On Drag Over
| Code | Puede ser llamado por | Definición |
|---|---|---|
| 21 | 4D Write Pro area - Button - Button Grid - Check Box - Dropdown list - Hierarchical List - Input - List Box - List Box Column - Picture Button - Picture Pop up menu - Plug-in Area - Progress Indicators - Radio Button - Ruler - Spinner - Splitter - Stepper - Tab control | Los datos se pueden soltar en un objeto |
Descripción
The On Drag Over event is repeatedly sent to the destination object when the mouse pointer is moved over the object. Normalmente, en respuesta a este evento:
- Get the data and signatures found in the pasteboard (via the
GET PASTEBOARD DATAcommand). - Depending on the nature and type of data in the pasteboard, you accept or reject the drag and drop.
To accept the drag, the destination object method must return 0 (zero), so you write $0:=0.
To reject the drag, the object method must return -1 (minus one), so you write $0:=-1.
During an On Drag Over event, 4D treats the object method as a function. Si no se devuelve ningún resultado, 4D asume que el arrastre es aceptado.
Si acepta el arrastre, el objeto de destino se resalta. Si rechaza el arrastre, el destino no se resalta. Aceptar el arrastre no significa que los datos arrastrados vayan a ser insertados en el objeto de destino. It only means that if the mouse button was released at this point, the destination object would accept the dragged data and the On Drop event would be fired.
If you do not process the On Drag Over event for a droppable object, that object will be highlighted for all drag over operations, no matter what the nature and type of the dragged data.
The On Drag Over event is the means by which you control the first phase of a drag-and-drop operation. No sólo puede probar si los datos arrastrados son de un tipo compatible con el objeto de destino, y luego aceptar o rechazar el arrastre; puede notificar simultáneamente al usuario de este hecho, porque 4D resalta (o no) el objeto de destino, basándose en su decisión.
The code handling an On Drag Over event should be short and execute quickly, because that event is sent repeatedly to the current destination object, due to the movements of the mouse.