@mhartington It works great! A really helpful basis, thanks.
There would be some extra features in order to mimic foursquare’s views (they seemed to me general enough the be mentioned in the forum). I will list list them below. The first two seem to me easy, and I should probably solve them by myself. But the last to look harder and any help/suggestion would be much appreciated.
By default, the map should be shrinked at its minimum size (not maximum). This should be easy.
When the map is rolled out at its maximum size, it zooms-in in a little bit automatically. This should be also easy.
In foursquare, when I shrink the map, it dinamically resizes. in other words, it maintains the red flag always in the middle, while in the example above it is static. This seems harder to implement.
There should be just two positions when the drag is released, namely minimum os maximum map size. If the dragging ends before reaching one of the two end positions, it should automatically go for one of the two options (e.g., by picking the nearest). This is done with an animation that continues the dragging for the user up to the end position. This seems also harder to me.