领域迁移 android addRealmObjectField

Question

我有以下课程

\n\n

   public class Settings extends RealmObject {\n\n     private String something;\n\n   }\n

\n\n

我想添加以下字段

\n\n

    public class AndroidBuild extends RealmObject {\n\n      int one;\n      int two;\n\n    }\n

\n\n

所以看起来像

\n\n

   public class Settings extends RealmObject {\n\n     private String something;\n     private AndroidBuild androidBuild;\n\n   }\n

\n\n

所以，我的迁移看起来像

\n\n

if (oldVersion == 1) {\n        RealmObjectSchema settingsSchema = schema.get("Settings");\n        RealmObjectSchema androidBuildSchema = schema.get("AndroidBuild");\n\n        if (settingsSchema != null) {\n            settingsSchema.addRealmObjectField("androidBuild", androidBuildSchema);\n            oldVersion++;\n        }\n    }\n

\n\n

它崩溃了

\n\n

07-11 15:05:06.384 9046-9046/com.cassby.terminal.cassby E/AndroidRuntime: FATAL EXCEPTION: main\nProcess: com.cassby.terminal.cassby, PID: 9046\njava.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\n    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)\n    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)\n    at android.app.ActivityThread.-wrap11(Unknown Source:0)\n    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)\n    at android.os.Handler.dispatchMessage(Handler.java:106)\n    at android.os.Looper.loop(Looper.java:164)\n    at android.app.ActivityThread.main(ActivityThread.java:6494)\n    at java.lang.reflect.Method.invoke(Native Method)\n    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)\n    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)\n Caused by: java.lang.NullPointerException: Attempt to invoke virtual method \'java.lang.String io.realm.RealmObjectSchema.getClassName()\' on a null object reference\n    at io.realm.MutableRealmObjectSchema.addRealmObjectField(MutableRealmObjectSchema.java:126)\n    at com.cassby.terminal.cassby.Services.Database.RealmMigrations.migrate(RealmMigrations.java:36)\n    at io.realm.BaseRealm$6.onMigrationNeeded(BaseRealm.java:714)\n    at io.realm.internal.OsSharedRealm.runMigrationCallback(OsSharedRealm.java:520)\n    at io.realm.internal.OsSharedRealm.nativeGetSharedRealm(Native Method)\n    at io.realm.internal.OsSharedRealm.<init>(OsSharedRealm.java:184)\n    at io.realm.internal.OsSharedRealm.getInstance(OsSharedRealm.java:254)\n    at io.realm.BaseRealm.<init>(BaseRealm.java:124)\n    at io.realm.BaseRealm.<init>(BaseRealm.java:93)\n    at io.realm.Realm.<init>(Realm.java:153)\n    at io.realm.Realm.createInstance(Realm.java:424)\n    at io.realm.RealmCache.doCreateRealmOrGetFromCache(RealmCache.java:342)\n    at io.realm.RealmCache.createRealmOrGetFromCache(RealmCache.java:282)\n    at io.realm.Realm.getDefaultInstance(Realm.java:332)\n    at com.cassby.terminal.cassby.UserStories.Launch.LaunchActivity.resolveStartingActivity(LaunchActivity.java:35)\n    at com.cassby.terminal.cassby.UserStories.Launch.LaunchActivity.onCreate(LaunchActivity.java:29)\n    at android.app.Activity.performCreate(Activity.java:7009)\n    at android.app.Activity.performCreate(Activity.java:7000)\n    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)\n    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)\n    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)\xc2\xa0\n    at android.app.ActivityThread.-wrap11(Unknown Source:0)\xc2\xa0\n    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)\xc2\xa0\n    at android.os.Handler.dispatchMessage(Handler.java:106)\xc2\xa0\n    at android.os.Looper.loop(Looper.java:164)\xc2\xa0\n    at android.app.ActivityThread.main(ActivityThread.java:6494)\xc2\xa0\n    at java.lang.reflect.Method.invoke(Native Method)\xc2\xa0\n    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)\xc2\xa0\n    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)\xc2\xa0\n

\n\n

我究竟做错了什么 ？

\n

Answer 1

您需要先添加表，所以

 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++;
            }
        })
);