Chris Martin and Dakota Johnson Back Together in the Hamptons

Chris Martin and Dakota Johnson are proving old flames die hard ... especially when ice cream's involved.

The Coldplay frontman and 'Fifty Shades' star -- decked out in a red jumpsuit -- were out Monday in the Hamptons, hanging with his son and his buds. They plopped themselves on a picnic table and enjoyed lunch before scarfing down some ice cream.

It's quite the family scene, considering Dakota and Chris had supposedly broken up a couple months ago. All signs pointed to a split ... because a week after their reported breakup, he was seen hopping on a helicopter with a mystery woman.