Realm数据库在迁移期间插入行

Question

我有一个小的迁移类，当应用程序启动时，我不想创建带有一些预定义行的SportTypes表。我尝试了migrate方法下的注释解决方案，但没有机会。

public class SportTypes extends RealmObject {
@PrimaryKey
private Integer id;
private String name;
private RealmList<SportTypes> sportTypes;

public String getName() {
return name;
}

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

public Integer getId() {
return id;
}

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

public RealmList<SportTypes> getSportTypes() {
return sportTypes;
}

public void setSportTypes(RealmList<SportTypes> sportTypes) {
this.sportTypes = sportTypes;
}
}

public class RealmMigrations implements RealmMigration {
@Override
public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {

RealmSchema schema = realm.getSchema();
schema.create("SportTypes")
.addField("id", Integer.class, FieldAttribute.PRIMARY_KEY)
.addField("name", String.class);

//        schema.get("SportTypes")
//                .transform(new RealmObjectSchema.Function() {
//                    @Override
//                    public void apply(DynamicRealmObject obj) {
//                        Realm realm = Realm.getDefaultInstance();
//                        realm.beginTransaction();
//                        SportTypes sport = realm.createObject(SportTypes.class);
//                        sport.setId(0);
//                        sport.setName("cycling");
//                        sport.getSportTypes().add(sport);
//                        realm.commitTransaction();
//                        realm.close();
//                    }
//                });
//        schema.get("SportTypes").transform(new RealmObjectSchema.Function() {
//            @Override
//            public void apply(DynamicRealmObject obj) {
//                obj.setInt("id", 0);
//                obj.setInt("id", 1);
//                obj.setInt("id", 2);
//                obj.setInt("id", 3);
//                obj.setInt("id", 4);
//                obj.setString("name", "Running");
//                obj.setString("name", "Cycling");
//                obj.setString("name", "Swimming");
//                obj.setString("name", "IndoorRunning");
//                obj.setString("name", "IndoorCycling");
//            }
//        });
// Deliberately not using old version to run upper lines
if (oldVersion == 0) {
oldVersion++;
}
}
}

我在活动的onCreate方法中调用以下部分。我还手动更改了版本以触发迁移类的迁移事件，但无法获取任何行。

Realm.init(this);
final RealmConfiguration configuration = new RealmConfiguration.Builder().name("sports1761.realm").schemaVersion(1).migration(new RealmMigrations()).build();
Realm.setDefaultConfiguration(configuration);
//        try {
//            Realm.migrateRealm(configuration);
//        } catch (FileNotFoundException e) {
//            e.printStackTrace();
//        }
Realm realm = Realm.getDefaultInstance();
RealmObjectSchema schema = realm.getSchema().get("SportTypes");
final RealmResults<SportTypes> sports = realm.where(SportTypes.class).findAll();
Integer size = sports.size();

Answer 1

我找到了解决方案。您应该首先获得架构并创建DynamicRealmObject，在添加新记录之前删除旧记录，然后只添加新记录。如果你的对象有一个主键，你应该使用字段&createObject方法的主键重载。

public class RealmMigrations implements RealmMigration {
@Override
public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {
if (oldVersion == 0) {
RealmSchema schema = realm.getSchema();
RealmObjectSchema sportTypesSchema = schema.get("SportTypes");
realm.delete("SportTypes");
DynamicRealmObject sportType = realm.createObject("SportTypes", 0);
sportType.setString("name", "Running");
DynamicRealmObject sportType1 = realm.createObject("SportTypes", 1);
sportType.setString("name", "Cycling");
DynamicRealmObject sportType2 = realm.createObject("SportTypes", 2);
sportType.setString("name", "Swimming");
DynamicRealmObject sportType3 = realm.createObject("SportTypes", 3);
sportType.setString("name", "Indoor Running");
DynamicRealmObject sportType4 = realm.createObject("SportTypes", 4);
sportType.setString("name", "Indoor Cycling");
RealmList<DynamicRealmObject> listItems = sportType.getList("sportTypes");
List<DynamicRealmObject> values = Arrays.asList(sportType, sportType1, sportType2, sportType3, sportType4);
listItems.addAll(values);
oldVersion++;
}
}
}