DropHandler (JNA API)

java.lang.Object
- com.sun.jna.platform.dnd.DropHandler

All Implemented Interfaces:

DropTargetListener, EventListener
```
public abstract class DropHandler
extends Object
implements DropTargetListener
```
Provides simplified drop handling for a component. Usage:
```
 int actions = DnDConstants.MOVE_OR_COPY;
 Component component = ...;
 DropHandler handler = new DropHandler(component, actions);
 
```
- Accept drops where the action is the default (i.e. no modifiers) but the intersection of source and target actions is not the default. Doing so allows the source to adjust the cursor appropriately.
- Refuse drops where the user modifiers request an action that is not supported (this works for all cases except when the drag source is not a DragHandler and the user explicitly requests a MOVE operation; this is indistinguishable from a drag with no modifiers unless we have access to the key modifiers, which DragHandler provides).
- Drops may be refused based on data flavor, location, intended drop action, or any combination of those, by overriding canDrop(java.awt.dnd.DropTargetEvent, int, java.awt.Point).
- Custom decoration of the drop area may be performed in paintDropTarget(DropTargetEvent, int, Point) or by providing a DropTargetPainter.
The method getDropAction(DropTargetEvent) follows these steps to determine the appropriate action (if any).
- isSupported(DataFlavor[]) determines if there are any supported flavors
- getDropActionsForFlavors(DataFlavor[]) reduces the supported actions based on available flavors. For instance, a text field for file paths might support DnDConstants.ACTION_COPY_OR_MOVE on a plain string, but DnDConstants.ACTION_LINK might be the only action supported on a file.
- getDropAction(DropTargetEvent, int, int, int) relax the action if it's the default, or restrict it for user requested actions.
- canDrop(DropTargetEvent, int, Point) change the action based on the location in the drop target component, or any other criteria.
Override drop(DropTargetDropEvent, int) to handle the drop. You should invoke DropTargetDropEvent.dropComplete(boolean) as soon as the Transferable data is obtained, to avoid making the DnD operation look suspended.
Author:

twall

See Also:
DragHandler

Constructor Summary

Constructors
Constructor and Description
`DropHandler(Component c, int acceptedActions)` Create a handler that allows the given set of actions.
`DropHandler(Component c, int acceptedActions, DataFlavor[] acceptedFlavors)` Enable handling of drops, indicating what actions and flavors are acceptable.
`DropHandler(Component c, int acceptedActions, DataFlavor[] acceptedFlavors, DropTargetPainter painter)` Enable handling of drops, indicating what actions and flavors are acceptable, and providing a painter for drop target feedback.

Method Summary

Methods
Modifier and Type	Method and Description
`protected int`	`acceptOrReject(DropTargetDragEvent e)` Accept or reject the drag represented by the given event.
`protected boolean`	`canDrop(DropTargetEvent e, int action, Point location)` Indicate whether the given drop action is acceptable at the given location.
`void`	`dragEnter(DropTargetDragEvent e)`
`void`	`dragExit(DropTargetEvent e)`
`void`	`dragOver(DropTargetDragEvent e)`
`void`	`drop(DropTargetDropEvent e)` Indicates the user has initiated a drop.
`protected abstract void`	`drop(DropTargetDropEvent e, int action)` Handle an incoming drop with the given action.
`void`	`dropActionChanged(DropTargetDragEvent e)`
`protected int`	`getDropAction(DropTargetEvent e)` Calculate the effective action.
`protected int`	`getDropAction(DropTargetEvent e, int currentAction, int sourceActions, int acceptedActions)`
`protected int`	`getDropActionsForFlavors(DataFlavor[] dataFlavors)` Indicate the actions available for the given list of data flavors.
`protected DropTarget`	`getDropTarget()`
`boolean`	`isActive()` Whether this drop target is active.
`protected boolean`	`isSupported(DataFlavor[] flavors)` Return whether any of the flavors in the given list are accepted.
`protected boolean`	`modifiersActive(int dropAction)` Returns whether there are key modifiers active , or false if they can't be determined.
`protected void`	`paintDropTarget(DropTargetEvent e, int action, Point location)` Update the appearance of the target component.
`void`	`setActive(boolean active)` Set whether this handler (and thus its drop target) will accept any drops.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - DropHandler
```
public DropHandler(Component c,
           int acceptedActions)
```
    Create a handler that allows the given set of actions. If using this constructor, you will need to override isSupported(java.awt.datatransfer.DataFlavor[]) to indicate which data flavors are allowed.
  - DropHandler
```
public DropHandler(Component c,
           int acceptedActions,
           DataFlavor[] acceptedFlavors)
```
    Enable handling of drops, indicating what actions and flavors are acceptable.
    
    Parameters:
    c - The component to receive drops
    acceptedActions - Allowed actions for drops
    acceptedFlavors - Allowed data flavors for drops
    See Also:
    isSupported(java.awt.datatransfer.DataFlavor[])
  - DropHandler
```
public DropHandler(Component c,
           int acceptedActions,
           DataFlavor[] acceptedFlavors,
           DropTargetPainter painter)
```
    Enable handling of drops, indicating what actions and flavors are acceptable, and providing a painter for drop target feedback.
    
