter {

    @TypeConverter
    public static String toStr(BigDecimal decimal) {
        return decimal == null ? null : decimal.toString();
    }

    @TypeConverter
    public static BigDecimal toDecimal(String str) {
        return str == null ? null : new BigDecimal(str);
    }
}

public void selectAll(Consumer<List<BsGoods>> fun) {
    BsGoodsDao dao = bsGoodsDao();

    Observable.just("select")
            .map(s -> dao.selectAll())
            .subscribeOn(Schedulers.io())// 给上面的操作分配异步线程
            .observeOn(AndroidSchedulers.mainThread())// 给终点分配安卓主线程
            .subscribe(new Observer<List<BsGoods>>() {
                @Override
                public void onSubscribe(@NonNull Disposable d) {

                }

                @Override
                public void onNext(@NonNull List<BsGoods> bsGoods) {
                    fun.accept(bsGoods);
                }

                @Override
                public void onError(@NonNull Throwable e) {

                }

                @Override
                public void onComplete() {

                }
            });
}