function MaterialsFilePicker() {
  this.selectedMaterials = {};
}

MaterialsFilePicker.prototype.pick = function(div) {
  var courseId = gon.course;
  var that = this;
  $.ajax({
    url: '/courses/' + courseId + '/materials.json',
    success: function(rootNode) { that.onWorkbinStructureReceived(rootNode); }
  });
  
  var htmlContent = '<div class="modal-header">\
  <h3>Select Files</h3>\
  </div>\
  <div class="modal-body">\
  <div id="file-picker-tree"></div>\
  </div>\
  <div class="modal-footer">\
    <div id="done-picking" data-dismiss="modal" class="btn btn-primary">\
      Done\
    </div>\
    <button data-dismiss="modal" class="btn">\
      Cancel\
    </button>\
  </div>';

  $(div).html(htmlContent);
  this.treeElement = $('#file-picker-tree', div);
  
  $("#done-picking").on('click', this.onDone(this));
}

MaterialsFilePicker.prototype.onDone = function(context) {
  var that = context;
  return function() {
    console.log("Test.");
    var selectedItems = [];
    for (var id in that.selectedMaterials) {
      var currentTuple = that.selectedMaterials[id];
      selectedItems.push(currentTuple);
    }
  
    that.onSelectionCompleted(selectedItems);
  };
};

MaterialsFilePicker.prototype.onWorkbinStructureReceived = function(rootNode) {
  var shouldIncludeFiles = true;
  var treeData = parseFileJsonForJqTree(rootNode, shouldIncludeFiles);
  
  this.treeElement.tree({
    data: treeData,
    autoOpen: true,
    keyboardSupport: false
  });
  this.treeElement.bind('tree.click', this.onNodeClicked(this));
};

MaterialsFilePicker.prototype.onNodeClicked = function(context) {
  var that = context;
  return function(event) {
    // Disable single selection: click to select for everything.
    event.preventDefault();
    
    var selectedNode = event.node;
    var nodeId = selectedNode.id;
    
    var isNodeSelected = context.treeElement.tree('isNodeSelected', selectedNode);
    var isNodeAFile = nodeId.indexOf && nodeId.indexOf("file") !== -1;
    
    // We don't bother with folders - only individual files.
    if (isNodeAFile) {
      var indexAfterPrefix = nodeId.indexOf("_") + 1;
      var id = nodeId.slice(indexAfterPrefix);
      
      // <ID, Type, Name, URL>
      if (isNodeSelected) {
        context.treeElement.tree('removeFromSelection', selectedNode);
        
        var tuple = [id, "Material", selectedNode.label, selectedNode.url];
        context.selectedMaterials[id] = tuple;
      } else {
        context.treeElement.tree('addToSelection', selectedNode);
        delete context.selectedMaterials[id];
      }
    }
  };
};
@@ -788,16 +788,21 @@
 picking%22
+, div
 ).on('cl

Fix context issue with Done button.