Summary
SystemLocationDataSource on Android can malfunction because its internal AndroidCompassProvider obtains an IWindowManager from the Android application context instead of an activity context. The application context is not guaranteed to be associated with a window, so the display properties retrieved from it may not reflect the actual display/rotation of the visible activity, leading to incorrect compass alignment and/or crashes due to disposed object.
Internal anatomy (relevant private structure)
SystemLocationDataSource
└── AndroidCompassProvider (private field)
└── IWindowManager (private field)
The IWindowManager instance is used to query device display properties, which are then used to align the compass direction.
Root cause
The IWindowManager is created from the Android application context. Because the application context is not guaranteed to be tied to a window, the display information it returns can be wrong. The instance should instead be created from an activity context, which is associated with an actual window and display.
Workaround
- Create a new IWindowManager instance from the correct activity context.
- Use reflection to replace the private IWindowManager field inside the private AndroidCompassProvider field of SystemLocationDataSource.
Timing is critical: the replacement must be performed after SystemLocationDataSource.StartAsync() completes, because StartAsync() instantiates a new AndroidCompassProvider. The provider is set to null on StopAsync(), so the workaround must be re-applied after every restart.
Suggested fix
Note that IWindowManager.getDisplay() is deprecated precisely because of this class of problem. The recommended approach is to migrate to the newer display APIs rather than continuing to rely on the deprecated call.
