How to keep map state on device rotation?

问题:

I have a nested fragment that i would like to maintain the state when the device orientation changed.

It is something like this:

I'm instantiate a mapView in the nested fragment and when the device is rotated the user must be in the same place where it was. How can I accomplish this?

Thank you

回答1:

Ok, so i was making a mistake. I was calling the function setRetainInstance(true) on the fragment parent and i shouldn't.

After deleting that line, it was very simple to keep the map state on device orientation. All i had to do was to save some values on onSaveInstanceState like this:

bundle.putDouble("lat", mMap.getCameraPosition().target.latitude);
bundle.putDouble("lon", mMap.getCameraPosition().target.longitude);
bundle.putFloat("zoom", mMap.getCameraPosition().zoom);

Then on onCreate, i restore the map state like this:

bundle.getDouble("lat");
bundle.getDouble("lon");
bundle.getDouble("zoom");

回答2:

You could use it like this because CameraPosition class implements Parcelable:

1. save it

if (null != mMap) {
   outState.putParcelable("map_camera_position", mMap.getCameraPosition());
}

2. retrieve it in onCreate()

if (null != savedInstanceState) {
    mCameraPosition = savedInstanceState.getParcelable("map_camera_position");
}

3. set it to move the camera

if (null != mCameraPosition) {
   mMap.moveCamera(CameraUpdateFactory.newCameraPosition(mCameraPosition));
}