android - Offseting the center of the MapFragment for an animation moving both the target lat/lng and the zoom level

Question

I've got a UI that has a MapFragment with a transparent View overlaid on top of it. The map takes up the entire screen, whereas the View is just the left third of the screen. As a result, the default "center" of the map is off. When someone clicks on a marker, I want to center that marker in the wholly visible area of the MapFragment (not the center of the MapFragment itself).

Since this is hard to describe with words, let me use a few pictures. Suppose this is how my UI looks:

When the user clicks a marker, I want to both center it and zoom in to see it closer. Without any adjustments, this is what you'll get:

What I want is for the marker to be centered, but in the space to the right, like this:

It's very easy to achieve this feat if you're not changing the zoom level using the map's projection:

// Offset the target latitude/longitude by preset x/y ints
LatLng target = new LatLng(latitude, longitude);
Projection projection = getMap().getProjection();
Point screenLocation = projection.toScreenLocation(target);
screenLocation.x += offsetX;
screenLocation.y += offsetY;
LatLng offsetTarget = projection.fromScreenLocation(screenLocation);

// Animate to the calculated lat/lng
getMap().animateCamera(CameraUpdateFactory.newLatLng(offsetTarget));

However, if you're changing the zoom level at the same time, the above calculations don't work (since the lat/lng offsets change at different zoom levels).

Let me run down a list of attempted fixes:

• Changing the zoom level quickly, doing the calculations, zooming back to the original camera position, then animating. Unfortunately the sudden camera change (even if it's only for a split second) is unfortunately very obvious and I'd like to avoid the flicker.

• Overlaying two MapFragments on top of each other, having one do the calculations while the other displays. I've found that MapFragments are not really built to be layered on top of each other (there are unavoidable bugs down this route).

• Modifying the screen location's x/y by the difference in zoom level squared. Theoretically this should work but it's always off by quite a bit (~.1 latitude/longitude, which is enough to be way off).

Is there a way to calculate the offsetTarget even with the zoom level changing?

Answer 1

The most recent version of the play services library adds a setPadding() function to GoogleMap. This padding will project all camera movements to the offset map center. This document further describes how the map padding behaves.

The question originally asked here can now simply be solved by adding left padding equivalent to the width of the left-side layout.

mMap.setPadding(leftPx, topPx, rightPx, bottomPx);