小编Raz*_*zon的帖子

我试图使用LiveData和viewmodel从房间中获取自定义对象数据的列表。使用Livedata的getValue（）方法时，返回null，但获取列表直接显示实际数据。如何在Viewmodel类中使用LiveData获得Period类的列表。

实体类

@Entity
public class Period {

@PrimaryKey
@NonNull
String header;
@TypeConverters(WritterConverter.class)
ArrayList<Writter> writters;

public Period(String header, ArrayList<Writter> writters) {
    this.header = header;
    this.writters = writters;
}

public String getHeader() {
    return header;
}

public ArrayList<Writter> getWritters() {
    return writters;
}


}

@Entity
public class Writter {

String birth;
String death;
String name;
ArrayList<String> novels;

public Writter(){}

public Writter(String birth, String death, String name, ArrayList<String> novels) {
    this.birth = birth;
    this.death = death;
    this.name = name;
    this.novels = novels;
} …