java - 如何在 Android Realm 中保存对象列表？

Question

我想保存一个具有列表的对象，问题是当我添加列表时它显示错误

这是对象:

public class SaveRealm extends RealmObject {

    private String id;
    private RealmList<AnswersBean> answers;

    public SaveRealm(){}
    public SaveRealm(String id, RealmList<AnswersBean> answers) {
        this.id = id;
        this.answers = answers;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }


    public RealmList<AnswersBean> getAnswers() {
        return answers;
    }

    public void setAnswers(RealmList<AnswersBean> answers) {
        this.answers = answers;
    }
}

这是 AnswersBean:

    public class AnswersBean extends RealmObject {
    private String text;
    private boolean belongsToCurrentUser;

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    public boolean isBelongsToCurrentUser() {
        return belongsToCurrentUser;
    }

    public void setBelongsToCurrentUser(boolean belongsToCurrentUser) {
        this.belongsToCurrentUser = belongsToCurrentUser;
    }
    public AnswersBean(){}
    public AnswersBean(String text, boolean belongsToCurrentUser) {
        this.text = text;
        this.belongsToCurrentUser = belongsToCurrentUser;
    }

}

在我保存 Realm 的 Activity 中，我执行以下操作:

final AnswersBean receptor = new AnswersBean("test", false);
RealmList<AnswersBean> answersList = new RealmList<>();
answersList.add(receptor);
 SaveRealm saveRealm = myRealm.createObject(SaveRealm.class);
 saveRealm.setId("s");
 saveRealm.setAnswers(answersList);
 myRealm.commitTransaction();

但我收到以下错误

java.lang.NullPointerException: Attempt to invoke interface method 'long io.realm.internal.Row.getIndex()' on a null object reference

我在saveRealm.setAnswers(answersList)行上收到此错误

如何保存列表？

Answer 1

在您的 SaveRealm 类中，answers 字段是一个列表。当您使用 myRealm.createObject 创建对象时(我只能假设是 ChatRealm.class 的拼写错误)，该成员就会被创建。您无法将该成员重新分配到另一个列表，而是修改现有列表。

例如，您的 SaveRealm.setAnwers 方法可能如下所示:-

public void setAnswers(RealmList<AnswersBean> answers) {
    this.answers.clear();
    this.answers.addAll(answers);
}