HERE Android SDK Developer's Guide

Development Tips

This section provides tips on building your application using the HERE Android SDK.

Lapsed Listeners and Garbage Collection

The HERE SDK provides a number of listener interfaces, such as Map.OnSchemeChangedListener, Map.OnTransformListener, and MapGesture.OnGestureListener. To use these listeners, you are required to implement and create a listener instance, then register it with another object (using a method such as addSchemeChangedListener()) to receive event notifications. Unfortunately, this coding pattern can also lead to the lapsed listener problem, where available memory is consumed by listener objects that are not explicitly unregistered and not garbage collected.

To mitigate this problem, the HERE SDK, in some cases, accepts listener objects in WeakReference containers. This has the advantage of avoiding lapsed listeners, but it also means that you must be aware of registered listeners becoming garbage collected. To avoid any unintended issues with this coding pattern, be sure to retain a strong reference to your listener instances (for example, by assigning it to a class variable) if you would like to manage its garbage collection lifecycle. Listener objects are not garbage collected as long as a strong reference exists.

Working with Getters

Classes in the HERE SDK return copies of objects in its getters. For example, MapPolyline.getPolyline() does not return the same GeoPolyline instance that was used to construct the MapPolyline object; instead, a copy of the GeoPolyline is returned. Since this returned object is a copy, you cannot dynamically modify the MapPolyline instance by modifying this object. If you would like to make changes to MapPolyline, you must call setGeoPolyline(GeoPolyline) instead.

Map Object Limitations

The HERE SDK does not limit the number of map markers, polygons, and polylines that can be added to a map. However, rendering a large number of map objects can cause performance degradation in your application. It is recommended that you use techniques such as viewport clipping to avoid these issues.

Doze and App Standby

If you are using Android 6.0 (API level 23) or above, be aware that the Doze and App Standby features may impact your HERE SDK app by disabling network access when the device is unplugged, stationary, and has the screen off for a period of time. While the HERE Android SDK has the ability to work offline, you should design your app with these operating system features in mind.

For more information about Doze and App Standby, including how to use notifications and whitelisting to ensure your app functions properly, see the Android article, "Optimizing for Doze and App Standby".

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