Realm migration android addRealmObjectField

Question

I have following class

   public class Settings extends RealmObject {

     private String something;

   }

I want to add the following field

    public class AndroidBuild extends RealmObject {

      int one;
      int two;

    }

so it looks like

   public class Settings extends RealmObject {

     private String something;
     private AndroidBuild androidBuild;

   }

So, my migration looks like

if (oldVersion == 1) {
        RealmObjectSchema settingsSchema = schema.get("Settings");
        RealmObjectSchema androidBuildSchema = schema.get("AndroidBuild");

        if (settingsSchema != null) {
            settingsSchema.addRealmObjectField("androidBuild", androidBuildSchema);
            oldVersion++;
        }
    }

and it crashes

07-11 15:05:06.384 9046-9046/com.cassby.terminal.cassby E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.cassby.terminal.cassby, PID: 9046
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.cassby.terminal.cassby/com.cassby.terminal.cassby.UserStories.Launch.LaunchActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String io.realm.RealmObjectSchema.getClassName()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
    at android.app.ActivityThread.-wrap11(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String io.realm.RealmObjectSchema.getClassName()' on a null object reference
    at io.realm.MutableRealmObjectSchema.addRealmObjectField(MutableRealmObjectSchema.java:126)
    at com.cassby.terminal.cassby.Services.Database.RealmMigrations.migrate(RealmMigrations.java:36)
    at io.realm.BaseRealm$6.onMigrationNeeded(BaseRealm.java:714)
    at io.realm.internal.OsSharedRealm.runMigrationCallback(OsSharedRealm.java:520)
    at io.realm.internal.OsSharedRealm.nativeGetSharedRealm(Native Method)
    at io.realm.internal.OsSharedRealm.<init>(OsSharedRealm.java:184)
    at io.realm.internal.OsSharedRealm.getInstance(OsSharedRealm.java:254)
    at io.realm.BaseRealm.<init>(BaseRealm.java:124)
    at io.realm.BaseRealm.<init>(BaseRealm.java:93)
    at io.realm.Realm.<init>(Realm.java:153)
    at io.realm.Realm.createInstance(Realm.java:424)
    at io.realm.RealmCache.doCreateRealmOrGetFromCache(RealmCache.java:342)
    at io.realm.RealmCache.createRealmOrGetFromCache(RealmCache.java:282)
    at io.realm.Realm.getDefaultInstance(Realm.java:332)
    at com.cassby.terminal.cassby.UserStories.Launch.LaunchActivity.resolveStartingActivity(LaunchActivity.java:35)
    at com.cassby.terminal.cassby.UserStories.Launch.LaunchActivity.onCreate(LaunchActivity.java:29)
    at android.app.Activity.performCreate(Activity.java:7009)
    at android.app.Activity.performCreate(Activity.java:7000)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
    at android.app.ActivityThread.-wrap11(Unknown Source:0) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

What am I doing wrong ?

Answer 1

You need to add Table first, so

 Realm.setDefaultConfiguration(new RealmConfiguration.Builder()
        .name(DB_NAME)
        .schemaVersion(SCHEMA_VERSION)
        .migration((realm, oldVersion, newVersion) -> {
            RealmSchema schema = realm.getSchema();
            if (oldVersion == OLD_VERSION) {
                schema.create("AndroidBuild")
                        .addField("one", int.class)
                        .addField("two", int.class);
                schema.get("Settings")
                        .addRealmObjectField("androidBuild", schema.get("AndroidBuild"))
                oldVersion++;
            }
        })
);