    Parameters:
    c - The component to receive drops
    acceptedActions - Allowed actions for drops
    acceptedFlavors - Allowed data flavors for drops
    painter - Painter to handle drop target feedback
    See Also:
    paintDropTarget(java.awt.dnd.DropTargetEvent, int, java.awt.Point)
- Method Detail
  - getDropTarget
```
protected DropTarget getDropTarget()
```
  - isActive
```
public boolean isActive()
```
    Whether this drop target is active.
  - setActive
```
public void setActive(boolean active)
```
    Set whether this handler (and thus its drop target) will accept any drops.
  - getDropActionsForFlavors
```
protected int getDropActionsForFlavors(DataFlavor[] dataFlavors)
```
    Indicate the actions available for the given list of data flavors. Override this method if the acceptable drop actions depend on the currently available DataFlavor. The default returns the accepted actions passed into the constructor.
    
    Parameters:
    dataFlavors - currently available flavors
    See Also:
    getDropAction(DropTargetEvent, int, int, int), canDrop(DropTargetEvent, int, Point)
  - getDropAction
```
protected int getDropAction(DropTargetEvent e)
```
    Calculate the effective action. The default implementation checks whether any DataFlavors are supported, and if so, will change the current action from DnDConstants.ACTION_NONE to something in common between the source and destination. Refuse user-requested actions if they are not supported (rather than silently accepting a non-user-requested action, which is the Java's DnD default behavior). The drop action is forced to DnDConstants.ACTION_NONE if there is no supported data flavor.
    
    See Also:
    isSupported(DataFlavor[]), getDropActionsForFlavors(java.awt.datatransfer.DataFlavor[]), getDropAction(DropTargetEvent, int, int, int), canDrop(DropTargetEvent, int, Point)
  - getDropAction
```
protected int getDropAction(DropTargetEvent e,
                int currentAction,
                int sourceActions,
                int acceptedActions)
```
  - modifiersActive
```
protected boolean modifiersActive(int dropAction)
```
    Returns whether there are key modifiers active , or false if they can't be determined. We use the DragHandler hint, if available, or fall back to whether the drop action is other than the default (move).
  - acceptOrReject
```
protected int acceptOrReject(DropTargetDragEvent e)
```
    Accept or reject the drag represented by the given event. Returns the action determined by getDropAction(DropTargetEvent).
  - dragEnter
```
public void dragEnter(DropTargetDragEvent e)
```
    Specified by:
    
    dragEnter in interface DropTargetListener
  - dragOver
```
public void dragOver(DropTargetDragEvent e)
```
    Specified by:
    
    dragOver in interface DropTargetListener
  - dragExit
```
public void dragExit(DropTargetEvent e)
```
    Specified by:
    
    dragExit in interface DropTargetListener
  - dropActionChanged
```
public void dropActionChanged(DropTargetDragEvent e)
```
    Specified by:
    
    dropActionChanged in interface DropTargetListener
  - drop
```
public void drop(DropTargetDropEvent e)
```
    Indicates the user has initiated a drop. The default performs all standard drop validity checking and handling, then invokes drop(DropTargetDropEvent,int) if the drop looks acceptable.
    
    Specified by:
    
    drop in interface DropTargetListener
  - isSupported
```
protected boolean isSupported(DataFlavor[] flavors)
```
    Return whether any of the flavors in the given list are accepted. The list is compared against the accepted list provided in the constructor.
  - paintDropTarget
```
protected void paintDropTarget(DropTargetEvent e,
                   int action,
                   Point location)
```
    Update the appearance of the target component. Normally the decoration should be painted only if the event is an instance of DropTargetDragEvent with an action that is not DragHandler.NONE. Otherwise the decoration should be removed or hidden.
    For an easy way to highlight the drop target, consider using a single instance of AbstractComponentDecorator and moving it according to the intended drop location.
    
    Parameters:
    e - The drop target event
    action - The action for the drop
    location - The intended drop location, or null if there is none
  - canDrop
```
protected boolean canDrop(DropTargetEvent e,
              int action,
              Point location)
```
    Indicate whether the given drop action is acceptable at the given location. This method is the last check performed by getDropAction(DropTargetEvent). You may override this method to refuse drops on certain areas within the drop target component. The default always returns true.
  - drop
```
protected abstract void drop(DropTargetDropEvent e,
        int action)
                      throws UnsupportedFlavorException,
                             IOException
```
    Handle an incoming drop with the given action. The action passed in might be different from DropTargetDropEvent.getDropAction(), for instance, if there are no modifiers and the default action is not supported. Calling DropTargetDropEvent.dropComplete(boolean) is recommended as soon as the Transferable data is obtained; this allows the drag source to reset the cursor and any drag images which may be in effect.
    
    Throws:
    
    UnsupportedFlavorException
    
    IOException

Class DropHandler

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

DropHandler

DropHandler

DropHandler

Method Detail

getDropTarget

isActive

setActive

getDropActionsForFlavors

getDropAction

getDropAction

modifiersActive

acceptOrReject

dragEnter

dragOver

dragExit

dropActionChanged

drop

isSupported

paintDropTarget

canDrop

drop