RealmのinitalDataでハマったので覚書 ref: https://qiita.com/k_keisuke/items/24e8a5bbf69a5c963945

ApplicationModule.kt

    @Provides
    fun provideRealm(application: MainApplication): Realm {
        val builder = RealmConfiguration.Builder().name(APP_KEY)
        builder.initialData { /*引き継ぎ処理*/ } //追加
        return if (BuildConfig.DEBUG) {
            Realm.getInstance(builder.deleteRealmIfMigrationNeeded().build())
        } else {
            Realm.getInstance(builder.build())
        }
    }

file2.txt

java.lang.RuntimeException: java.lang.IllegalArgumentException: Configurations cannot be different if used to open the same file. 
    Cached configuration: 

file6.txt

    @Provides
    fun provideRealm(transaction: Realm.Transaction): Realm {
        val builder = RealmConfiguration.Builder().name(APP_KEY)
        builder.initialData(transaction)
        return if (BuildConfig.DEBUG) {
            Realm.getInstance(builder.deleteRealmIfMigrationNeeded().build())
        } else {
            Realm.getInstance(builder.build())
        }
    }

    @Provides
    fun provideTransaction(application: MainApplication) = application.transaction

kotlin

    @Provides
    fun provideRealm(application: MainApplication): Realm {
        val builder = RealmConfiguration.Builder().name(APP_KEY)
        builder.initialData { /*初期化処理*/ } //ラムダ式なので毎回異なるインスタンス
        return if (BuildConfig.DEBUG) {
            Realm.getInstance(builder.deleteRealmIfMigrationNeeded().build())
        } else {
            Realm.getInstance(builder.build())
        }
    }

MainApplication

class MainApplication : DaggerApplication() {
    val transaction: Realm.Transaction by lazy { 
    Realm.Transaction { /* 初期化処理 */}
 }

RealmCache.java

    private void validateConfiguration(RealmConfiguration newConfiguration) {
        if (configuration.equals(newConfiguration)) {
            // Same configuration objects.
            return;
        }

// 中略

            throw new IllegalArgumentException("Configurations cannot be different if used to open the same file. " +
                    "\nCached configuration: \n" + configuration +
                    "\n\nNew configuration: \n" + newConfiguration);
        }
    }

RealmConfiguration.java

    @Override
    public boolean equals(Object obj) {
        if (this == obj) { return true; }
        if (obj == null || getClass() != obj.getClass()) { return false; }

        RealmConfiguration that = (RealmConfiguration) obj;

        if (schemaVersion != that.schemaVersion) { return false; }
        if (deleteRealmIfMigrationNeeded != that.deleteRealmIfMigrationNeeded) { return false; }
        if (readOnly != that.readOnly) { return false; }
        if (isRecoveryConfiguration != that.isRecoveryConfiguration) { return false; }
        if (realmDirectory != null ? !realmDirectory.equals(that.realmDirectory) : that.realmDirectory != null) {
            return false;
        }
        if (realmFileName != null ? !realmFileName.equals(that.realmFileName) : that.realmFileName != null) {
            return false;
        }
        if (!canonicalPath.equals(that.canonicalPath)) { return false; }
        if (assetFilePath != null ? !assetFilePath.equals(that.assetFilePath) : that.assetFilePath != null) {
            return false;
        }
        if (!Arrays.equals(key, that.key)) { return false; }
        if (migration != null ? !migration.equals(that.migration) : that.migration != null) {
            return false;
        }
        if (durability != that.durability) { return false; }
        if (!schemaMediator.equals(that.schemaMediator)) { return false; }
        if (rxObservableFactory != null ? !rxObservableFactory.equals(that.rxObservableFactory) : that.rxObservableFactory != null) {
            return false;
        }
        if (initialDataTransaction != null ? !initialDataTransaction.equals(that.initialDataTransaction) : that.initialDataTransaction != null) {
            return false;
        }
        return compactOnLaunch != null ? compactOnLaunch.equals(that.compactOnLaunch) : that.compactOnLaunch == null;
    }