Realm更新字段

// Initialize Realm. Should only be done once when the application starts.
Realm.init(this);
// Example migration adding a new class
RealmMigration migration = new RealmMigration() {
  @Override
  public void migrate(DynamicRealm realm, long oldVersion, long newVersion) {

     // DynamicRealm exposes an editable schema
     RealmSchema schema = realm.getSchema();

     // Migrate to version 1: Add a new class.
     // Example:
     // public Person extends RealmObject {
     //     private String name;
     //     private int age;
     //     // getters and setters left out for brevity
     // }
     if (oldVersion == 0) {
        schema.create("Person")
            .addField("name", String.class)
            .addField("age", int.class);
        oldVersion++;
     }

     // Migrate to version 2: Add a primary key + object references
     // Example:
     // public Person extends RealmObject {
     //     private String name;
     //     @PrimaryKey
     //     private int age;
     //     private Dog favoriteDog;
     //     private RealmList<Dog> dogs;
     //     // getters and setters left out for brevity
     // }
     if (oldVersion == 1) {
        schema.get("Person")
            .addField("id", long.class, FieldAttribute.PRIMARY_KEY)
            .addRealmObjectField("favoriteDog", schema.get("Dog"))
            .addRealmListField("dogs", schema.get("Dog"));
        oldVersion++;
     }
  }
};

RealmConfiguration realmConfiguration = new RealmConfiguration.Builder()
                  .schemaVersion(2)
                  .migration(migration)
                  .build();
Realm.setDefaultConfiguration(realmConfiguration);