PrimaryKeyFactory.java

import android.util.Log;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicLong;
import io.realm.Realm;
import io.realm.RealmConfiguration;
import io.realm.RealmObject;
import io.realm.RealmObjectSchema;
import io.realm.RealmSchema;

import static java.lang.String.format;

/**
 * Created by zacheusz on 16/03/16.
 * https://github.com/realm/realm-java/issues/469#issuecomment-196798253
 */
public class PrimaryKeyFactory {

    /** primary key field name */
    private static final String PRIMARY_KEY_FIELD = "id";

    /**
     * Singleton instance.
     */
    private final static PrimaryKeyFactory instance = new PrimaryKeyFactory();

    /**
     * Maximum primary key values.
     */
    private Map<Class<? extends RealmObject>, AtomicLong> keys;

    /**
     * get the singleton instance
     * @return singleton instance
     */
    public static PrimaryKeyFactory getInstance() {
        return instance;
    }

    /**
     * Initialize the factory. Must be called before any primary key is generated
     * - preferably from application class.
     */
    public synchronized void initialize(final Realm realm) {
        if (keys != null) {
            throw new IllegalStateException("already initialized");
        }
        // keys field is used as an initialization flag at the same time
        keys = new HashMap<>();
        final RealmConfiguration configuration = realm.getConfiguration();
        final RealmSchema realmSchema = realm.getSchema();
        //using RealmConfiguration#getRealmObjectClasses because
        // RealmSchema#getAll() returns RealmObjectSchema with simple class names only
        for (final Class<? extends RealmObject> c : configuration.getRealmObjectClasses()) {

            final RealmObjectSchema objectSchema = realmSchema.get(c.getSimpleName());
            Log.i(getClass().getSimpleName(), format("schema for class %s : %s", c.getName(), objectSchema));
            if (objectSchema != null && objectSchema.hasPrimaryKey()) {
                Number keyValue = null;
                try {
                    keyValue = realm.where(c).max(PRIMARY_KEY_FIELD);
                } catch (ArrayIndexOutOfBoundsException ex) {
                    Log.d(getClass().getSimpleName(), format("error while getting number primary key %s " +
                            " for %s",PRIMARY_KEY_FIELD, c.getName()), ex);
                }
                if (keyValue == null) {
                    Log.w(getClass().getSimpleName(), format("can't find number primary key %s " +
                            " for %s.",PRIMARY_KEY_FIELD, c.getName()));
                } else {
                    keys.put(c, new AtomicLong(keyValue.longValue()));
                }
            }
        }
    }

    /**
     *  Automatically create next key for a given class.
     */
    public synchronized long nextKey(final Class<? extends RealmObject> clazz) {
        if (keys == null) {
            throw new IllegalStateException("not initialized yet");
        }
        AtomicLong l = keys.get(clazz);
        if (l == null) {
            Log.i(getClass().getSimpleName(), "There was no primary keys for " + clazz.getName());
            //RealmConfiguration#getRealmObjectClasses() returns only classes with existing instances
            //so we need to store value for the first instance created
            l = new AtomicLong(0);
            keys.put(clazz, l);
        }
        return l.incrementAndGet();
    }

}

@jalqa +1 exactly what I did and it works too though I was initially uncomfortable and wondered whether the wildcard class extending RealmModel would work.

tldr; replace all instances of RealmObject with RealmModel and it should just work.

I initialised the code but i'm wondering how do i initialize the xml .As in do you leave the id value empty or use same id in all textviews?

if i add data,then delete data，”nextKey” has problem!

Misayanice commented on 15 Mar
if i add data,then delete data，”nextKey” has problem!

What problem?