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# YUI Library Examples: Drag & Drop: Drag and Drop Interaction Groups

# Drag & Drop: Drag and Drop Interaction Groups

Using interaction groups, this example demonstrates how to tie into the Drag & Drop Utility's interesting moments to provide visual affordances for the current drag operation.

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## Drag and Drop Interaction Groups and Affordances

The YUI Drag & Drop Utility lets you make HTML elements draggable.

All drag and drop instances are assigned to an interaction group. If a group is not specified in the constuctor, it is assigned to the `default` group. A given instance can belong to more than one group.

In this example, we have two interaction groups, `topslots` and `bottomslots`. The grey squares are the "slots", so #1 and #2 are the `topslots` and the others are the `bottomslots`. These are `YAHOO.util.DDTarget` instances, which means they can be targeted, but not dragged.

The colored "player" squares below are draggable. #1 and #2 are in the `topslots` group, #3 and #4 are in the `bottomslots` group, and #5 and #6 are assigned to both groups. When the drag starts, we use the highlight the slots that can be targeted by checking the group information.

Markup:

<div class="slot" id="t1" >1</div> <div class="slot" id="t2" >2</div> <div class="slot" id="b1" >3</div> <div class="slot" id="b2" >4</div> <div class="slot" id="b3" >5</div> <div class="slot" id="b4" >6</div> <div class="player" id="pt1" >1</div> <div class="player" id="pt2" >2</div> <div class="player" id="pb1" >3</div> <div class="player" id="pb2" >4</div> <div class="player" id="pboth1" >5</div> <div class="player" id="pboth2" >6</div>

Code:

<script type="text/javascript"> (function() { YAHOO.example.DDPlayer = function(id, sGroup, config) { YAHOO.example.DDPlayer.superclass.constructor.apply(this, arguments); this.initPlayer(id, sGroup, config); }; YAHOO.extend(YAHOO.example.DDPlayer, YAHOO.util.DDProxy, { TYPE: "DDPlayer", initPlayer: function(id, sGroup, config) { if (!id) { return; } var el = this.getDragEl() YAHOO.util.Dom.setStyle(el, "borderColor", "transparent"); YAHOO.util.Dom.setStyle(el, "opacity", 0.76); // specify that this is not currently a drop target this.isTarget = false; this.originalStyles = []; this.type = YAHOO.example.DDPlayer.TYPE; this.slot = null; this.startPos = YAHOO.util.Dom.getXY( this.getEl() ); YAHOO.log(id + " startpos: " + this.startPos, "info", "example"); }, startDrag: function(x, y) { YAHOO.log(this.id + " startDrag", "info", "example"); var Dom = YAHOO.util.Dom; var dragEl = this.getDragEl(); var clickEl = this.getEl(); dragEl.innerHTML = clickEl.innerHTML; dragEl.className = clickEl.className; Dom.setStyle(dragEl, "color", Dom.getStyle(clickEl, "color")); Dom.setStyle(dragEl, "backgroundColor", Dom.getStyle(clickEl, "backgroundColor")); Dom.setStyle(clickEl, "opacity", 0.1); var targets = YAHOO.util.DDM.getRelated(this, true); YAHOO.log(targets.length + " targets", "info", "example"); for (var i=0; i<targets.length; i++) { var targetEl = this.getTargetDomRef(targets[i]); if (!this.originalStyles[targetEl.id]) { this.originalStyles[targetEl.id] = targetEl.className; } targetEl.className = "target"; } }, getTargetDomRef: function(oDD) { if (oDD.player) { return oDD.player.getEl(); } else { return oDD.getEl(); } }, endDrag: function(e) { // reset the linked element styles YAHOO.util.Dom.setStyle(this.getEl(), "opacity", 1); this.resetTargets(); }, resetTargets: function() { // reset the target styles var targets = YAHOO.util.DDM.getRelated(this, true); for (var i=0; i<targets.length; i++) { var targetEl = this.getTargetDomRef(targets[i]); var oldStyle = this.originalStyles[targetEl.id]; if (oldStyle) { targetEl.className = oldStyle; } } }, onDragDrop: function(e, id) { // get the drag and drop object that was targeted var oDD; if ("string" == typeof id) { oDD = YAHOO.util.DDM.getDDById(id); } else { oDD = YAHOO.util.DDM.getBestMatch(id); } var el = this.getEl(); // check if the slot has a player in it already if (oDD.player) { // check if the dragged player was already in a slot if (this.slot) { // check to see if the player that is already in the // slot can go to the slot the dragged player is in // YAHOO.util.DDM.isLegalTarget is a new method if ( YAHOO.util.DDM.isLegalTarget(oDD.player, this.slot) ) { YAHOO.log("swapping player positions", "info", "example"); YAHOO.util.DDM.moveToEl(oDD.player.getEl(), el); this.slot.player = oDD.player; oDD.player.slot = this.slot; } else { YAHOO.log("moving player in slot back to start", "info", "example"); YAHOO.util.Dom.setXY(oDD.player.getEl(), oDD.player.startPos); this.slot.player = null; oDD.player.slot = null } } else { // the player in the slot will be moved to the dragged // players start position oDD.player.slot = null; YAHOO.util.DDM.moveToEl(oDD.player.getEl(), el); } } else { // Move the player into the emply slot // I may be moving off a slot so I need to clear the player ref if (this.slot) { this.slot.player = null; } } YAHOO.util.DDM.moveToEl(el, oDD.getEl()); this.resetTargets(); this.slot = oDD; this.slot.player = this; }, swap: function(el1, el2) { var Dom = YAHOO.util.Dom; var pos1 = Dom.getXY(el1); var pos2 = Dom.getXY(el2); Dom.setXY(el1, pos2); Dom.setXY(el2, pos1); }, onDragOver: function(e, id) { }, onDrag: function(e, id) { } }); var slots = [], players = [], Event = YAHOO.util.Event, DDM = YAHOO.util.DDM; Event.onDOMReady(function() { // slots slots[0] = new YAHOO.util.DDTarget("t1", "topslots"); slots[1] = new YAHOO.util.DDTarget("t2", "topslots"); slots[2] = new YAHOO.util.DDTarget("b1", "bottomslots"); slots[3] = new YAHOO.util.DDTarget("b2", "bottomslots"); slots[4] = new YAHOO.util.DDTarget("b3", "bottomslots"); slots[5] = new YAHOO.util.DDTarget("b4", "bottomslots"); // players players[0] = new YAHOO.example.DDPlayer("pt1", "topslots"); players[1] = new YAHOO.example.DDPlayer("pt2", "topslots"); players[2] = new YAHOO.example.DDPlayer("pb1", "bottomslots"); players[3] = new YAHOO.example.DDPlayer("pb2", "bottomslots"); players[4] = new YAHOO.example.DDPlayer("pboth1", "topslots"); players[4].addToGroup("bottomslots"); players[5] = new YAHOO.example.DDPlayer("pboth2", "topslots"); players[5].addToGroup("bottomslots"); DDM.mode = document.getElementById("ddmode").selectedIndex; Event.on("ddmode", "change", function(e) { YAHOO.util.DDM.mode = this.selectedIndex; }); }); })(); </script>

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### Drag & Drop Examples:

### More Drag & Drop Resources:

- User's Guide (external)
- API Documentation
- Cheat Sheet PDF (external)

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