Cluster Manager Save Instance State
sshrop opened this issue · 2 comments
Is your feature request related to a problem? Please describe.
Throughout a Fragment's lifecycle, Android can be quite aggressive when destroying and recreating a fragment's view. It's almost certain to require instance state restoration when a user navigates from a fragment that hosts a MapView.
In my case, I'm forced to recreate a ClusterManager to redraw my markers when the host fragment is made visible again. Recreating custom markers can be a time consuming process, and a visual blip in the map can negatively affect the user experience.
Describe the solution you'd like
A first-class feature that allows the ClusterManger to be rebound to a newly created map view, allowing for fast recovery of the MapView's state including all markers and state of interaction e.g. restoration of a visible item info window that was activated before the view was destroyed.
Describe alternatives you've considered
I haven't seen any documentation on how to handle UI state restoration. I'm wondering if I need to:
- Cache custom marker Bitmaps in memory
- Keep track of active item info windows
Additional context
Thanks in advance. I can provide additional context as needed to clarify my concern.
@sshrop you might check out the clustering ViewModel demo. The clustering Algorithm holds the marker state in the ViewModel, which is retained across configuration changes. This allows for quickly restoring marker cluster state after a configuration change. The only state that should be updated is the view size, so the appropriate map view port is used.
Without a ViewModel, marshalling all marker objects through onSaveInstanceState would be difficult, as ClusterItems aren't required to be Parcelable. Retaining the ClusterItem marker objects is faster than serializing and deserializing them through saved instance state as well.