如何通过查询自动获取外部DatabaseField？

Question

我在 Android 应用中使用 ORMLite (v4.48)。我有 table "Contact" 可以包含多个 "Email" (ForeignCollectionField) 和一个 "Personal" (DatabaseField) 对象。当我从数据库中获取联系人对象时，我想自动获取（或延迟加载）具有相同联系人 ID 的个人对象。

它已经自动获取我可以访问的电子邮件对象。但是出于某种原因，即使个人 table.

中有一个条目，个人对象始终是 "null"

这是我的类:

@DatabaseTable(tableName = "Contact", daoClass = ContactDao.class)
public class Contact {

    @DatabaseField(generatedId = true, columnName = PersistentObject.ID) 
    int id;

    @DatabaseField(index = true)
    String contactName;

    @ForeignCollectionField(eager = false)
    ForeignCollection<Email> emails;

    @DatabaseField(foreign = true)
    public Personal personal;

    public ForeignCollection<Email> getEmails() {
        return emails;
    }

    public void setEmails(ForeignCollection<Email> emails) {
        this.emails = emails;
    }

    public Personal getPersonal() {
        return personal;
    }

    public void setPersonal(Personal personal) {
        this.personal = personal;
    }
    ...
}

和

@DatabaseTable(tableName = "Email", daoClass = EmailDao.class)
public class Email {

    @DatabaseField(generatedId = true, columnName = PersistentObject.ID)
    int id;

    @DatabaseField(foreign = true, foreignAutoRefresh = true, columnName = PersistentObject.CONTACT_ID_FIELD_NAME) // contact_id
    Contact contact;

    @DatabaseField
    String emailType;

    @DatabaseField(canBeNull = false)
    String email;

    public Email() {
    }

    public Email(int id, Contact Contact, String emailType, String email) {

        this.id = id;
        this.contact = contact;
        this.emailType = emailType;
        this.email = email;
    }

    public int getId() {

        return id;
    }

    public Contact getContact() {
        return contact;
    }

    public void setContact(Contact contact) {
        this.contact = contact;
    }

    public String getEmailType() {
        return emailType;
    }

    public void setEmailType(String emailType) {
        this.emailType = emailType;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    ...
}

和

@DatabaseTable(tableName = "Personal", daoClass = PersonalDao.class)
public class Personal {

    @DatabaseField(generatedId = true, columnName = PersistentObject.ID)
    int id;

    @DatabaseField(foreign = true, foreignAutoRefresh = true, columnName = PersistentObject.CONTACT_ID_FIELD_NAME)
    Contact contact;

    @DatabaseField
    int age;

    @DatabaseField
    int weight; // in grams

    @DatabaseField
    int height; // in cm

    public Personal() {
    }

    public int getId() {
        return id;
    }

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

    public Contact getContact() {
        return contact;
    }

    public void setContact(Contact contact) {
        this.contact = contact;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getWeight() {
        return weight;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }

}

我是这样从数据库中获取数据的：

QueryBuilder<Contact, Integer> queryBuilder = mContactDao.queryBuilder();
queryBuilder.orderBy("lastViewed", false);
queryBuilder.limit(limit);

PreparedQuery<Contact> preparedQuery = queryBuilder.prepare();
List<Contact> contactList = mContactDao.query(preparedQuery);

到目前为止一切正常。然后进一步深入代码，我可以像这样访问电子邮件对象：

ForeignCollection<Email> emails = contact.getEmails();
Iterator<Email> iter = emails.iterator();
while (iter.hasNext()) {
    Email iAddress = iter.next();
    Log.d(TAG, "EMAIL: " + iAddress.getEmail());
    Log.d(TAG, "EMAIL TYPE: " + iAddress.getEmailType());
}

这也很完美。只有当我想访问 Personal 对象时，我总是得到 NULL。

Personal personal = contact.getPersonal(); // is always NULL

我不明白这是为什么。我是否需要在查询构建器中手动添加 JOIN？我认为一旦我使用 getPersonal() 访问它，它也会延迟加载数据，就像使用 getEmails()?

Answer 1

您没有说明实体实例是如何创建的，但我假设个人是在插入联系人后创建的。如果是这种情况，那么在插入个人后你应该做 contact.setPersonal(personal)，和 contactDao.update(contact) - 这样 personal_id 将存储在联系人行

如何通过查询自动获取外部DatabaseField？

How to get foreign DatabaseField automatically with query?

android

ormlite

android-database