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.

Use the Feature Configuration

With feature configurations you can specify how much map data should be loaded when panning the MapView or when downloading a new Region for offline usage. For example, if a feature like turn-by-turn navigation is never used in an application, it can be removed.

As a result, when panning the MapView less data will be downloaded into the cache. In addition, when downloading a new Region, its size will be smaller.

If a "FeatureConfiguration" is present in the AndroidManifest, then only the listed features will be enabled, all others will be disabled. If you want to disable only one feature, then all other features need to be present, or they will be also disabled.

For example, the following enables only navigation and truck features and disables all others:

<meta-data
  android:name="com.here.sdk.feature_configuration"
  android:value="NAVIGATION, TRUCK" />

As of now, these features can be specified:

1. "DETAIL_RENDERING": Additional rendering details like buildings. Only used for the MapView. When not set, the data will be excluded when downloading offline regions or prefetching areas that contain such data. However, during online usage such data may still be downloaded into the cache and shown.
2. "NAVIGATION": Map data that is used for map matching during navigation. When not set, navigation may not work properly when being used online or offline.
3. "OFFLINE_SEARCH": Map data that is used to search. When not set, the OfflineSearchEngine may not work properly when being used.
4. "OFFLINE_ROUTING": Map data that is used to calculate routes. When not set, the OfflineRoutingEngine may not work properly when being used.
5. "TRUCK": Map data that is used to calculate truck routes. When not set, the OfflineRoutingEngine may not work properly when being used to calculate truck routes. It is also used for map matching during truck navigation. When not set, truck navigation may not work properly when being used offline. Online truck navigation will still work when the device has an online connection.
6. "LANDMARKS_3D": Map data that is used to render textured 3D landmarks. When not set, the data will be excluded when downloading offline regions or prefetching areas that contain such data. When the LANDMARKS layer is set to be visible for a MapScene, 3D landmarks will still be visible during online usage.
7. "JUNCTION_VIEW_3X4", "JUNCTION_VIEW_16X9": 3D visuals for complex junctions. This asset data can be used to show SVG images during guidance. If enabled, downloaded regions will include junction view images to be used with the corresponding JunctionViewWarning event. This could be useful to download the assets before starting a trip. If not enabled, the required data will be downloaded when needed. Each image can occupy up to 15 MB. Note that future releases of the HERE SDK will optimize the size by reducing the level of realism. By default, the layer is not enabled.
8. "JUNCTION_SIGN_3X4", "JUNCTION_SIGN_16X9": Signpost visuals. This asset data can be used to show SVG images during guidance. If enabled, downloaded regions will include junction view images to be used with the corresponding SignpostWarning event. If not enabled, the required data will be downloaded when needed. Each image can occupy up to 300 KB. If not enabled, the required data will be downloaded when needed. By default, the layer is not enabled.
9. "RENDERING": A basic set of rendering features such as carto POIs.
10. "TRAFFIC": Map data that provides traffic broadcast functionality using RDS-TMC format. It should be used when there is no internet connection, so that the routing module can utilize traffic data coming over the radio channel to create routes with the OfflineRoutingEngine.
11. "EV": Offline map data for EV charging stations.
12. "TRUCK_SERVICE_ATTRIBUTES": Enables truck related attributes to be returned by OfflineSearchEngine.
13. "FUEL_STATION_ATTRIBUTES": Enables fuel attributes to be returned by OfflineSearchEngine.
14. "OFFLINE_BUS_ROUTING": Map data that is used to calculate bus routes. When not set, the OfflineRoutingEngine may not be able to calculate routes with BusOptions.

Only "OFFLINE_SEARCH", "OFFLINE_ROUTING", "TRUCK", "NAVIGATION", "RENDERING", "DETAIL_RENDERING", "TRAFFIC" are enabled, by default. All other layers are disabled, by default. The "RENDERING" layer is a base layer that cannot be disabled.

Note: The "DETAILRENDERING" feature is not relevant for the _Headless Edition.

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.

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.

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.

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.

Remove Unused Fonts

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

More Options

Other options to optimize the HERE SDK include:

• Optimize the map cache.
• Manually initialize the HERE SDK only when it is needed.
• Adjust the frame rate of the MapView.
• Use custom map styles that contain less elements to render.
• Preload map data with offline maps.

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.