Question

如果已经存在于realm数据库中，如何更新值; 我尝试构建一个应用程序，以显示着名作者的一些引用，该应用程序将有一些作者，每个作者都会有一些引用，当我第一次运行应用程序时它运行完美但当我再次尝试运行时它会显示值已存在错误这是我的模型类

public class Author extends RealmObject {
@PrimaryKey
private String name;
private RealmList<Quotes>quote;

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Author() {

}

public RealmList<Quotes> getQuote() {
    return quote;
}

public void setQuote(RealmList<Quotes> quote) {
    this.quote = quote;
}

public Author(String name, RealmList<Quotes> quote) {

    this.name = name;
    this.quote = quote;

}

}

public class Categories extends RealmObject {
@PrimaryKey
private String category;

public String getCategory() {
    return category;
}

public void setCategory(String category) {
    this.category = category;
}

public Categories() {

}

public Categories(String category) {

    this.category = category;
}

}

public class Quotes extends RealmObject {
private String Quote;
private Categories category;

public Categories getCategory() {
    return category;
}

public void setCategory(Categories category) {
    this.category = category;
}

public String getQuote() {
    return Quote;
}

public void setQuote(String quote) {
    Quote = quote;
}

public Quotes() {

}

public Quotes(Categories category, String quote) {

    this.category = category;
    Quote = quote;
}

}

这是我的mainActivity，我设置数据库并获取错误：值已存在

public class MainActivity extends AppCompatActivity {
Realm mRealm;
Categories wisdom;
Categories fear;
Categories motivation;
Categories life;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RealmConfiguration configuration=new RealmConfiguration.Builder(this).build();
    Realm.setDefaultConfiguration(configuration);
    mRealm=Realm.getDefaultInstance();

    mRealm.beginTransaction();


    wisdom=mRealm.createObject(Categories.class);
    fear=mRealm.createObject(Categories.class);
    wisdom.setCategory("wisdom");
    fear.setCategory("fear");
    life.setCategory("Life");
    motivation.setCategory("Motivation");

    Author john_green=mRealm.createObject(Author.class);
    john_green.setName("John Green");

    Quotes john_green_1=mRealm.createObject(Quotes.class);
    john_green_1.setQuote("My thoughts are stars I can't fathom into constellations.");
    john_green_1.setCategory(motivation);
    john_green.getQuote().add(john_green_1);

    Quotes john_green_2=mRealm.createObject(Quotes.class);
    john_green_2.setQuote("What is the point of being alive if you don’t at least try to do something remarkable?");
    john_green_2.setCategory(motivation);
    john_green.getQuote().add(john_green_2);

    mRealm.commitTransaction();
}

}

Answer 1

首先尝试找到它，如果找不到它（返回null），则创建对象。

mRealm=Realm.getDefaultInstance();
mRealm.executeTransaction(new Realm.Transaction() {
    @Override
    public void execute(Realm realm) {
        Category wisdom = realm.where(Categories.class).equalTo("category", "wisdom").findFirst();
        if(wisdom == null) {
            wisdom = realm.createObject(Categories.class);
            wisdom.setCategory("wisdom");
        }
        //more code
    }
});

如果值已存在，如何更新领域数据库

1 个答案: