Optimize the HERE SDK

This optimization guide lists several options to shrink the size of the HERE SDK and to optimize the runtime behavior by reducing the data that needs to loaded or processed.

Note that each of the listed features relates to one or more OCM layer groups. The names of the OCM layer groups can be seen per feature in the API Reference. However, for most use cases knowing the related OCM layer name is not relevant.

In addition, there are two layers, ADAS and EHORIZON (Electronic Horizon), that are currently not relevant for use with the HERE SDK editions and can be ignored for now. By default, they are already disabled.

If a feature is disabled, then it means that required data for that feature will not occupy space in the cache or as part of a Region download. It also means, that the feature cannot be used offline. And sometimes even an error may occur - for example, when trying to use the OfflineSearchEngine although OFFLINE_SEARCH has been disabled. Find more details below.

As listed above, for some disabled features, a device may still download corresponding data when a device has online connectivity and the feature is needed. For example, when the "LANDMARKS_3D" feature is disabled, but the corresponding MapScene layer is enabled, then the device will still download the needed textures to render a 3D landmark when it becomes visible in the MapView viewport.

For all listed features from above - except for OFFLINE_SEARCH and OFFLINE_ROUTING, the HERE SDK will first check if the needed data is available in the cache. If not found there, it will look if there is a downloaded Region for offline use. If not found, the HERE SDK will try to download the needed data over the air. For OFFLINE_SEARCH and OFFLINE_ROUTING the behavior will be the same, but no data will be requested over the air.

Updating the feature configuration

Feature configurations can be updated after the installation of the next application update by calling mapUpdater.performFeatureUpdate(). Call this method once a feature configuration has been updated in the AndroidManifest file.

As a result, the cached map data will be deleted and subsequently updated. Also, the downloaded regions will be updated to reflect the changes.

Note that it is the developer's responsibility to decide when to perform the update. The HERE SDK does not decide or notify when such an update can be made. Calling performFeatureUpdate() is only necessary once - after an application has been updated. It is not necessary to call this, when the feature configuration has not been changed by a developer.

Remove unused voices

By removing unused voice guidance files you can reduce the size of the HERE SDK.

These files are only needed when you want to use turn-by-turn navigation with text-to-speech voice messages.

Do the following to remove the unused files:

1. Unzip the HERE SDK framework and search for the assets/voice_assets folder.
2. If you want to shrink the size of the framework, you can remove the voice packages you do not need.
3. Re-archive the AAR with Android Studio.

Here you can find a list of all supported voice languages together with the name of the related voice skin that is stored inside the HERE SDK framework.

Remove unused fonts

By removing unused fonts you can reduce the size of the HERE SDK. This is explained here.

ABI splits

Size management: With ABI splits you can reduce the size of the HERE SDK AAR binary file. As a result, your application will occupy less storage space on a device.

By default, the HERE SDK for Android includes the following ABIs: armeabi-v7a, arm64-v8a (mainly used for devices) and x86, x86_64 (mainly used for emulators). You can enable ABI splits to build your app, for example, only for the armeabi-v7a or arm64-v8a architectures.

Do this by modifying your app's build.gradle file:

android {
  (...)
  splits {
    abi {
      enable true
      reset()
      include 'x86_64', 'arm64-v8a' // Choose what you need.
      universalApk false
    }
  }
  (...)
}

Now, when you execute ./gradlew assembleRelease from command line, the following two APKs are generated: app-x86_64-release.apk and app-arm64-v8a-release.apk. Each APK contains only the desired ABI and is therefore much smaller in size. If you change the splits block to set universalApk true, then also a universal APK is generated that contains all ABIs, which is obviously much bigger.

For more information about the splits Gradle block, see Configure Multiple APKs for ABIs.

More options

Other options to optimize the HERE SDK include:

• Optimize the map cache.
• Manually initialize the HERE SDK only when it is needed.

In addition, all engines contain several options that allow how to configure a feature. For example, when using the SearchEngine, you can specify SearchOptions to limit the returned search results.