Skip to main content

Arranging elements in a Grid by drag&drop


I have some elements in a Grid. I want to change their positions within that Grid. Can I swap their positions just by dragging cursor on to them?


For example


       Grid[{{1, 2, 5, 7, 9}, {3, 4, 8, 4, 2}, {5, 12, 7, 3, 8}}]

I want to swap positions of 8 and 2 in drag&drop fahion. Is it possible?



Answer



While drag'n'drop isn't officially supported in Mathematica currently (Depending on your definition of support), I believe Wolfram is working on it for a future version, or at least more direct support. I can't remember which screencast, but something was mentioned about this in one of Steven Wolframs talks posted on the official Mathematica blog.


Now to the code, what I do is simply spray around a lot of eventhandlers that set an Id when the mouse is over them, and then wrap my dynamic interface in an eventhandler that calls whatever action I need when you drag from one id to another.



SetAttributes[idElement,HoldFirst]
idElement[currentId_,content_,id_]:=EventHandler[content,{"MouseMoved":>(currentId=id)}]

In this case the action we want to perform is to switch the two elements that have been selected:


action[from_,to_] := If[from!=to,
   {mygrid[[Sequence@@from]],mygrid[[Sequence@@to]]}//
        ({mygrid[[Sequence@@to]],mygrid[[Sequence@@from]]}=#)&]

Now it's just a case of defining the outer EventHandler that calls the action, and a DynamicModule to scope the variables used, just to keep the code nice.


mygrid = {{1, 2, 5, 7, 9}, {3, 4, 8, 4, 2}, {5, 12, 7, 3, 8}};


DynamicModule[{currentId, from},
    EventHandler[Dynamic[

    Grid[MapIndexed[idElement[currentId, #1, #2] &, mygrid, {2}]]

    ],{
      "MouseDown" :> (from = currentId),
      "MouseUp" :> action[from, currentId]
     }]

]

This implementation is however not "just" allowing elements to be swapped, and depending on what you are doing, you may need a lot more interactivity added. For instance you can't edit the number anymore for this simple Grid example


Update:


A slightly nicer method which used unevaluated idTags which are only later replaced to allows a nicer call syntax:


SetAttributes[idTag,Protected]
SetAttributes[idSetter,HoldAll]
idSetter[var_]:=Function[{content,id},EventHandler[content,{"MouseMoved":>(var=id)}]]

 SetAttributes[dragNdrop,HoldFirst]

 dragNdrop[content_,action_]:=
 DynamicModule[{currentId,from},
 EventHandler[

 Dynamic[Block[{idTag=idSetter[currentId]},content]]

 ,{
  "MouseDown":>(from=currentId),
  "MouseUp":> action[from,currentId]}]
]


So then a call to add a dragNdrop fuctionality on some code is simply:


mygrid = {{1, 2, 5, 7, 9}, {3, 4, 8, 4, 2}, {5, 12, 7, 3, 8}};
dragNdrop[
    Grid[MapIndexed[idTag, mygrid, {2}]]
,action]

Added Variable descriptions


currentId stores the id of the element the mouse last moved over, this is used to determine both the element you drag from and the element you drag to. from is used to store the id you dragged from, since it needs to be saved for when actionis called. in idSetter, content is simply the content of the individual items that can be dragged, so in the Grid example, content would be the individual number in the grid.


Comments

Post a Comment

Popular posts from this blog

front end - keyboard shortcut to invoke Insert new matrix

I frequently need to type in some matrices, and the menu command Insert > Table/Matrix > New... allows matrices with lines drawn between columns and rows, which is very helpful. I would like to make a keyboard shortcut for it, but cannot find the relevant frontend token command (4209405) for it. Since the FullForm[] and InputForm[] of matrices with lines drawn between rows and columns is the same as those without lines, it's hard to do this via 3rd party system-wide text expanders (e.g. autohotkey or atext on mac). How does one assign a keyboard shortcut for the menu item Insert > Table/Matrix > New... , preferably using only mathematica? Thanks! Answer In the MenuSetup.tr (for linux located in the $InstallationDirectory/SystemFiles/FrontEnd/TextResources/X/ directory), I changed the line MenuItem["&New...", "CreateGridBoxDialog"] to read MenuItem["&New...", "CreateGridBoxDialog", MenuKey["m", Modifiers-...
Post a Comment
Read more

How to thread a list

I have data in format data = {{a1, a2}, {b1, b2}, {c1, c2}, {d1, d2}} Tableform: I want to thread it to : tdata = {{{a1, b1}, {a2, b2}}, {{a1, c1}, {a2, c2}}, {{a1, d1}, {a2, d2}}} Tableform: And I would like to do better then pseudofunction[n_] := Transpose[{data2[[1]], data2[[n]]}]; SetAttributes[pseudofunction, Listable]; Range[2, 4] // pseudofunction Here is my benchmark data, where data3 is normal sample of real data. data3 = Drop[ExcelWorkBook[[Column1 ;; Column4]], None, 1]; data2 = {a #, b #, c #, d #} & /@ Range[1, 10^5]; data = RandomReal[{0, 1}, {10^6, 4}]; Here is my benchmark code kptnw[list_] := Transpose[{Table[First@#, {Length@# - 1}], Rest@#}, {3, 1, 2}] &@list kptnw2[list_] := Transpose[{ConstantArray[First@#, Length@# - 1], Rest@#}, {3, 1, 2}] &@list OleksandrR[list_] := Flatten[Outer[List, List@First[list], Rest[list], 1], {{2}, {1, 4}}] paradox2[list_] := Partition[Riffle[list[[1]], #], 2] & /@ Drop[list, 1] RM[list_] := FoldList[Transpose[{First@li...
Post a Comment
Read more

dynamic - How can I make a clickable ArrayPlot that returns input?

I would like to create a dynamic ArrayPlot so that the rectangles, when clicked, provide the input. Can I use ArrayPlot for this? Or is there something else I should have to use? Answer ArrayPlot is much more than just a simple array like Grid : it represents a ranged 2D dataset, and its visualization can be finetuned by options like DataReversed and DataRange . These features make it quite complicated to reproduce the same layout and order with Grid . Here I offer AnnotatedArrayPlot which comes in handy when your dataset is more than just a flat 2D array. The dynamic interface allows highlighting individual cells and possibly interacting with them. AnnotatedArrayPlot works the same way as ArrayPlot and accepts the same options plus Enabled , HighlightCoordinates , HighlightStyle and HighlightElementFunction . data = {{Missing["HasSomeMoreData"], GrayLevel[ 1], {RGBColor[0, 1, 1], RGBColor[0, 0, 1], GrayLevel[1]}, RGBColor[0, 1, 0]}, {GrayLevel[0], GrayLevel...
Post a Comment
Read more