| J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | <!-- |
| 2 | Copyright 1998-1999 Sun Microsystems, Inc. All Rights Reserved. |
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| 25 | |
| 26 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
| 27 | <html> |
| 28 | <body bgcolor="white"> |
| 29 | |
| 30 | Drag and Drop is a direct manipulation gesture found in many Graphical |
| 31 | User Interface systems that provides a mechanism to transfer |
| 32 | information between two entities logically associated with presentation |
| 33 | elements in the GUI. Normally driven by a physical gesture of a |
| 34 | human user using an appropriate input device, Drag and Drop provides both |
| 35 | a mechanism to enable continuous feedback regarding the |
| 36 | possible outcome of any subsequent data transfer to the user during |
| 37 | navigation over the presentation elements in the GUI, and the facilities |
| 38 | to provide for any subsequent data negotiation and transfer. |
| 39 | <P> |
| 40 | This package defines the classes and interfaces necessary to perform Drag |
| 41 | and Drop operations in Java. It |
| 42 | defines classes for the drag-source and the drop-target, as well as |
| 43 | events for transferring the data being dragged. This package also provides |
| 44 | a means for giving visual feedback to the user throughout the |
| 45 | duration of the Drag and Drop operation. |
| 46 | <P> |
| 47 | A typical Drag and Drop operation can be decomposed into the following |
| 48 | states (not entirely sequentially): |
| 49 | <UL> |
| 50 | <LI>A <code>DragSource</code> comes into existence, |
| 51 | associated with some presentation |
| 52 | element (<code>Component</code>) in the GUI, to initiate a Drag and Drop of |
| 53 | some potentially <code>Transferable</code> data. |
| 54 | <P> |
| 55 | <LI>1 or more <code>DropTarget</code>(s) come into/go out of |
| 56 | existence, associated |
| 57 | with presentation elements in the GUI (Components), potentially |
| 58 | capable of consuming <code>Transferable</code> data types. |
| 59 | <P> |
| 60 | <LI> A <code>DragGestureRecognizer</code> is |
| 61 | obtained from the <code>DragSource</code> and is |
| 62 | associated with a <code>Component</code> in order |
| 63 | to track and identify any Drag |
| 64 | initiating gesture by the user over the <code>Component</code>. |
| 65 | <P> |
| 66 | <LI> A user makes a Drag gesture over the <code>Component</code>, |
| 67 | which the registered |
| 68 | <code>DragGestureRecognizer</code> detects, and notifies its |
| 69 | <code>DragGestureListener</code> of. |
| 70 | <P> |
| 71 | Note: Although this API consistently refers to the stimulus for a |
| 72 | drag and drop operation being a physical gesture by a human user, this |
| 73 | does not preclude a programmatically driven DnD operation given the |
| 74 | appropriate implementation of a <code>DragSource</code>. This package |
| 75 | contains the abstract class <code>MouseDragGestureRecognizer</code> for |
| 76 | recognizing mouse device gestures. Other abstract subclasses may be |
| 77 | provided by the platform to support other input devices or |
| 78 | particular <code>Component</code> class semantics. |
| 79 | <P> |
| 80 | <LI> The <code>DragGestureListener</code> causes the |
| 81 | <code>DragSource</code> to initiate the Drag |
| 82 | and Drop operation on behalf of the user, perhaps animating the |
| 83 | GUI Cursor and/or rendering an <code>Image</code> of the item(s) that are the |
| 84 | subject of the operation. |
| 85 | <P> |
| 86 | <LI> As the user gestures navigate over <code>Component</code>(s) |
| 87 | in the GUI with |
| 88 | associated <code>DropTarget</code>(s), the <code>DragSource</code> |
| 89 | receives notifications in order |
| 90 | to provide "Drag Over" feedback effects, and the <code>DropTarget</code>(s) |
| 91 | receive notifications in order to provide "Drag Under" feedback effects |
| 92 | based upon the operation(s) supported and the data type(s) involved. |
| 93 | </UL> |
| 94 | <P> |
| 95 | |
| 96 | The gesture itself moves a logical cursor across the GUI hierarchy, |
| 97 | intersecting the geometry of GUI Component(s), possibly resulting in |
| 98 | the logical "Drag" cursor entering, crossing, and subsequently |
| 99 | leaving <code>Component</code>(s) and associated <code>DropTarget</code>(s). |
| 100 | <P> |
| 101 | The <code>DragSource</code> object manifests "Drag Over" feedback to the user, in the typical case by animating the GUI <code>Cursor</code> associated with the |
| 102 | logical cursor. |
| 103 | <P> |
| 104 | <code>DropTarget</code> objects manifest "Drag Under" feedback to the user, in |
| 105 | the typical case, by rendering animations into their associated GUI |
| 106 | <code>Component</code>(s) under the GUI Cursor. |
| 107 | <P> |
| 108 | The determination of the feedback effects, and the ultimate success |
| 109 | or failure of the data transfer, should one occur, is parameterized |
| 110 | as follows: |
| 111 | <UL> |
| 112 | <LI> By the transfer "operation" selected by the user, and supported by |
| 113 | both the <code>DragSource</code> and <code>DropTarget</code>: Copy, Move or Reference(link). |
| 114 | <P> |
| 115 | <LI> By the intersection of the set of data types provided by the |
| 116 | <code>DragSource</code> and the set of data types comprehensible by the |
| 117 | <code>DropTarget</code>. |
| 118 | <P> |
| 119 | <LI>When the user terminates the drag operation, normally resulting in a |
| 120 | successful Drop, both the <code>DragSource</code> and <code>DropTarget</code> |
| 121 | receive |
| 122 | notifications that include, and result in the type negotiation and |
| 123 | transfer of, the information associated with the <code>DragSource</code> via a |
| 124 | <code>Transferable</code> object. |
| 125 | </UL> |
| 126 | |
| 127 | <!-- |
| 128 | <h2>Package Specification</h2> |
| 129 | |
| 130 | ##### FILL IN ANY SPECS NEEDED BY JAVA COMPATIBILITY KIT ##### |
| 131 | <ul> |
| 132 | <li><a href="">##### REFER TO ANY FRAMEMAKER SPECIFICATION HERE #####</a> |
| 133 | </ul> |
| 134 | |
| 135 | <h2>Related Documentation</h2> |
| 136 | |
| 137 | For overviews, tutorials, examples, guides, and tool documentation, please see: |
| 138 | <ul> |
| 139 | <li><a href="">##### REFER TO NON-SPEC DOCUMENTATION HERE #####</a> |
| 140 | </ul> |
| 141 | --> |
| 142 | |
| 143 | @since 1.2 |
| 144 | </body> |
| 145 | </html> |