The Yoix^® Scripting Language

The type that is assigned to the event argument in the declaration of dragOver selects the events that dragOver receives. If event is declared to be a DropTargetEvent then DragSourceEvents will not arrive, if it is declared to be a DragSourceEvent then DropTargetEvents will not arrive, but if event is an Object then DropTargetEvents and DragSourceEvents can arrive and dragOver should check event, usually using instanceof, to decide what to do.

dragOver behaves something like dragEnter, but it is called whenever the cursor moves, so there is lots of overhead. It can be used for fancy visual effects or to handle a complicated drop target that needs to accept of reject data based on the cursor's position, but other than that there is not much that dragOver should be used for.

dragOver receives DropTargetEvents when its declaration lets them through and the cursor moves over the component. dragOver usually examines fields, like dragowner, location, mimetypes, and transferable in its event argument and then returns a Number that is non-zero if it accepts and zero if it rejects the data that is being transferred by the drag and drop operation. A return value that is missing or the wrong type (e.g., a String) is ignored and no changes are made, which is a little different than dragEnter's behavior.

dragOver receives DragSourceEvents when its declaration lets them through and the cursor moves over any component that has accepted the data that this component's dragGestureRecognized exported. DragSourceEvents stop arriving if the component that accepted the data decides to reject it. dragOver may choose to change the cursor field in its event argument if a visual effect is called for, but in this case nothing special is required and any return value from dragOver will be ignored.

Some Swing components provide automatic drag and drop handling that currently must be disabled by storing NULL in their transferhandler field before your drag and drop event handlers will start working. In other words, you probably should include a declaration that looks something like,

Object transferhandler = NULL;