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If your app uses native libraries that don't ship with support for 64-bit architectures, Android will fail to load Realm's librealm-jni.so file on ARM64 devices. This happens because Android cannot load 32-bit and 64-bit native libraries concurrently. Ideally, all libraries could provide the same set of supported ABIs, but sometimes that may not be doable when using a 3rd-party library.

To work around this issue, you can exclude Realm's ARM64 library from the APK file by adding the following code to the application's build.gradle. You can refer to Mixing 32- and 64-bit Dependencies in Android for more information.

android {
//...
packagingOptions {
exclude "lib/arm64-v8a/librealm-jni.so"
}
//...
}
Tip
See also:

For more information, see Mixing 32- and 64-bit Dependencies in Android.

Realm collects anonymous analytics when you run the Realm bytecode transformer on your source code. This is completely anonymous and helps us improve the product by flagging:

  • which version of the SDK you use
  • which operating system you use
  • if your application uses Kotlin
  • if your application uses local-only Realm Database or Realm Sync

Analytics do not run when your application runs on user devices - only when you compile your source code. To opt out of analytics, you can set the REALM_DISABLE_ANALYTICS environment variable to true.

Due to a change in the Linux kernel, object, collection, and realm notifications do not work in SDK versions below 10.5.1 on devices running certain early versions of Android 12.

This change effects Linux kernel versions beginning with 5.5. Linux kernel version 5.14-rc4 fixed the issue. The fix was also backported to LTS 5.10.56 and LTS 5.13.8. All mainline and LTS Android 12 branches contain the fix or a backport of it.

If you experience this issue, you can restore notification functionality with the following fixes:

  • upgrade to a version of the SDK later than 10.5.1.
  • upgrade to a version of Android 12 that uses a Linux kernel release that contains the fix (kernel commit 3a34b13a88caeb2800ab44a4918f230041b37dd9) or the backport of the fix (kernel commit 4b20d2de0b367bca627b49efd8d2e9e01bb66753).

Realm Database runs checks whenever you open a realm file to avoid corruption. In order to avoid accidentally opening a realm file with incompatible settings, the SDK uses Java's equals() method to compare RealmConfiguration objects. This prevents the SDK from opening a single realm file with different schemas, durability levels, or writability settings. However, configurations that include lambda functions, such as those passed to initialData() and compactOnLaunch(), can break this equals() comparison, since two different lambdas are never considered equal using Java's built-in comparison. To avoid this error when using lambdas, you can either:

  1. Store a single configuration statically in your application, so that separate realm instances use the exact same RealmConfiguration object and it passes the check.
  2. Override the default equals check of the RealmConfiguration:

    val config = RealmConfiguration.Builder()
    .initialData(object: Realm.Transaction {
    override fun execute(realm: Realm) {
    TODO("Not yet implemented")
    }
    override fun equals(other: Any?): Boolean {
    return true
    }
    override fun hashCode(): Int {
    return 37
    }
    }).build()

If you experience an exception in the Kapt library with a description like the following:

A failure occurred while executing org.jetbrains.kotlin.gradle.internal.KaptWithoutKotlincTask$KaptExecutionWorkAction

This most likely means there is an issue with one of your model classes. Possible causes include:

  • introducing a field type that is not supported by the SDK
  • using a visibility type other than open or public for a realm object model class
  • using a Realm annotation on an incompatible field

If you experience this error, check any recent updates to your schema for problems.

Once your app is built for release and split for distribution, the SDK should only add about 800KB to your APK in most cases. The releases are significantly larger because they include support for more architectures, such as ARM7, ARMv7, ARM64, x86, and MIPS. The APK file contains all supported architectures, but the Android installer only installs native code for the device's architecture. This means that the installed app is smaller than the size of the APK file.

You can reduce the size of the Android APK itself by splitting the APK into a version for each architecture. Use the Android Build Tool ABI Split support by adding the following to your build.gradle:

android {
splits {
abi {
enable true
reset()
include 'armeabi-v7a', 'arm64-v8a', 'x86', 'x86_64'
}
}
}

Select the architectures that you'd like to include to build a separate APK for each.

Tip
See also:

If you don't want to handle multiple APKs, you can restrict the number of architectures supported in a single APK. This is done by adding abiFilters to your build.gradle:

android {
defaultConfig {
ndk {
abiFilters 'armeabi-v7a', 'arm64-v8a', 'mips', 'x86', 'x86_64'
}
}
}
Tip
See also:

For more details about ABI splits and filters, see Controlling APK Size When Using Native Libraries.

Realm uses a Gradle plugin because it makes it easier to set up a large number of dependencies. Unfortunately this also makes it a bit harder to ignore specific transitive dependencies.

If you want to customize Realm beyond what is exposed by the plugin, you can manually set up all the dependencies and ignore the Gradle plugin. The following example demonstrates how to set up the SDK for an Android application using Kotlin manually:

buildscript {
ext.kotlin_version = '1.5.21'
ext.realm_version = '10.11.0'
repositories {
jcenter()
mavenCentral()
}
dependencies {
classpath "io.realm:realm-transformer:$realm_version"
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'
import io.realm.transformer.RealmTransformer
android.registerTransform(new RealmTransformer(project))
dependencies {
api "io.realm:realm-annotations:$realm_version"
api "io.realm:realm-android-library:$realm_version"
api "io.realm:realm-android-kotlin-extensions:$realm_version"
kapt "io.realm:realm-annotations-processor:$realm_version"
}
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