Room IllegalArgumentException：int 无法转换为元素

我在尝试编译项目时遇到此错误：

错误：任务“：app：compileDebugJavaWithJavac”执行失败。 java.lang.IllegalArgumentException：int无法转换为元素

还有这个警告：

警告：注释处理器“android.arch.persistence.room.RoomProcessor”支持的源版本“RELEASE_7”小于-source“1.8”

这些是我的数据库相关类：

@Entity(tableName = "users")
public class SerializedUser {

    @PrimaryKey(autoGenerate = true)
    private int id;

    @ColumnInfo(name = "first_name")
    private String firstName;

    @ColumnInfo(name = "last_name")
    private String lastName;

    @ColumnInfo(name = "username")
    private String username;

    public SerializedUser(int id, String firstName, String lastName, String username) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.username = username;
    }

    public int getId() {
        return id;
    }

    public String getFirstName() {
        return firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public String getUsername() {
        return username;
    }
}

@android.arch.persistence.room.Database(entities = {SerializedUser.class}, version = 4)
public abstract class Database extends RoomDatabase {
    public abstract UserDao userDao();

    private static final String DATABASE_NAME = "weather";

    // For Singleton instantiation
    private static final Object LOCK = new Object();
    private static volatile Database i;

    public static Database init(Context context) {
        if (i == null) {
            synchronized (LOCK) {
                if (i == null) {
                    i = Room.databaseBuilder(context.getApplicationContext(),
                            Database.class, Database.DATABASE_NAME)
                            .fallbackToDestructiveMigration().build();
                }
            }
        }
        return i;
    }

    public static boolean isInited(){
        return i != null;
    }

    public static Database getInstance(){
        if(i == null)
            throw new NullPointerException("Database.getInstance called when Database not initialized");
        return i;
    }
}

@Dao
public abstract class UserDao {

    Converters converters;

    public void inject(Converters converters) {
        this.converters = converters;
    }

    @Insert(onConflict = REPLACE)
    public abstract void saveNow(SerializedUser user);

    @Delete
    public abstract void deleteNow(int id);

    @Query("DELETE FROM users")
    public abstract void deleteAllNow();

    @Query("SELECT * FROM users")
    public abstract List<SerializedUser> getAllNow();

    @Query("SELECT * FROM users ORDER BY last_name ASC")
    public abstract LivePagedListProvider<Integer, SerializedUser> usersByLastName();
}

那么当它尝试实现数据库类时会发生错误吗？ SerializedUser上的那个id不是问题，我已经注释掉了，问题还是一样。尝试清理并重建项目并重新启动Android Studio（无效并重新启动）。

remove

@Delete
public abstract void deleteNow(int id);

从你的道它会起作用